Astronomers have detected a new, potentially deadly emanation coming from Uranus: X-rays. While most of these are likely produced by the sun and then reflected by the blue planet, the team is excited about the possibility of a local source of X-rays adding to these emissions.
The seventh planet from the sun has the distinction of being our only neighbor that rotates on its side. But that’s not the only secret this blue, frigid dot in space seems to hide, according to new research. The planet also seems to be radioactive — after a fashion. This discovery currently leaves us with more questions than answers, but it could help us better understand Uranus in the long run.
Deep space rays
Since it’s so far away, we’ve had precious few opportunities to interact with the planet. In fact, the only human spacecraft to ever come near Uranus was Voyager 2, and that happened in 1986. So most of our data regarding the frozen giant comes from telescopes, such as NASA’s Chandra X-ray Observatory and the Hubble Space Telescope.
A new study based on snapshots of Uranus taken by Chandra in 2002 and 2017. These revealed the existence of X-rays in the data from 2002, and a possible burst of the same type of radiation in the second data set. The 2017 dataset was recorded when the planet was approximately at the same orientation relative to Earth as it was in 2002.
The team explains that the source of these X-rays, or at least the chief part of them, is likely the Sun. This wouldn’t be unprecedented: both Jupiter and Saturn are known to behave the same way, scattering light from the Sun (including X-rays) back into the void. Earth’s atmosphere, actually, behaves in a similar way.
But, while the team was expecting to observe X-rays coming off of Uranus due to these precedents, what really surprised them is the possibility that another source of radiation could be present. While still unconfirmed, such a source would have important implications for our understanding of the planet.
One possible source would be the rings of Uranus; we know from our observations of Saturn that planetary ring systems can emit X-rays, produced by collisions between them and charged particles around the planets. Uranus’ auroras are another contender, as we have registered emissions coming from them on other wavelengths. These auroras are also produced by interactions with charged particles, much like the northern lights on Earth. Auroras are also known to emit X-rays both on Earth and other planets.
The piece that’s missing in the aurora picture, however, is that researchers don’t understand what causes them on Uranus.
Its unique magnetic field and rapid rotation could create unusually complex auroras, the team explains, which further muddies our ability to interpret the current findings; there are too many unknown variables in this equation. Hopefully, however, the current findings will help point us towards the answers we need.
The paper “A Low Signal Detection of X‐Rays From Uranus” has been published in the Journal of Geophysical Research: Space Physics.
The gas planets, the giants of the solar system, the jovian planets — call them what you will, these planets have fascinated mankind for centuries, and they’re still one of the more intriguing astronomical bodies out there.
Jovian literally means “Jupiter-like”, from “Jove” — another name for the Roman god Jupiter (called Zeus by the Greeks). They are primarily composed of gas or ice and are much larger than the Earth. They’re also much easier to detect than other planets — largely because they’re so big.
You can’t walk on a jovian planet
Jovian planets are comprised of fluid (gases or ices) rather than rock or other solid matter. Although giant rocky planets can exist, these are thought to be much rarer than gas or ice giants.
Jupiter is made up almost entirely of hydrogen and helium — the same elements found in the Sun, though at different temperatures and pressures. Here on Earth, hydrogen and helium are gases, but under the huge temperatures and pressures of Jupiter, hydrogen can be a liquid or even a kind of metal. We’re not entirely sure what lies at the center of Jupiter, but researchers believe that most likely, the core is similar to a thick, boiling-hot soup with a temperature of about 55,000 Fahrenheit (30,000 Celsius).
Saturn has a similar structure, with layers of metallic hydrogen, liquid hydrogen, and gaseous hydrogen, covered by a layer of visible clouds. Unlike Jupiter and Saturn, Uranus and Neptune have cores of rock and metal and different chemical compositions.
We’re not sure exactly what the surface of jovian planets is like, but based on all we know, it’s not something you can walk on. Jovian planets tend to have very thick clouds (the clouds on Jupiter, for instance, are 30 miles or 50 km thick). After that, there’s gaseous hydrogen and helium, then more and more condensed gas, until you ultimately end up in liquid, metallic hydrogen. Saturn has a similar structure, though it is far less massive than Jupiter.
You might even have trouble realizing where the atmosphere ends and where the “planet” begins.
Uranus and Neptune, much smaller than both Jupiter and Saturn, have gaseous hydrogen surrounding a mantle of ice and a rocky core.
Jovian planets also have atmospheres with bands of circulating material. These bands typically encircle the planet parallel to the equator, with lighter bands lying at higher altitudes and being areas of higher pressure, and darker bands being lower in the atmosphere as low-pressure regions. This atmospheric circulation is similar only in principle to that on Earth, it has a very different structure.
There are also other, smaller visible structures. The most famous of these is Jupiter’s Great Red Spot, which is essentially a giant storm that has been active for centuries. Saturn’s hexagon is another very well-known feature — both of these are much larger than the Earth itself.
