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Astronomie - Die Suche nach Planet 9 -Update

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10.02.2016

The Kuiper Belt is a massive collection of dwarf planet and asteroid-sized worlds orbiting far past Neptune. Is the hypothetical Planet 9 really a second such belt? Image Credit: T. Pyle (SSC)/JPL-Caltech/NASA

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The announcement of a possible large ninth planet in our Solar System way beyond Neptune last month caused a lot of excitement, needless to say. If confirmed, it may be similar to “super-Earth” type exoplanets which have been found to be plentiful around other stars, although none, that we knew of, around ours. At this point, however, it is still a well-presented theory. Now, there’s another possibility which has been offered to explain the weird orbits of some of the small Kuiper Belt objects – not a large planet, but rather a second Kuiper Belt consisting of many smaller objects instead.
The new findings have been presented by researchers Ann-Marie Madigan and Michael McCourt at Harvard University, who suggest that “Planet 9” may really be ““a new Kuiper Belt that’s far more massive than the current-day Kuiper Belt, at larger distances, and preferentially lifted off the plane of the major planets,” as noted in New Universe Daily. The theory will be published soon in the Monthly Notices of the Royal Astronomical Society.
The hypothesis is similar to the ninth planet one in that it says that there must be more mass farther out in the Solar System to account for the odd orbits of some of the Kuiper Belt objects. But whether that mass is one larger planet or several, or more, smaller ones, isn’t known yet. The new theory says that multiple smaller objects, like those found in the known Kuiper Belt, are more likely than one larger planet.
“We need more mass in the outer Solar System,” Madigan said. “So it can either come from having more minor planets, and their self-gravity will do this to themselves naturally, or it could be in the form of one single massive planet – a Planet Nine. So it’s a really exciting time, and we’re going to discover one or the other.”
The theorized Planet 9 hasn’t actually been seen yet, it’s existence was inferred from the data about the strange orbits of six Kuiper Belt objects. As Madigan noted in Space.com, the “argument of perihelion,” of those objects, the ratio of how much they pitch (wobble forward or backward) to how much they roll (move left or right) as they orbit the Sun, should be random, but in this case, they’re not. She compared them to several boats moving across San Francisco Bay, all pitching and rolling in the same direction at the same time.
“That would be really strange,” she said. “And so this is why it’s so strange that these minor planets in the outer Solar System are doing this.”
Since the movements are not as random as they should be, something must be gravitationally influencing them. That’s where the two different theories come in.
Madigan and McCourt suggest that the objects in the second theorized Kuiper Belt could “self-organize” by pushing and pulling on each other. The resulting odd orbits would have been shaped within the first 600 million years of the Solar System’s birth, if there was at least the equivalent of the Earth’s mass among the separate objects.
“So we really need that much mass in minor planets for this to happen in the Solar System,” Madigan said. “If there was much less mass, this wouldn’t occur [with]in the age of the Solar System.”
If this model is accurate, it would imply the existence of a second Kuiper Belt, farther out and more massive than the one we already know about.
“We should have a new Kuiper Belt that’s far more massive than the current-day Kuiper Belt, at larger distances, and preferentially lifted off the plane of the major planets,” Madigan said.
Konstantin Batygin and Mike Brown at Caltech, who announced the possible Planet 9 discovery last month, say they considered this possibility of additional small objects, but still favor the larger planet hypothesis.
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Diagram of the Kuiper Belt, out past the orbit of Neptune. Is there also a second massive Kuiper Belt even further out? The red line depicts the path of the New Horizons spacecraft. Image Credit: The Johns Hopkins University Applied Physics Laboratory LLC
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As they mentioned in Space.com, “To this end, it is worth noting that although the primordial planetesimal disk of the Solar System likely comprised tens of Earth masses, the vast majority of this material was ejected from the system by close encounters with the giant planets during, and immediately following, the transient dynamical instability that shaped the Kuiper Belt in the first place,” they said. “The characteristic timescale for depletion of the primordial disk is likely to be short compared with the timescale for the onset of the inclination, calling into question whether the inclination instability could have actually proceeded in the outer solar system,” they added.
Basically, they propose, there aren’t enough smaller bodies left from the Solar System’s formation to account for the findings.
“We need more mass in the outer Solar System,” Madigan said. “So it can either come from having more minor planets, and their self-gravity will do this to themselves naturally, or it could be in the form of one single massive planet – a Planet Nine. So it’s a really exciting time, and we’re going to discover one or the other.”
In the meantime, Batygin and Brown are still confident in their Planet 9 interpretation.
“Although we were initially quite skeptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we become increasingly convinced that it is out there,” said Batygin, an assistant professor of planetary science. “For the first time in over 150 years, there is solid evidence that the Solar System’s planetary census is incomplete.”
As Brown had also surmised in Nature, “If I read this paper out of the blue, my first reaction would be that it was crazy. But if you look at the evidence and statistics, it’s very hard to come away with any other conclusion.”
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Diagram of the orbits of the six Kuiper Belt objects from the first study, along with the calculated orbit of Planet 9. Image Credit: Caltech/R. Hurt
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Their findings are in the new paper “Evidence for a Distant Giant Planet in the Solar System,” which is in the current issue of the Astronomical Journal.
If Planet 9 actually does exist, it would impact how astronomers view our Solar System. The Caltech study suggests it is about 10 times more massive than Earth, making it larger than Earth but smaller than Uranus or Neptune, and orbits about 20 times farther from the Sun than Neptune. Many such worlds, so-called “super-Earths,” are being found orbiting other stars, which has led to the question of why our Solar System doesn’t have one also. Or does it, after all? Is our Solar System more similar to those other ones than previously thought, or is it just weirdly different? Discovering the true nature of Planet 9, whether a planet or a large collection of much smaller worlds, will help astronomers understand this question better. Of course, many people still consider Pluto to be the ninth planet, but that is an entire debate in itself.
The New Horizons spacecraft is presently in the Kuiper Belt, having long passed Pluto and now en route to its next destination, the much smaller Kuiper Belt object called 2014 MU69, which it is due to reach on Jan. 1, 2019. Even then, it is still a very long ways from either the second Kuiper Belt or ninth planet.
Astronomers will now be using large telescopes such as the Subaru Telescope in Hawaii to try to actually image Planet 9, and should be able to, if it’s there. Conversely, other surveys will search for the putative second Kuiper Belt. Whichever theory turns out to be the correct one, with a current lack of other possibilities, it will be a very interesting discovery. There have been various searches and claims before which never panned out, but the evidence for something else out there this time around is compelling.
Quelle: AS
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Update: 6.04.2016
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Mysterious Gravitational Tug on Orbiter May Help Find Planet Nine

