The solar system doesn’t end at Pluto or the icy belt of asteroids in the Oort cloud. In fact, the solar system is so huge that Voyager 1, the most distant human-made object, has been in space for more than 40 years and it still has not escaped the influence of the sun. The spacecraft is about 14 billion miles (22.5 billion km) away from the sun — about four times the average distance from the Sun to icy Pluto.
Although much of the solar system looks like empty space, it is in fact populated by solar wind and other electromagnetic radiation emanating from the sun. The sun’s sphere of influence is divided into various key regions, one of which is the heliosphere.
The heliosphere is a bubble-like region of the solar system, which is shaped like a long windsock as it moves with the sun through interstellar space. It is filled with the solar magnetic field and the protons and electrons of the solar wind (charged particles emanating from the sun).
Now, for the first time ever, astronomers have mapped out the heliosphere in three dimensions. The analysis confirmed suspicions from theoretical models that the heliosphere is shaped a bit like a comet, having a tail that’s about 350 astronomical units (one astronomical unit is roughly the distance from Earth to the Sun).
This is where the final frontier truly lies
The heliosphere’s outer boundary is known as heliopause. This is where the pressure from the solar wind, which is severely weakened so far away from the sun, is canceled by the pressure of interstellar space.
Using data from NASA’s Earth-orbiting Interstellar Boundary Explorer (IBEX) satellite, which measures charged particles flung from the very outer region of the heliosphere, researchers at the Los Alamos National Laboratory mapped the region in unprecedented detail. In the process, the three-dimensional map will now allow scientists to gain a better understanding of how solar and interstellar winds interact.
“Physics models have theorized this boundary for years,” said Dan Reisenfeld, a scientist at Los Alamos National Laboratory and lead author on the study, which was published in the Astrophysical Journal. “But this is the first time we’ve actually been able to measure it and make a three-dimensional map of it.”
Reisenfeld used a clever technique similar to how bats use sonar to detect their surroundings. Rather than detecting reflected acoustic waves, the astronomers measured energetic neutral atoms (ENAs) — particles resulting from the collisions between the solar and interstellar winds — to create a map of the heliosphere. Where the ENA count goes up, this could only mean that the boundary is close.
“The solar wind ‘signal’ sent out by the Sun varies in strength, forming a unique pattern,” explained Reisenfeld. “IBEX will see that same pattern in the returning ENA signal, two to six years later, depending on ENA energy and the direction IBEX is looking through the heliosphere. This time difference is how we found the distance to the ENA-source region in a particular direction.”
“In doing this, we are able to see the boundary of the heliosphere in the same way a bat uses sonar to ‘see’ the walls of a cave,” he added.
Previously, simulations that crunched numbers from measurements of galactic cosmic rays (an indirect indicator of ENAs), concluded that the solar system’s heliosphere is shaped croissant-like rather than like a comet. However, this newly published 3-D map suggests that the solar wind bubble is comet-like after all, although there are still uncertainties as to the heliosphere’s true shape due to the inherent limits of IBEX’s reach.
This isn’t the final word. The heliosphere may indeed have a more wacky shape and determining it is actually important from a practical standpoint. The heliosphere blocks 75% of galactic cosmic rays, which can catastrophically damage spacecraft and the DNA of any voyaging astronauts.
Using data collected by the Very Large Telescope (VLT) a team of astronomers has discovered iron and nickel in the atmosphere of around 20 different solar system comets–including some located far away from the Sun.
These findings will come as a surprise to astronomers because even though such heavy metals have been known to exist in solid form within comet interiors before, the vapour of such elements has only previously been associated with cometary atmospheres in hot environments.
This is the first time such vapour has been seen in the cooler atmospheres of comets that exist far from a star and could indicate some previously unknown mechanism or material on the surface of comets.
“It was a big surprise to detect iron and nickel atoms in the atmosphere of all the comets we have observed in the last two decades, about 20 of them, and even in ones far from the Sun in the cold space environment,” says Jean Manfroid, of the University of Liège, Belgium.
This wasn’t the only surprise the team found, however. The Belgian astronomers–who have been studying comets with the VLT for 20 years–observed nickel and iron in the atmosphere of the comet in equal amounts.
Generally, iron is about ten times more abundant in the solar system than nickel, and comets are believed to be material left over from the formation of planetary bodies within the solar system. That means it’s something of a mystery why the comets the team observed should have such a relatively large abundance of nickel.
“Comets formed around 4.6 billion years ago, in the very young Solar System, and haven’t changed since that time. In that sense, they’re like fossils for astronomers,” Emmanuel Jehin, also from the University of Liège. “This discovery went under the radar for many years.”
Manfroid and Jehin are two of the authors of a paper published in the latest edition of the journal Nature documenting the team’s findings. And that isn’t the only research revealing metal in the atmosphere of such a body published in Nature this month.
The discovery is accompanied by the revelation that a separate team of researchers, this time located in Poland, has also found traces of nickel vapour in the atmosphere around the interstellar visitor 2l/Borisov.
This comet may sound familiar as it made headlines in 2019 when it became only the second object found within the solar system which originated from outside our planetary system.
A paper detailing this second finding is also published in this month’s Nature.
Heavy Metal Rocks
Astronomers have known for some time that a variety of metals exist within the icy and rocky interiors of comets. There have even been suggestions that spent comets could be mined for precious or useful metals like gold, silver, platinum and iron.
These solid metals within comets were not expected to be found as gases in the body’s atmosphere, though, unless that body is passing within close vicinity to a star.
It is the heat from these close brushes with stars like the Sun that causes solid metals within comets to ‘sublimate’–the process by which solid material changes directly into a gaseous state.
That means that distant comets in the cold environment of space away from the heat of the Sun shouldn’t have heavy metal atmospheres.
Yet, despite this, researchers have now found nickel and iron vapour in the atmospheres of comets up to 480 million kilometres from the Sun. A distance that is three astronomical units, or three times the distance between the Sun and the Earth.
In order to make this discovery, the team employed the technique of spectroscopy which reveals the signatures of specific chemical elements and the Ultraviolet and Visual Echelle Spectrograph (UVES) instrument on the VLT to assess the chemical composition of comets’ atmospheres.
The spectral lines of nickel and iron found by the team in comets’ atmospheres were extremely faint, which leads them to believe that the reason such elements have been missed in past is due to their tiny abundance. The team says that for every 100kg of water in the atmosphere of the comets they studied there is just one gram of iron and nickel respectively.
The Belgian astronomers believe that the equal amounts of iron and nickel together with the sublimation at low temperatures means there is something undiscovered at the surface of the comets they studied.
“Usually there is 10 times more iron than nickel, and in those comet atmospheres we found about the same quantity for both elements,” explains Damien Hutsemékers, also a member of the Belgian team from the University of Liège.”We came to the conclusion they might come from a special kind of material on the surface of the comet nucleus, sublimating at a rather low temperature and releasing iron and nickel in about the same proportions.”
The team intends to attempt to use new telescope technology such as the Mid-infrared ELT Imager and Spectrograph (METIS) on ESO’s upcoming Extremely Large Telescope (ELT)–currently under construction in the Atacama Desert region of Northern Chile– to discover what this material is.
The findings of this team are accompanied by the revelation that nickel vapour has also been discovered in the atmosphere of 2I/Borisov.
2I/Borisov: The Interstellar Intruder that keeps giving
The discovery that metal is also present in the atmosphere of the interstellar visitor 2I/Borisov was made by a team of astronomers in Poland. The team also used the VLT to catch a glimpse of the interstellar comet as it passed through the solar system.
The data collected with the VLT’s X-Shooter spectrograph revaled nickel vapour in the cold envlope surround 2I/Borisov.
ESO/L. Calçada/O. Hainaut, P. Guzik and M. Drahus
The discovery marks another surprise for astronomers, as again it details the discovery of sublimated heavy metals in a cold atmosphere.
“At first we had a hard time believing that atomic nickel could really be present in 2I/Borisov that far from the Sun,” says Piotr Guzik, the Jagiellonian University, Poland, a co-author on this second study. “It took numerous tests and checks before we could finally convince ourselves.”
This latter study shows that nickel was not uniquely present during the formation of our solar system, but as it can be seen in a comet from another planetary grouping, it may well be common in many such conglomerations.
“All of a sudden we understood that gaseous nickel is present in cometary atmospheres in other corners of the Galaxy,” Michał Drahus, also from the Jagiellonian University and another of the paper’s co-authors, says.
In unison, both these studies indicate that the comets of this solar system and the interstellar visitor 2I/Borisov share many similarities. Dahus adds: “Now imagine that our Solar System’s comets have their true analogues in other planetary systems — how cool is that?”
Jehin, meanwhile, believes these studies could inspire future research into cometary bodies and their atmospheres, and a re-examination of data already collected.
“Now people will search for those lines in their archival data from other telescopes,” the University of Liège researcher concludes. “We think this will also trigger new work on the subject.”
Using the aftermath of a comet collision in 1994 astronomers have measured the winds blowing across Jupiter‘s stratosphere for the first time. The team has discovered that these winds raging around the middle atmosphere of the solar system’s largest planet are incredibly powerful–reaching speeds of up to 400 metres per second at the poles.
The team’s findings represent a significant breakthrough in planetary metrology and mark the gas giant out as what the team are describing as a ‘unique metrological beast in the solar system.’
To conduct the research the astronomers diverged from the usual methods used to measure the winds of Jupiter. Previous attempts to measure the gas giant’s winds have hinged on measuring swirling clouds of gas–seen as the planet’s distinctive red and white bands–but this method is only effective in measuring winds in the lower atmosphere. Whereas, by using aurorae at Jupiter’s poles researchers have been able to model winds in the upper atmosphere. But, both of these methods, even when used in conjunction, have left the winds in the middle section of the gas giant’s atmosphere–the stratosphere– something of a mystery.
