Out of all the planets in the solar system, Neptune is the one that looks most peaceful. When seen through a telescope, the eighth and most distant planet from the sun appears sky-blue or as a uniform, peaceful ocean world that would have made the Roman god of the sea proud.
In reality, Neptune is anything but peaceful and its atmosphere is actually mainly made of three gases: hydrogen (80%), helium (19%), and methane (1%).
It’s actually clouds of methane gas that are responsible for the distant planet’s blue marble appearance. Despite the fact it makes up a relatively tiny proportion of Neptune’s atmosphere, methane absorbs red wavelengths of light and reflects blue light outward.
A distant blue gem
Neptune is the only planet in the solar system that isn’t visible to the naked eye. As such, it was among the last to be discovered in 1846 by Johann Galle, based on mathematical predictions made by Urbain Le Verrier.
But during these initial observations, astronomers had no idea what Neptune looked like.
The planet, which is about four times larger than Earth, was first visited by a spacecraft in 1989 when NASA’s Voyager 2 made a flyby. Voyager beamed back images showing Neptune’s ocean-like hue for the first time. It was really a stroke of luck that Neptune was so aptly named when astronomers could not have known that the planet is all blue.
Similarly to Uranus, Neptune is one-fifth hydrogen and helium by mass. The bulk of the planet’s mass, however, is owed to heavier molecules such as ammonia, methane, carbon, oxygen, and water.
Despite their similarities in size and composition, Neptune and Uranus are distinctly colored. This is explained by different chemical components in each of the planets’ upper atmospheres, particularly in the global cloud deck.
Neptune’s clouds are known to vary with altitude, just like on Earth. Methane clouds condense in the highest layers of the planet’s atmosphere due to frigidly cold temperatures. Further down, there may be clouds of hydrogen sulfide, ammonium sulfide, ammonia, and water. The blue-toned methane isn’t evenly distributed; ten to a hundred times more methane, ethane, and ethyne can be found at Neptune’s equator than at its poles.
Being present in the outermost layer of the atmosphere, the most important compound that influences the color of both planets’ atmospheres is methane. The greenhouse gas absorbs red light at wavelengths of 600 billionths of a meter, reflecting back bluer light. Uranus, however, is more azure, blue-green in appearance due to an additional chromophore that Neptune seems to lack. This particular chromophore hasn’t been identified yet so the true nature of Neptune’s color is still a mystery.
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.
Gas giants like Jupiter and Saturn are mind-bogglingly huge, but that’s because their atmospheres are exceptionally thick. In fact, to this day, scientists aren’t sure what lies beneath their atmospheric shell of hydrogen and nitrogen. But a distant ‘failed’ gas giant may offer some clues.
A team of astronomers led by researchers at Warwick University has identified the first core of a gaseous world, offering an unprecedented glimpse into what such solid core might look like.
The researchers were initially running a survey of exposed planetary cores from data gathered by the TESS space telescope. That’s when they came across TOI 849 b, a large object circling a sun-like star about 730 light-years away from Earth.
Follow-up observations with the HARPS spectrograph in Chile confirmed that the object was truly massive. Although the exoplanet is three-and-a-half times larger than Earth, it’s around 39 times more massive.
Considering its size and density, the only viable explanation is that TOI 849 b is actually the core of a former gas giant — now, just a rocky giant.
It might not be a pretty sight either. The core is estimated to complete a full orbit around its parent star every 18 hours, which means it’s mighty close to solar radiation. Its surface temperature is believed to be around 1,527 degrees Celsius as a result.
Although it’s not clear how TOI 849 b lost its gaseous envelope, the astronomers have proposed two plausible scenarios. The most likely explanation is that extremely powerful tidal forces generated by the close orbit ripped apart the gas atmosphere. Alternatively, the former gas giant may have collided with another planet.