These spinning balls of gas and liquids are truly impressive, and we’re still learning new things about them.
Jovian planets in our solar system
Not all gas planets are alike. In fact, the reason why some astronomers prefer the term jovian planets to gas giants is that not all jovian planets are made of gas.
For instance, just Jupiter and Saturn are true gas giants, whereas Uranus and Neptune are ice giants. However, even this is a bit misleading: at the temperature and pressures on these planets, distinct gas and liquid phases cease to exist. Even so, the chemistry of the two groups is different: hydrogen and helium dominate Jupiter and Saturn, whereas, in the case of Uranus and Neptune, it’s water, methane, and ammonia. The two latter planets are thought to have a slushie-like mantle that spans over half of the planet diameter.
All four of these planets have large systems of satellites, and these satellites can be very interesting in their own right (we’ll get to that in a minute — there’s a good chance that life may be hiding in the jovian satellites). Saturn, for instance, has 82 designated satellites, and countless undesignated moonlets. Despite being larger, Jupiter “only” has 79 known satellites. Uranus has 27 and Neptune has 14.
All these four planets also have rings, though Saturn’s are by far the most pronounced.
Much of what we know about gas and ice giants in general, we extrapolate from what we see in our own solar system. This being said, astronomers are aware that jovian planets can be very different and have a much greater variety than we see in our solar system.
Extrasolar Jovian planets
Roughly speaking, jovian planets can be split into 4 categories:
gas giants (like Jupiter and Saturn) — mostly consisting of hydrogen and helium, and only 3-13% heavier elements;
ice giants (like Neptune and Uranus) — a hydrogen-rich atmosphere covering an icy layer of water;
massive solid planets (somewhat similar to the Earth, but huge) — tangible evidence for this type of planet only emerged in 2014, and these planets are still poorly understood. Astronomers suspect that solid planets up to thousands of Earth masses may be able to form, but only around massive stars;
super puffs — planets comparable in size with Jupiter, but in mass with the Earth. These planets are super rarefied, and were only discovered in the past decade; the most extreme examples known are the three planets around Kepler-51.
Based on what we’ve seen so far, jovian planets seem pretty common across our galaxy. However, we’ve only started discovering exoplanets very recently, and it’s hard to say whether the planets we’ve found so far are representative of the larger picture.
However, based on the fact that researchers have discovered far more Neptune-sized planets than Jupiter-sized planets (although the latter are easier to discover), it’s pretty safe to say that it’s the Neptune-sized planets that are more common.
A particularly interesting class of jovian planets is the so-called Hot Jupiters.
Hot Jupiters are the easiest planets to detect. As the name implies, they are Jupiter-sized planets, but they lie very close to their stars and have a rapid orbital period that produces effects that are more easily detected. For instance, one such planet revolved around its star in only 18 hours, making for one very short year. Another freakish example of a Hot Jupiter is believed to have surface temperatures of 4,300°C (7,800°F) — which is hotter than some stars we know.
Extrasolar planets, and Hot Jupiters in particular, can shed a lot of light on the evolution of solar systems. It is believed that these planets form in the outer parts of solar systems (like Jupiter), but they slowly migrate towards the star, drawn by gravitational attraction. As they do so, they could wreak havoc on the entire solar system, much like a big billiards ball.
Some jovian planets get so large that they blur the line between a planet and a brown dwarf. Brown dwarfs are neither truly stars nor planets. As a rule of thumb, jovian planets are only “planets” until they are 15 times the mass of Jupiter — after that, they “become” brown dwarfs.
Because of the limited techniques currently available to detect and study exoplanets, there are still many things we don’t know about exoplanets, even those as big as Jupiter. We tend to associate these planets by size with the ones in our own solar system, piecing together other available information (which is scarce). As our telescopes, equipment, and theoretical models become better, we will no doubt better our understanding of jovian planets, and exoplanets in general.
Life around Jovian planets
Jovian planets are not exactly life-friendly — at least not directly. A giant, spinning, mass of fluid you can’t even stand on, either very hot or very cold, doesn’t sound very attractive to life forms. But jovian satellites are a different story. In fact, astronomers are starting to believe that the satellites of Jupiter and Saturn may be the best places to look for extraterrestrial life in our solar system.
Both Jupiter and Saturn lie rather far from the Sun. They are cold, frigid places, as are their satellites — at least on the surface.
Researchers now believe that some of the icy satellites of Jupiter and Saturn (especially Europa and Enceladus) could host life under their frozen surfaces.
Although the surface temperatures are extremely low on these satellites, astronomers have some clues that both satellites may harbor oceans of liquid water beneath the frozen surface. Basically, the huge gravitational effect from their host planets causes friction and shear in the ice, which produces sufficient heat to melt the ice. This is called tidal heating. Geothermal and geological activity may also contribute to this effect, creating a liquid, salty water beneath the ice — and while this has not yet been confirmed, these could be suitable conditions for life to emerge.
