Artist’s impression shows the distant dwarf planet Eris. Credit: ESO
In 2005, astronomer Mike Brown and his colleagues Chad Trujillo and David Rabinowitz announced the discovery of a previously unknown planetoid in the Kuiper Belt beyond Neptune’s orbit. The team named this object Eris after the Greek personification of strife and discord, which was assigned by the IAU a year later. Along with Haumea and Makemake, which they similarly observed in 2004 and 2005 (respectively), this object led to the “Great Planet Debate,” which continues to this day. Meanwhile, astronomers have continued to study the Trans-Neptunian region to learn more about these objects.
While subsequent observations have allowed astronomers to get a better idea of Eris’ size and mass, there are many unresolved questions about the structure of this “dwarf planet” and how it compares to Pluto. In a recent study, Mike Brown and University of California Santa Cruz professor Francis Nimmo presented a series of models based on new mass estimates for Eris’ moon Dysnomia. According to their results, Eris is likely differentiated into a convecting icy shell and rocky core, which sets it apart from Pluto’s conductive shell.
Artist concept of Haumea, with the correct proportions of the main body and the ring. The ring is at a distance of 2287 kilometers from the center of the main body and is darker than the surface of the dwarf planet itself. Credit: Instituto de Astrofísica de Andalucía.
A unique opportunity to study the dwarf planet Haumea has led to an intriguing discovery: Haumea is surrounded by a ring.
Add this to the already long list of unique things about the weird-shaped world with a dizzying rotation and a controversial discovery.
On January 21, 2017 Haumea passed in front of a distant star, in an event known as an occultation. The background star can – pardon the pun – shine a light on the object passing in front, providing information about a distant object — such as size, shape, and density — that is otherwise difficult to obtain. Since an occultation with Haumea had never been observed before, scientists were first eager, and then surprised.
“One of the most interesting and unexpected findings was the discovery of a ring around Haumea,” said said Pablo Santos-Sanz, from the Institute of Astrophysics of Andalusia (IAA-CSIC) in a statement.
This is the first time a ring has been discovered around a trans-neptunian object, and the team said this discovery shows that the presence of rings could be much more common than was previously thought, in our Solar System as well as in other planetary systems.
“Twelve telescopes from ten different European observatories converged on the phenomenon,” said José Luis Ortiz, who led the observational effort, and is also from IAA-CSIC. “This deployment of technical means allowed us to reconstruct with a very high precision the shape and size of dwarf planet Haumea, and discover to our surprise that it is considerably bigger and less reflecting than was previously believed. It is also much less dense than previously thought, which answered questions that had been pending about the object.”
The team said their data shows that the egg-shaped Haumea measures 2,320 kilometers in its largest axis. Previous estimates from various observations put the size at roughly 1,400 km. It takes 3.9 hours for Haumea rotate around its axis, much less than any other body in the Solar System that measures more than a hundred kilometers long. This rotational speed likely caused Haumea to flatten out, giving it an ellipsoid shape. It orbits the Sun in an elliptical loop that takes 284 years to complete. Additionally Haumea has two small moons.
Artist’s impression of the dwarf planet Haumea and its moons, Hi’aka and Namaka. Credit: NASA
Ortiz and team say their data shows the newly discovered ring lies on the equatorial plane of the dwarf planet, and it “displays a 3:1 resonance with respect to the rotation of Haumea, which means that the frozen particles which compose the ring rotate three times slower around the planet than it rotates around its own axis.”
Ortiz says there might be a few possible explanations for the formation of the ring; it may have originated in a collision with another object, or in the dispersal of surface material due to the planet’s high rotational speed.
Of course, other objects in our Solar System have rings: all the giant planets have rings, with Saturn’s being the most massive and well know. But small centaur asteroids located between Jupiter and Neptune were found to have rings, too.
“Now we have discovered that bodies even farther away than the centaurs, bigger and with very different general characteristics, can also have rings,” said Santos-Sanz.
You may recall there was great controversy over the discovery of Haumea. The discovery was originally announced in 2005 by Mike Brown from Caltech, along with his colleagues Chad Trujillo of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz, of Yale University.
But then Ortiz and Santos-Sanz attempted to scoop Brown et. al by sending in their claim to discovery to the Minor Planet Center before Brown’s paper was published. It was later learned that Ortiz and colleagues had accessed the Caltech observing logs remotely, looking at when and where Brown was looking with his telescopes. Ortiz and team initially denied the claims, but later conceded accessing the observation logs, maintaining they were just verifying whether they had discovered a new object in observations from 2003.