The second possibility is that TOI 849 b never had the chance to complete its gaseous atmosphere. This may have occurred due to a gap in the disc of gas and dust from which it was forged. However, the researchers are less inclined to lean on this hypothesis.
“I think one of the biggest clues is that we found the planet inside the ‘Hot Neptunian desert’, which is this region of parameter space where we don’t typically find planets,” lead author David Armstrong told BBC News.
“That hints that it has gone through quite an unusual evolution. To me that hints that it is more likely that it did lose its atmosphere… but we’ll need some more observations to be sure.”
Although TOI 849 b is hundreds of light-years away, the rocky core might provide invaluable insights about planets closer to home.
Initially, scientists believed that Jupiter would have a solid core covered in a ‘crust’ of liquid hydrogen that is bombarded by helium rain. However, relatively recent observations performed by the Juno spacecraft showed that the gravitational measurements don’t add up, pointing instead towards “a core that is not solid like Earth’s, but “fuzzy” and dilutely mingled with the overlying metallic hydrogen layer,”New Scientist reports.
But, the jury is still out and there are many unknowns regarding the nature of Jupiter’s core, or those of Neptune or Saturn for that matter. Perhaps TOI 849 b can teach us a thing or two about what gas giants look like beneath their thick atmosphere. At the very least, the new study shows that rocky cores exist, and astronomers can now be on the lookout for more.
Our little corner of the universe just got a little bigger.
Data from the Dark Energy Survey (DES) helped researchers identify over 300 new trans-Neptunian objects (TNOs), minor planets located beyond the orbit of Neptune. A new study describes the methodology used, which the team hopes will be adapted in the search for the hypothetical Planet Nine and other undiscovered planets.
“The number of TNOs you can find depends on how much of the sky you look at and what’s the faintest thing you can find,” says Gary Bernstein, a Chair Professor at the University of Notre Dame’s College of Engineering and paper co-author.
“Dedicated TNO surveys have a way of seeing the object move, and it’s easy to track them down. One of the key things we did in this paper was figure out a way to recover those movements.”
The DES, which completed six years of data collection in January, captures high-fidelity images of the southern skies in an effort to understand the nature of dark energy. However, researchers seem to have been intent on teaching it a few tricks, and used the data to look for TNOs.
While the DES was designed to take wide-angle, high-quality shots of galaxies and supernovas, the team had to adapt it to be able to track the movement of (tiny, by comparison) TNOs.
They started with a dataset comprising 7 billion “dots”, which are points of interest identified by automated software. These points were brighter than the background behind them, which could be indicative of a planet reflecting light. The next step was to remove any of them that were present on multiple nights — this signified that they were bodies such as stars or galaxies far, far away — slimming the list down to only 22 million points.
The last step involved trying to group these together into nearby pairs of triplets and check if these reappeared on several nights. By this point, the team was left with around 400 candidates. In order to establish whether these were TNOs, the team revisited the images they had for each object. Pedro Bernardinelli, a PhD candidate in physics & astronomy at the University of Pennsylvania and lead author of the paper, developed a way to stack multiple images to create a sharper view, which helped confirm whether a detected object was a real TNO. In order to verify their method, they applied it to known TNOs and introduced fake objects into the images — these were spotted as fake by the system.
After the months-long process, the team reported on 316 TNOs, including 245 discoveries made by DES and 139 new objects that were not previously published — this total represents 10% of all known TNOs. The objects orbit from around Pluto to nearly twice as far away.
The team now plans to re-run their system on the DES dataset using a lower detection threshold.
The paper “Trans-Neptunian Objects Found in the First Four Years of the Dark Energy Survey” has been published in The Astrophysical Journal Supplement Series.
Thirty years ago, NASA’s Voyager 2 mission flew by Neptune, capturing the first detailed images of the gas giant. Before this, Neptune was only known as a fuzzy blue dot.