In addition to Europa and Enceladus, several other jovian satellites could harbor life (with various degrees of likelihood): Callisto, Ganymede, Io, Triton, Dione, and even Pluto’s moon Charon could all have a liquid ocean compatible with life. NASA’s Clipper mission is set for launch in 2024, with the goal of exploring Europa’s potential habitability. Some scientists believe there are as many habitable exomoons as there are habitable exoplanets.
Jovian planets seem to play a key role in the structure of solar systems. Whether their satellites can hold life or not, they are an extremely important puzzle piece in our understanding of how solar systems form, evolve, and how the Earth fits in this grand cosmic puzzle.
More than 30 years ago, NASA’s Voyager 2 spacecraft flew over Uranus, getting as close as 50,600 miles to the planet’s clouds.
The data collected back revealed new rings and moons. But there was another finding as well, which remained hidden for a long time.
A team of researchers from NASA took a new look at the data from the spacecraft, discovering that the voyager had passed through a gigantic magnetic bubble, also called a plasmoid – a giant structure comprised of plasma and the planet’s magnetic field.
Space physicists Gina DiBraccio and Dan Gershman, both from NASA’s Goddard Space Flight Center, reviewed the Uranus data because they wanted to understand its strange behavior. “The structure, the way that it moves …,” DiBraccio said, “Uranus is really on its own.”
Unlike any other planet in our solar system, Uranus turns almost perfectly sideways, like a rolling barrel. This axis of rotation points in a direction 60 degrees apart from its axis of the magnetic field, making its magnetosphere wobble chaotically as it rotates.
The researchers downloaded the readings obtained by Voyager 2’s magnetometer, which monitored the strength and direction of Uranus’ magnetic field as it flew over the planet. They were much more thorough than previous studies, to the point of reviewing measurements every 1.92 seconds.
Everything seemed ordinary, but the magnetometer marked a kind of zigzag at one point during its travels. The signal corresponded to a huge bubble of electrified gas: a cylindrical plasmoid at least 204,000 kilometers long and up to 400,000 kilometers wide.
Plasmoids are recognized as an important way for planets to lose mass. They detach from the part of the magnetic field of a planet that is expelled by the Sun. This phenomenon had been observed on Earth and other planets, but never on Uranus.
Over time, the plasma in plasmoids that escapes into space drains ions from the planet’s atmosphere, significantly altering their composition. In the case of Mars, the process ended up transforming it radically: it went from being a humid planet with a thick atmosphere to the dry world that we see today.
It’s not clear yet how Uranus’ atmospheric escape has affected the planet thus far, as scientists only got a tiny glimpse at this process. But the new discovery can help get some answers. “It’s why I love planetary science,” DiBraccio said. “You’re always going somewhere you don’t really know.”
Near-infrared image of Uranus ring system taken with the Adaptive Optics system on the 10-m Keck telescope in July 2004.
Uranus’ ring system isn’t nearly as spectacular as Saturn’s, but that doesn’t make them any less fascinating. Discovered very recently, in 1977, Uranus’ thin rings are impossible to discern with all but the largest telescopes. Using two such telescopes perched in the deserts of Chile, the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Telescope (VLT), astronomers have now revealed spicy insights about the planet’s rings, including the first measurement of their temperature.
The observations suggest that Uranus’ rings — 13 in total, from what we know — have a temperature of 77 degrees Kelvin (-196°C) or just about the boiling point of liquid nitrogen.
Uranus’ rings reflect only very little light in the visible and near-infrared spectrum, which has made observations so far incredibly difficult. Most of what we know about these rings is due to the Voyager 2 spacecraft which flew by the planet in 1986 and photographed them. Thanks to this mission we know that Uranus’ main rings lack dust-sized particles, and are instead composed of centimeter-sized or larger particles of sheets of dust.
“Saturn’s mainly icy rings are broad, bright and have a range of particle sizes, from micron-sized dust in the innermost D ring, to tens of meters in size in the main rings,” said Imke de Pater, a University of California Berkeley professor of astronomy. “The small end is missing in the main rings of Uranus; the brightest ring, epsilon, is composed of golf ball-sized and larger rocks.”
Composite image of Uranus’s atmosphere and rings at radio wavelengths, taken with the ALMA array in December 2017. The image shows thermal emission (heat) from the rings of Uranus for the first time, enabling scientists to determine their temperature: a frigid 77 Kelvin (-320 F). Credit: UC Berkeley
Epsilon, the brightest and densest ring of Uranus, is unique to the solar system, compared to structures in other known ring systems. Now, these new observations have magnified smaller features that weren’t visible until now, confirming that Epsilon and Uranus’ other rings are quite different, providing a big step forward towards understanding their composition and whether or not these rings come from the same source.