That is until now. This team of astronomers used the Atacama Large Millimetre Array (ALMA) to track molecules left in Jupiter’s atmosphere by the collision with the comet Shoemaker-Levy 9 in 1994.
“We had to use ALMA’s ability to quickly map Jupiter’s spectral emission at very high spatial and spectral resolution in the submillimeter and observe the Doppler shifts induced by the winds on the spectral line we targeted,” team leader Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France, exclusively tells ZME Science. “We could deduce the wind speeds just like you could deduce the speed of a passing fire engine by the change in frequency of its siren. This spectral line is formed in the stratosphere, giving us access to the winds at this altitude.
“It is the first time we achieve measuring directly winds in the stratosphere of Jupiter, which lacks visual tracers such as clouds.”
Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France.
Cavalié explains that the team had to use ALMA’s ability to quickly map Jupiter’s spectral emission at very high spatial and spectral resolution in the submillimeter and observe the Doppler shifts induced by the winds on the spectral line they targeted.
“We could deduce the wind speeds just like you could deduce the speed of a passing fire engine by the change in frequency of its siren,” the researcher continues. “This spectral line is formed in the stratosphere, giving us access to the winds at this altitude.”
What the astronomers discovered was powerful winds in the middle atmosphere of Jupiter in two different locations. One set of winds conformed to expectations, but the other came as a surprise.
Jupiter’s ‘Supersonic Jet’ Winds
Cavalié explains that the team first found a 200 metres per second eastward jet just north of the equator in ‘super-rotation–meaning that the wind rotates faster around the planet than the planet rotates itself. “Winds at such latitudes were expected from models and previous temperature measurements at these low latitudes,” the astronomer adds.
But, not everything observed by the team conformed to expectations.
“Most surprisingly, we identified winds located under the main UV auroral emission near Jupiter’s poles. These winds have velocities of 300 to 400 meters per second,” Cavalié says. “While the equatorial winds were kind of anticipated, the auroral winds and their high speed were absolutely unexpected.”
To put this into perspective, the fastest winds ever recorded on earth reached a speed of just 103 metres per second–measured at the Mount Washington Observatory in 1931. These auroral winds even beat the winds recorded in Jupiter’s Great Red Spot–an ongoing raging storm on the surface of the gas giant–which have been clocked at around 120 metres per second.
The speed of these jets isn’t their only intimidating quality, however. The jets seem to behave like a giant vortex with a diameter around four times that of our entire planet, reaching a height of around 900 kilometres.
“A vortex of this size would be a unique meteorological beast in our Solar System.”
Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France.
The team’s measurements and stunning discovery, documented in a paper published in the latest edition of Astronomy & Astrophysics, wouldn’t have been possible without a violent incident in Jupiter’s recent history.
Shoemaker-Levy 9 Still has Impact
The impact of Shoemaker-Levy 9 upon the surface of Jupiter was an event–or more precisely a series of events– that had already made history before its effects made this research possible.
The comet broke up in the planet’s atmosphere resulting in a series of impacts that had never been studied prior to 1994, and its somewhat ironic that thanks to this study, Shoemaker-Levy 9 is still having an impact today. The comet left traces of hydrogen cyanide swirling in Jupiter’s atmosphere which the team was able to track.
“The team measured the Doppler shift of hydrogen cyanide molecules — tiny changes in the frequency of radiation emitted by the molecules — caused by their motion driven by stratospheric winds on Jupiter,” says Thomas K Greathouse, Senior Research Scientist at Southwest Research Institute (SwRI), responsible for the development of the study and analysis of the observational results. “
“The high spectral and spatial resolution and the exquisite sensitivity of the observations at the wavelengths covered by ALMA allowed us to map such small Doppler shifts caused by the winds in the stratosphere all along the limb of Jupiter.”
Thomas K Greathouse, Senior Research Scientist at Southwest Research Institute (SwRI).
The fact that the team was able to obtain all the measurements they did with just 30 minutes of operating time with ALMA is a striking testament to the power and precision of the 66 antennas that make up the telescope array located in the Atacama Desert of Nothern Chile, currently the most powerful radio telescope on Earth.
“It was the availability of ALMA that made these measurements possible. Previous radio observatory facilities did not have the combination of spectral and spatial resolution along with the high sensitivity needed to measure the winds as was done in this study,” Greathouse tells ZME Science. “Making further observations using ALMA to capture Jupiter at different orientations will allow us to study these winds in more detail and allow us to look for temporal variability in them as well.
“Additionally, more extensive measurements will be possible from the JUICE mission and its Submillimetre Wave Instrument slated for launch in 2022.”
The Future of Jupiter Investigations
JUICE or JUpiter ICy moons Explorer is the first large-class mission in the European Space Agency’s (ESA) Cosmic Vision program and will arrive at Jupiter in 2029 when it will begin a three-year mission observing the gas giant in intense detail.
“This is why science is so much fun. We have worked hard to understand a system–Jupiter’s stratosphere in this case–as best we can, we make our predictions about something–stratospheric wind behaviour–and then go test those predictions. If we are right, fantastic, we move on to the next problem, but if we are wrong we have learned something new and unique and can then continue making further studies to come to a more complete understanding of the system.”
Thomas K Greathouse, Senior Research Scientist at Southwest Research Institute (SwRI).
For Cavalié, who has been involved with the measurement of Jupiter’s winds since 2009, the future is bright for such investigations and what they can tell us about the solar system’s largest planet and gas giants in general. “We now want to use ALMA again to characterize the temporal variability of the equatorial winds,” the astronomer says. “It is expected from temperature measurements and models that the direction of the equatorial winds should oscillate from eastward to westward with a period of about 4 years.”
The scientist is also clear, just because he and his colleagues have achieved a first, that doesn’t mean they are prepared to rest on their laurels. There are a lot of exciting developments on the way, and thus a lot of work to be done.
“We also want to observe the auroral winds during a Juno perijove pass to compare our data with observations of the poles by the spacecraft to better understand their origin and what maintains them,” he explains. “In addition, this study is a stepping stone for future investigations to be conducted using the same technique with JUICE and its Submillitre Wave Instrument.”
In addition to these missions, the ESO’s Extremely Large Telescope (ELT)–due to start operations later this decade–will also join investigations of Jupiter and should be capable of providing highly detailed investigations of the gas giant’s atmosphere.
“Jupiter and the giant planets are fascinating worlds. Understanding how these planets formed and how they work is a source of daily motivation, especially when working with world-class observatories like ALMA and participating in space missions to explore Jupiter and its satellites.”
Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France.
New research from the National Science Foundation’s NOIRLab confirms: the most distant object in our Solar System is indeed “Farfarout”.
The name is not a typo. Back in 2018, the Subaru Telescope on Maunakea in Hawai’i discovered a stellar body moving through the solar system much farther away than anything ever seen before. We weren’t even able to determine how far, or where it was going, but we knew it was a long way away at the time. Based on its appearance (it was quite bright), the team assumed it was made of ice and probably around 250 miles (400 kilometers) in diameter, barely enough to be considered a dwarf planet.
In a bout of Internet humor that I can’t help but admire, they christened the body “Farfarout” and set to work on observing it further. We now have enough data to tell how far away it is and where it is going — Farfarout is now, appropriately, officially recognized by the International Astronomical Union as the farthest object in the Solar System.
A planet far far away
“At that time we did not know the object’s orbit as we only had the Subaru discovery observations over 24 hours, but it takes years of observations to get an object’s orbit around the Sun,” explained co-discoverer Scott Sheppard of the Carnegie Institution for Science.
“All we knew was that the object appeared to be very distant at the time of discovery.”
Together with David Tholen of the University of Hawai’i and Chad Trujillo of Northern Arizona University, Sheppard spent the last few years tracking the object with the Gemini North telescope (also on Maunakea in Hawai’i) and the Magellan Telescopes in Chile to determine where Farfarout was going.
Since then, they have been able to confirm that Farfarout is currently at around 132 AU (astronomical units) from the Sun, meaning it’s 132 times farther from our star than the Earth. Pluto, for comparison, sits at around 39 AU on average away from the Sun. This makes Farfarout the most remote object to ever be discovered in the Solar System, dethroning the previous record-holder, “Farout” (previously designated 2018 VG18). You won’t be surprised to hear that Farout was discovered and named by the same team.
As far as the orbit of Farfarout is concerned, the team explains that it is quite elongated, taking it from between 175 AU to 27 AU (bringing it closer to the Sun than Neptune). This weird shape for an orbit can offer some clues as to the history of Farfarout and the solar system at large.
“Farfarout was likely thrown into the outer Solar System by getting too close to Neptune in the distant past,” said Trujillo. “Farfarout will likely interact with Neptune again in the future since their orbits still intersect.”
The IAU’s Minor Planet Center in Massachusetts has announced that it will give Farfarout the provisional designation 2018 AG37. Its official christening will take place after we learn more about it and its properties, although I do think the current nickname should stick. It’s only appropriate.
Still, all things must pass and Farfarout’s title of farthest-out object in the solar system might well be one of them. The team remains confident that even more distant objects remain to be discovered.
“Farfarout takes a millennium to go around the Sun once,” said Tholen. “Because of this, it moves very slowly across the sky, requiring several years of observations to precisely determine its trajectory.”
“The discovery of Farfarout shows our increasing ability to map the outer Solar System and observe farther and farther towards the fringes of our Solar System,” said Sheppard. “Only with the advancements in the last few years of large digital cameras on very large telescopes has it been possible to efficiently discover very distant objects like Farfarout.”
“Even though some of these distant objects are quite large — the size of dwarf planets — they are very faint because of their extreme distances from the Sun. Farfarout is just the tip of the iceberg of objects in the very distant Solar System.”
Life-sustaining water could have existed miles beneath the surface of Mars thanks to the melting of thick ice sheets by geothermal heat, new research has found. The discovery, made by a team led by Rutgers University scientists, suggests that 4 billion years ago the most likely place for life to prosper on the Red Planet was beneath its surface.
