Oh Planet Nine, when will you stop toying with us?
Whether you call it Planet Nine, Planet X, the Perturber, Jehoshaphat, “Phattie,” or any of the other proposed names—either serious or flippant—this scientific back and forth over its existence is getting exhausting.
Is this what it was like when they were arguing whether Earth is flat or round?
What’s going on in the distant reaches of our Solar System? Is there a Planet 9 out there?
Out in the frigid expanse of our System, there are bodies on orbital paths that don’t make sense in terms of our eight-planet Solar System. There seems to be an undiscovered body out there, several times more massive than Earth, shaping the orbits of some Kuiper Belt Objects (KBOs), and driving astronomers to look deeper and more thoroughly into the extreme reaches of our System.
What they’re looking for is the mysterious, and so far unproven, ninth planet.
Remember Far Out, the distant planet at the far reaches of the Solar System, that was discovered in December, 2018? Well, it has been kicked unceremoniously off its pedestal as the most distant object after a short, two-month reign. In its place is the very newly-discovered FarFarOut (FFO.)
And if it weren’t for a heavy snowfall, things might have turned out differently.
Is there or isn’t there a Planet 9? Is there a planet way out on the outskirts of our Solar System, with sufficient mass to explain the movements of distant objects? Or is a disc of icy material responsible? There’s no direct evidence yet of an actual Planet 9, but something with sufficient mass is affecting the orbits of distant Solar System objects.
A new study suggests that a disc of icy material causes the strange movements of outer Solar System objects, and that we don’t need to invent another planet to explain those movements. The study comes from Professor Jihad Touma, from the American University of Beirut, and Antranik Sefilian, a PhD student in Cambridge’s Department of Applied Mathematics and Theoretical Physics. Their results are published in the Astronomical Journal.
Astronomers have found a new dwarf planet way out beyond Pluto that never gets closer than 65 AUs to the Sun. It’s nicknamed “The Goblin” which is much more interesting than its science name, 2015 TG387. The Goblin’s orbit is consistent with the much-talked-about but yet-to-be-proven Planet 9.
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” (or “Planet X”, to those who contest the controversial 2006 Resolution by the IAU), this hypothetical body was believed to orbit at an extreme distance from our Sun, as evidenced by the fact that certain Trans-Neptunian Objects (TNOs) all seem to be pointing in the same direction.
Since that time, other lines of evidence have emerged that have bolstered the existence of Planet 9/Planet X. However, a team of researchers from CU Boulder recently proposed an alternative explanation. According to their research, it could be interactions between Kuiper Belt Objects (KBOs) themselves that might explain the strange dynamics of “detached objects” at the edge of the Solar System.
The researchers presented their findings at the 232nd meeting of the American Astronomical Society, which ran from June 3-7 in Denver, Colorado. The presentation took place on June 4th during a press conference titled “Minor Planets, Dwarf Planets & Exoplanets”. The research was led Jacob Fleisig, an undergraduate studying astrophysics at CU Boulder, and included Ann-Marie Madigan and Alexander Zderic – an assistant professor and a graduate student at CU Boulder, respectively.
For the sake of their study, the team focused on icy bodies like Sedna, a minor planet that orbits the Sun at a distance ranging from 76 AU at perihelion to 936 AU at aphelion. Along with a handful of other objects at this distance, such as Eris, Sedna appears to be separated from the rest of the Solar System – something which astronomers have struggled to explain ever since it was discovered.
Sedna was also discovered by Michael Brown who, along with Chad Trujillo of the Gemini Observatory and David Rabinowitz of Yale University, spotted it on November 14th, 2003, while conducting a survey of the Kuiper Belt. In addition to orbiting our Sun with a period of over 11,000 years, this minor planet and other detached objects has a huge, elliptical orbit.
What’s more, this orbit does not take them Sedna or these other objects anywhere near to Neptune or any other gas giant. Unlike Pluto and other Trans-Neptunian Objects (TNOs), it is therefore a mystery how they achieved their current orbits. The possible existence of a as-yet-undiscovered planet (Planet 9/Planet X), which would be about 10 times the size of Earth, is one hypothetical explanation.
After years of searching for this planet and attempting to determine where its orbit would take it, astronomers have yet to find Planet 9/Planet X. However, as Prof. Madigan explained in a recent CU Boulder press release, there is another possible explanation for the gravitational weirdness going on out there:
“There are so many of these bodies out there. What does their collective gravity do? We can solve a lot of these problems by just taking into account that question… Once you get further away from Neptune, things don’t make any sense, which is really exciting.”