I asked Brown today if anything was ever officially resolved about the controversy.
“I think the resolution is that it is generally accepted that they stole our positions, but no one wants to think about it anymore,” he said via email.
But the discovery of a ring Haumea, Brown said, looks solid.
“I will admit to being wary of anything Ortiz says, so I checked the data very carefully,” Brown said. “Even I have to agree that the detection looks pretty solid. Haumea is weird, so it’s less surprising than, say, finding rings around something like Makemake. But, still, this was not something I was expecting!”
Artist's impression of Planet Nine, blocking out the Milky Way. The Sun is in the distance, with the orbit of Neptune shown as a ring. Credit: ESO/Tomruen/nagualdesign
Planet 9 cannot hide forever, and new research has narrowed the range of possible locations further! In January of 2016, astronomers Mike Brown and Konstantin Batygin published the first evidence that there might be another planet in our Solar System. Known as “Planet 9” (“Planet X” to some), this hypothetical body was believed to orbit at an extreme distance from our Sun, as evidenced by the orbits of certain extreme Kuiper Belt Objects (eKBOs).
Since that time, multiple studied have been produced that have attempted to place constraints on Planet 9’s location. The latest study once again comes from Brown and Batygin, who conducted an analytical assessment of all the processes that have indicated the presence of Planet 9 so far. Taken together, these indications show that the existence of this body is not only likely, but also essential to the Solar System as we know it.
The study, titled “Dynamical Evolution Induced by Planet Nine“, recently appeared online and has been accepted for publication in The Astronomical Journal. Whereas previous studies have pointed to the behavior of various populations of KBOs as proof of Planet 9, Brown and Batygin sought to provide a coherent theoretical description of the dynamical mechanisms responsible for these effects.
In the end, they concluded that it would be more difficult to imagine a Solar System without a Planet 9 than with one. As Konstantin Batygin explained in a recent NASA press statement:
“There are now five different lines of observational evidence pointing to the existence of Planet Nine. If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve. All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them.”
In 2016, Brown and Batygin described the first three lines of observational evidence for Planet 9. These include six extreme Kuiper Belt Objects which follow highly elliptical paths around the Sun, which are indicative of an unseen mechanism affecting their orbit. Second is the fact that the orbits of these bodies are all tilted the same way – about 30° “downward” to the plane of the Kuiper Belt.
The third hint came in the form of computer simulations that included Planet 9 as part of the Solar System. Based to these simulations, it was apparent that more objects should be tilted with respect to the Solar plane, on the order of about 90 degrees. Thanks to their research, Brown and Batygin found five such objects that happened to fit this orbital pattern, and suspected that more existed.
Caltech professor Mike Brown and assistant professor Konstanin Batygin have been working together to investigate Planet Nine. Credit: Lance Hayashida/Caltech
Since the publication of the original paper, two more indications have emerged for the existence of Planet 9. Another involved the unexplained orbits of more Kuiper Belt Objects which were found to be orbiting in the opposite direction from everything else in the Solar System. This was a telltale indication that a relatively close body with a powerful gravitational force was affecting their orbits.
And then there was the argument presented in a second paper by the team – which was led by Elizabeth Bailey, Batygin’s graduate student. This study argued that Planet 9 was responsible for tilting the orbits of the Solar planets over the past 4.5 billion years. This not only provided additional evidence for Planet 9, but also answered a long standing mystery in astrophysics – why the planets are tilted 6 degrees relative to the Sun’s equator.
As Batygin indicated, all of this adds up to a solid case for the existence of a yet-to-discovered massive planet in the outer Solar System:
“No other model can explain the weirdness of these high-inclination orbits. It turns out that Planet Nine provides a natural avenue for their generation. These things have been twisted out of the solar system plane with help from Planet Nine and then scattered inward by Neptune.”
A predicted consequence of Planet Nine is that a second set of confined objects (represented in blue) should also exist. Credit: Caltech/R. Hurt (IPAC)
Recent studies have also shed some light on how and where Planet 9 originated. Whereas some suggested that the planet moved to the edge of the Solar System after forming closer to the Sun, others have suggested that it might be an exoplanet that was captured early in the Solar System’s history. At present, the favored theory appears to be that it formed closer to the Sun and migrated outward over time.
