The NY Times covers the story well:<p><a href="http://www.nytimes.com/2016/01/21/science/space/ninth-planet-solar-system-beyond-pluto.html" rel="nofollow">http://www.nytimes.com/2016/01/21/science/space/ninth-planet...</a><p>EDIT: After reading the comments in this discussion, many of which are addressed in the NYT article, I'd say the NYT article is almost certainly worth reading.
We have been looking for a "missing" objects for a while. The nemesis star theory says the sun has a brown dwarf companion. This object would interact with the Oort Cloud instead of the Kuiper belt. But this theory has been pretty much refuted.<p>This theory definitely looks more promising. Finding eccentric Kuiper belt objects, and aligning them with a missing object seems to be a good bet. Giving the object an orbit should make the search easier, and we will probably have a conclusion one way or another within a few years.<p><a href="https://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)" rel="nofollow">https://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)</a>
No one's mentioned Tyche yet?<p><a href="https://en.wikipedia.org/wiki/Tyche_%28hypothetical_planet%29" rel="nofollow">https://en.wikipedia.org/wiki/Tyche_%28hypothetical_planet%2...</a><p>In searching for Tyche, the WISE missions ruled out the possibility of anything larger than Saturn (95x the mass of Earth) out to about 10000 AU and anything larger than Jupiter (317x the mass of Earth) out to about 26000 AU. WISE was able to detect objects the size of Neptune (17x the mass of Earth) out to about 700 AU, so it should be possible to find the object proposed by the Caltech astronomers here (10x the mass of Earth at around 600 AU). I don't know if WISE's current condition would allow it to perform such a search, as it's completely out of coolant.
Skepticism is warranted, but keep in mind that Mike "pluto killer" Brown, one of the authors, has an impressive track record. He discovered Eris and Sedna.
If it holds up, this is fantastic. Given how interesting the Pluto system has turned out to be, I can only fantasise about a potential super-earth system relatively nearby.<p>However, to be completely pedantic: would this actually be a <i>planet</i>? Or still a <i>dwarf planet</i>, despite its massive size? Keep in mind that the definition of planethood is not only that it's large enough to be rounded by its own gravity, but that it has also "cleared its orbit". I get the impression that this would cut through broad swathes of the still-cluttered Kuiper belt, and thus would only qualify as a "dwarf" despite its massive size.<p>I checked the original papers for references to whether it had cleared its orbit, and couldn't find any. Correct me if I'm wrong?
I don't seem to have a grasp of our visibility of our solar system. We can see a number of the planets with the naked eye, a number of the moons with binoculars and a few hundred $/£/€/.. telescope. Yet even with these great big radio telescopes, antenna arrays, Hubble, etc, we seem to be quite unaware of what's in our neighbourhood. Anyone have figures of how much we've surveyed?
There is an awesome summary by Emili Lakdawala at the Planetary Society (as is often the case with such news).<p><a href="http://www.planetary.org/blogs/emily-lakdawalla/2016/01200955-theoretical-evidence-for-planet-9.html" rel="nofollow">http://www.planetary.org/blogs/emily-lakdawalla/2016/0120095...</a>
Link to paper by Batygin and Brown: <a href="http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22/pdf" rel="nofollow">http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22...</a>
Giant, weird orbit, debate ... there can be only one name. This is Planet X.<p>Also because X would be 10th discovered planet, a reference that pluto, while not a planet today, was indeed the ninth _discovered_ planet.
> Batygin and Brown inferred its presence from the peculiar clustering of six previously known objects that orbit beyond Neptune.<p>This raised a big red flag in my mind. This must produce a literally astronomical multiple comparisons problem. Yes they reported sigma = 3.8, but if they didn't do their multiple comparisons correction right (which I am in no position to determine), they're basically reading tea leaves.<p>If you're not familiar with multiple comparisons, it's kind of like [this](<a href="https://www.goodreads.com/quotes/649893-you-know-the-most-amazing-thing-happened-to-me-tonight" rel="nofollow">https://www.goodreads.com/quotes/649893-you-know-the-most-am...</a>) or [this](<a href="https://xkcd.com/882/" rel="nofollow">https://xkcd.com/882/</a>). If you look at enough extra-neptunian bodies, some of them are going to be in an odd looking cluster.