While Madigan and her team did not originally set out to find another explanation for the orbits of “detached objects”, they ended up pursuing the possibility thanks to Jacob Fleisig’s computer modelling. While developing simulations to explore the dynamics of the detached objects, he noticed something very interesting about the region of space they occupy.
Having calculated the orbits of icy objects beyond Neptune, Fleisig and the rest of the team noticed that different objects behave much like the different hands on a clock. Whereas asteroids move like the minute hand (relatively fast and in tandem), larger objects like Sedna move more slowly like the hour hand. Eventually, the hands intersect. As Fleisig explained:
“You see a pileup of the orbits of smaller objects to one side of the sun. These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape.”
What Fleisig’s computer model showed was that Sedna’s orbit goes from normal to detached as a result of those small-scale interactions. It also showed that the larger the detached object, the farther it gets away from the Sun – something which agrees with previous research and observations. In addition to explaining why Sedna and similar bodies behave the way they do, these findings may provide clues to another major event in Earth’s history.
This would be what caused the extinction of the dinosaurs. Astronomers have understood for a long time that the dynamics of the outer Solar System often end up sending comets towards the inner Solar System on a predictable timescale. This is the result of icy objects interacting with each other, which causes their orbits to tighten and widen in a repeating cycle.
And while the team is not able to say that this pattern was responsible for the impact that caused the Cretaceous–Paleogene extinction event (which resulted in the extinction of the dinosaurs 66 million years ago), it is a fascinating possibility. In the meantime, the research has shown just how fascinating the outer Solar System is, and how much remains to be learned about it.
“The picture we draw of the outer solar system in textbooks may have to change,” said Madigan. “There’s a lot more stuff out there than we once thought, which is really cool.”
The research was made possible thanks to the support of the NASA Solar System Workings and the Rocky Mountain Advanced Computing Consortium Summit Supercomputer.
In the past few decades, thanks to improvements in ground-based and space-based observatories, astronomers have discovered thousands of planets orbiting neighboring and distant stars (aka. extrasolar planets). Strangely enough, it is these same improvements, and during the same time period, that enabled the discovery of more astronomical bodies within the Solar System.
These include the “minor planets” of Eris, Sedna, Haumea, Makemake, and others, but also the hypothesized planetary-mass objects collectively known as Planet 9 (or Planet X). In a new study led by Northern Arizona University and the Lowell Observatory, a team of researchers hypothesize that the Large Synoptic Survey Telescope (LSST) – a next-generation telescope that will go online in 2022 – has a good chance of finding this mysterious planet.
Their study, titled “On the detectability of Planet X with LSST“, recently appeared online. The study was led by David E. Trilling, an astrophysicist from the Northern Arizona University and the Lowell Observatory, and included Eric C. Bellm from the University of Washington and Renu Malhotra of the Lunar and Planetary Laboratory at The University of Arizona.
Located on the Cerro Pachón ridge in north-central Chile, the 8.4-meter LSST will conduct a 10-year survey of the sky that will deliver 200 petabytes worth of images and data that will address some of the most pressing questions about the structure and evolution of the Universe and the objects in it. In addition to surveying the early Universe in order to understand the nature of dark matter and dark energy, it will also conduct surveys of the remote areas of the Solar System.
Planet 9/X is one such object. In recent years, the existence of two planetary-mass bodies have been hypothesized to explain the orbital distribution of distant Kuiper Belt Objects. While neither planet is thought to be exceptionally faint, the sky locations of these planets are poorly constrained – making them difficult to pinpoint. As such, a wide area survey is needed to detect these possible planets.
In 2022, the LSST will carry out an unbiased, large and deep survey of the southern sky, which makes it an important tool when it comes to the search of these hypothesized planets. As they state in their study:
“The possibility of undiscovered planets in the solar system has long fascinated astronomers and the public alike. Recent studies of the orbital properties of very distant Kuiper belt objects (KBOs) have identified several anomalies that may be due to the gravitational influence of one or more undiscovered planetary mass objects orbiting the Sun at distances comparable to the distant KBOs.
These studies include Trujillo & Sheppard’s 2014 study where they noticed similarities in the orbits of distant Trans-Neptunian Objects (TNOs) and postulated that a massive object was likely influencing them. This was followed by a 2016 study by Sheppard & Trujillo where they suggested that the high perihelion objects Sedna and 2012 VP113 were being influence by an unknown massive planet.