Granted, there is not yet a scientific consensus when it comes to Planet 9 and other astronomers have offered other possible explanations for the evidence cited by Batygin and Brown. For instance, a recent analysis based on the Outer Solar System Origins Survey – which discovered more than 800 new Trans-Neptunian Objects (TNOs) – suggests that the evidence could also be consistent with a random distribution of such objects.
In the meantime, all that remains is to find direct evidence of the planet. At present, Batygin and Brown are attempting to do just that, using the Subaru Telescope at the Mauna Kea Observatory in Hawaii. The detection of this planet will not only settle the matter of whether or not it even exists, it will also help resolve a mystery that emerged in recent years thanks to the discovery of thousands of extra-solar planets.
In short, thanks to the discovery of 3,529 confirmed exoplanets in 2,633 solar systems, astronomers have noticed that statistically, the most likely types of planets are “Super-Earths” and “mini-Neptunes” – i.e. planets that are more massive than Earth but not more than about 10 Earth masses. If Planet 9 is confirmed to exist, which is estimated to have 10 times the Mass of Earth, then it could explain this discrepancy.
Planet 9, we know you’re out there and we will find you! Unless you’re not, in which case, disregard this message!
The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the solar system. Batygin and Brown show that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech/R. Hurt (IPAC); [Diagram created using WorldWide Telescope.]
Last year, Caltech astronomers Mike Brown and Konstantin Batygin found indirect evidence for the existence of a large planet in the outer reaches of our Solar System — likely located out past Pluto — and since then, the search has been on. The latest research continues to show signs of an unseen planet, the hypothetical Planet 9.
Astronomers using the Gran Telescopio CANARIAS (GTC) in the Canary Islands looked at two distant asteroids called Extreme Trans Neptunian Objects’ (ETNOs), and spectroscopic observations show and their present-day orbits could be the result of a past interaction with a large “superearth”-type object orbiting the Sun at a distance between 300 to 600 AU.
Researchers say the orbits of asteroids 2004 VN112 and 2013 RF98 suggest that the two were once a binary asteroid which separated after an encounter a large body, with a mass of between 10 and 20 Earth masses.
“The similar spectral gradients observed for the pair 2004 VN112 – 2013 RF98 suggests a common physical origin,” said Julia de León, the first author of a new paper, and who is an astrophysicist at the Instituto de Astrofísica de Canarias (IAC). “We are proposing the possibility that they were previously a binary asteroid which became unbound during an encounter with a more massive object.”
Sequence of images taken with the Gran Telescopio CANARIAS (GTC) to identify one of the ETNO´s studied in this article, 2013 RF98, where one can see how it moves during four consecutive nights. Below, right, visible spectra obtained with the GTC of the two objects 2004 VN112 and 2013 RF98. The red lines show the gradients of the spectra. Credit: Julia de León (IAC).
To test their hypothesis, the team performed thousands of simulations to see how the poles of the orbits would separate as time went on. The results of these simulations suggest that a possible Planet 9 could have separated the pair of asteroids around 5 to 10 million years ago.
de León said this could explain, in principle, how these two asteroids, starting as a pair orbiting one another, became gradually separated in their orbits after an encounter with a much more massive object at a particular moment in time.
The tale of Planet 9 started in 2014, when astronomers Chad Trujillo and Scott Shepard were studying the motions of large objects in the Kuiper Belt and realized that a large planet in the outer Solar System must be altering orbits of several ETNOs the in Kuiper Belt.
Brown and Batygin were looking to verify or refute the research of Trujillo and Shepard, and they painstakingly analyzed the movement of various KBOs. They found that six different objects all seem to follow a very similar elliptical orbit that points back to the same region in space.
All the bodies were found to be inclined at a plane of about 30-degrees different from almost everything else in the Solar System. Brown said the odds of these orbits all occurring randomly are about 1 in 100.
But calculations revealed the orbits could be influenced by a massive planet way out beyond the orbit of Pluto, about 200 times further than the distance from the Sun to the Earth. This planet would be Neptune-sized, roughly 10 times more massive than Earth.
It hasn’t been found yet, but the hunt is on by large telescopes around the world, and a new citizen science project allows people around the world to join in the search.
The latest findings of by de León and team could help point the way to where Planet 9 might be lurking.
Artist concept of Planet 9. Credit: NASA/JPL-Caltech.
Citizen science projects are a great way for anyone to be involved in the scientific process. Average, everyday folks have discovered things like supernovae, previously unseen craters on the Moon and Mars and even new planets orbiting a distant star.