The study, published in the latest edition of the journal Science Advances, could solve a problem that also has implications for the existence of liquid water–and thus the early development of life–on our planet too. Thus far, researchers looking into the existence of liquid water early in both Earth and Mars’histories have been puzzled by the fact that the Sun would have been up to 70% less intense in its stellar-youth.
This lack of intensity coupled with findings of liquid water at this stage in the solar system’s history is referred to as ‘the faint-sun paradox,’ and should mean that Mars conditions were cold and arid in its deep history. This conclusion was contradicted by geological evidence of liquid water on the young planet. The problem could now be solved, for Mars at least, by geothermal activity.
“Even if greenhouse gases like carbon dioxide and water vapour are pumped into the early Martian atmosphere in computer simulations, climate models still struggle to support a long-term warm and wet Mars,” explains lead author Lujendra Ojha, assistant professor in the Department of Earth and Planetary Sciences in the School of Arts and Sciences at Rutgers University, New Brunswick. “We propose that the faint young sun paradox may be reconciled, at least partly, if Mars had high geothermal heat in its past.”
The status of Mars climate billions of years ago and if freshwater could have existed its this point early in its history has been a source of heated debate in the scientific community for decades. The discussion has been further complicated by the question of whether water would have existed on the planet’s surface or deep underground? Climate models produced for Mars thus far have suggested average surface temperatures below the melting point of water at this point in its history.
Ojha and his team investigated this seeming contradiction in our understanding of Mars by modelling the average thickness of ice deposits in the Red Planet’s southern highlands. They also examined data collected by NASA’s InSight lander, which has been measuring the ‘vitals’ of the Red Planet since 2018.
Discovering that the thickness of these ice deposits did not exceed an average thickness of 2 kilometres, the team complemented this finding with estimates of both the planet’s average annual surface temperature and the flow of heat from its interior to its surface. The aim of this was to discover if the surface heat flow would have been strong enough to melt Mars’ ice sheets.
Indeed, the study seems to show that the flow of heat from both the crust and mantle of Mars would have been intense enough to begin melting at the base of its ice sheets.
Did Life on Mars prosper Beneath its Surface?
The wider implication of this revelation is that whatever the climate of Mars was like billions of years in its history if life once existed on the Red Planet, its subsurface would have been its most habitable region. Thus, life could have prospered, say the team, miles beneath the surface of our neighbour, sustained by the flow of freshwater.
Significantly, this supply of water would have existed even as Mars lost its magnetic field and its atmosphere was stripped away by harsh solar winds and blistering radiation. The process which ultimately deprived Mars of its surface liquid water. This means that life could have survived on the planet, hidden miles underground for much longer than the surface remained habitable.
“At such depths, life could have been sustained by hydrothermal activity and rock-water reactions,” says Ojha. “So, the subsurface may represent the longest-lived habitable environment on Mars.”
Out beyond the orbit of Neptune and the solar system’s seven other major planets lies a ring of icy bodies known as the Kuiper Belt. The disc that is 20 times as wide and an estimated 200 times as dense as the asteroid belt houses a wide array of objects, including its most famous inhabitant — the dwarf planet Pluto. But, it holds more than objects of ice and rock. The Kuiper Belt may hold the secrets of how the planets of the solar system formed, and the raw materials that created the worlds around us and our own planet.
“The Kuiper Belt is a repository of the solar system’s most primordial material and the long-sought nursery from which most short-period comets originate,” explains David C. Jewitt, an astronomer based at the University of California, Los Angeles, who is renowned for his study of the solar system and its smaller bodies. “The scientific impact of the Kuiper Belt has been huge, in many ways reshaping our ideas about the formation and evolution of the Solar System.”
Researchers now stand on the verge of unlocking these secrets with the investigation of the Kuiper Belt contact binary Arrokoth (previously known as ‘Ultima Thule’). On January 2019, the object — named for the Native American word for ‘sky’ — became the most distant object ever visited by a man-made spacecraft.
“Most of what we know about the belt was determined using ground-based telescopes. As a result, Kuiper Belt studies have been limited to objects larger than about 100 km because the smaller ones are too faint to easily detect,” says Jewitt. “Now, 5 years after its flyby of the 2000-km-diameter Kuiper Belt object Pluto, NASA’s New Horizons spacecraft has provided the first close-up look at a small, cold classical Kuiper Belt object.”
The data collected by the New Horizons probe has allowed three separate teams of researchers to conduct the most in-depth investigation of a Kuiper Belt object ever undertaken. In the process, they discovered that our current knowledge of how these objects form is very likely incorrect. From all the evidence the three teams collected, it seems as Kuiper Belts form as a result of a far more delicate, low-velocity process than previously believed. As most astrophysicists believe that these objects — planetesimals — acted as the seeds from which the planets grew, this new model changes our idea of how the solar system formed.
How Kuiper Belt Bodies Get in shape
The majority of the clues as to Arrokoth’s low-velocity formation originate from its unusual binary lobed shape. The larger lobe is joined to the smaller lobe by an extremely narrow ‘neck.’ What is especially interesting about this shape — reminiscent of a bowling pin or a snowman — is that the lobes are perfectly aligned.
John Spencer, Institute Scientist in the Department of Space Studies, Southwest Research Institute in Boulder, Colorado, led a team of researchers that reconstructed Arrokoth’s 3-dimensional shape from a series of high resolution black and white images. Spencer’s paper concludes that Arrokoth’s lobes are much flatter than was previously believed but despite this, both lobes are denser than expected.
William McKinnon, Professor of Earth and Planetary Sciences at the Califonia Institute of Technology, and his team ran simulations of different formation methods to see which conditions led to the shape recreated and Spencer and his colleagues.
McKinnon and his team discovered that the shape of Arrokoth could only be achieved as a result of a low-velocity formation–around 3 m/s. This presents a problem to current theories of how planetesimals form.
The suggested method of planetesimal formation suggests high-velocity particles smashing together in a process called hierarchical accretion. The simulations that McKinnon produced suggest that such high-velocity collisions would not have created a larger body, but rather, would have blown it apart. The geometrical alignment of the larger and smaller lobes indicates to the team that they were once co-orbiting bodies which gradually lost angular momentum and spiralled together, resulting in a merger.
“Arrokoth’s delicate structure is difficult to reconcile with alternative models in which Arrokoth Kuiper Belt objects are fragments of larger objects shattered by energetic collisions,” Jewitt says. This supports a method of planetesimal formation called ‘cloud collapse.’
“A variety of evidence from Arrokoth points to gravitational collapse as the formation mechanism. The evidence from the shape is probably most compelling,” William Grundy of Lowell Observatory says. “Gravitational collapse is a rapid but gentle process, that only draws material from a small region. Not the much more time consuming and violent process of hierarchical accretion – merging dust grains to make bigger ones, and so on up through pebbles, cobbles, boulders, incrementally larger and larger, with more and more violent collisions as the things crashing into each other.”
Grundy, whose team analysed the thermal emissions from Arrokoth’s ‘winter’ side, goes on to explain that the speed at which cloud collapse occurs and the fact that all the material that feeds it is local to it means that all the Kuiper planetesimals should be fairly uniform.
Cold Classicals: Untouched and unpolluted
Arrokoth is part of a Kuiper Belt population referred to as ‘cold classicals,’ this particular family of bodies is important to astrophysicists researching the origins of the solar systems. This is because, at their distance from the Sun within the Kuiper Belt, they have remained virtually untouched by both other objects and by the violent radiation of the Sun.
As many of these objects, Arrokoth in particular, date back 4 billion years to the very origin of the solar system, they hold an uncontaminated record of the materials from which the solar system emerged and of the processes at play in its birth.
Arrokoth has a relatively smooth surface in comparison with other comets, moons and planets within the solar system. It does show the signs of a few impacts, with one very noticeable 7km wide impact crater located of the smaller lobe. This few craters dotted across Arrokoth’s surface do seem to point to a few small high-velocity impacts. The characteristics of Arrokoth’s cratering allowed the team in infer its age of around 4 billion years. This places its birth right around the time the planets had begun to form in the solar system.
“The smooth, relatively un-cratered surface shows that Arrokoth is relatively pristine, so evidence of its formation hasn’t been destroyed by subsequent collisions,” Spencer explains. “The number of craters nevertheless indicates that the surface is very old, likely dating back to the time of accretion.
“The almost perfect alignment of the two lobes, and the lack of obvious damage where they meet, indicate gentle coalescence of two objects that formed in orbit around each other, something most easily accomplished by local cloud collapse.”
As mentioned above, Will Grundy and his team were tasked with the analysis of thermal emissions in the radio band emitted by the side of Arrokoth facing away from the Sun.
“We looked at the thermal emission at radio wavelengths from Arrokoth’s winter night side. Arrokoth is very cold, but it does still emit thermal radiation,” Grundy says. “The signal we saw was brighter, corresponding to a warmer temperature than expected for the winter surface temperature. Our hypothesis is that we are seeing emission from below the surface, at depths where the warmth from last summer still lingers.”
Grundy’s team also looked at the colour imaging of Arrokoth with the aim of determining what it is composed of. “We looked at the variation of colour across the surface, finding it to be quite subtle,” he says. “There are variations in overall brightness, but the colour doesn’t change much from place to place, leading us to suspect that the brightness variations are more about regional differences in surface texture than compositional differences.”
The team determined that Arrokoth’s dark red colouration is likely to be a result of the presence of ‘messy’ molecular jumbles of organic materials that occur when radiation drives the construction of increasingly complex molecules–known as tholins.
“One open question is where Arrokoth’s tholins came from,” Grundy says. “Were they already present in the molecular cloud from which the Solar System formed? Did they form in the protoplanetary nebula before Arrokoth accreted? Or did they form after Arrokoth accreted, through radiation from the Sun itself?”