“The rings of Uranus are compositionally different from Saturn’s main ring, in the sense that in optical and infrared, the albedo is much lower: they are really dark, like charcoal,” graduate student Edward Molter said in a statement. “They are also extremely narrow compared to the rings of Saturn. The widest, the epsilon ring, varies from 20 to 100 kilometers wide, whereas Saturn’s are 100’s or tens of thousands of kilometers wide.”
“It’s cool that we can even do this with the instruments we have,” he said. “I was just trying to image the planet as best I could and I saw the rings. It was amazing.”
Uranus’ rings could be the result of asteroids captured by the planet’s gravity, fragments of moons that crashed into one another in ancient times, or debris from the time of the planet’s formation more than 4.5 billion years ago. Astronomers are set to find out more about Uranus’ rings once the upcoming James Webb Space Telescope’s advanced spectroscopes come into operation this decade.
A cataclysmic collision with an enormous cosmic body twice the size of Earth may have caused Uranus to tilt and could explain its freezing temperatures.
The collision with Uranus of a massive object twice the size of Earth caused the planet’s unusual spin. Credit: Jacob Kegerreis/Durham University.
Uranus’ spins on its side, its axis pointing almost at right angles relative to all the other planets in our solar system. This behavior suggests that the planet almost certainly got knocked over by some giant impact, so the real questions astronomers have been asking are how all of this panned out and how else such a violent impact affected the planet.
Jacob Kegerreis and colleagues at Durham University’s Institute for Computational Cosmology performed over 50 different high-resolution computer simulations of massive collisions with the gas giant in order to answer these questions.
The conditions that lead to outcomes that most closely resemble what Uranus is doing right now suggest that the planet was most likely impacted by a young proto-planet mode of rock and ice during the solar system’s chaotic formation about 4 billion years ago. Since Uranus is so massive — it has about 14 times the mass of Earth and is around four times larger in radius — whatever hit the planet was huge, and scientists think it used to be between two and three Earth-masses.
According to the same simulations, the impact could have also released debris that formed a thin shell around the edge of the planet’s ice layer, trapping heat emanating from the planet’s core. This can partly explain Uranus’ ungodly cold temperature in the outer atmosphere, which averages around -216 degrees Celsius (-357 degrees Fahrenheit). Some of Uranus’ 27 moons — including 13 so-called ‘inner moons’ — might have formed as a result of the spewed debris.
“Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today,” Kegerreis said in a statement.
The collision wasn’t head-on. The cosmic body grazed Uranus instead, allowing the planet to retain the majority of its atmosphere. However, it was enough to affect the planet’s tilt.
2004 infrared composite image of the two hemispheres of Uranus obtained with Keck Telescope adaptive optics. The planet is tilted at almost a 90-degree angle with respect to the other planets in the solar system. Credit: Lawrence Sromovsky, University of Wisconsin-Madison/W.W. Keck Observatory.
The impact could have created molten ice and lopsided lumps of rock inside the planet, explaining not only Uranus’ excentric tilt but also its off-center magnetic field.
I know, I know — another Uranus joke. But in all seriousness, scientists just reported in the journal Nature Astronomy that the icy planet’s atmosphere contains significant amounts of hydrogen sulfide. Apart from the poetic significance of knowing Uranus basically smells like farts, the discovery might actually help astronomers understand how our early solar system formed and evolved.
Uranus as a featureless disc, photographed by Voyager 2 in 1986. Credit: Wikimedia Commons.
For some time, scientists had presumed that the planet’s clouds contained hydrogen sulfide and ammonia. However, this was more of an inference rather than a direct observation and was hinted by the absence of certain wavelengths of light. Now, new and improved measurements obtained by using the 8-meter Gemini North telescope on Hawaii’s Mauna Kea have detected the presence of hydrogen sulfide (an unpleasant gas that most people avoid) in Uranus’s cloud tops.
The telescope’s spectrometer measured reflected sunlight from a region directly above the main visible cloud layer in Uranus’s atmosphere, according to Patrick Irwin, lead author of the new paper and researcher at the University of Oxford, UK. It’s interesting to note that Gemini’s Near-Infrared Integral Field Spectrometer (NIFS) was designed to study explosive environments around the supermassive black holes found at the center of far-away galaxies. The fact that its use has been extended to solve a longstanding mystery in our solar system is impressive, to say the least.
Uranus and Neptune both formed in the colder part of the solar nebulae that seeded the planets billions of years ago. The team directly detected hydrogen sulfide at 0.4-0.8 parts per million as ice in its cloud tops. At this concentration, an astronaut sniffing Uranus’ air would sense a rotten-egg, fart-like smell (ignoring the fact that the cold and the rest of the atmosphere’s composition would kill him). This is an observation that contrasts sharply with the inner gas giant planets Jupiter and Saturn, where no hydrogen sulfide is seen above the clouds — instead, ammonia is observed. What’s more, the spectral lines suggest that there is less ammonia in Uranus than expected, which is another clue speaking to the difference in the formation of the two sets of planets.