Now, you could be part of one of the most exciting quests yet: finding a mysterious, unseen planet in the far reaches of our own solar system. Last year, Caltech astronomers Mike Brown and Konstantin Batygin found indirect evidence for the existence of a large planet, likely located out past Pluto, and since then, the search has been on. But so far, it has come up empty. And so, astronomers decided they would bring in a little help: You.
“Backyard Worlds: Planet 9 has the potential to unlock once-in-a-century discoveries, and it’s exciting to think they could be spotted first by a citizen scientist,” said UC Berkeley postdoctoral researcher Aaron Meisner, who is helping to head up this latest citizen science project.
A previously cataloged brown dwarf named WISE 0855?0714 shows up as a moving orange dot (upper left) in this loop of WISE images spanning five years. By viewing movies like this, anyone can help discover more brown dwarfs or even a 9th planet. Credit: NASA/WISE.
People who sign on to the Backyard World: Planet 9 website will be basically using the same type of technique that was used to find the last planet discovered in our solar system, Pluto. Clyde Tombaugh used a special machine that systematically switched images on glass astronomical plates back and forth, looking for any objects in the night sky that ‘moved’ between the images.
For Backyard Worlds: Planet 9, users will view brief “flipbook” movies made from images captured by NASA’s Wide-field Infrared Survey Explorer (WISE) mission. A faint spot seen moving through background stars might be a new and distant planet in our solar system. Or it could be a nearby brown dwarf star, which would be another exciting discovery.
WISE’s infrared images cover the entire sky about six times over. This has allowed astronomers to search the images for faint, glowing objects that change position over time, which means they are relatively close to Earth. Objects that produce their own faint infrared glow would have to be large, Neptune-size planets or brown dwarfs, which are slightly smaller than stars. WISE images have already turned up hundreds of previously unknown brown dwarfs, including the objects fairly close to us, so astronomers hope that the Backyard Worlds search will turn up a new nearest neighbor to our sun.
NASA wants to bring in all the humans it can for this search, because the human eye is much better than computers at seeing changes between images.
“Automated searches don’t work well in some regions of the sky, like the plane of the Milky Way galaxy, because there are too many stars, which confuses the search algorithm,” said Meisner.
“There are just over four light-years between Neptune, the farthest known planet in our solar system, and Proxima Centauri, the nearest star, and much of this vast territory is unexplored,” said NASA astronomer Marc Kuchner, the lead researcher and an astrophysicist at NASA’s Goddard Space Flight Center. “Because there’s so little sunlight, even large objects in that region barely shine in visible light. But by looking in the infrared, WISE may have imaged objects we otherwise would have missed.”
At this point, I think the astronomy textbook publishers should just give up. They’d like to tell you how many planets there are in the Solar System, they really would. But astronomers just can’t stop discovering new worlds, and messing up the numbers.
Things were simple when there were only 6 planets. The 5 visible with the unaided eye, and the Earth, of course. Then Uranus was discovered in 1781 by William Herschel, which made it 7. Then a bunch of asteroids, like Ceres, Vesta and Pallas pushed the number into the teens until astronomers realized these were probably a whole new class of objects. Back to 7.
Then Neptune in 1846 by Urbain Le Verrier and Johann Galle, which makes 8. Then Pluto in 1930 and we have our familiar 9.
But astronomy marches onward. Eris was discovered in 2005, which caused astronomers to create a whole new classification of dwarf planet, and ultimately downgrading Pluto. Back to 8.
It seriously looked like 8 was going to be the final number, and the textbook writers could return to their computers for one last update.
A predicted consequence of Planet Nine is that a second set of confined objects should also exist. These objects are forced into positions at right angles to Planet Nine and into orbits that are perpendicular to the plane of the solar system. Five known objects (blue) fit this prediction precisely. Credit: Caltech/R. Hurt (IPAC) [Diagram was created using WorldWide Telescope.]Astronomers, however, had other plans. In 2014, Chad Trujillo and Scott Shepard were studying the motions of large objects in the Kuiper Belt and realized that a large planet in the outer Solar System must be messing with orbits in the region.
This was confirmed and fine tuned by other astronomers, which drew the attention of Mike Brown and Konstantin Batygin. The name Mike Brown might be familiar to you. Perhaps the name, Mike “Pluto Killer” Brown? Mike and his team were the ones who originally discovered Eris, leading to the demotion of Pluto.