Voyager 2 was launched in 1977, to study the outer planets and to date, is the only shuttle to visit the icy planets Uranus and Neptune. Its primary mission ended with the exploration of the Neptunian system on October 2, 1989, after it conducted a grand tour of the solar system’s gas giants: Jupiter, Saturn, Uranus, and Neptune. It was to Neptune what New Horizons is now to Pluto, helping us gain a close view of a planet we only vaguely knew beforehand.
“We had the opportunity to get a close flyby with Voyager 2,” said Suzanne Dodd, Voyager Project Manager. “Because of the planetary alignment when the probes launched in 1977, the four giant outer planets were all aligned on the same side of the sun, so we could go from one to the next to the next. It was a really great opportunity.”
Voyager 2 discovered previously unknown Neptunian rings and confirmed six new moons: Despina, Galatea, Larissa, Proteus, Naiad and, Thalassa. It also identified the “Great Dark Spot”, which seems to have disappeared since, according to observations by the Hubble Space Telescope.
The picture above became the default image of Neptune as we know it. It was produced from the last whole planet images taken through the green and orange filters on the spacecraft’s narrow angle camera.
At its core, the Voyager missions were about pure science — expanding our understanding of the universe. Ed Stone, a professor of physics at Caltech and Voyager’s project scientist since 1975, said:
The Voyager planetary program really was an opportunity to show the public what science is all about. Every day we learned something new.
Sending data to Earth wasn’t easy, but the Voyagers (Voyager 2 and Voyager 1, its sister mission) communicated with the Earth using Deep Space Network, which utilizes radio antennas at sites in Madrid (Spain), Canberra (Australia), and Goldstone (California). The three largest antennas at the time were 64 meters (210 feet) wide, and were expanded to 70 meters (230 feet) for the Neptune encounter. There was no internet at the time, Stone continues.
“One of the things that made the Voyager planetary encounters different from missions today is that there was no internet that would have allowed the whole team and the whole world to see the pictures at the same time. The images were available in real time at a limited number of locations.”
NASA has spotted one of Neptune’s Great Dark Spots as it was forming, a new study reports. This is the first time humanity has witnessed such an event.
“Does this picture make my spot look dark?” Image credits NASA / JPL / Voyager 2.
By peering through the lens of the Hubble Space Telescope, NASA researchers have captured one of Neptune’s storms at is was brewing. While six such dark spots have been observed on Neptune in the past, this is the first time we’ve seen one during formation.
The findings will help us better understand our neighboring planets, as well as those far away — exoplanets — in general, as well as the weather patterns and nature of gas giants in particular.
There be a storm a’brewin!
“If you study the exoplanets and you want to understand how they work, you really need to understand our planets first,” said Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland and lead author of the new study.
“We have so little information on Uranus and Neptune.”
Jupiter’s Great Red Spot is perhaps the best-known alien storm — but it’s far from the only one. Neptune, as well as our other gaseous-if-somewhat-unfortunately-named neighbor Uranus also boast their own storms in the form of Great Spots.
Neptune’s storms take the shape of Great Dark Spots. Researchers have, so far, spotted six such Spots on Neptune since 1989, when Voyager 2 identified the first two. Hubble has spotted four more since its launch in 1990. The authors of this study have analyzed images Hubble has taken of Uranus over the past several years to chronicle the growth of a new Great Dark Spot that became visible in 2018. The wealth of data recorded by Hubble helped the team understand how often Neptune develops dark spots and how long they last, and gain a bit of insight into the inner workings of ice giant planets.
Voyager 2 saw two storms on Neptune, the (Earth-sized) Great Dark Spot and the Dark Spot 2, in 1989. Images taken by Hubble five years later revealed that both spots had vanished.
“It was certainly a surprise,” Simon said. “We were used to looking at Jupiter’s Great Red Spot, which presumably had been there for more than a hundred years.”