The researcher says that all three are possible, but he considers the uniformity of Arrokoth’s colouration to favour the first two possibilities over the third. The team also searched Arrokoth for more recognisable organic molecules, spotting methanol–albeit frozen solid–but, not finding any trace of water. Something which came as a surprise to Grundy. “It was surprising not to see a clear signature of water ice since that’s such a common material in the outer solar system. Typically, comets have around 1% methanol, relative to their water ice.”
The team believe that this disparity arises from the fact that Arrokoth accreted in a very distinct chemical environment at the extreme edge of the nebula which collapsed to create the solar system.
“If it was cold enough there for carbon monoxide (CO) and methane (CH4) to freeze as ice onto dust grains, that would enable chemical mechanisms that create methanol and potentially destroy water, too. But those mechanisms could only work where these gases are frozen solid,” Grundy says. “Arrokoth appears to be sampling a region of the nebula where such conditions held.
“We have not seen comets so rich in methanol, which probably means we have not seen comets that formed in this outermost part of the nebula. Most of them probably originally formed closer to the Sun (or else at a different time in nebular history when the chemical conditions were somewhat different).”
Looking to future Kuiper Belt investigations
Investigating Kuiper Belt objects is no walk in the park, with difficulties arising from both the disc’s distance from the Sun and from the fact that Kuiper Belt objects tend to be very small. Grundy explains that as sunlight falls off by the square of its distance, object s as far away as the Kuiper Belt require the most powerful telescopes to do much of anything.
“Sending a spacecraft for a close-up look is great to do, but it took New Horizons 13 years to reach Arrokoth,” Grundy says. “It’ll probably be some time yet before another such object gets visited up-close by a spacecraft.”
“For flybys, the journey times are very long–we flew for 13 years to get there–navigation is difficult because we don’t know the orbits of objects out there very well, we’d only been tracking Arrokoth for 4 years,” Spencer explains. “The round-trip light time is long, which makes controlling the spacecraft more challenging, and light levels are very low, so taking well-exposed, unblurred, images is difficult.”
Spencer adds that from Earth, objects like Arrokoth are mostly very faint, meaning only a small fraction of them have been discovered and learning about their detailed properties is difficult even with large telescopes. These difficulties mean that one of the things left to discover is just how common bi-lobed contact binaries like Arrokoth are in the Kuiper Belt. “Some evidence from lightcurves suggests up to 25% of cold classical could be contact binaries,” he says. ” We know that many of them are binaries composed of two objects orbiting each other, however.”
Fortunately, telescope technology promises to make leaps and bounds over the coming decades, with the launch of the space-based James Webb Space Telescope (JWST) in 2021 and the completion of the Atacama Desert based Extremely Large Telescope (ELT) in 2026.
“Both will help,” says Grundy. “Larger telescopes are needed to collect more light and feed it to more sensitive instruments. JWST and the new generation of extremely large telescopes set to come online over the coming years will enable new investigations of these objects.”
In terms of future spacecraft visits, Grundy believes that researchers and engineers should be thinking small, literally: “If technical advances were to enable highly miniaturized spacecraft to be flown to the Kuiper belt more quickly, that could enable a lot of things. The big obstacles to doing that with today’sCubeSats are power, longevity, and communications, but the rapid advance of technology makes me hopeful that it will be possible to do a whole lot more with tiny little spacecraft within a few decades.
“It’s funny how progress calls for ever bigger telescopes and ever smaller spacecraft.”
Of course one of the most lasting changes that result from this landmark triad of studies on Arrokoth published in Science is the move away from hierarchical formation models and the adoption of a gravitational or cloud collapse model to explain the creation of planetesimals. This shift will resolve one of the long-standing issues with the hierarchical model, the fact that they work quite well to grow things from dust size to pebble size, but once pebble size is reached, the particles quickly spiral-in toward the Sun.
“I think it will shift the focus to the circumstances that trigger the collapse. It’s a very fast way of making a planetesimal–decades instead of hundreds of millennia–but the circumstances have to be right for instabilities to concentrate solids enough for them to collapse,” Grundy explains. “It will be interesting to map out where and when planetesimals should form, what their size distributions should be, and where the solids that they are formed from should have originated.”
W. M. Grundy et al., Science
W. B. McKinnon et al.,
J. R. Spencer et al., Science 10.1126/science.aay3999 (2020).
D. C. Jewitt et al., Science 10.1126/science.aba6889 (2020).
Located beyond the orbit of Neptune and within the Kuiper Belt — a massive circumstellar disc of small remnants left over from the formation of the solar system — Arrokoth (previously known as ‘Ultima Thule’) represents the most distant and primitive object ever to visited by a man-made space probe.
Revealed in a small amount of data collected during a January 2019 flyby conducted by the New Horizons probe, the double-lobed contact binary— or Kuiper Belt object 2014 MU69 to give it its formal name — is the subject of three new papers due to be published in the journal Science. The key findings of these studies were revealed at a press briefing held in Seattle, Washington, on 13th February 2020.
The research provides us with a stunningly detailed picture of the compact binary’s composition and origins and suggests a rethink of how planetary building blocks–planetesimals form.
“Data from Arrokoth has given us clues about the formation of planets and our cosmic origins,” says Marc Buie, of the Southwest Research Institute, who was part of the New Horizons team that first discovered the object. “We believe this ancient body, composed of two distinct lobes that merged into one entity, may harbour answers that contribute to our understanding of the origin of life on Earth.”
The authors believe that their results could help rule out a hierarchical formation model of planetesimal formation, in which objects from different areas of the nebula of gas and dust violently collide to create larger bodies.
The shape of Arrokoth, with its two distinctive lobes, seems to favour a much more delicate formation process, that of local cloud collapse. This would involve regions of the nebula collapsing with smaller particles gradually accumulating together.
If planetesimals form differently then previously modelled, the fact that they are the building blocks of the planets means that we may also have to revise our ideas of how the planets themselves form.
As the planetesimal is composed of pure and unchanged material, its detailed study could answer long-standing questions about the elements which were present during the solar system’s planet-formation phase.
“The mission of the New Horizon probe was to explore the solar system’s ‘third zone’,” Alan Stern, the principal investigator of the New Horizons mission says describing the Kuiper Belt where icy planetesimals and dwarf planets lurk. “It is the best-preserved region of the solar system, important for understanding its origins.”
Each of the three separate papers focuses on different aspects of Arrokoth’s formation and composition, offering new insights into planetesimals and the conditions and composition of the early solar system.
Three papers, three lines of evidence pointing to a new paradigm of planetesimal formation
William McKinnon and his team investigated how Arrokoth got its unique binary shape discovering that its two ‘lobes’ were once separate independent bodies.
McKinnon and his team believe that the two separate objects which comprise Arrokoth formed in the same vicinity joined together in a surprisingly gentle process. As hierarchical accretion, is anything but gentle McKinnon and his team think that Arrokoth formed as a result of a local collapse of the nebula.
“They’re just touching, it’s almost as if they’re kissing,” McKinnon, Professor of Earth and Planetary Sciences at the California Institute of Technology about the two lobes of Arrokoth. “There’s no evidence that the merger of these two lobes was violent. There’s no sign of catastrophic disruption.
“The merger speed must have been very low.”
Whilst McKinnon and his team focused on the formation of Arrokoth’s distinctive shape, researchers led by John Spencer were studying that shape in painstaking detail.
Spencer and his colleagues reveal that Arrokoth’s binary lobes are flattened in shape with a greater volume than originally believed. They are also almost perfectly aligned. “This tells us these are not objects that just blundered together,” Spencer “They have orbited each other for a long time, gently drifting together.”
The team have also been able to ascertain details about the surface of the contact binary, describing in their paper a smooth face with only slight cratering. This means that Arrokoth stands out from previously visited bodies within the solar system, having been struck by very few other objects. The greater consequence is that Arrokoth’s composition is unpolluted and thus may represent our best chance of studying the building blocks of the solar system.
Other comets that form closer to the Sun evolve very quickly as a result of the intense environments they find themselves in. In comparison, planetesimals that form far away from the Sun remain relatively unchanged, in Arrokoth’s case, for 4 billion years.
Will Grundy and the research team he worked with were charged with investigating the composition, colour, and temperature of Arrokoth’s surface. They found that the planetesimal’s distinctive and uniform red hue is a result of the presence of unidentified complex organic molecules — molecules formed from carbon, nitrogen, oxygen amongst other elements–present with methanol ice.
Grundy’s paper puts forward several suggestions as to how this frozen methanol could have formed on the Kuiper Belt object, including formation by irradiation of mixed water and methane ice by cosmic rays. The team was unable to detect the presence of water on Arrokoth, but they believe it could yet be present, currently ‘masked’ or hidden from view.
The uniformity of the compact binary’s surface colour and composition provide the third line of evidence in support of the theory that it formed as a result of local nebula collapse.
Stern does not downplay the significance of this evidence supporting a new paradigm of planetesimal formation–local cloud collapse. Comparing it to the discovery of the Cosmic Background Radiation which finally settled competition between different models of the origin of the universe he says: “This is a wonderful scientific present. It is truly a watershed moment.”
Stern concludes that every one of the attributes of Arrokoth observed point towards the cloud collapse model. As for the future, he says that the New Horizons mission has inspired other researchers to revisit another occupant of the Kuiper Belt– the dwarf planet Pluto.
Stern also points out that even though the New Horizons probe has “plenty of gas left in the tank,” the ideal mission would study Pluto for a period of a few years before moving off and investigating other bodies in the Kuiper Belt.
“We’re pretty excited, but it’s going to take a lot of work.”
NASA has spacecraft and rovers in several parts of our solar system — and sometimes, things start to break. This was the case recently with Voyager 2, one of the two Voyager spacecraft that were launched in 1979 and have since left the solar system, relaying information about the interstellar space.
For no clear reason, Voyager 2 stopped sending data and seemed to simply shut off.