Brown and Batygin were looking to find flaws in the research of Trujillo and Shepard, and they painstakingly analyzed the movement of various Kuiper Belt Objects. They found that six different objects all seem to follow a very similar elliptical orbit that points back to the same region in space.
All these worlds are inclined at a plane of about 30-degrees from pretty much everything else in the Solar System. In the words of Mike Brown, the odds of these orbits all occurring like this are about 1 in 100.
Animated diagram showing the spacing of the Solar Systems planet’s, the unusually closely spaced orbits of six of the most distant KBOs, and the possible “Planet 9”. Credit: Caltech/nagualdesign
Instead of a random coincidence, Brown and Batygin think there’s a massive planet way out beyond the orbit of Pluto, about 200 times further than the distance from the Sun to the Earth. This planet would be Neptune-sized, roughly 10 times more massive than Earth.
But why haven’t they actually observed it yet? Based on their calculations, this planet should be bright enough to be visible in mid-range observatories, and definitely within the capabilities of the world’s largest telescopes, like Keck, Palomar, Gemini, and Hubble, of course.
The trick is to know precisely where to look. All of these telescopes can resolve incredibly faint objects, as long as they focus in one tiny spot. But which spot. The entire sky has a lot of tiny spots to look at.
Artist’s impression of Planet Nine, blocking out the Milky Way. The Sun is in the distance, with the orbit of Neptune shown as a ring. Credit: ESO/Tomruen/nagualdesign
Based on the calculations, it appears that Planet 9 is hiding in the plane of the Milky Way, camouflaged by the dense stars of the galaxy. But astronomers will be scanning the skies, and hope a survey will pick it up, anytime now.
But wait a second, does this mean that we’re all going to die? Because I read on the internet and saw some YouTube videos that this is the planet that’s going to crash into the Earth, or flip our poles, or something.
Nope, we’re safe. Like I just said, the best astronomers with the most powerful telescopes in the world and space haven’t been able to turn anything up. While the conspiracy theorists have been threatening up with certain death from Planet X for decades now – supposedly, it’ll arrive any day now.
But it won’t. Assuming it does exist, Planet 9 has been orbiting the Sun for billions of years, way way out beyond the orbit of Pluto. It’s not coming towards us, it’s not throwing objects at us, and it’s definitely not going to usher in the Age of Aquarius.
Once again, we get to watch science in the making. Astronomers are gathering evidence that Planet 9 exists based on its gravitational influence. And if we’re lucky, the actual planet will turn up in the next few years. Then we’ll have 9 planets in the Solar System again.
Titan's dense, hydrocarbon rich atmosphere remains a focal point of scientific research. Credit: NASA
Titan is a moon shrouded in mystery. Despite multiple flybys and surface exploration conducted in the past few decades, this Cronian moon still manages to surprise us from time to time. In addition to having a dense atmosphere rich in hydrocarbons, which scientists believe may be similar to what Earth’s own atmosphere was like billions of years ago, it appears that methane is to Titan what water is to planet Earth.
In addition, methane fog was also observed by the Cassini space probe back in 2009 as it conducted a flyby of Titan. But recent findings by a team of researchers from York University indicates that the Huygens lander also detected fog during its descent towards the surface in 2005. This evidence, combined with the data obtained by Cassini, have helped to shed light on the weather patterns of this mysterious moon.
Based on a careful study of Saturn's orbit and using mathematical models, French scientists were able to whittle down the search region for Planet Nine to "possible" and "probable" zones. Source: CNRS, Cote d'Azur and Paris observatories. Credit:
An imagined view from Planet Nine looking back toward the Sun. Astronomers think the massive, distant planet is gaseous, similar to the other giant planets in our Solar System. Credit: Wikipedia
Last month, planetary scientists Mike Brown and Konstantin Batygin of the California Institute of Technology found evidence of a giant planet tracing a bizarre, highly elongated orbit in the outer Solar System. Nicknamed Planet Nine, it’s estimated to be 10 times more massive than Earth with a diameter as large as 16,000 miles (25,750 km). The putative planet orbits about 20 times farther from the Sun on average than Neptune or some 56 billion miles away; at that tremendous distance it would take between 10,000 and 20,000 years to complete one orbit around the Sun.