Astronomers are homing in on the whereabouts of a hidden giant planet in our solar system, and could discover the unseen beast in roughly a year

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Artist's impression of Planet Nine as an ice giant eclipsing the central Milky Way, with a starlike sun in the distance. Neptune's orbit is shown as a small ellipse around the sun.
Tomruen/Wikimedia Commons, CC BY-SA 4.0
The hunt is on to find “Planet Nine”—a large undiscovered world, perhaps 10 times as massive as Earth and four times its size—that scientists think could be lurking in the outer solar system. After Konstantin Batygin and Mike Brown, two planetary scientists from the California Institute of Technology, presented evidence for its existence this January, other teams have searched for further proof by analyzing archived images and proposing new observations to find it with the world’s largest telescopes.
Just this month, evidence from the Cassini spacecraft orbiting Saturn helped close in on the missing planet. Many experts suspect that within as little as a year someone will spot the unseen world, which would be a monumental discovery that changes the way we view our solar system and our place in the cosmos. “Evidence is mounting that something unusual is out there—there's a story that's hard to explain with just the standard picture,” says David Gerdes, a cosmologist at the University of Michigan who never expected to find himself working on Planet Nine. He is just one of many scientists who leapt at the chance to prove—or disprove—the team’s careful calculations.
Batygin and Brown made the case for Planet Nine’s existence based on its gravitational effect on several Kuiper Belt objects—icy bodies that circle the sun beyond Neptune’s orbit. Theoretically, though, its gravity should also tug slightly on the planets, moons and even any orbiting spacecraft. With this in mind, Agnès Fienga at the Côte d’Azur Observatory in France and her colleagues checked whether a theoretical model (one that they have been perfecting for over a decade) with the new addition of Planet Nine could better explain slight perturbations seen in Cassini’s orbit. Without it, the eight planets in the solar system, 200 asteroids and five of the most massive Kuiper Belt objects cannot perfectly account for it. The missing puzzle piece might just be a ninth planet.
So Fienga and her colleagues compared the updated model, which placed Planet Nine at various points in its hypothetical orbit, with the data. They found a sweet spot—with Planet Nine 600 astronomical units (about 90 billion kilometers) away toward the constellation Cetus—that can explain Cassini’s orbit quite well. Although Fienga is not yet convinced that she has found the culprit for the probe’s odd movements, most outside experts are blown away. “It’s a brilliant analysis,” says Greg Laughlin, an astronomer at Lick Observatory, who was not involved in the study. “It’s completely amazing that they were able to do that so quickly.” Gerdes agrees: “That’s a beautiful paper.”
The good news does not end there. If Planet Nine is located toward the constellation Cetus, then it could be picked up by the Dark Energy Survey, a Southern Hemisphere observation project designed to probe the acceleration of the universe. “It turns out fortuitously that the favored region from Cassini is smack dab in the middle of our survey footprint,” says Gerdes, who is working on the cosmology survey. “We could not have designed our survey any better.” Although the survey was not planned to search for solar system objects, Gerdes has discovered some (including one of the icy objects that led Batygin and Brown to conclude Planet Nine exists in the first place).
Laughlin thinks this survey has the best immediate chance of success. He is also excited by the fact that Planet Nine could be so close. Although 600 AUs—roughly 15 times the average distance to Pluto—does sound far, Planet Nine could theoretically hide as far away as 1,200 AUs. “That makes it twice as easy to get to, twice as soon,” Laughlin says. “And not just twice as bright but 16 times as bright.”
And the Dark Energy Survey is not the only chance to catch the faint world. It should be possible to look for the millimeter-wavelength light the planet radiates from its own internal heat. Such a search was proposed by Nicolas Cowan, an exoplanet astronomer at McGill University in Montreal, who thinks that Planet Nine might show up in surveys of the cosmic microwave background (CMB), the pervasive afterglow of the big bang. “CMB experiments have historically used solar system giant planets to calibrate their instruments, so we know that current and planned CMB experiments are sensitive enough to measure the flux from Planet Nine if it is as bright as we think it is,” Cowan says.