The problem occurred as Voyager 2 attempted to rotate 360 degrees in order to calibrate one of its instruments. This movement was energy-intensive and might have triggered protection software — every time the software detects an unusual power consumption, it switches off to save energy. Since Voyager 2 has a finite power source, that makes sense. NASA explains:
“Multiple fault protection routines were programmed into both Voyager 1 and Voyager 2 in order to allow the spacecraft to automatically take actions to protect themselves if potentially harmful circumstances arise. “
So Voyager’s engineers tried to reset the system and start the spacecraft. But considering that it takes 17 hours to send information from Earth to the spacecraft and another 17 hours to send it back from the spacecraft to Earth, it’s quite a tedious process.
Thankfully, everything seemed to go according to plan, and Voyager 2 is back online — gathering and relaying scientific information just as before.
“Mission operators report that Voyager 2 continues to be stable and that communications between Earth and the spacecraft are good. The spacecraft has resumed taking science data, and the science teams are now evaluating the health of the instruments following their brief shutoff,” a NASA press release explains.
As of writing, NASA hasn’t confirmed or denied whether that is what actually happened. Only time will tell whether the agency ever gets an answer to what went wrong. But for now, we can all rest assured that Voyager 2’s mission is far from over yet. If all goes well, it should have another five years of life left, meaning five more years of data collection from an area of space we humans have no other way of studying.
The fact that engineers can address a software failure from 11.5 billion miles (18.5 billion kilometers) away, from a spacecraft launched over 40 years ago, is simply fantastic — and it’s a testament to how good NASA has become at fixing things from far away.
Engineering? That’s nice. Remote engineering — that’s where it’s at.
Around 2 billion years ago, two large rock bodies hit each other in the main asteroid belt, a region between the orbits of Mars and Jupiter populated by fragments of rocks of various sizes. The impactor, with a size ranging from 75 to 150 kilometers in diameter, hit a body at least 4 times larger. Astronomers have known about this impact for a long time because it created a whole family of asteroids in the main asteroid belt, formed by the celestial body Hygiea and almost 7,000 smaller asteroids that have similar orbits.
Hygiea itself has been considered an asteroid since it was discovered in 1849 by Italian astronomer Annibale de Gasparis. With a diameter just over 430 kilometers, it is the fourth-largest object in the main asteroid belt. New observations obtained with the Very Large Telescope (VLT), located in Chile and operated by the European Southern Observatory, have revealed that Hygiea is also round.
Determining the shape of Hygiea doesn’t have any practical implications for its orbit or behavior, but it’s enough to propel Hygiea from asteroid to dwarf planet, according to current scientific classifications.
There are four conditions that solar system objects must meet to be classified as dwarf planets: They must orbit the Sun, not be a satellite orbiting another body, not be massive enough to clear their orbit from other objects, and have a round shape due to their own gravity.
Fulfilling all the requirements makes Hygiea the smallest dwarf planet in the solar system, as researchers report in Nature Astronomy, taking the position from Ceres, which has a diameter of 950 kilometers. Pluto is the largest dwarf planet, with a diameter of 2,400 kilometers. For reference, our own Moon has a diameter of 3,474 kilometers, larger than any of the dwarf planets.
Observations with SPHERE
These new observations benefited from a new instrument, the Spectro-Polarimetric High-contrast Exoplanet Research instrument (SPHERE), installed in 2014 on one of the four 8.2-meter individual telescopes that form the VLT. SPHERE was designed to detect and study new giant exoplanets orbiting nearby stars, but it can also be used to observe small objects within our solar system with unprecedented resolution, as this study has shown.
“The revolution with SPHERE is that it works at the refraction limit of the telescope,” said Pierre Vernazza, an astronomer at the Laboratoire d’Astrophysique de Marseille in France and first author of the new study. “The combo of SPHERE and VLT is currently the most powerful imaging system in the world. Objects that were just a few pixels across before become really visible, and we can see craters that are just 30 kilometers in size and do geology from the ground thanks to this improvement.”
The team also showed that Hygiea rotates with a period of 13.8 hours, half the previously accepted value.
“It is solid work showing off amazing capabilities from Earth that we previously thought could only be possible from space,” said Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology who wasn’t involved in the study. “It is a combination of large telescope aperture, clever optical design, and high-speed computing to cancel out the blurring effects of Earth’s atmosphere, much like how noise-canceling headphones deliver a clear sound in the hubbub of an airport.”
A Smooth Surface Reveals a Violent Past
What really came as a surprise, Vernazza said, is that Hygiea’s surface is smooth, lacking signs of large impacts. Researchers were expecting to find some sort of a large impact basin, as is the case on the asteroid Vesta, which bears the mark of a massive impact on its south pole. Vesta also has its own family of asteroids, albeit smaller than Hygiea’s.
What Hygiea’s smooth surface reveals, according to the new study, is that the impact that created Hygiea was so powerful that it completely shattered its parent body. The fragments then coalesced again, assuming a round shape, and a fraction of the mass was ejected to form Hygiea’s asteroid family.
“Most of the mass was reaccreted to form Hygiea, and the reaccreting body behaves as a fluid during a few hours,” Vernazza said, “and that’s what allowed it to acquire a shape that is roughly spherical.”
To test this hypothesis, the team created a series of computer simulations that show that the most likely scenario involved a fast-traveling impactor between 75 and 150 kilometers in diameter and that the whole process probably took just a few hours to complete.
As telescopes keep improving and astronomers are able to observe more distant objects, the list of dwarf planets is sure to grow. “There are a lot of candidates among trans-Neptunian objects, and as far as we know, there are more than a hundred bodies with diameters above 400 kilometers, and for sure most of these bodies will be roughly spherical,” Vernazza said. To be able to obtain direct imaging observations of these bodies, equivalent to what the VLT has done with Hygiea, astronomers will have to wait until the next generation of 30- to 40-meter telescopes is available at some point within the next decade.
“We’re still in the reconnaissance phase of exploring our solar system,” Binzel said.
More than four decades after it began its epic journey, the Voyager 2 spacecraft has now officially reached interstellar space. In a new study, scientists have confirmed that the spacecraft is now outside the bubble-shaped region created by the sun’s wind, known as the heliosphere. This is the second interstellar spacecraft to reach so far from home, joining Voyager 1 which exited the solar system in 2012.
The sun constantly gushes out a flow of charged particles, known as plasma, known as solar wind. As this solar wind radially sweeps out into space, it creates a bubble filled with radiation and magnetic fields that trail all the way back to the sun. Ultimately, this solar blanket has a crucial impact on the formation and evolution of planetary systems by acting as a huge shield that blocks galactic radiation.
But now Voyager 2 has crossed this barrier that separates the solar system from the rest of the galaxy. Scientists are sure of this since the plasma wave instrument onboard the spacecraft has measured a significant increase in plasma density, up from the hot, low-density plasma characteristic of the solar wind. This plasma density jump was also recorded during Voyager 1’s exit out of the solar system.
According to Don Gurnett, the principal investigator on the plasma wave instrument aboard both Voyager 2 and Voyager 1, the spacecraft entered the interstellar medium at 119.7 astronomical units (AU), or more than 11 billion miles (17.7 billion km) from the sun. Voyager 2 is only the second spacecraft to travel beyond the confines of the heliosphere. The craft was launched slightly ahead of its twin Voyager 1 in 1977.
“In a historical sense, the old idea that the solar wind will just be gradually whittled away as you go further into interstellar space is simply not true,” says Don Gurnett, corresponding author on the study, published in the journalNature Astronomy.
“We show with Voyager 2–and previously with Voyager 1–that there’s a distinct boundary out there. It’s just astonishing how fluids, including plasmas, form boundaries.”
Voyager 1 crossed into interstellar space at about 122.6 AU, but at a different point in the solar system since it had different goals and trajectories through space. This implies that the heliosphere is symmetric.
“There’s almost a spherical front to this,” adds Gurnett. “It’s like a blunt bullet.”
However, damage to the plasma instrument meant that complete data on the transition could not be gathered.
The new study also provides new insight into the thickness of the heliosheath — the region where solar wind piles up against the approaching interstellar wind. Gurnett likens it to the effect of a snowplow on a city street during winter.
According to data from both Voyager spacecraft, the heliosheath has varying thickness. For instance, Voyager 1 had to travel 10 AU farther than Voyager 2 in order to reach the heliopause — the boundary point where the solar wind and interstellar wind are in balance. This is considered the crossing point to interstellar space.
Voyager 1 is still up and about, and its instruments are recording that the plasma density is rising. The spacecraft is so far away that it now takes 19 hours for data to be transmitted to Earth. And as the spacecraft ventures even farther into interstellar space, communications are expected to suffer.
According to astronomers, both Voyagers are on an orbit around the galaxy for five billion years or longer. They will likely not run into anything and could very well outlast planet Earth. “They might look a little worn by then,” Gurnett joked.
The findings include two mini-Neptunes and a rocky super-Earth.
Artistic depiction of the newly-discovered planets around their star, with the Earth for reference. Image credits: NASA’s Goddard Space Flight Center/Scott Wiessinger.
It seems hard to believe that we only discovered our first exoplanet — a planet outside of our solar system — in the 1990s. We now know thousands of exoplanets, and astronomers are verifying even more potential candidates. Much of what we know about exoplanets comes from the Kepler telescope, which was retired recently after 9 years of service.
But Kepler’s successor, TESS, is already bringing in results.
Researchers working with NASA’s Transiting Exoplanet Survey Satellite (TESS) have discovered three new worlds in our cosmic neighborhood, a mere 73 light-years away. The planets are all in a solar system that seems very different from our own.
For starters, the planets in our solar system are extremes — we have everything from the very large Jupiter and Neptune down to Earth and Mars, and to smaller rocky planets like Mercury. This new planetary system, which has been dubbed TOI-270, seems to have planets much closer in size to each other. All three planets are intermediate planets — something which is lacking from our solar system.