The six most distant known objects in the Solar System with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the solar system. Batygin and Brown showed that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech/R. Hurt (IPAC); Diagram created using WorldWide TelescopePlanet Nine’s existence is inferred through mathematical modeling and computer simulations based on the clustering of six remote asteroids in the Kuiper Belt, a vast repository of icy asteroids and comets beyond Neptune. Brown and Batyginsay there’s only a 0.007% chance or about 1 in 15,000 that the clustering could be a coincidence.
All well and good. But with such an enormous orbit, astronomers face the daunting task of searching vast swaths of space for this needle in a haystack. Where to begin? A study done by a team of French scientists may help narrow the search. In a recent paper appearing in Astronomy and Astrophysics, astronomerAgnes Fienga and colleagues looked at what effect a large Kuiper Belt planet would have on the orbits of other planets in the Solar System, focusing their study on Saturn. Thanks to NASA’s Cassini orbiter, which has been orbiting Saturn since 2004, we can precisely calculate Saturn’s position along its orbit.
Based on a careful study of Saturn’s orbit and using mathematical models, French scientists were able to whittle down the search region for Planet Nine to “possible” and “probable” zones. Source: CNRS, Cote d’Azur and Paris observatories , created by the author
Based on the planet’s “residuals”, the difference between the calculated position of Saturn versus what was actually observed, the team was able to exclude two sections of its potential orbit and home in on “probable” swath and a much larger “possible” section of the orbit. The process may sound familiar, since it was the one used to discover another planet more than 150 years ago — Neptune. Back then, irregularities (residuals) in the motion of Uranus led astronomers in 1847 to predict a more distant 8th planet as the cause. On September 24, 1846, Johann Galle discovered Neptune only 1° from its position predicted by French mathematician Urbain LeVerrier.
While the current solution for Planet Nine doesn’t come anywhere near as close, it’s a step in the right direction.
Artist's concept of the hypothetical "Planet Nine." Could it have moons? Credit: NASA/JPL-Caltech/Robert Hurt
Artistic rendering shows the distant view from theoretical Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Credit: Caltech/R. Hurt (IPAC)
The astronomer known worldwide for vigorously promoting the demotion of Pluto from its decades long perch as the 9th Planet, has now found theoretical evidence for a new and very distant gas giant planet lurking way beyond Pluto out to the far reaches of our solar system.
An artist's conception of 2007 OR10, nicknamed Snow White. Astronomers suspect that its rosy color is due to the presence of irradiated methane. [Credit: NASA]
Over the course of the past decade, more and more objects have been discovered within the Trans-Neptunian region. With every new find, we have learned more about the history of our Solar System and the mysteries it holds. At the same time, these finds have forced astronomers to reexamine astronomical conventions that have been in place for decades.
Consider 2007 OR10, a Trans-Neptunian Object (TNO) located within the scattered disc that at one time went by the nicknames of “the seventh dwarf” and “Snow White”. Approximately the same size as Haumea, it is believed to be a dwarf planet, and is currently the largest object in the Solar System that does not have a name.
Discovery and Naming:
2007 OR10 was discovered in 2007 by Meg Schwamb, a PhD candidate at Caltech and a graduate student of Michael Brown, while working out of the Palomar Observatory. The object was colloquially referred to as the “seventh dwarf” (from Snow White and the Seven Dwarfs) since it was the seventh object to be discovered by Brown’s team (after Quaoar in 2002, Sedna in 2003, Haumea and Orcus in 2004, and Makemake and Eris in 2005).
Comparison of Sedna with the other largest TNOs and with Earth (all to scale). Credit: NASA/Lexicon
At the time of its discovery, the object appeared to be very large and very white, which led to Brown giving it the other nickname of “Snow White”. However, subsequent observation has revealed that the planet is actually one of the reddest in the Kuiper Belt, comparable only to Haumea. As a result, the nickname was dropped and the object is still designated as 2007 OR10.
The discovery of 2007 OR10 would not be formally announced until January 7th, 2009.
Size, Mass and Orbit:
A study published in 2011 by Brown – in collaboration with A.J. Burgasser (University of California San Diego) and W.C. Fraser (MIT) – 2007 OR10’s diameter was estimated to be between 1000-1500 km. These estimates were based on photometry data obtained in 2010 using the Magellan Baade Telescope at the Las Campanas Observatory in Chile, and from spectral data obtained by the Hubble Space Telescope.
However, a survey conducted in 2012 by Pablo Santos Sanz et al. of the Trans-Neptunian region produced an estimate of 1280±210 km based on the object’s size, albedo, and thermal properties. Combined with its absolute magnitude and albedo, 2007 OR10 is the largest unnamed object and the fifth brightest TNO in the Solar System. No estimates of its mass have been made as of yet.