However, a new Dark Spot reared its head on the face of Neptune in 2015. While Simon’s team was busy analyzing Hubble images of this spot, they found some mysteriously-white clouds in the area where the Great Dark Spot used to be. Then, in 2018, a new Great Dark Spot splashed across its surface; it was nearly identical in size, shape, and position as the one seen in 1989, the team reports, right where those clouds used to be.
“We were so busy tracking this smaller storm from 2015, that we weren’t necessarily expecting to see another big one so soon,” Simon said.
These high-altitude white clouds, the team says, are made up of methane ice crystals. The team suspected they somehow accompany the storms that form dark spots, likely hovering above them the same way that lenticular clouds cap tall mountains here on Earth.
A lenticular cloud spotted over a mountain in the Snæfellsjökull National Park, Iceland. Image credits joiseyshowaa / Flickr.
So the team set out to track these clouds from 2016 (when they were first spotted) to 2018 (when the Spot gobbled them up). They were brightest in 2016 and 2017, the team found, just before the new Great Dark Spot emerged. The team turned to computer models of Neptune’s atmosphere to understand what they were seeing. According to the results, these companion clouds are brighter over deep storms. The fact that they appeared two years before the Great Dark Spot and then lost some brightness when it became visible suggests dark spots may originate much deeper in Neptune’s atmosphere than previously thought, the team explains.
They also used data from Voyager 2 and Hubble to measure how long these storms last, and how frequently they occur, on which they report in a second study. Each storm can last up to six years, though most only survive for two, the paper reads, and the team suspects new storms appear on Neptune every four to six years or so. This last tidbit would make the Great Dark Spots of Neptune different from those on Jupiter, whose Great Red Spot is at least 350 years old (it was first seen in 1830).
Jupiter’s storms endure as they’re caged in by thin jet streams, which keep them from changing latitude (north-south) and hold them together. Neptunian winds flow in much wider bands, and instead push storms like the Great Dark Spot slowly across latitudes. They can generally survive the planet’s westward equatorial winds, and eastward-blowing currents close to the equator, before getting ripped apart in higher latitudes.
“We have never directly measured winds within Neptune’s dark vortices, but we estimate the wind speeds are in the ballpark of 328 feet (100 meters) per second, quite similar to wind speeds within Jupiter’s Great Red Spot,” said Wong.
Simon, Wong and Hsu also used images from Hubble and Voyager 2 to pinpoint how long these storms last and how frequently they occur. They report in a second study published today in the Astronomical Journal that they suspect new storms crop up on Neptune every four to six years. Each storm may last up to six years, though two-year lifespans are more likely, according to the findings.
The paper “Formation of a New Great Dark Spot on Neptune in 2018” has been published in the journal Geophysical Research Letters.
No, it’s not a camp for hippos — it’s Neptune’s “new” moon, Hippocamp.
The image in which Hippocamp was discovered. The moon is visible inside the red box; an enlarged version is inset at upper right. Image credits: Mark R. Showalter, SETI Institute.
The planet Neptune was predicted through mathematics before it was actually discovered. The mathematician Urbain Le Verrier used Newtonian calculations to conclude that a planet must exist in Neptune’s place, and his prediction was amazingly confirmed one year later. As the papers of the time wrote, Le Verrier had discovered a planet “with the tip of his pen.” Now, astronomers have used much more than the tip of a pen to discover Neptune’s “new” moon.
Our knowledge of Neptune’s moons was largely provided by the Voyager 2 spacecraft, which spotted six small inner moons orbiting Neptune when it flew by the planet in 1989. All these moons are thought to be younger than Neptune and its largest moon, Triton.
Now, Mark Showalter and colleagues at SETI studied Neptune’s inner moons and rings using the Hubble Space Telescope, and they found yet another Neptunian moon, which they have named Hippocamp, after the mythological Greek sea monster which had the upper body of a horse and the lower body of a fish (yes, that’s also what after a region in our brain is named after).