Already, cosmologists have started to comb through data from existing experiments, and astronomers with many different specialties have also joined in on the search. “I love that we can take this four-meter telescope and find a rock 100 kilometers in diameter that is a billion kilometers past Neptune with the same instrument that we are using to do extragalactic stuff and understand the acceleration of the universe,” Gerdes says.
In the meantime Batygin and Brown are proposing a dedicated survey of their own. In a recent study they searched through various sky maps to determine where Planet Nine cannot be. “We dumpster-dived into the existing observational data to search for Planet Nine, and because we didn't find it we were able to rule out parts of the orbit,” Batygin says. The zone where the planet makes its farthest swing from the sun as well as the small slice of sky where Fienga thinks the planet could be now, for example, have not been canvassed by previous observations. To search the unmapped zones, Batygin and Brown have asked for roughly 20 observing nights on the Subaru Telescope on Mauna Kea in Hawaii. “It's a pretty big request compared to what other people generally get on the telescope,” Brown says. “We'll see if they bite.” If they do, Brown is convinced he will have his planet within a year.
“I really want to see what it looks like,” says Batygin, who adds that his aspiration drives him to search for the unseen world. But Laughlin takes it a step further: “I think [the discovery] would provide amazing inspiration for the next stage of planetary exploration,” he says. We now have another opportunity to see one of the worlds of our own solar system for the first time. “If Planet Nine isn't out there, we won't have that experience again.”
Quelle: Scientific America
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Update: 9.04.2016
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Saturn Spacecraft Not Affected by Hypothetical Planet 9

Saturn as seen by NASA's Cassini spacecraft in 2008. Long-term tracking of the spacecraft's position has revealed no unexplained perturbations in Cassini's orbit.
Credits: NASA/JPL/Space Science Institute
Full image and caption
Contrary to recent reports, NASA's Cassini spacecraft is not experiencing unexplained deviations in its orbit around Saturn, according to mission managers and orbit determination experts at NASA's Jet Propulsion Laboratory in Pasadena, California.
Several recent news stories have reported that a mysterious anomaly in Cassini's orbit could potentially be explained by the gravitational tug of a theorized massive new planet in our solar system, lurking far beyond the orbit of Neptune. While the proposed planet's existence may eventually be confirmed by other means, mission navigators have observed no unexplained deviations in the spacecraft's orbit since its arrival there in 2004.
"An undiscovered planet outside the orbit of Neptune, 10 times the mass of Earth, would affect the orbit of Saturn, not Cassini," said William Folkner, a planetary scientist at JPL. Folkner develops planetary orbit information used for NASA's high-precision spacecraft navigation. "This could produce a signature in the measurements of Cassini while in orbit about Saturn if the planet was close enough to the sun. But we do not see any unexplained signature above the level of the measurement noise in Cassini data taken from 2004 to 2016."
A recent paper predicts that, if data tracking Cassini's position were available out to the year 2020, they might be used to reveal a "most probable" location for the new planet in its long orbit around the sun. However, Cassini's mission is planned to end in late 2017, when the spacecraft -- too low on fuel to continue on a longer mission -- will plunge into Saturn's atmosphere.
"Although we'd love it if Cassini could help detect a new planet in the solar system, we do not see any perturbations in our orbit that we cannot explain with our current models," said Earl Maize, Cassini project manager at JPL.
The Cassini-Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington.
Quelle: NASA
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Update: 4.05.2016
 