This was followed in 2016 by Konstantin Batygin and Michael E. Brown of Caltech suggesting that an undiscovered planet was the culprit. Finally, Malhotra et al. (2016) noted that the most distant KBOs have near-integer period ratios, which was suggestive of a dynamical resonance with a massive object in the outer Solar System. Between these studies, various mass and distance estimates were formed that became the basis of the search for this planet.
Overall, these estimates indicated that Planet 9/X was a super-Earth with anywhere between 5 to 20 Earth masses, and orbited the Sun at a distance of between 150 – 600 AU. Concurrently, these studies have also attempted to narrow down where this Super-Earth’s orbit will take it throughout the outer Solar System, as evidenced by the perturbations it has on KBOs.
Unfortunately, the predicted locations and brightness of the object are not yet sufficiently constrained for astronomers to simply look in the right place at the right time and pick it out. In this respect, a large area sky survey must be carried out using moderately large telescopes with a very wide field of view. As Dr. Trilling told Universe Today via email:
“The predicted Planet X candidates are not particularly faint, but the possible locations on the sky are not very well constrained at all. Therefore, what you really need to find Planet X is a medium-depth telescope that covers a huge amount of sky. This is exactly LSST. LSST’s sensitivity will be sufficient to find Planet X in almost all its (their) predicted configurations, and LSST will cover around half of the known sky to this depth. Furthermore, the cadence is well-matched to finding moving objects, and the data processing systems are very advanced. If you were going to design a tool to find Planet X, LSST is what you would design.”
However, the team also acknowledges that within certain parameters, Planet 9/X may not be detectable by the LSST. For example, it is possible that that there is a very narrow slice of predicted Planet 9/X parameters where it might be slightly too faint to be easily detected in LSST data. In addition, there is also a small possibility that irregularities in the Planet 9/X cadence might lead to it being missed.
There is the even the unlikely ways in which Planet 9/X could go undetected in LSST data, which would come down to a simple case of bad luck. However, as Dr. Trilling indicated, the team is prepared for these possibilities and is hopeful they will find Planet 9/X, assuming there’s anything to find:
“The more likely conclusion if planet X is not detected in LSST data is that planet X doesn’t exist – or at least not the kind of planet X that has been predicted. In this case, we’ve got to work harder to understand how the Universe created this pattern of orbits in the outer Solar System that I described above. This is a really fun part of science: make a prediction and test it, and find that the result is rarely what is predicted. So now we’ve got to work harder to understand the universe. Hopefully this new understanding makes new predictions that we then can test, and we repeat the cycle.”
The existence of Planet 9/X has been one of the more burning questions for astronomers in recent years. If its existence can be confirmed, astronomers may finally have a complete picture of the Solar System and its dynamics. If it’s existence can be ruled out, this will raise a whole new series of questions about what is going on in the Outer Solar System!
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 those who reject the controversial 2006 Resolution by the IAU), this hypothetical body was believed to orbit at an extreme distance from our Sun, as evidenced by the fact that certain Trans-Neptunian Objects (TNOs) all seem to be pointing in the same direction.
Since that time, more and more evidence has been produced that show how the presence of Planet 9 affected the evolution of the Solar System, leading it to become as it is today. For example, a recent study by a team of researchers from the University of Michigan has shown how Planet 9 may have kept certain TNOs from being destroyed or ejected from the Solar System over the course of billions of years.
For the sake of their study, Becker and her colleagues conducted a large set of computer simulations that examined the stability of Trans-Neptunian Objects (TNOs) who’s orbits are believed to have been influenced by Planet 9. In each simulation, the researchers tested a different version of Planet 9 to see if its gravitational influence would result in the Solar System as we know it today.
From this, they uncovered two key findings. First, the simulations showed that Planet 9 may have led to the current Solar System by preventing these TNOs from being destroyed or ejected from the Solar System. Second, the simulations indicated that TNOs can jump between stable orbits, a process they refer to as “resonance hopping”. This would prevent these same TNOs from being thrown out of the Kuiper Belt.
“From that set of simulations, we found out that there are preferred versions of Planet Nine that make the TNO stay stable for longer, so it basically increases the probability that our solar system exists the way it does. Through these computer simulations, we were able to determine which realization of Planet Nine creates our solar system—the whole caveat here being, if Planet Nine is real.”
Next, Becker and her team examined the TNOs to see if they experienced resonance with Planet 9. This phenomena, which occurs as a result of objects exerting a gravitational influence on each other, causes them to line up in a pattern. What they found was that, on occasion, Neptune will push a TNOs out of its orbital resonance, but does not disturb it enough to send it towards the Sun.