“During our Solar System’s formation the balance between nitrogen and sulfur (and hence ammonia and Uranus’s newly-detected hydrogen sulfide) was determined by the temperature and location of planet’s formation,” said Leigh Fletcher, a member of the research team from the University of Leicester in the UK.
According to Fletcher, this was a very challenging work because when a cloud deck forms, it locks gases away in a deep internal reservoir, hidden away beneath the levels that we can usually see with our telescopes.
“Only a tiny amount remains above the clouds as a saturated vapour,” said Fletcher. “And this is why it is so challenging to capture the signatures of ammonia and hydrogen sulfide above cloud decks of Uranus. The superior capabilities of Gemini finally gave us that lucky break,” concludes Fletcher.
Although it might smell foul, Uranus has many valuable lessons to teach scientists about the early history of the solar systems and the conditions required for icy worlds to form around stars light-years away from our sun.
Scientific reference: Patrick G. J. Irwin et al, Detection of hydrogen sulfide above the clouds in Uranus’s atmosphere, Nature Astronomy (2018). DOI: 10.1038/s41550-018-0432-1.
Scientists fired lasers onto the humble polystyrene to recreate a luxurious sight thought to be common on the farthest-flung planets of the solar system: diamond rain.
Scientists have long throught that high temperature and pressure deep in Neptune and Uranus’ atmosphere are enough to form diamond rain. Now, we have lab confirmation of this hypothesis. Credit: Greg Stewart / SLAC National Accelerator Laboratory.
The two blue marbles of Neptune and Uranus are the least visited planets in our Solar System. Up until now, the only vehicle that has ever visited Uranus and Neptune was NASA’s Voyager 2, which launched in 1977. This flyby, however, raised more questions than it answered. For instance, these two outermost planets of the solar system are some times referred to as the ‘ice giants’ but the reality is we don’t know that much about what they’re made of. We know both have a solid core, that temperatures and pressure can be very high or that both have a dense atmosphere. We don’t know very specifically what’s inside behind their blue blankets since all the data we have comes from a single flyby mission and Earth-based telescope.
This massive gap in knowledge might hopefully be bridged if a NASA mission to send three orbiters to Uranus and Neptune by 2030s gets the resources it needs. Until then, scientists have to do with what they got.
British researchers, for instance, have mimicked the atmospheric conditions on both planets to test whether a long-standing and curious assumption has any footing. For many years scientists have posited that it rains diamonds on both planets, a hypothesis that has long proved very tricky to confirm in the lab. But now, an international team of scientists led by Dominik Kraus from German research lab Helmholtz-Zentrum Dresden-Rossendorf has finally done it.
A diamond furnace
To achieve their goal, the team fired a high-power laser at polystyrene, a common household material here on Earth but also a complex molecule that mimics the hydrocarbon soup seen in the atmosphere of the ice giants. Inside a treated environment, when the first laser pulse hit the foam, an initial shock wave was ejected. A second shock wave, this time faster, was made by a second pulse. When the two waves met, some very extreme conditions were created: temperatures and pressures of about 5,000 Kelvin and 150 GPa or roughly about as hot as the sun’s surface and one a half million times more pressure than at Earth’s sea level, respectively.
All of this was hot enough to break the bonds between the carbon and hydrogen inside the polystyrene. The pressure was also high enough to cause the carbon to bind together and form diamonds, which the scientists observed in minute molecular detail using very short pulses of X-rays.
Inside the lab, it rained with nanoparticles of diamonds but inside Neptune’s atmosphere, these might be far bigger, the team reported inNature Astronomy.
Once these diamond drops fall on the planet’s surface, they’ll sink down to the very bottom. This is another reason why this paper is neat. You see, for some time physicists have been debating the structure of both planets. It’s thought that the atmosphere — the outermost layer – is made of hydrogen, helium, and methane, which sits atop a liquid hydrogen layer including helium and methane. The lowest layer is liquid hydrogen compounds, oxygen, and nitrogen, while the core is thought to be made of ice and rock. Now, these little diamonds will help other scientists better test and piece together what these planets’ structure looks like.
“These diamonds will sink down because they are heavier than the surrounding medium and when they sink down there will be friction with the surrounding medium, and at some point they will be stopped when they reach the core – and all this generates heat,” Kraus told The Guardian.
There might also be a practical dimension to the team’s findings. Kraus says that the market is in demand for artificial diamonds and some applications require finely sized ones — sounds like a perfect fit to me, though it remains to be seen whether it will also be economically feasible.
In any event, it’s amazing to not only hear about how it might rain freaking diamonds on an alien planet but also get a chance to experiment and prove it could happen.