Planet Nine: A World That Shouldn't Exist
Cambridge, MA -Earlier this year scientists presented evidence for Planet Nine, a Neptune-mass planet in an elliptical orbit 10 times farther from our Sun than Pluto. Since then theorists have puzzled over how this planet could end up in such a distant orbit.
New research by astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) examines a number of scenarios and finds that most of them have low probabilities. Therefore, the presence of Planet Nine remains a bit of a mystery.
"The evidence points to Planet Nine existing, but we can't explain for certain how it was produced," says CfA astronomer Gongjie Li, lead author on a paper accepted for publication in the Astrophysical Journal Letters.
Planet Nine circles our Sun at a distance of about 40 billion to 140 billion miles, or 400 - 1500 astronomical units. (An astronomical unit or A.U. is the average distance of the Earth from the Sun, or 93 million miles.) This places it far beyond all the other planets in our solar system. The question becomes: did it form there, or did it form elsewhere and land in its unusual orbit later?
Li and her co-author Fred Adams (University of Michigan) conducted millions of computer simulations in order to consider three possibilities. The first and most likely involves a passing star that tugs Planet Nine outward. Such an interaction would not only nudge the planet into a wider orbit but also make that orbit more elliptical. And since the Sun formed in a star cluster with several thousand neighbors, such stellar encounters were more common in the early history of our solar system.
However, an interloping star is more likely to pull Planet Nine away completely and eject it from the solar system. Li and Adams find only a 10 percent probability, at best, of Planet Nine landing in its current orbit. Moreover, the planet would have had to start at an improbably large distance to begin with.
CfA astronomer Scott Kenyon believes he may have the solution to that difficulty. In two papers submitted to the Astrophysical Journal, Kenyon and his co-author Benjamin Bromley (University of Utah) use computer simulations to construct plausible scenarios for the formation of Planet Nine in a wide orbit.
"The simplest solution is for the solar system to make an extra gas giant," says Kenyon.
They propose that Planet Nine formed much closer to the Sun and then interacted with the other gas giants, particularly Jupiter and Saturn. A series of gravitational kicks then could have boosted the planet into a larger and more elliptical orbit over time.
"Think of it like pushing a kid on a swing. If you give them a shove at the right time, over and over, they'll go higher and higher," explains Kenyon. "Then the challenge becomes not shoving the planet so much that you eject it from the solar system."
That could be avoided by interactions with the solar system's gaseous disk, he suggests.
Kenyon and Bromley also examine the possibility that Planet Nine actually formed at a great distance to begin with. They find that the right combination of initial disk mass and disk lifetime could potentially create Planet Nine in time for it to be nudged by Li's passing star.
"The nice thing about these scenarios is that they're observationally testable," Kenyon points out. "A scattered gas giant will look like a cold Neptune, while a planet that formed in place will resemble a giant Pluto with no gas."
Li's work also helps constrain the timing for Planet Nine's formation or migration. The Sun was born in a cluster where encounters with other stars were more frequent. Planet Nine's wide orbit would leave it vulnerable to ejection during such encounters. Therefore, Planet Nine is likely to be a latecomer that arrived in its current orbit after the Sun left its birth cluster.
Finally, Li and Adams looked at two wilder possibilities: that Planet Nine is an exoplanet that was captured from a passing star system, or a free-floating planet that was captured when it drifted close by our solar system. However, they conclude that the chances of either scenario are less than 2 percent.