A size comparison between the seven inner moons of Neptune, along with the planet’s bluish figure at right. Image credits: Mark R. Showalter, SETI Institute.
The reason why this moon has escaped detection for so long is that it’s really, really small. At just 34 kilometers across, it resembles a giant rock more than a proper moon. It orbits close to Proteus, the largest and outermost of Neptune’s inner moons. Showalter and colleagues believe that Hippocamp may have formed from ejected fragments of larger satellites, after a large comet impact.
This is coherent with previous studies, which claimed that Neptune’s inner moons were shaped by numerous comet impacts.
This further adds to Neptune’s already impressive collection of moons. With Hippocamp, Neptune (itself named after the Roman equivalent to Poseidon, the god of the seas and oceans) has 15 known moons, all named for water deities or creatures in Greek Mythology By far, the largest and most interesting of them is Triton, which is also unique because its orbit is retrograde to Neptune’s rotation and inclined relative to the planet’s equator. This suggests that Triton was not formed in orbit around Neptune, but somehow wandered nearby Neptune and was captured by its gravitational field. The next largest moon, Phoebe, only has 0.03% of Triton’s mass.
Dark spot on Neptune full color (left) and blue light (right).
Although not as famous and easily visible as the Great Red Spot, Neptune’s Great Dark Spot (creative names, I know) has its own remarkable history. Also an anticyclonic storm, the first Dark Spot was first observed in 1989 by NASA’s Voyager 2. It was big enough to cover the entire Atlantic, from the US to Europe’s West Coast, but unlike Jupiter’s storm, it had a much shorter lifespan. I say “the first” Dark Spot because, since its discovery in 1989, several others have appeared and disappeared, and the initial one is long gone. Hubble discovered two dark storms that appeared in the mid-1990s and then vanished. The current storm was first observed in 2015, but it’s already shrinking.
We don’t really know that much about Neptune. The farthest planet from the Sun (sorry Pluto) remains largely a mystery, with most of our information coming from remote observations or from the Voyager days. The way it was discovered says a lot about this: Neptune was the first and only planet in our Solar System found by mathematical prediction rather than by empirical observation. Astronomers believe that Neptune has a solid rock core, a mantle consisting of water, ammonia and methane ices, and an atmosphere. The top of the atmosphere is covered by top clouds, while the rest consists of hydrogen, helium, and methane The Dark Spot is interesting because it allows astronomers to indirectly deduce certain aspects about Neptune’s atmosphere.
The Great Dark Spot is thought to represent a hole in the methane cloud deck of Neptune, generating large white clouds made of frozen methane. The dark spot itself might also contain hydrogen sulfide, a substance commonly found in crude petroleum, natural gas, volcanic gases, and hot springs.
It seems a bit strange if you think about it — why would white clouds, including ice, create a dark spot? Well, it isn’t that they’re necessarily dark, just that they’re less bright than the rest of the atmosphere. Joshua Tollefson from the University of California at Berkeley explained.
“The particles themselves are still highly reflective; they are just slightly darker than the particles in the surrounding atmosphere.”
This series of Hubble Space Telescope images taken over 2 years tracks the demise of a giant dark vortex on the planet Neptune. The oval-shaped spot has shrunk from 3,100 miles across its long axis to 2,300 miles across, over the Hubble observation period. Image credits: NASA, ESA, and M.H. Wong and A.I. Hsu (UC Berkeley).
But other than this, we don’t really know much about the nature of these storms. We don’t know why or how they form, and no missions other than Voyager and Hubble are able to visualize them.
“We have no evidence of how these vortices are formed or how fast they rotate,” said Agustín Sánchez-Lavega from the University of the Basque Country in Spain. “It is most likely that they arise from an instability in the sheared eastward and westward winds.”
