More Evidence for Ninth Planet on Solar System's Fringes

a reply to: Char-Lee
You're right, we haven't discussed this new object here. But whether L91 serves as evidence for Planet Nine is questionable: www.nature.com...

Bannister and her colleagues think the object may have been banished as far as 2,000 au from the Sun before it began easing its way back towards the star’s gravitational pull. L91’s orbit “is changing in quite a remarkable way”, she said.

But Konstantin Batygin, an astronomer at the California Institute of Technology in Pasadena, isn’t so sure. He thinks Bannister’s suggestion that L91 was first tossed towards the Oort cloud and is now moving inward is too complicated. He argues that an unseen giant planet — such as Planet Nine, which he and a colleague proposed in January — might instead be shepherding L91’s orbit more simply and directly.

Bannister counters that L91 travels an orbit that is almost within the plane of the Solar System, rather than being tilted at high angles, as might be expected if it were being battered around by a Planet Nine.

a reply to: wildespace

ou're right, we haven't discussed this new object here. But whether L91 serves as evidence for Planet Nine is questionable: www.nature.com...

Evidence of there being something large out there is what the thread was about I believe. The extreme distance this travels must mean something is unknown.

It is possible that this object's orbit could be a result of gravitational perturbations by the hypothetical "Planet 9", but it is far too early to rule out other explanations. I think that we need to be careful not to instantly assume that "Planet 9" is responsible for the orbits of every object that is discovered beyond the outer fringes of the Kuiper Belt.

Well, planet 9 itself may not come closer than 200 AUs to the sun, but a body orbiting it might do so.

I.e. planet 9 may be a brown dwarf with planets orbiting it, which may come closer than 200 AUs to the sun.

originally posted by: masterp
Well, planet 9 itself may not come closer than 200 AUs to the sun, but a body orbiting it might do so.

I.e. planet 9 may be a brown dwarf with planets orbiting it, which may come closer than 200 AUs to the sun.

They deduced the potential existence of Planet 9 by noticing oddities in the orbits of Kuiper Belt Objects -- i.e., a bunch of them all have their orbital apogees and perigees all on the same side of the Sun.

Unless they've found similar oddities in the orbits of closer-in objects such as Eris, Pluto, and Neptune (and they haven't), it seems unlikely some planet-sized object gets that close.

A brown dwarf at even 200AUs would easily be massive enough to perturb the orbits of the Kuiper Belt objects (and even the outer planets), and it would also be considerably brighter than the hypothetical "Planet 9".

Perhaps the Wide Field Infrared Survey Telescope (WFIRST) will detect the Planet Nine. This new infrared telescope will be able to perform surveys of large parts of the sky, like WISE did, but at the same resolution as the Hubble telescope.