2007 OR10 also has a highly eccentric orbit (0.5058) with an inclination of 30.9376°. What this means is that at perihelion, it is roughly 33 AU (4.9 x 109 km/30.67 x 109 mi) from our Sun while at aphelion, it is as distant as 100.66 AU (1.5 x 1010 km/9.36 x 1010 mi). It also has an orbital period of 546.6 years, which means that the last time it was at perihelion was 1857 and it won’t reach aphelion until 2130. As such, it is currently the second-farthest known large body in the Solar System, and will be farther out than both Sedna and Eris by 2045.
Composition:
According to the spectral data obtained by Brown, Burgasser and Fraser, 2007 OR10 shows infrared signatures for both water ice and methane, which indicates that it is likely similar in composition to Quaoar. Concurrent with this, the reddish appearance of 2007 OR10 is believed to be due to presence of tholins in the surface ice, which are caused by the irradiation of methane by ultraviolet radiation.
The presence of red methane frost on the surfaces of both 2007 OR10 and Quaoar is also seen as an indication of the possible existence of a tenuous methane atmosphere, which would slowly evaporate into space when the objects are closer to the Sun. Although 2007 OR10 comes closer to the Sun than Quaoar, and is thus warm enough that a methane atmosphere should evaporate, its larger mass makes retention of an atmosphere just possible.
Also, the presence of water ice on the surface is believed to imply that the object underwent a brief period of cryovolcanism in its distant past. According to Brown, this period would have been responsible not only for water ice freezing on the surface, but for the creation of an atmosphere that included nitrogen and carbon monoxide. These would have been depleted rather quickly, and a tenuous atmosphere of methane would be all that remains today.
However, more data is required before astronomers can say for sure whether or not 2007 OR10 has an atmosphere, a history of cryovolcanism, and what its interior looks like. Like other KBOs, it is possible that it is differentiated between a mantle of ices and a rocky core. Assuming that there is sufficient antifreeze, or due to the decay of radioactive elements, there may even be a liquid-water ocean at the core-mantle boundary.
Classification:
Though it is too difficult to resolve 2007 OR10’s size based on direct observation, based on calculations of 2007 OR10’s albedo and absolute magnitude, many astronomers believe it to be of sufficient size to have achieved hydrostatic equilibrium. As Brown stated in 2011, 2007 OR10 “must be a dwarf planet even if predominantly rocky”, which is based on a minimum possible diameter of 552 km and what is believed to be the conditions under which hydrostatic equilibrium occurs in cold icy-rock bodies.
That same year, Scott S. Sheppard and his team (which included Chad Trujillo) conducted a survey of bright KBOs (including 2007 OR10) using the Palomar Observatory’s 48 inch Schmidt telescope. According to their findings, they determined that “[a]ssuming moderate albedos, several of the new discoveries from this survey could be in hydrostatic equilibrium and thus could be considered dwarf planets.”
Currently, nothing is known of 2007 OR10’s mass, which is a major factor when determining if a body has achieved hydrostatic equilibrium. This is due in part to there being no known satellite(s) in orbit of the object, which in turn is a major factor in determining the mass of a system. Meanwhile, the IAU has not addressed the possibility of accepting additional dwarf planets since before the discovery of 2007 OR10 was announced.
Alas, much remains to be learned about 2007 OR10. Much like it’s Trans-Neptunian neighbors and fellow KBOs, a lot will depend on future missions and observations being able to learn more about its size, mass, composition, and whether or not it has any satellites. However, given its extreme distance and fact that it is currently moving further and further away, opportunities to observe and explore it via flybys will be limited.
However, if all goes well, this potential dwarf planet could be joining the ranks of such bodies as Pluto, Eris, Ceres, Haumea and Makemake in the not-too-distant future. And with luck, it will be given a name that actually sticks!
![A predicted consequence of Planet Nine is that a second set of confined objects should also exist. These objects are forced into positions at right angles to Planet Nine and into orbits that are perpendicular to the plane of the solar system. Five known objects (blue) fit this prediction precisely. Credit: Caltech/R. Hurt (IPAC) [Diagram was created using WorldWide Telescope.]](https://www.universetoday.com/wp-content/uploads/2016/01/p9_kbo_extras_orbits_2_1-580x326.jpg)