Unlike Jupiter’s storms, Neptune’s storms don’t last as long. Neptune doesn’t have atmospheric conveyor belts, which keep the storm trapped, and it doesn’t have the proper atmospheric conditions to fuel the storm. So quite soon, the Dark Spot will fade away — but another one will eventually rise up to take its place.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect,” said Michael H. Wong of the University of California at Berkeley, referring to work by Ray LeBeau (now at St. Louis University) and Tim Dowling’s team at the University of Louisville.
Observations show how Neptune’s dark vortex is slowly fading into oblivion. Credit: NASA, UC Berkeley.
Since 2015, astronomers have been following a dark vortex the size of China swirling over Neptune, the solar system’s outermost planet. The vortex is packed with hydrogen sulfide — aka the chemical that makes farts or rotten eggs smell awful — which it swept from deep within the planet’s atmosphere. Now, researchers say that what may quite possibly be the biggest fart in the solar system is slowly fading away.
Mysterious (and stinky)
Such dark vortices aren’t a novelty. The first features were spotted in the 1980s by NASA’s Voyager 2 spacecraft. Overall, scientists have documented five of the dark streaks over Neptune’s atmosphere. The most recent one was discovered by the Hubble Space Telescope in 2015.
The vortex, dubbed SDS-2015, is normally invisible, being shrouded by Neptune’s cloudy surface. But Hubble can see it thanks to its Wide Field Camera 3 which can probe the hazy atmosphere at blue optical wavelengths.
“We have no evidence of how these vortices are formed or how fast they rotate,” Agustín Sánchez-Lavega from the University of the Basque Country, said in the statement. “It is most likely that they arise from an instability in the sheared eastward and westward winds.”
Scientists have a hunch though that these vortices form when gas and air from the planet’s atmosphere swirl and freeze, turning into a mass than drifts into the upper atmosphere guided by currents. As the storm rages on, it pulls up material from the lower atmosphere, including the stinky hydrogen sulfide — and in copious amounts judging from spectrometry readings.
We still don’t know a lot about these somewhat mysterious features. Many questions still remain pertaining to their origin, drift and oscillation mechanics, and how they eventually dissipate. It is this latter question that a new study attempts to clear up.
The slow death of a storm. Credit: UC Berkeley.
The team of researchers at the University of California Berkeley and the University of Basque Country, Spain, analyzed observations of the dark vortex made between 2015 and 2017. They learned that the contrast to the surrounding area of the dark vortex dropped from 7 percent to 3 percent over this period, as reported in the Astronomical Journal.
This is essentially the first time that scientists have documented a vortex’s decline in action. Previously, models that predicted the movement of SDS-2015 suggested that the dark vortex should drift toward the equator, guided by wind shear. Once it got too close to the equator, the vortex would break up, creating a flashy outburst of cloud activity — or so the prediction went. In reality, the vortex is not breaking up spectacularly. Instead, it’s just fading away steadily and rather uneventfully.
Like Jupiter’s Great Red Spot (GRS), the storm swirls in an anticyclonic direction. But unlike Jupiter‘s GRS, our smelly dark vortex isn’t constrained by as many alternating wind jets (the gas giant’s colorful bands). Neptune only has three broad jets: a westward one at the equator, and eastward ones around the north and south poles. Scientists expect to see the vortex change lanes and cruise anywhere between these three jets before it succumbs.
“No facilities other than Hubble and Voyager have observed these vortices. For now, only Hubble can provide the data we need to understand how common or rare these fascinating neptunian weather systems may be,” said co-author Michael H. Wong of the University of California at Berkeley.
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.
A team of astronomers has discovered a new dwarf planet in the outskirts of our solar system beyond Neptune, joining the ranks of Pluto, Ceres and other celestial objects on the smaller end of the size spectrum. The planet – tentatively named 2015 RR245 – possesses one of the largest orbits among dwarf planets, orbiting the sun just once every 700 years.
“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the sun,” said Michele Bannister of the University of Victoria in British Columbia, who participated in the research. “They let us piece together the history of our solar system. But almost all of these icy worlds are painfully small and faint: It’s really exciting to find one that’s large and bright enough that we can study it in detail.”