Li and Adams' paper has been accepted for publication in the Astrophysical Journal Letters and is available online. Kenyon and Bromley have submitted their findings to the Astrophysical Journal in two papers available online: one on in-situ formation and one on gas-giant scattering.
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.
Quelle: HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS
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Update: 1.06.2016
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Ist 'Planet 9' ein Kidnapped Ex-Exoplanet?
The mysterious origin of the hypothetical planet that may be lurking in the outermost regions of the solar system just got weirder.
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Astronomers are working hard to track down any visible signs of a large undiscovered planet pottering around in a distant corner of the solar system. We have a pretty good idea that it exists -- its gravity seems to be tugging on a few Kuiper belt objects (KBOs) -- but there has yet to be any direct visual clue that it's really out there.
The fact that it hasn't been picked up by infrared or optical surveys is actually a fairly good indicator as to how far away and how big this thing is; by ruling out where we know it isn't, we can put limits on the planet's physical size and take a stab at its composition. Granted, this isn't the first time astronomers have found clues to a massive object lurking in the outer solar system, but this time the evidence is pretty compelling.
NEWS: 9th Planet May Lurk in the Outer Solar System
Astronomers have already done some work in guessing what Planet 9 might be made of, but on Tuesday (May 31) researchers threw a wildcard into the mix: What if Planet 9 isn't from 'round these parts? Could it be an alien world, kidnapped by our sun from its home star billions of years ago? In other words, is Planet 9 an ex-exoplanet?
"It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there's probably one hiding in our own backyard," said astronomer Alexander Mustill, of Lund University, Sweden, in a statement.
By Mustill's reckoning, around 4.5 billion years ago, when our sun was a baby, solar gravity likely interfered with the orbit of a planet around a neighboring star. This idea isn't such a stretch; stars are often born in molecular clouds that form dense clusters of stars. As planets form around these stars, their orbits may become destabilized and flung into interstellar space or shared between stellar neighbors. The gravitational environment would have been a mess.
ANALYSIS: Could 'Planet X' Cause Comet Catastrophes on Earth?
As time went on, the young stars drifted apart and their planetary systems settled -- but these systems could easily contain planets that weren't formed around the star they currently call home. Did this happen to Planet 9? Computer simulations carried out by Mustill and his team certainly suggest it's a possibility.
"Planet 9 may very well have been 'shoved' by other planets, and when it ended up in an orbit that was too wide around its own star, our sun may have taken the opportunity to steal and capture Planet 9 from its original star. When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the sun," said Mustill.
Calculations of Planet 9's mass puts it at around 10 Earth masses -- so it could be a really big rocky world or a small Neptune-like ice giant. For now, it's composition is speculative at best. However, if this mysterious world wasn't born from our sun's protoplanetary disk, and is in fact a planet from another star, it may be a very alien world indeed. How would its composition differ from the other planets in the solar system?
ANALYSIS: The Hunt for Planet 9: What's It Made Of?
As noted by the researchers, it would be ironic if we do find Planet 9 to be from another star system -- it would be the closest (ex-)exoplanet to Earth and possible exploration destination for our spacecraft. The enthusiasm was high for sending NASA's New Horizons mission to Pluto, imagine the excitement surrounding the possibility of sending a robotic probe to Planet 9 if it was found to be a late addition to our solar system's planetary family?
Quelle: Seeker
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Update: 14.06.2016
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Extreme trans-Neptunian objects lead the way to Planet Nine