A plausible explanation for this behavior was the gravitational influence of another object, which serves to catch any TNOs and confine them to a different resonance. In addition, the team also considered a newly-discovered TNO that was recently detected by The Dark Energy Survey collaboration – a group of 400 scientist from 26 institutions in seven countries, which includes several members from the University of Michigan.
This object has a high orbital inclination compared to the plane of the Solar System, where it is tilted at 54° relative to the Sun’s ecliptic. After analyzing this new object, Becker and team concluded that the object also experiences resonance hopping, which is consistent with the existence of Planet 9. This, along with other recent studies, are creating a picture where it is harder to imagine the Solar System without Planet 9 than with it.
As Becker explained, all that remains now is to observe Planet 9 directly.”The ultimate goal would be to directly see Planet Nine—to take a telescope, point it at the sky, and see reflected light from the sun bouncing off of Planet Nine,” she said. “Since we haven’t yet been able to find it, despite many people looking, we’re stuck with these kinds of indirect methods.”
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.
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.”
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!
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”, this hypothetical body was believed to orbit at an extreme distance from our Sun. Since that time, multiple studies have been produced that have had tried to address the all-important question of where Planet 9 could have come from.
Whereas some studies have 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. A recent study by a team of astronomers has cast doubt on this latter possibility, however, and indicates that Planet 9 likely formed closer to the Sun and migrated outward during its history.
Their study, titled “Was Planet 9 Captured in the Sun’s Natal Star-Forming Region?“, recently appeared in the Monthly Notices of the Royal Astronomical Society. The team was led by Dr. Richard Parker from the University of Sheffield’s Department of Physics and Astronomy, with colleagues from ETH Zurich. Together, they conducted simulations that cast doubt on the “capture” scenario.
The existence of Planet 9 (or Planet X, for those who maintain that Pluto is still a planet) was first suggested in 2014 by astronomers Chad Trujillo and Scott S. Sheppard, based on the unusual behavior of certain populations of extreme Trans-Neptunian Objects (eTNOs). From a number of studies that took place over the next few years, constraints were gradually placed on the basic parameters of this planet.
Essentially, Planet 9 is believed to be at least ten times as massive as Earth and two to four times the size. It also believed to have a highly elliptical orbit around the Sun, at an average distance (semi-major axis) of approximately 700 AU and ranging from about 200 AU at perihelion to 1200 AU at aphelion. Last, but not least, scientists have estimated that Planet 9 takes between 10,000 and 20,000 years to complete a single orbit of the Sun.
Because of this, it appears unlikely that Planet 9 could have formed in its current location. Hence why astronomers have argued that it either formed closer to the Sun or was captured from another star system billions of years ago. As Dr. Parker explained in University of Sheffield press statement:
“We know that planetary systems form at the same time as stars, and when stars are very young they are usually found in groups where interactions between stellar siblings are common. Therefore, the environment where stars form directly affects planetary systems like our own, and is usually so densely populated that stars can capture other stars or planets.”
For the sake of their study, the team conducted simulations of the Solar System when it was still in its “nursery” phase – i.e. in the early process of formation. While interactions with other star systems (and their planets) are known to be common in this period, the team found that even where conditions were optimized for the sake of capturing free-floating planets, the odds of Planet 9 being captured were quite low.
Overall, their simulations indicated that with an orbit like that of Planet 9, only 5 to 10 planets out of 10,000 would be captured when the Solar System was still young. In short, the likelihood that Planet 9 could have been booted out of another star system and captured by our Sun was a paltry 1 out of a 1,000 to 2,000. Not exactly betting odds! As Dr. Parker summarized:
“In this work, we have shown that – although capture is common – ensnaring planets onto the postulated orbit of Planet 9 is very improbable. We’re not ruling out the idea of Planet 9, but instead we’re saying that it must have formed around the sun, rather than captured from another planetary system.”
If Planet 9 was not captured, then there remains only one possibility: ut formed closer to our Sun and gradually migrated beyond the orbit of Neptune, reaching distances occupied only by the most extreme Kuiper Belt Objects. And while the hunt of this elusive and mysterious planet is ongoing, any research which places additional constraints on its characteristics and origin are extremely useful.
By ruling out different scenarios in which the planet formed, researchers are also raising new questions about the history and evolution of our Solar System. From when did all the planets we know come from? Did they form in their current orbits, or did migration play a role? These and other questions are sure to be raised and addressed as we close in on Planet 9.