The planet was first spotted in February earlier this year after the examination of images from the ongoing Outer Solar System Origins Survey (OSSOS) survey. Although its exact size is not yet known, the team believes that it falls into one of two broad categories: broad and shiny or large and dull.
Unlike most dwarf planets that were destroyed or ejected from our solar system to make way for larger planets, RR245 has survived until the present along with other large dwarf planets such as Pluto and Eris.
RR245 likely possesses unique geology composed of numerous kinds of frozen materials. However, as it has only been observed for one of the 700 years in its orbital period, further research will need to be conducted in order to reveal its exact landscapes and orbit.
“OSSOS was designed to map the orbital structure of the outer solar system to decipher its history,” said Brett Gladman, a professor from the University of British Columbia in Vancouver who participated in the research along with Bannister. “While not designed to efficiently detect dwarf planets, we’re delighted to have found one on such an interesting orbit.”
RR245 is the largest planet to be discovered by the OSSOS and will likely be the last until the mid 2020s when other larger telescopes will begin their search for celestial bodies in the outer reaches of our solar system.
Astronomers using the Hubble telescope have identified a warm Neptune-sized planet that is “bleeding” a huge hydrogen cloud – thus increasing the odds of finding liquid oceans on gas giants.
The Orion Nebula, where the planet “resides”
This phenomenon has been observed before, but at a much smaller scale – it’s the first time it’s been studied at such an amplitude. The cloud of hydrogen has been dubbed as “The Behemoth” bleeding; it’s evaporating from the planet due to extreme radiation, but even with this immense emission, the planet itself is not threatened.
“This cloud is very spectacular, though the evaporation rate does not threaten the planet right now,” said the study’s leader, David Ehrenreich from the Observatory of the University of Geneva in Switzerland. “But we know that in the past, the star, which is a faint red dwarf, was more active. This means that the planet evaporated faster during its first billion years of existence. Overall, we estimate that it may have lost up to 10 per cent of its atmosphere,” said Ehrenreich.
With a mass approximately 23 times that of our Earth located 33 light years away, the exoplanet GJ436b is extremely close to its star and revolves around it in less than three days. Due to its proximity to the star, it’s also very hot. Some scientists believe that Earth too may have once had a hydrogen atmosphere that was slowly burned away. If so, Earth may previously have sported a comet-like tail, but this is only a supposition at this point.
Astronomers were able to study this planet because the hydrogen absorbs the ultraviolet light of the parent star and reflects it back to Hubble – in other words, you can identify hydrogen even from light years away.
A lost moon of Neptune has not been seen since its discovery in the late 1980s – until now, that is.
A new announcement from the 45th Meeting of the Division for Planetary Sciences of the American Astronomical Society revealed the rediscovery of the moon of Neptune which was only glimpsed briefly back in the 1989 flyby of Voyager 2.
Naiad, the innermost moon of Neptune, was spotted by the SETI institute – in case you’re wondering what alien intelligence has to do with Neptune’s moons, SETI is studying the long-term dynamics of many-moon and ring systems, which is very important for the viability of life on moons in systems like that.
“Naiad has been an elusive target ever since Voyager left the Neptune system,” Showalter said in a recent SETI Institute press release. Voyager 2 has, to date, been the only mission to explore Uranus and Neptune.
As it seems to happen more and more lately, the discovery came as a result of new techniques applied to old images. Showalter and his team applied new analyzing techniques which filtered for glare and image artifacts that tend to “spill over” from Neptune. A few of Neptune’s other moons (Galatea and Thalassa) were also found in these images, as was an entirely new moon (S/2004 N1) which was revealed earlier this year.
The orbit of the moon was pretty surprising, as it was discovered in an entirely different position than was expected – probably as a result of interactiosn with Neptune’s other moons.