The two mini-Neptunes are exciting for astronomers because they represent a “missing link” in planetary formation. Mini-Neptunes are, as the name implies, Neptune-like planets with deep layers of ice and liquid (not necessarily from water, though). However, unlike Neptune, whose mass is 17 times larger than that of the Earth, mini-Neptunes are at most 10 times more massive.
“There are a lot of little pieces of the puzzle that we can solve with this system,” says Maximilian Günther, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research and lead author of a study published in Nature Astronomy that details the discovery. “You can really do all the things you want to do in exoplanet science, with this system.”
There’s another interesting peculiarity of the system: the planets line up in what astronomers call a resonant chain.
Example of resonant chain from our own solar system (via Wikipedia).
In other words, the planets’ orbits are aligned in a way that is very close to whole integers. In this case, it’s 2:1 for the outer pair, and 3:5 for the inner pair. In our solar system, the moons of Jupiter are lined up in such a way (and researchers have found evidence of other exoplanets arranged in a similar way).
“For TOI-270, these planets line up like pearls on a string,” Günther says. “That’s a very interesting thing, because it lets us study their dynamical behavior. And you can almost expect, if there are more planets, the next one would be somewhere further out, at another integer ratio.”
As for habitability, TOI-270 also raises some interesting questions. The rocky super-Earth and one of the mini-Neptunes are too close to their star. However, the other mini-Neptune, called TOI-270-d appears to lie in the habitable zone, where temperatures might be sufficient to host liquid water and possibly life. However, although the planet lies in the right area, this is still quite unlikely, the new study reveals.
TOI-270-d most likely has a thick atmosphere which produces an intense greenhouse effect, causing the planet’s surface to be too hot for habitation. But the system could still hold other planets — if these planets have a similar structure but lie farther away from the star, the temperature might be just right.
Thankfully, the host star, TOI-270, is remarkably well-suited for habitability searches, “as it is particularly quiet”, researchers write. The team now wants to focus other instruments, especially the upcoming James Webb Space Telescope on the star and its solar system to see if there are indeed other planets and to assess their physical parameters. It’s safe to say that we will probably be hearing about the system in the not-too-distant future.
“TOI-270 is a true Disneyland for exoplanet science, and one of the prime systems TESS was set out to discover,” Günther says. “It is an exceptional laboratory for not one, but many reasons — it really ticks all the boxes.”
The study “A super-Earth and two sub-Neptunes transiting the bright, nearby and quiet M-dwarf TOI-270” has been published in Nature Astronomy.
Jupiter traveled a bit in its youth, evidence from asteroids around the planet reveals. This brown gas giant formed four times as far away from the sun than the orbit it’s currently on and inched closer over the last 700,000 years.
Jupiter and its moon Io. Image via Pixabay.
New research led by members from the Lund University is revealing Jupiter’s wandering past based on the company it keeps. Using computer simulations to look at the distribution of near-Jupiter asteroids called Trojans, the team reports that their current layout in space can only be explained by Jupiter forming far away and then migrating to a closer orbit around the sun.
The prodigal son
“This is the first time we have proof that Jupiter was formed a long way from the sun and then migrated to its current orbit,” explains Simona Pirani, doctoral student in astronomy at Lund University, and the lead author of the study. “We found evidence of the migration in the Trojan asteroids orbiting close to Jupiter.”
Gas giants, as a rule of thumb, orbit pretty close to their host stars. To the best of our knowledge. that’s not where they form, however — these ponderous bodies of gas accrete further away and then migrate closer to the star.
In order to find out if Jupiter behaved the same way, Pirani’s team used computer simulations to estimate its movements over the past 4.5 billion years. The solar system was quite young in that day, its planets freshly-minted from the primordial dust which circled around the sun in a disk. At that time, 4.5 billion years ago, Jupiter was no larger than our own planet, the team reports.
It was also four times further away from the sun that it is now.
The Trojans Pirani talks about consist of two groups of thousands of asteroids that float around roughly on the same orbit as Jupiter — one group a bit in front and the other a bit behind the planet’s exact orbit. There are also 50% more Trojans in front of Jupiter rather than behind it, the team explains, a feature which helped them understand how the planet migrated over time.
“The asymmetry has always been a mystery in the solar system,” says Anders Johansen, professor of astronomy at Lund University and one of the paper’s co-authors.
We never really understood why there were more Trojans in front of Jupiter rather than behind it up to now. The team’s simulations suggest this happened because Jupiter gradually corralled in asteroids as it moved towards the sun. Based on the ratio between the two bodies of Trojans, the team says Jupiter likely formed four times farther out in the solar system than it is today. During its journey towards the sun, the planet’s gravity then drew in more Trojans in front of it than behind it.
According to their study, Jupiter’s migration took around 700,000 years, roughly 2-3 million years after it first started accreating. It moved closer to the center of the solar system on a spiral trajectory, as Jupiter orbited the sun in on increasingly tight orbit, goaded on by shifting gravitational forces from the gases surrounding the Sun, the team says.
The Trojans joined Jupiter while it was still a young planet — just a solid core without any atmosphere. This suggests that the Trojans are probably hewn of the same (or similar) matter that formed Jupiter’s core. NASA’s upcoming Lucy mission (scheduled for 2021) will allow the team a closer look at the Trojans.
“We can learn a lot about Jupiter’s core and formation from studying the Trojans,” says Anders Johansen.
The authors believe that the gas giant Saturn and ice giants Uranus and Neptune could have migrated in a similar way to Jupiter during their history.
The paper “Consequences of planetary migration on the minor bodies of the early solar system” has been published in the journal Astronomy & Astrophysics.
Artist impression of 2018 VG18, or “Farout.” Credit: Roberto Molar Candanosa/Carnegie Institution for Science.
Until not too long ago, Pluto’s orbit represented the known edge of our solar system. Then, new astronomical technology and improved observation methods revealed that our solar system is much more vast than initially thought. Astronomers have since discovered all sorts of icy objects beyond the Kuiper belt, the circumstellar disc that extends beyond the orbit of Neptune. To get an idea of our solar system’s expanse, imagine that recently researchers have found an object that orbits at more than 100 times the distance from Earth to the sun — it’s the farthest object we’ve encountered thus far.
Early last month, the Japanese Subaru 8-meter telescope at Mauna Kea, Hawaii, caught sight of a faint pink dot that was moving very slowly. Follow-up observations performed at the Las Campanas Observatory in Chile confirmed that the faint dot is actually a 300-mile-wide icy world. That would make it spherical and a dwarf planet.
This week, the International Astronomical Union’s Minor Planet Center announced the discovery and gave this object the designation 2018 VG18. However, it has a much more memorable (and fitting) nickname: ‘Farout’.
The distance of 2018 VG18 from the sun compared to other known Solar System objects. Credit: Roberto Molar Candanosa/Scott S. Sheppard/Carnegie Institution for Science.
Farout lies about 120 astronomical units (AU) from the sun — where one AU is the distance between Earth and the sun — which translates into about 93 million miles. That’s also about where the solar system starts to blend with interstellar space. Recently, NASA’s Voyager 2 spacecraft traveled more than 120 AUs, leaving the sun’s heliopause — the theoretical boundary where the Sun’s solar wind is stopped by the interstellar medium.
At such a great distance, the gravitational influence of the sun is less pronounced, so objects orbit at a much slower speed. For instance, Farout takes more than a 1,000 years to complete a full orbit around the sun.
Two photos of 2018 VG18 taken on November 10, 2018, one hour apart. The distant object is so far away from the sun that it takes more than 1,000 years to complete a full orbit. Image: Scott S. Sheppard/David Tholen.
But while Farout now holds the record for the most distant object ever observed in the solar system that doesn’t mean that there aren’t other things even farther away. As Space.com notes, “the dwarf planet Sedna gets more than 900 AU away on its highly elliptical orbit, for example, and there are probably trillions of comets in the Oort Cloud, which lies between about 5,000 AU and 100,000 AU from the sun.”
“2018 VG18 is much more distant and slower moving than any other observed solar system object, so it will take a few years to fully determine its orbit,” Scott Sheppard, a researcher at the Carnegie Institution for Science said in the statement. “But it was found in a similar location on the sky to the other known extreme solar system objects, suggesting it might have the same type of orbit that most of them do. The orbital similarities shown by many of the known small, distant solar system bodies was the catalyst for our original assertion that there is a distant, massive planet at several hundred AU shepherding these smaller objects.”
Astronomers were actually fixing their telescopes in search for a much more interesting prize — the elusive Planet Nine, which indirect evidence suggests it is pulling strings throughout the solar system by stretching the orbits of distant bodies and, perhaps, even tilting the plane of the entire solar system on one side. Astronomers think that Planet Nine can be found in an orbit that lies between hundreds of AUs and thousands of AUs.
“This would be a real ninth planet,” said Mike Brown, a planetary astrophysicist at the California Institute of Technology (Caltech) and one of the people responsible for de-classifying Pluto as a planet. “There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting.”
‘Oumuamua is the first interstellar object astronomers have detected in our solar system. For decades, scientists had been expecting to come across such an object, but it only happened in October 2017, while the Pan-STARRS 1 telescope on Haleakala, Hawaii was surveying near-Earth asteroids. Astronomers tried pointing NASA’s mighty Spitzer Space Telescope onto ‘Oumuamua, however, the comet-like object was too faint to observe directly — but this was a valuable result in and of itself.
According to a new study that worked with Spitzer data, previous estimates of ‘Oumuamua’s size have been too generous. In reality, the intriguing cosmic object is much smaller than scientists initially thought.
“‘Oumuamua has been full of surprises from day one, so we were eager to see what Spitzer might show,” David Trilling, lead author on the new study and a professor of astronomy at Northern Arizona University, said in a statement. “The fact that ‘Oumuamua was too small for Spitzer to detect is actually a very valuable result.”