The magnetosphere on Uranus is not in sync with the planet’s rotation, causing it to switch off sometimes.
Uranus as a featureless disc, photographed by Voyager 2 in 1986.
Although it’s been 30 years since Voyager 2 sped past Uranus, we’re still analyzing the data and learning new things about the planet. This time, it’s about the planet’s magnetosphere.
A geometric nightmare
The magnetosphere is basically a region of space surrounding a planet (or any object), in which charged particles are controlled by that object’s magnetic field. In a planet like Earth, the magnetosphere is crucial because is mitigates or even blocks the negative effects of cosmic radiation. But on Earth, the magnetic field is nearly perfectly aligned with the spin axis, meaning that the same alignment of Earth’s magnetosphere is always facing toward the sun. In turn, this means that the magnetic field threaded in the ever-present solar wind must change direction in order to reconfigure Earth’s field from closed to open. This frequently occurs with strong solar storms. But our planet is privileged, and not the same can be said about Uranus.
The gas giant spins on its side and has a lopsided magnetic field, tilted by 60 degrees. So the magnetic field also tumbles asymmetrically relative to the solar wind direction. Since Uranus spins quite quickly (taking 17.24 hours to complete a full rotation), this leads to a periodic open-close-open-close scenario as it tumbles through the solar wind, leaving wide gaps open — like chinks in the planet’s magnetic defense. If that’s hard to picture… well, it is.
“Uranus is a geometric nightmare,” said Carol Paty, the Georgia Tech associate professor who co-authored the study. “The magnetic field tumbles very fast, like a child cartwheeling down a hill head over heels. When the magnetized solar wind meets this tumbling field in the right way, it can reconnect and Uranus’ magnetosphere goes from open to closed to open on a daily basis.”
Artistic depiction of the Earth’s magnetosphere. Image via Wiki Commons.
At this moment, we don’t know if Uranus is a typical case and the Earth is the odd one out, if it’s the other way around, or if there’s some innate characteristic of the planets that determine how the magnetosphere behaves. Understanding Uranus might serve as a stepping stone to understanding other planets outside our solar system — but unfortunately, the Voyager data is all we have.
“The majority of exoplanets that have been discovered appear to also be ice giants in size,” said Xin Cao, the Georgia Tech Ph.D. candidate in earth and atmospheric sciences who led the study. “Perhaps what we see on Uranus and Neptune is the norm for planets: very unique magnetospheres and less-aligned magnetic fields. Understanding how these complex magnetospheres shield exoplanets from stellar radiation is of key importance for studying the habitability of these newly discovered worlds.”
Journal Reference: Xin Cao, Carol Paty — Diurnal and seasonal variability of Uranus’s magnetosphere. DOI: 10.1002/2017JA024063.
Uranus might hold some surprises. Image credits: E. Karkoschka et al, NICMOS, HST, NASA
Astronomers have re-analyzed data captured by the Voyager 2 spacecraft from 1986, finding two dark shapes hidden in the rings of Uranus. They believe they might be two new moons.
Although Saturn is famous for its impressive rings, it’s not the only planet to boast them. The other gas giants, Jupiter and Uranus, also have their own ring systems. But unlike Saturn and Jupiter, Uranus is much less studied and far less understood. We don’t have as much data on it – in fact, most of the data we have on it comes from Voyager 2’s flyby 30 years ago.
Since that’s pretty much all we have to go on, a duo from the University of Idaho decided to comb Voyager 2’s data once again and see what they can find. Their search wasn’t in vain. By analyzing an unusually wavy shadow pattern in the Uranus rings, they came to the conclusion that two new moons lurk close to the planet’s ring system.
Rob Chancia and Matthew Hedman went further and crunched some simulation numbers, arriving at the conclusion that if the moons exist they measure a meager 4 and 14 km (2 to 9 miles) across. Still, while the existence of these moons is far from being confirmed, it seems to be a definite possibility.
Mark Showalter of the SETI Institute in California, who has previously discovered moons around Uranus but was not involved in this study, told Ken Croswell over at New Scientistthat the existence of the two new moons is “certainly a very plausible possibility”. At the moment, the paper is going through the process of peer review and we’ll learn much more when that’s done.
But if we really want to see if there are moons there, we should do the basic thing and start looking there. Of course, “looking” in this case means through a telescope, namely through Hubble. Showalter argues that’s the “best bet” for finding these new Uranian satellites. But if that fails then maybe Uranus should get its own orbiter mission. Jupiter got it, Saturn got it… let’s make Uranus great again
The most detailed observations of the icy world of Uranus, the seventh planet from the sun, show complex weather patterns and other features that scientists have yet to fully describe.
The two faces of Uranus as seen through the adaptive optics on the near-infrared camera of the Keck II telescope in Hawaii. (c) Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater.