“We don’t quite have enough observations to establish a refined orbit,” Mr. Showalter told Universe Today, noting that there may still be some tantalizing clues waiting to be uncovered from the data.
In Greek mythology, Naiads are a type of nymphs in charge over fountains, wells, springs, streams, brooks and other bodies of freshwater (distinct from river gods).
An US astronomer recently reported that he and his team have discovered a new moon orbiting the eighth and farthest planet from the sun, Neptune. Designated S/2004 N 1, this is the 14th known moon to circle the giant planet.
This composite of Hubble Space Telescope images taken in August 2009 shows the location of a newly discovered moon, designated S/2004 N 1, orbiting the giant planet Neptune. NASA / ESA / M. Showalter (SETI Inst.)
Some of you might find it odd that we’ve yet to spot all the moons orbiting around the planet in our solar system, when almost each day we learn how astronomers find new distant worlds or other cosmic bodies thousands of light years away from us. The truth is however, this new moon, much like all the others found in the solar system in recent years, is so tiny and dim that it’s no wonder it has eluded detection. Imagine that in 1989 Voyager failed to report it either, and the probe actually traveled very close to Neptune.
Luckily Mark Showalter (SETI Institute) was very vigilant and discovered the moon after investigating a faint speck that was repeatedly showing up in Hubble Space Telescope images of Neptune taken between 2004 and 2009.
“The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system,” Mr Showalter explained.
“It’s the same reason a sports photographer tracks a running athlete – the athlete stays in focus, but the background blurs.”
Nasa said the moon was roughly 100 million times dimmer than the faintest star visible to the naked eye, which serves to explain how it went unnoticed all this while. Combined with the fact that it measures a mere 20 kilometers in diameter and moves really fast completing one revolution in just 23 hours, this rock was really hard to spot.
This illustration shows the approximate location of S/2004 N 1, a tiny new moon of Neptune discovered in Hubble Space Telescope images, with respect to Neptune’s rings and other nearby moons. Don Davis / The New Solar System
Despite all the magnificent advancements in the field, we are still in the infancy of our research on extraterrestrial planets, so it shouldn’t really surprise anybody if a new type of planet is found.
Mysterious dense bodies outside the Solar System which have puzzled astronomers for quite a while may in fact be remnants of Neptune-like planets which went too close to their Sun and got compressed.
NASA’s Kepler space mission to find exoplanets, which launched in 2009 found bodies which appeared to be simply too heavy for their size – the planets in case have radiuses similar to Earth’s, but are denser than pure iron. No conventional planet forming theory can explain this.
“There is no way to explain that in the Solar System,” says Olivier Grasset, a geophysicist at the University of Nantes in France.
Grasset and his team put forth an interesting theory which claims that these planets are actually fossil remains of much larger bodies, which were stripped of their outer, frozen crust – leaving us today with the fossil core.
If these planets were formed far from their stars, but in time, migrated closer to their star – possibly as cloe as Mercury is today, then the hot temperatures of the star would evaporate the outer layers of the planet, which are made mostly from volatile elements (hydrogen, helium and water). The only thing that would remain would be the core (consisting of rock and metal, just like Earth’s) – which is very dense, because during its initial stage (before the outer layers were evaporated) it was formed at about 5 million times atmospheric pressure on Earth and temperatures of approximately 6000 Celsius degrees.
Lars Stixrude, a geologist at University College London, calls the idea “fascinating”, but he does mention that we still don’t understand the behaviour of materials under the extreme temperatures and pressures of an ice-giant core is still incomplete. William Borucki, a space scientist at NASA’s Ames Research Center in Moffett Field, California, and leader of the Kepler mission adds that the theory is plausible, but there are plenty of other ways through which the outer layers could be blasted away. The process could be the result of a cataclysmic collision with another planet-sized object, for example. Either way, the Kepler mission is definitely updating how we understand the Universe we live in.
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 :)