Vents on the surface of the interstellar object probably emit jets of gases, propelling the object slightly. The jets were detected by measuring the position of the object as it passed by Earth in 2017. Credit: NASA/JPL-Caltech.
Besides setting new upper and lower boundaries for the size of ‘Oumuamua (pronounced oh MOO-uh MOO-uh, meaning ‘scout’ in Hawaiian), the study also reveals new spicy details about our lone interstellar visitor. One rather amazing finding is that ‘Oumuamua is expelling gas, which acts like a small thruster pushing the small asteroid. This explains the slight changes in speed and direction of the object when scientists tracked it last year.
In the months following is discovery, astronomers conducted multiple observations with ground-based telescopes but also using NASA’s Hubble Space Telescope. These optical observations reported large variations in brightness, suggesting that ‘Oumuamua has an elongated shape, resembling a cigar, and that it probably measures less than half a mile (800 m) across its longest side.
However, Spitzer’s instruments can see things in infrared, meaning it can measure how much heat ‘Oumuamua radiates — and this can be helpful in measuring the object’s size with better accuracy than optical evaluations alone could. By measuring infrared light emitted by an object, scientists can essentially measure temperature which, in turn, can be used to determine the reflectivity of an object’s surface — what’s technically called albedo.
The new study estimates what ‘Oumuamua’s diameter would be if it were spherical. Trilling and colleagues used three separate models, each with its own different assumptions about the object’s composition but which only slightly differed from one another, and ultimately came up with three possible diameters for ‘Oumuamua: 1,440 feet (440 meters), 460 feet (140 meters) or even as small as 320 feet (100 meters).
Images of an interloper from beyond the solar system as seen on Oct. 27 by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz. Credit: WIYN OBSERVATORY/RALF KOTULLA.
The findings suggest that ‘Oumuamua may be up to 10 times more reflective than the comets we can find our solar system. A typical comet will constantly change its albedo as its ice warms and turns into gas during its close approaches to the Sun. However, ‘Oumuamua likely traveled through interstellar space for millions of years before entering our solar system, far from a star’s ‘touch’. Once it actually made it close to the sun, ‘Oumuamua’s surface likely suffered some transformations. For instance, some of the released gas may have covered the surface of the object with ice and snow that increase reflectivity.
At the moment, ‘Oumuamua is beyond Saturn’s orbit and is exiting the solar system. But scientists expect other interstellar visitors to follow. In the meantime, data gathered on the asteroid could shed light on how planet form in the solar system.
Jupiter and its shrunken Great Red Spot. Credit: Wikimedia Commons.
A new factor has been added to the debate on whether or not living organisms could exist on Jupiter. You probably know Jupiter is a Jovian planet, a giant formed primarily out of gases. So how could alien life be able to exist in an environment where most of the phases of matter are absent? The answer is simply found in the element of water.
Within the rotating, turbulent Great Red Spot, perhaps Jupiter’s most distinguishable characteristic, are water clouds. Many of the other clouds in this enormous perpetual storm are comprised of ammonia and/or sulfur. Life theoretically cannot be sustained in water vapor alone; it thrives in liquid water. But according to some researchers, the fact alone that water exists in any form on the planet is a good first step.
The Great Red Spot is still a planetary feature which stumps much of the scientific community today. As it has been observed for the past century and a half, the Great Red Spot has been noticeably shrinking. The discovery of water clouds may lead to a deeper understanding of the planet’s past, including whether or not it might have sustained life, as well as weather-related information.
Some scientists have pondered the possibility that, due to the hydrogen and helium content in its atmosphere, Jupiter could be a diamond-producing “factory.” They have further speculated that these diamonds could enter into a liquid state and a rainfall of liquid diamonds would be in the Jovian’s weather forecast.
Likewise, the presence of water clouds means that water rain (a liquid) is not entirely impossible. Máté Ádámkovics, an astrophysicist at Clemson University in South Carolina, had this to say on the matter:
“…where there’s the potential for liquid water, the possibility of life cannot be completely ruled out. So, though it appears very unlikely, life on Jupiter is not beyond the range of our imaginations.”
Scientists are acting accordingly, researching the part which water plays in the atmosphere and other natural systems on Jupiter. They remain skeptical but eager to follow up on the new discovery. They shall also strive to find out just how much water the planet really holds.
Researchers have discovered an enormous body of interstellar dust that predates the formation of our solar system 4.6 billion years ago. The findings might revolutionize our understanding of how the solar system came to be, as well as all other planetary bodies.
Artist impression of an early solar system. Credit: NASA.
It sounds unbelievable, but some of the original interstellar dust that went to form the sun, Earth, and all the other planets in the solar system can be still be found floating around in our neighborhood, even hitting our atmosphere from time to time. Presolar dust particles can no longer be found in the inner solar system, as it was long ago destroyed, reformed, and reaggregated in multiple phases. However, presolar dust can still be found in the outer solar system, specifically in some comets.
When these comets pass close enough to the sun, they release presolar dust that can reach Earth’s orbit and settle through the atmosphere, where it can be collected and later studied. Dr. Hope Ishii of the University of Hawai’i at Manoa and her colleagues used electron microscopy to study such dust particles, as well as data gathered from the Cosmic Dust Analyzer (CDA) aboard the Cassini Saturn orbiter during its two-decade mission.
The presolar dust particles in question are actually called GEMS – or ‘glass embedded with metal and sulfide’. They’re less than one hundredth the width of a human hair in diameter and contain a variety of carbon known to decompose when exposed to even relatively gentle heating.
An electron micrograph of an interplanetary dust particle of likely cometary origin. Credit: Hope Ishii
Ishii and colleagues write that the GEMS likely formed in the interstellar medium due to grain shattering, amorphization, and erosion from supernovae shocks, then later went through subsequent periods of aggregation. Irradiation likely provided enough energy for the amorphous silicates which comprise the dust to absorb small amounts of metal atoms, the authors reported in the journal Proceedings of the National Academy of Sciences.
“With repeated cycling in and out of cold molecular clouds, mantled dust and any aggregates were repeatedly and progressively partially destroyed and reformed. Cassini mission data suggest the presence of iron metal in contemporary interstellar dust,” the researchers wrote in their study.
This first generation of GEMS aggregated with crystalline grains that were likely transported from the hot inner-solar nebula, creating second-generation aggregates. Later this 2nd generation of aggregates was likely incorporated into small, icy cometary bodies.
The researchers concluded that the grains they studied represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars. As such, they provide unique insight into a pre-solar system environment, ultimately telling us how our planet and others like it came to be. We only have a rough picture of how our solar system formed from a huge disk of dust and gas, and these little grains could be the missing pieces that complete the puzzle. In the future, the researchers plan on collecting more comet dust, particularly that sourced from more well-protected comets that pass by the sun.
The odd behavior of a newly discovered distant object suggests it’s being influenced by a large, yet unidentified planet in our solar system. This planet is tentatively called Planet Nine until scientists can confirm or rule out its existence.
Artist’s impression of Planet Nine as an ice giant eclipsing the central Milky Way, with a star-like Sun in the distance. Neptune’s orbit is shown as a small ellipse around the Sun. The sky view and appearance are based on the conjectures of its co-proposer, Mike Brown. Credit: Tom Ruen, Wikimedia Commons.
It all started in early 2016, when Konstantin Batygin and Mike Brown, two planetary astrophysicists at the California Institute of Technology (Caltech) in Pasadena, predicted that an unidentified new planet is chilling somewhere in the outer fringes of the solar system. Their calculations suggest a number of objects from the Kuiper Belt — the circumstellar disc beyond the known planets — were aligning in a strange way, without any consistent explanation. After many iterations, no model could explain this erratic behavior other than the existence of a new planet roughly ten times more massive than Earth and about 20 times farther from the Sun than Neptune. Such planets, by virtue of their size, are called Super-Earths by scientists.
“This would be a real ninth planet,” Brown, who is one of the people responsible for de-classifying Pluto as a planet, said at the time of the controversial announcement. “There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting.”
The unusually closely spaced orbits of six of the most distant objects in the Kuiper Belt indicate the existence of a ninth planet whose gravity affects these movements. Credit: Nagual Design, Wikimedia Commons.
Now, a large international team of researchers is pointing towards new evidence supporting the Planet Nine hypothesis. The new study suggests that a certain Trans-Neptunian object (TNO) called 2015 BP519, or Caju for short, is behaving erratically due to the gravitational influence of the mysterious planet. The shape of the TNO’s orbit is nearly perpendicular to the plane in which all the known planets orbit. Previously, Brown and Batygin ran a simulation that predicted the orbital angle of such an object — and now we just happened to find a match.
“We also consider the long term orbital stability and evolutionary behavior within the context of the Planet Nine hypothesis, and find that 2015 BP519 adds to the circumstantial evidence for the existence of this proposed new member of the solar system,” wrote the authors of the new study, which is available now on preprint website Arxiv, before it will eventually appear in The Astronomical Journal.
Previous observations of Caju failed to explain its orbit. No model could explain the object’s behavior other than a simulation where a large planet with Planet Nine’s characteristics has been added.
As remarkable as it may seem to find a new planet in our solar system in the 21st century, there’s really a lot of evidence pointing towards the fact. All that remains is for someone to actually find this elusive planet, wherever it may be lurking.
Artist impression of an early solar system. Credit: NASA.
About a decade ago, a violent explosion roughly 23 miles above the surface sent incendiary fragments hurling towards the dunes of the Nubian desert in Sudan. In and of itself, the event was not necessarily impressive, apart from the fancy light show — after all, our planet is constantly bombarded by relatively small objects. But, according to a new study, these meteorites have a much more dramatic origin and history than meets the eye. Scientists say that under the meteorites’ thick carbonized exterior hid diamonds which enclosed remnants of a long-lost planet or planetary embryo during the crazy days of the early solar system.