FECYT - SPANISH FOUNDATION FOR SCIENCE AND TECHNOLOGY

IMAGE: THE MOTIONS OF THE EXTREME TRANS-NEPTUNIAN OBJECTS (AS ILLUSTRATED ON THE RIGHT) SUGGEST THAT THERE IS AN UNKNOWN PLANET (LEFT) IN THE CONFINES OF THE SOLAR SYSTEM. view more 
CREDIT: JOSÉ ANTONIO PEÑAS (SINC)
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In the race towards the discovery of a ninth planet in our solar system, scientists from around the world strive to calculate its orbit using the tracks left by the small bodies that move well beyond Neptune. Now, astronomers from Spain and University of Cambridge have confirmed, with new calculations, that the orbits of the six extreme trans-Neptunian objects that served as a reference to announce the existence of Planet Nine are not as stable as it was thought.
At the beginning of this year, the astronomers K. Batygin and M. Brown from the California Institute of Technology (Caltech, USA) announced that they had found evidence of the existence of a giant planet with a mass ten times larger than Earth's in the confines of the Solar System. Moving in an unusually elongated orbit, the mysterious planet will take between 10,000 and 20,000 years to complete one revolution around the Sun.
In order to arrive at this conclusion, Batygin and Brown run computer simulations with input data based on the orbits of six extreme trans-Neptunian objects (ETNOs). Specifically, these ETNOs are: Sedna, 2012 VP113, 2004 VN112, 2007 TG422, 2013 RF98 and 2010 GB174.
Now, however, brothers Carlos and Raúl de la Fuente Marcos, two freelance Spanish astronomers, together with scientist Sverre J. Aarseth from the Institute of Astronomy of the University of Cambridge (United Kingdom), have considered the question the other way around: How would the orbits of these six ETNOs evolve if a Planet Nine such as the one proposed by K. Batygin and M. Brown really did exist? The answer to this important question has been published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).
"With the orbit indicated by the Caltech astronomers for Planet Nine, our calculations show that the six ETNOs, which they consider to be the Rosetta Stone in the solution to this mystery, would move in lengthy, unstable orbits," warns Carlos de la Fuente Marcos.
"These objects would escape from the Solar System in less than 1.5 billion years, -he adds-, and in the case of 2004 VN112, 2007 TG422 and 2013 RF98 they could abandon it in less than 300 million years; what is more important, their orbits would become really unstable in just 10 million years, a really short amount of time in astronomical terms."
According to this new study, also based on numerical (N-body) simulations, the orbit of the new planet proposed by Batygin and Brown would have to be modified slightly so that the orbits of the six ETNOs analysed would be really stable for a long time.
These results also lead to a new question: Are the ETNOs a transient and unstable population or, on the contrary, are they permanent and stable? The fact that these objects behave in one way or another affects the evolution of their orbits and also the numerical modelling.
"If the ETNOs are transient, they are being continuously ejected and must have a stable source located beyond 1,000 astronomical units (in the Oort cloud) where they come from", notes Carlos de la Fuente Marcos. "But if they are stable in the long term, then there could be many in similar orbits although we have not observed them yet".
In any case, the statistical and numerical evidence obtained by the authors, both through this and previous work, leads them to suggest that the most stable scenario is one in which there is not just one planet, but rather several more beyond Pluto, in mutual resonance, which best explains the results. "That is to say we believe that in addition to a Planet Nine, there could also be a Planet Ten and even more," the Spanish astronomer points out.
International race to discover Planet Nine
These studies are only a few of the countless international peer-reviewed articles published or in preparation about the search for Planet Nine with the help of N-body simulations and other techniques. Batygin and Brown are going to present soon new models of the orbit of the mysterious Planet Nine with up-to-date data. On the other side of the Atlantic, in France, Professor Jacques Laskar's team from the Paris Observatory is also attempting to be the first to compute the position of the hypothetical Planet Nine in order to then observe it.
This situation is reminiscent of the discovery of Neptune, in which the French mathematician Urbain Le Verrier was the first to "discover" a new planet using laborious hand calculations based on the positions of Uranus; later, the German astronomer J. G Galle directly observed it.
"If Neptune was the first planet discovered using pen and paper, Planet Nine could be the first to be discovered using entirely computerized numerical calculations." notes de la Fuente Marcos, although he points out that the results of the French team are based on residuals in the tracking data from the Cassini spacecraft, in orbit around Saturn, caused by the presence of the hypothetical planet, but NASA has denied it, suggesting that it could simply be statistical noise in the signal.
Could Planet Nine be an exoplanet?
One of the most revolutionary studies from recent months, also with computational simulations and participation of French institutions, was led by the researcher Alexander Mustill from Lund University (Sweden), who raised the idea that Planet Nine may have come from outside the Solar System, that is to say, that it could be an exoplanet.
His hypothesis is that around 4.5 billion years ago, our then young Sun "stole" this planet from a neighbouring star with the help of a series of favourable conditions (proximity of stars within a star cluster, a planet in a wide and elongated orbit,...). Other scientists, however, believe that this scenario is improbable.
The debate is on. What all astronomers do agree on is the importance of closely tracking the motions of the extreme trans-Neptunian objects to be able to adjust the calculations that should lead the way to the location of Planet Nine, without forgetting that the best evidence will be its direct observation, a race which several research teams are fighting to win.
Quelle: AAAS
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Update: 30.08.2016
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Washington, DC— In the race to discover a proposed ninth planet in our Solar System, Carnegie’s Scott Sheppard and Chadwick Trujillo of Northern Arizona University have observed several never-before-seen objects at extreme distances from the Sun in our Solar System. Sheppard and Trujillo have now submitted their latest discoveries to the International Astronomical Union’s Minor Planet Center for official designations. A paper about the discoveries has also been accepted to The Astronomical Journal.