Popular belief had Uranus depicted as a bland, pale green world based on the now iconic observations from Voyager’s 1986 flyby of the planet. Its instruments from the time, however, weren’t sensitive enough to catch a more in-depth view, and since the planet is 30 times farther away from the sun than Earth, ground based telescopes couldn’t peel through its atmosphere because of noise.
A novel technique employed by an international team of scientists with telescopes of the Keck Observatory allowed for the first most detailed view of Uranus by combining multiple images of the planet in near-infrared. Thus, the scientists were able to reduce the noise and image weather features that are otherwise obscure, and these couldn’t be more interesting. Observations reveal circulating clouds, enormous hurricanes, and an unusual swarm of convective features at its north pole.
“These images reveal an astonishing amount of complexity in Uranus’ atmosphere,” said Heidi Hammel of the Association of Universities for Research in Astronomy. “We knew the planet was active, but until now, much of the activity had been masked by the noise in the data.”
A 2007 image of Uranus from the Keck telescope shows far less surface detail. Image courtesy of Imke de Pater.UC Berkeley.
The planet, in fact, looks like many of the solar system’s other large planets — the gas giants Jupiter and Saturn, and the ice giant Neptune — said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and one of the team members.
Also atmospheric composition has been determined in greater detail than ever before, as data shows the clouds, which race at 560 miles per hour, are mainly composed of hydrogen, helium, and methane. This remarkable velocity came as a surprise to the researchers, since the planet is so far away from the sun, and thus should have lower energy available to drive these weather features.
“The sun is 900 times weaker than on Earth, so you don’t have the same intensity of solar energy driving the system as we do here,” said Larry Sromovsky, a planetary scientist at the University of Wisconsin, Madison, who lead the study. “Thus, the atmosphere of Uranus must operate as a very efficient machine with very little dissipation. Yet it undergoes dramatic variations that seem to defy that requirement.”
A distinct feature of Uranus, which greatly influences its now complex weather patterns, is the fact that it’s completely titled on its side. Opposite to how clouds travel from left to right on Earth, for instance, on Uranus the clouds run from up to down. Its North pole is, thus, on the right side. One new feature found by the group is a scalloped band of clouds just south of Uranus’ equator. The band may indicate atmospheric instability or wind shear.
“This is new, and we don’t fully understand what it means,” said Sromovsky. “We haven’t seen it anywhere else on Uranus.”
Like most large weather systems, which are probably much less violent than the storms we know on Earth, Uranus is fairly stable, despite exhibiting some strange patterns. Some stay at fixed latitudes and undergo large variations in activity, while others have been seen to drift towards the equator, while undergoing great changes in size and shape.
The findings will be presented at the American Astronomical Society’s Division of Planetary Sciences in Reno, Nev.
When Voyager 2 made its flyby near the planet of Uranus, astronomers got their first direct glimpse of what an aurora might look on the cold planet. However, such lights have never been observed from Earth – that is, until last year, when a team of scientists used careful planning and the Hubble Telescope to observe the lovely phenomena.
The international team will publish their discoveries in Geophysical Research Letters; wanting to catch auroras is a tricky deal, and one which requires a lot of careful planning, because they are caused by the interaction between charged particles from the sun and a planet’s magnetic field – something which doesn’t happen quite every day. The team first had to wait for a particular arrangement of planets which ensured that the solar wind from the Sun has a direct, open path to Uranus. Then, they had to wait until the sun let loose a burst of charged particles, which happened in September, last year.
After this happened, they calculated how much the solar wind would take to reach Uranus, which was November, then booked time on the Hubble during that exact same period. Their calculations proved correct, and they were able to witness the fascinating phenomena.
But observing the aurora on Uranus isn’t as simple as directing a telescope at the planet. Uranus not only spins nearly on its side, the planet also has an off-kilter magnetic field. By observing how the magnetic field of Uranus functions with something we understand as well as aurora, the researchers hoped to learn much more about the magnetosphere of planets.
“We have ideas of how things work on Earth and places like Jupiter and Saturn, but I don’t believe you really know how things work until you test them on a very different system.”, said Laurent Lamy, the lead researcher on the team, quote by the American Geophysical Union.
Near-infrared views of Uranus and its faint ring system, shown here to highlight the extent to which it is tilted. (c) Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.
Uranus, the seventh planet from the sun, is a definite oddball of the solar system. It has its axis titled by a whopping 98 degrees, which makes it orbit on its side. The general accepted theory is that a big impact with an object several times the size that of the Earth nodged its axis massively, however a new study presented recently at the EPSC-DPS Joint Meeting in Nantes rewrites our theories of how Uranus became so tilted and gives new valuable insight as to how giant planets form.