It was mighty crowded back then
A jeweler wants diamonds to be perfect, meaning impurities should be kept to a minimum, ideally none at all. However, a diamond with inclusions is far more valuable from a scientific standpoint than a so-called flawless jewel. Because diamonds are forged at immense pressures and temperatures, typically deep inside the planet, the various materials that get trapped inside are quite hard to get a hold of at the surface — and diamonds can preserve them for billions of years.
The team led by Farhang Nabiei of the Ecole Polytechnique Federale de Lausanne in Switzerland was initially investigating the relationship between the diamonds and the layers of graphite surrounding them, when they realized the small pockets of material trapped inside looked far more interesting. With the help of a high-power electron microscope, the researchers studied the tiny diamonds inside a thin section of the meteorite and were astonished to learn they were formed at incredibly high pressures — much higher than any kind of pressure the meteorites might have been subjected to when they crashed into Earth.
A chemical map shows sulfur (red) and iron (yellow) inside the inclusions in the diamond matrix. Credit: Dr. F. Nabiei/Dr. E. Oveisi, EPFL, Switzerland.
Specifically, the diamonds must have formed at 20 gigapascals, which is the kind of pressure found deep within a planet the size of Mars or Mercury — but the meteorites come from neither of these planets or any other planet that we know of for that matter. The meteorites have, in fact, been classed as ureilites — a rare type of stony meteorite that has a unique mineralogical composition, very different from that of other stony meteorites. Transmission electron microscopy also revealed traces of chromite, phosphate, and iron-nickel sulfides inside the larger diamonds, which are inclusions that can be found in Earth’s diamonds, too. It’s the first time such inclusions have been identified inside extraterrestrial diamonds.
A colorized image shows the diamond phase (blue), inclusions (yellow) and the graphite region. Credit: Dr. F. Nabiei/Dr. E. Oveisi/Prof. C. Hébert, EPFL, Switzerland.
The size of the diamonds is another clue that we’re dealing with some very peculiar objects. Their average size is about 100 microns, which is about the size of a human hair. That may not sound like much, but that’s still larger than any diamond that could possibly form by shock transformation of graphite (i.e. when a meteorite crashes on Earth). This suggests that the diamonds formed deep in a body’s interior and not on impact. Such a planetary-sized body is now long gone, having been destroyed in a cataclysmic game of billiard early on in the solar system’s history. These early proto-planets would have been hurled towards each other by a tug of war between the gravities of a young Jupiter and the sun. The environment likely looked very crowded too, with multiple Mars-sized protoplanets destined to collide into each other.
“This study provides convincing evidence that the ureilite parent body was one such large ‘lost’ planet before it was destroyed by collisions [some 4.5 billion years ago],” researchers wrote in the new paper on the subject, published this week in the journal Nature Communications.
The discovery offers new insight into our solar system’s tumultuous past, helping piece together how it all came to be. This is merely the beginning, as hundreds of other ureilites could offer new clues to the nature of the early solar system and the evolution of its planets.
Fragments from the Hypatia stone, which was discovered in south-west Egypt in the Libyan Desert Glass Field. Credit: Dr. Mario di Martino, INAF Osservatorio Astrofysico di Torino.
A unique stone discovered in 1992 in Egypt’s Sahara desert has quite the story. Scientists think that the Hypatia stone, named after an ancient astronomer from Alexandria, predates the formation of our solar system and may well be interstellar in nature.
Hypatia is, in fact, the first “comet nucleus” – the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball – found on Earth. Previously, tests run on Hypatia samples suggested it has a mineral composition like no other known meteorite.
Now, the same team of researchers at the University of Johannesburg that carried out the initial mineral analysis reports even wilder characteristics. Unlike chondritic meteorites, which formed in the cloud of dust and gas (a.k.a. the nebula) from which the rest of the solar system formed, Hypatia is very rich in carbon with trace amounts of silicon. Typically, the opposite is true for chondritic meteorites, which are rich is silicon and poor in carbon.
According to lead-author Prof. Jan Kramers, the Hypatia stone’s internal structure is somewhat like a fruitcake that has fallen off a shelf into some flour and cracked on impact.
“We can think of the badly mixed dough of a fruitcake representing the bulk of the Hypatia pebble, what we called two mixed ‘matrices’ in geology terms. The glace cherries and nuts in the cake represent the mineral grains found in Hypatia ‘inclusions’. And the flour dusting the cracks of the fallen cake represent the ‘secondary materials’ we found in the fractures in Hypatia, which are from Earth,” he said in a statement.
The carbon-silicon matrix of Hypatia is also comprised of polyaromatic hydrocarbons (PAH), commonly found in interstellar dust, “which existed even before our solar system was formed,” Kramers added. It’s these PAH molecules in Hypatia’s matrix that allowed the peculiar cosmic pebble to survive weathering over millions of years. Upon impact with Earth, the released energy was high enough to instantly convert the carbon-rich molecules into micro-diamonds, forming a crust that shielded Hypatia against the elements.
Hypatia is also dotted with inclusions — material trapped within the body of a crystal which is different from the primary elements, and which in our analogy represent the nuts and cherries of a fruitcake that comprised of surprising elements. For instance, aluminum was found in pure metallic form and not in a compound with other elements as one would expect.
“We also found silver iodine phosphide and moissanite (silicon carbide) grains, again in highly unexpected forms. The grains are the first documented to be found in situ (as is) without having to first dissolve the surrounding rock with acid,” adds co-author Georgy Belyanin. “There are also grains of a compound consisting of mainly nickel and phosphorus, with very little iron; a mineral composition never observed before on Earth or in meteorites,” he adds.
All of these characteristics suggest that Hypatia is an unchanged pre-solar system material. The inclusions themselves, however, likely formed in a post-solar system age, which makes this extraterrestrial puzzle even more complex. If Hypatia doesn’t predate the sun, then its features indicate that the solar nebula, from which all planets, moons, and the sun itself formed, was not homogenous, challenging the generally accepted idea of how the solar system was formed.
Kramers adds that the Hypatia pebble likely formed in a cold environment at extreme freezing temperatures — below that of liquid nitrogen on Earth (-196 Celsius). Most comets we’ve identified come from the Kuiper Belt, located well beyond Neptune’s orbit some 40 times farther from the Sun than Earth is. Other comets come from the Oort Cloud, which is even farther out. Hypatia might also come from the Oort Cloud, which contains objects whose mineral composition we know little about. Hypatia might one day help clear the fog around this nebulous region.
Scientific reference: Georgy A. Belyanin, Jan D. Kramers, Marco A.G. Andreoli, Francesco Greco, Arnold Gucsik, Tebogo V. Makhubela, Wojciech J. Przybylowicz, Michael Wiedenbeck. Petrography of the carbonaceous, diamond-bearing stone “Hypatia” from southwest Egypt: A contribution to the debate on its origin. Geochimica et Cosmochimica Acta, 2018; 223: 462 DOI: 10.1016/j.gca.2017.12.020
Astronomers have reported an alien visitor — a space rock — and it’s the first one we’ve ever seen.
We don’t really know what the object is made of or where it came from. Image credits: NASA / JPL.
For all the things our solar system has going for it, it doesn’t get that many visitors. Not much at all, actually. This is the first time in history that astronomers have surprised any such object entering our solar system — and they’ve been expecting it for quite a while.
“We have been waiting for this day for decades,” Paul Chodas, manager of the Center for Near-Earth Object Studies at the NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement.
“It’s long been theorized that such objects exist — asteroids or comets moving around between the stars and occasionally passing through our solar system — but this is the first such detection,” Chodas added. “So far, everything indicates this is likely an interstellar object, but more data would help to confirm it.”
The object appears to less than a half-kilometer in diameter, and it’s moving at just over 40 kilometers per second — faster than our speediest probes, but still pretty slow for an interstellar visitor. Astronomers have given it the cumbersome name A/2017 U1.
It’s long been assumed that objects like this lurk around our solar system. After all, planetary formation and large-scale processes generate whopping amounts of rocks and dust. But outer space is also incredibly vast, and it takes a certain amount of chance for something to stumble close enough for us to see it. Now, astronomers are trying to direct as many significant telescopes towards the object, in the hopes of better understanding it. Right now, we don’t really know what it’s made of (it could be rock, it could be ice), we don’t really know its color or spectrum, and we don’t really know where it came from. The one thing we do know is that the alien object came from outside our solar system.
“The orbit is very convincing. It is going so fast that it clearly came from outside the solar system,” Paul Chodas continued. “It’s whipping around the Sun, it has already gone around the Sun, and it has actually gone past the Earth on its way out.”
Diagram of the path of a space rock from outside our solar system — the first ever observed. Image credits: Brooks Bays / SOEST Publication Services / UH Institute for Astronomy.
The first one who witnessed A/2017 U1 was Rob Weryk, a postdoctoral researcher at the University of Hawaii. A week ago, on 19 October, he first spotted the object using Hawaii’s Pan-STARRS 1 telescope, which searches the sky for near-Earth objects, but didn’t make much sense of the data. A series of observations by Weryk’s advisor, astronomer Richard Wainscoat, confirmed the sighting, and things started to add up. Right now, it’s not clear how much scientists will be able to learn about, but perhaps the most important thing, Weryk says, is understanding how many of these objects are out there, and how can they affect us.
“The most important response to the ‘Okay, so what?’ question is ‘Well, where do these things come from, and are there more?’” he says. “There is still a lot we don’t know about the solar system, and finding objects like this could help improve our understanding of how the Earth and our solar system first came to be.”
If they want to get a more thorough understanding of it, astronomers should move swiftly. The object is moving out of sight fast, and it’s not returning. Even before it leaves our sight, the object will be hard to study. The more it goes away from our Sun, the less and less light strikes it, making observations increasingly difficult
“This is the most extreme orbit I have ever seen,” said CNEOS scientist Davide Farnocchia, who worked with others to trace A/2017 U1’s path through the solar system. “We can say with confidence that this object is on its way out of the solar system and not coming back.”