The more objects that are found at extreme distances, the better the chance of constraining the location of the ninth planet that Sheppard and Trujillo first predicted to exist far beyond Pluto (itself no longer classified as a planet) in 2014. The placement and orbits of small, so-called extreme trans-Neptunian objects, can help narrow down the size and distance from the Sun of the predicted ninth planet, because that planet’s gravity influences the movements of the smaller objects that are far beyond Neptune.  The objects are called trans-Neptunian because their orbits around the Sun are greater than Neptune’s.

In 2014, Sheppard and Trujillo announced the discovery of 2012 VP113 (nicknamed “Biden”), which has the most-distant known orbit in our Solar System. At this time, Sheppard and Trujillo also noticed that the handful of known extreme trans-Neptunian objects all cluster with similar orbital angles. This lead them to predict that there is a planet at more than 200 times our distance from the Sun. Its mass, ranging in possibility from several Earths to a Neptune equivalent, is shepherding these smaller objects into similar types of orbits. 

Some have called this Planet X or Planet 9. Further work since 2014 showed that this massive ninth planet likely exists by further constraining its possible properties. Analysis of “neighboring” small body orbits suggest that it is several times more massive than the Earth, possibly as much as 15 times more so, and at the closest point of its extremely stretched, oblong orbit it is at least 200 times farther away from the Sun than Earth. (This is over 5 times more distant than Pluto.)

“Objects found far beyond Neptune hold the key to unlocking our Solar System’s origins and evolution,” Sheppard explained. “Though we believe there are thousands of these small objects, we haven’t found very many of them yet, because they are so far away. The smaller objects can lead us to the much bigger planet we think exists out there. The more we discover, the better we will be able to understand what is going on in the outer Solar System.”

Sheppard and Trujillo, along with David Tholen of the University of Hawaii, are conducting the largest, deepest survey for objects beyond Neptune and the Kuiper Belt and have covered nearly 10 percent of the sky to date using some of the largest and most advanced telescopes and cameras in the world, such as the Dark Energy Camera on the NOAO 4-meter Blanco telescope in Chile and the Japanese Hyper Suprime Camera on the 8-meter Subaru telescope in Hawaii. As they find and confirm extremely distant objects, they analyze whether their discoveries fit into the larger theories about how interactions with a massive distant planet could have shaped the outer Solar System. 

“Right now we are dealing with very low-number statistics, so we don’t really understand what is happening in the outer Solar System,” Sheppard said. “Greater numbers of extreme trans-Neptunian objects must be found to fully determine the structure of our outer Solar System.” 

According to Sheppard, “we are now in a similar situation as in the mid-19th century when Alexis Bouvard noticed Uranus’ orbital motion was peculiar, which eventually led to the discovery of Neptune.”

The new objects they have submitted to the Minor Planet Center for designation include 2014 SR349, which adds to the class of the rare extreme trans-Neptunian objects. It exhibits similar orbital characteristics to the previously known extreme bodies whose positions and movements led Sheppard and Trujillo to initially propose the influence of Planet X. 

Another new extreme object they found, 2013 FT28, has some characteristics similar to the other extreme objects but also some differences. The orbit of an object is defined by six parameters.  The clustering of several of these parameters is the main argument for a ninth planet to exist in the outer solar system. 2013 FT28 shows similar clustering in some of these parameters (its semi-major axis, eccentricity, inclination, and argument of perihelion angle, for angle enthusiasts out there) but one of these parameters, an angle called the longitude of perihelion, is different from that of the other extreme objects, which makes that particular clustering trend less strong.

Another discovery, 2014 FE72, is the first distant Oort Cloud object found with an orbit entirely beyond Neptune. It has an orbit that takes the object so far away from the Sun (some 3000 times farther than Earth) that it is likely being influenced by forces of gravity from beyond our Solar System such as other stars and the galactic tide. It is the first object observed at such a large distance. 

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Caption: An illustration of the orbits of the new and previously known extremely distant Solar System objects. The clustering of most of their orbits indicates that they are likely be influenced by something massive and very distant, the proposed Planet X. Image is courtesy of Robin Dienel. 

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Caption: An artist’s conception of Planet X, courtesy of Robin Dienel.

