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  • Quanta Magazine

    https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/ May 15, 2018

    A New World’s Extraordinary Orbit Points toPlanet NineAstronomers argue that there’s an undiscovered giant planet far beyond the orbit of Neptune. Anewly discovered rocky body has added evidence to the circumstantial case for it.

    By Shannon Hall

    In early 2016, two planetary scientists declared that a ghost planet is hiding in the depths of thesolar system, well beyond the orbit of Pluto. Their claim, which they made based on the curiousorbits of distant icy worlds, quickly sparked a race to find this so-called Planet Nine — a planet thatis estimated to be about 10 times the mass of Earth. “It has a real magnetism to it,” said GregoryLaughlin, an astronomer at Yale University. “I mean, finding a 10-Earth-mass planet in our own solarsystem would be a discovery of unrivaled scientific magnitude.”

    Now, astronomers are reporting that they have spotted another distant world — perhaps as large asa dwarf planet — whose orbit is so odd that it is likely to have been shepherded by Planet Nine. Theobject confirms a specific prediction made by Konstantin Batygin and Michael Brown, theastronomers at the California Institute of Technology who first argued for Planet Nine’s existence.“It’s not proof that Planet Nine exists,” said David Gerdes, an astronomer at the University ofMichigan and a co-author on the new paper. “But I would say the presence of an object like this inour solar system bolsters the case for Planet Nine.”


  • Quanta Magazine

    https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/ May 15, 2018

    Lucy Reading-Ikkanda/Quanta Magazine

    Gerdes and his colleagues spotted the new object in data from the Dark Energy Survey, a projectthat probes the acceleration in the expansion of the universe by surveying a region well above theplane of the solar system. This makes it an unlikely tool for finding objects inside the solar system,since they mostly orbit within the plane. But that is exactly what makes the new object unique: Itsorbit is tilted 54 degrees with respect to the plane of the solar system. It’s something Gerdes did notexpect to see. Batygin and Brown, however, predicted it.

    Two years ago, Batygin and Brown made a case for Planet Nine’s existence based on the peculiarorbits of a handful of distant worlds known as Kuiper belt objects. That small population loops


  • Quanta Magazine

    https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/ May 15, 2018

    outward toward the same quadrant of the solar system, a phenomenon that would be extremelyunlikely to happen by chance. Batygin and Brown argued that a ninth planet must be shepherdingthose worlds into their strange orbits.

    What’s more, Batygin and Brown also predicted that over time, Planet Nine’s gravity would pushthese Kuiper belt objects out of their current plane and into ever-higher orbital inclinations.Although astronomers have already spotted a bizarre population of worlds that orbit the sunperpendicularly to the plane of the solar system, they had never caught an object transitioningbetween the two populations. “There’s no real way to put something on an orbit like that — exceptthat it’s exactly what we predicted from Planet Nine,” Brown said. Batygin notes that the new objectfits so perfectly with their model that it almost looks like one of the data points in their simulations.“A good theory reproduces data — but a great theory predicts new data,” he said.

  • Quanta Magazine

    https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/ May 15, 2018

    University of Michigan

    Juliette Becker, a doctoral student at the University of Michigan, led the analysis of the new object.

  • Quanta Magazine

    https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/ May 15, 2018

    The Dark Energy Survey first detected evidence for the new object in late 2014. Gerdes and hiscolleagues have spent the years since then tracking its orbit and trying to understand its origins. Inthe new paper, they describe how they ran many simulations of the object within the known solarsystem, letting the clock run forward and backward 4.5 billion years at a time. Nothing could explainhow the object landed in such a tilted orbit. It wasn’t until they added in a ninth planet — a planetwith characteristics that perfectly match Batygin and Brown’s predictions — that the wacky orbitfinally made sense. “The second you put Planet Nine in the simulations, not only can you formobjects like this object, but you absolutely do,” said Juliette Becker, a graduate student at Michiganand the lead author on the new paper. A strong and sustained interaction with Planet Nine appearsto be the only way to pump up the object’s inclination, pushing it away from the plane of the solarsystem. “There is no other reasonable way to populate the Kuiper belt with such highly inclinedbodies,” Batygin said. “I think the case for the existence of Planet Nine is now genuinely excellent.”

    Other astronomers aren’t so certain — in part because the early solar system remains a mystery.Scientists suspect that the sun was born within a cluster of stars, meaning that the early planetsmight have had many close encounters with other stars that sent them on paths that seemimpossible today. And even once the stars dispersed, the early solar system likely contained tens ofthousands of dwarf planets that could have provided the gravitational nudges needed to push 2015BP519, as the new object is called, into such an odd orbit. “To me, Planet Nine is one of a number ofways that the solar system could have unfolded,” said Michele Bannister, an astronomer at Queen’sUniversity Belfast who was not involved in the study. “It’s a potential idea.” But at the moment it isjust that — an idea.

    Yet when astronomers examine the larger universe, the idea doesn’t seem all that surprising. Planetsbetween two and 10 times the mass of Earth are incredibly common throughout the galaxy, whichmakes it odd that our solar system doesn’t harbor one. “If it wasn’t in our own solar system — if thestakes weren’t so high — I think that the hypothesis would almost certainly be correct,” Laughlinsaid. “It’s only the fact that it’s so amazing that tends to give me pause.” Finding a ninth planetwithin our solar system would be both transformative and extraordinarily inspiring, he said. “Itwould be this dramatic confirmation of the scientific method, which would be pretty refreshing inthe current age where the truth is on trial.”

    This article was reprinted on Wired.com, in Japanese at Wired.jp and in Spanish atInvestigacionyciencia.es


    A New World’s Extraordinary Orbit Points to Planet Nine