As a comparisson Jupiter’s spin axis is only tilted by 3 degrees; Earth’s, 23 degrees; Saturn and Neptune, 29 degrees. Seeing how Neptun’s axis is tilted more than 3 times that of the second titled axis in the solar system has always puzzled astronomers. For many years now, the leading hyphotesis was that of a giant space object, a few times the size of Earth, plunged into the giant planet and deviated its axis. The one, major flaw to this supposition, however, is that, if true, Uranus’ moons should have been left orbiting in their original angles, but they too lie at almost exactly 98 degrees.
The answer, scientists say, is that Neptun was struck in multiple high impacts, instead of one. Alessandro Morbidelli (Observatoire de la Cote d’Azur in Nice, France), lead study author, and his international team of scientists used complex planetary simulations to reproduce various impact scenarios in order to ascertain the most likely cause of Uranus’ tilt. They discovered that if Uranus had been hit when still surrounded by a protoplanetary disk – the material from which the moons would form – then the disk would have reformed into a fat doughnut shape around the new, highly-tilted equatorial plane.
Planet formation theory revised
With this set-up simulation in place, however, the moons displayed a retrograde motion, opposite to the motion that can be observed today. Their explanation: Uranus was not tilted in one go, as is commonly thought, but rather was bumped in at least two smaller collisions, then there is a much higher probability of seeing the moons orbit in the direction we observe.
“The formation history of Uranus and Neptune is one of the most important open problems in planetary science. Having shown that giant collisions had to happen frequently on these planets is an important piece of information on the way to understanding their origin,” lead author Alessandro Morbidelli, with the Observatory of Cote d’Azur in Nice, France, wrote in an email to Discovery News.
Morbidelli’s research is currently conflicting current planetary formation theories, which might need to be revised.
“The standard planet formation theory assumes that Uranus, Neptune and the cores of Jupiter and Saturn formed by accreting only small objects in the protoplanetary disk. They should have suffered no giant collisions. The fact that Uranus was hit at least twice suggests that significant impacts were typical in the formation of giant planets. So, the standard theory has to be revised.”
A probe that has been launched no less than 30 years ago has come across a force that has baffled the scientific world and could rewrite the laws of physics. In 1983, Pioneer 10 took some photos of Jupiter, then left the solar system. However, it’s being pulled back to the Sun by a force unlike any other seen before.
This unknown force doesn’t seem to get weaker as the probe goes further into space, and astronomers and physicists are seriously considering the possibility of a new force of nature.
Dr Philip Laing, a member of the research team tracking the craft, said: “We have examined every mechanism and theory we can think of and so far nothing works. If the effect is real, it will have a big impact on cosmology and spacecraft navigation,” said Dr Laing, of the Aerospace Corporation of California.
When scientists initially observed this effect, they believed it to be a gas or heat leak of some sort, but these theories have been proven wrong already. However, you shouldn’t think this force is extremely powerful. It’s in fact 10 billion times weaker than gravity, changing the probe speed at about 10 km/h per century. Still, the fact that the force doesn’t decrease with distance is extremely remarkable.
Of course, the next natural assumption was some sort of malfunction of the probes. However, at a closer look, the absolute same effect was observed on the Galileo and Ulysses probes.
Dr Duncan Steel, a space scientist at Salford University, says even such a weak force could have huge effects on a cosmic scale. “It might alter the number of comets that come towards us over millions of years, which would have consequences for life on Earth. It also raises the question of whether we know enough about the law of gravity.”
A new research published in Nature Physics showed that there may be oceans of diamonds (literally) on both Uranus and Neptune. The first ever study conducted on the melting point of diamond concluded that at that certain point, it behaves just like water, with the solid form floating in the liquid form (just imagine icebergs, or small chunks of ice floating in a puddle).
“Diamond is a relatively common material on Earth, but its melting point has never been measured,” said Jon Eggert (Lawrence Livermore National Laboratory). “You can’t just raise the temperature and have it melt, you have to also go to high pressures, which makes it very difficult to measure the temperature.”
This in itself made the measuring point difficult to find out; diamond doesn’t like to stay diamond when it’s really hot – it tends to turn to graphite (still Carbon, but different crystal properties), which then melts, so the challenge was to find out diamond’s melting point without turning into graphite, which is why they also had to apply pressure.
Now, about Uranus and Neptune. The thing with the two planets is they both have an anomaly; their geographical and magnetic poles have nothing to do with one another, so researchers concluded there has to be an anomaly responsible for the 60 degree deviation of the poles of the North-South axis; on a sidenote: Earth’s poles oscilate too. They even switch polarities, in a very slow and gradual process. They don’t follow the N-S axis, but rather a complicated curve, however, without deviating too much from it (just how much is still debatable).
So what could cause this huge deviation? According to researchers performing the study, it’s extremely likely an… ocean of diamonds. They constructed models which showed the same results and this would also fit with the planet’s chemical composition (over 10% carbon), so this seems more and more plausible. If this is indeed the case, Uranus is definitely Marilyn Monroe’s heaven.
EDIT: before any of you start with the boyish jokes… just don’t do it :)