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This research was funded by NASA Planetary Astronomy.

This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaborating institutions: Argonne National Lab, University of California Santa Cruz, University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid, University of Chicago, University College London, DES-Brazil consortium, University of Edinburgh, ETH-Zurich, University of Illinois at Urbana-Champaign, Institut de Ciencies de l'Espai, Institut de Fisicad'Altes Energies, Lawrence Berkeley National Lab, Ludwig-Maximilians Universitat, University of Michigan, National Optical Astronomy Observatory, University of Nottingham, Ohio State University, University of Pennsylvania, University of Portsmouth, SLAC National Lab, Stanford University, University of Sussex, and Texas A&M University. Funding for DES,including DECam, has been provided by the U.S. Department of Energy, National Science Foundation, Ministry of Education and Science (Spain), Science and Technology Facilities Council (UK), Higher Education Funding Council (England), National Center for Supercomputing Applications, Kavli Institute for Cosmological Physics, Financiadora de Estudos e Projetos, Fundao Carlos Chagas Filho de Amparo a Pesquisa, Conselho Nacional de Desenvolvimento Cient_co e Tecnolgico and the Ministrio da Cincia e Tecnologia (Brazil), the German Research Foundation-sponsored cluster of excellence "Origin and Structure of the Universe" and the DES collaborating institutions. Observations were partly obtained at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation. C.T. is supported by the Gemini observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., on behalf of the international Gemini partnership of Argentina, Australia, Brazil, Canada, Chile, the United Kingdom, and the United States of America.

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Update: 20.10.2016
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Curious Tilt of the Sun Traced to Undiscovered Planet

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Planet Nine—the undiscovered planet at the edge of the Solar System that was predicted by the work of Caltech's Konstantin Batygin and Mike Brown in January 2016—appears to be responsible for the unusual tilt of the sun, according to a new study.

The large and distant planet may be adding a wobble to the solar system, giving the appearance that the sun is tilted slightly.

"Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment," says Elizabeth Bailey, a graduate student at Caltech and lead author of a study announcing the discovery.

All of the planets orbit in a flat plane with respect to the sun, roughly within a couple degrees of each other. That plane, however, rotates at a six-degree tilt with respect to the sun—giving the appearance that the sun itself is cocked off at an angle. Until now, no one had found a compelling explanation to produce such an effect. "It's such a deep-rooted mystery and so difficult to explain that people just don't talk about it," says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.

Brown and Batygin's discovery of evidence that the sun is orbited by an as-yet-unseen planet—that is about 10 times the size of Earth with an orbit that is about 20 times farther from the sun on average than Neptune's—changes the physics. Planet Nine, based on their calculations, appears to orbit at about 30 degrees off from the other planets' orbital plane—in the process, influencing the orbit of a large population of objects in the Kuiper Belt, which is how Brown and Batygin came to suspect a planet existed there in the first place.

"It continues to amaze us; every time we look carefully we continue to find that Planet Nine explains something about the solar system that had long been a mystery," says Batygin, an assistant professor of planetary science.

Their findings have been accepted for publication in an upcoming issue of the Astrophysical Journal, and will be presented on October 18 at the American Astronomical Society's Division for Planetary Sciences annual meeting, held in Pasadena.

The tilt of the solar system's orbital plane has long befuddled astronomers because of the way the planets formed: as a spinning cloud slowly collapsing first into a disk and then into objects orbiting a central star.

Planet Nine's angular momentum is having an outsized impact on the solar system based on its location and size. A planet's angular momentum equals the mass of an object multiplied by its distance from the sun, and corresponds with the force that the planet exerts on the overall system's spin. Because the other planets in the solar system all exist along a flat plane, their angular momentum works to keep the whole disk spinning smoothly.

Planet Nine's unusual orbit, however, adds a multi-billion-year wobble to that system. Mathematically, given the hypothesized size and distance of Planet Nine, a six-degree tilt fits perfectly, Brown says.

The next question, then, is how did Planet Nine achieve its unusual orbit? Though that remains to be determined, Batygin suggests that the planet may have been ejected from the neighborhood of the gas giants by Jupiter, or perhaps may have been influenced by the gravitational pull of other stellar bodies in the solar system's extreme past.

For now, Brown and Batygin continue to work with colleagues throughout the world to search the night sky for signs of Planet Nine along the path they predicted in January. That search, Brown says, may take three years or more.

Quelle: Caltech

 

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