Caltech Researchers Find Evidence of a Planet Beyond Pluto

Link to paper by Batygin and Brown: http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22...

> * the putative ninth planet—at 5,000 times the mass of Pluto—is sufficiently large that there should be no debate about whether it is a true planet*

That's 10x the mass of the Earth, right, or about 3x the size of Neptune?

Provocative title for this Caltech press release.

Mike Brown, the co-author of the paper reported here, discovered Eris, a KBO like Pluto, in 2005. This discovery prompted the IAU in 2006 to demote Pluto out of the realm of "planet" into a "dwarf planet".

At the time, Alan Stern's New Horizons mission to Pluto had just been launched, it finally arrived last year. Stern was incensed that NH started out as a visitor to the 9th planet and was going to end up as a visitor to one of many KBOs, and not even the largest one (Eris is more massive).

The quotes given at the time (http://www.space.com/2791-pluto-demoted-longer-planet-highly...) are revealing:

"Pluto is dead." -- Mike Brown

"This definition stinks, for technical reasons...It's a farce." -- Alan Stern

For more: http://www.space.com/12709-pluto-dwarf-planet-decision-5-yea...

Stern is visiting Pasadena on a New Horizons victory lap next week. Should be interesting.

They do, and at the end of the press release it says that Brown has begun an observing campaign to find the planet. Unfortunately detecting these very distant objects is very difficult. The light we see from them is reflected light from the Sun, so their apparent brightness goes as 1/r^4, not 1/r^2 like most objects. And because they are so close, there is a strong parallax from the motion of the Earth. THe consequence from this is that the object will actually drift across the image as you are taking it, smearing it out. In order to detect it you either have to take very short images so that it doesn't move too much (in which case you don't get very much light), or have some idea as to the direction of the smear so that you can correct for it. Either way it's a very hard observation to make! Fortunately if this planet is as big as they claim it to be it should be relatively easy to detect compared to Sedna and the other Kuiper Belt objects.