This is pretty solid science, even if, as others have pointed out, there's a bit of academic drama-rama and green jellybean stuff going on. In particular, their model made a prediction that they didn't set out looking for, which corresponded to existing observations. And of course, the whole hypothesis is easily testable. While they don't know where the hypothetical planet might be on it's orbit, it sounds like there's a good shot that small telescopes should be able to spot it.<p>Exciting stuff.
More from the folks behind the paper: <a href="http://www.findplanetnine.com/" rel="nofollow">http://www.findplanetnine.com/</a>
Ah Planet X which is now planet IX with Pluto's demotion :-). I am guessing that you can confirm it by looking for star occulusions. Presumably the planet would blank out stars as it passed between earth and those stars. So would it be possible to find it using existing plates?
<a href="https://en.wikipedia.org/wiki/Zecharia_Sitchin" rel="nofollow">https://en.wikipedia.org/wiki/Zecharia_Sitchin</a><p>He believed this hypothetical planet of Nibiru to be in an elongated, elliptical orbit in the Earth's own Solar System, asserting that Sumerian mythology reflects this.
Very cool.<p>It reminds me about a book I read called "In Search of Planet Vulcan" (<a href="http://www.amazon.com/In-Search-Planet-Vulcan-Clockwork/dp/0738208892" rel="nofollow">http://www.amazon.com/In-Search-Planet-Vulcan-Clockwork/dp/0...</a>). Before Einstein, astronomers tried to explain the motion of Mercury by suggesting there might be another planet inside Mercury's orbit.
Reading the article I didn't see a mention of a previously hypothesised fifth gas giant... so here's a link in case anyone's interested or knows something more.<p><a href="https://en.wikipedia.org/wiki/Hypothetical_fifth_giant_planet" rel="nofollow">https://en.wikipedia.org/wiki/Hypothetical_fifth_giant_plane...</a>
At WWDC last year one of the lunchtime presentations was by Michael Brown, one of the researchers involved here. He was one of the people who proved that Pluto should not be considered a planet and went over the history of the discovery/classification of planet bodies. He also mentioned that they had <i>some</i> evidence of a planet body beyond Pluto due to its gravitational affect of some of the smaller bodies out there even then. Interesting to see this is finally coming to something! He has the appropriate/amusing twitter handle of <a href="http://twitter.com/plutokiller" rel="nofollow">http://twitter.com/plutokiller</a>
I'm puzzled by how a planet this big could form in an orbit so distant.<p>The fact that the material in that region is so spread out and the orbital period of such object is so long matters.<p>I would love to read some thoughts on that.
I've been seeing news stories about Planet X for far too long to take any of this seriously, no matter how seemingly trustworthy the news source is.
Thanks for the link. There's a course taught on Coursera by one of the CalTech researchers, Mike Brown, if anyone is interested. It's archived but they have kept it open.<p><a href="https://www.coursera.org/course/solarsystem" rel="nofollow">https://www.coursera.org/course/solarsystem</a>
Now only if they name the ninth planet starting with a 'P', my childhood mnemonic "My Very Educated Mother Just Served Us Nine Pizzas" would finally be complete again! :D My suggestion is 'Prometheus' - sounds tragic and bad ass at the same time!
At first I thought this was another one of those planet x articles that talks about some hypothetical planet way out but then I saw that Mike Brown was involved and immediately got really excited. I hope they find something out there and we can send a probe to it in my lifetime.
> * 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*<p>That's 10x the mass of the Earth, right, or about 3x the size of Neptune?
This is very cool. Along with a visible supernova and a super bright comet, this is one of those things I dreamed about as an astronomy nerd kid.<p>Though part of me wants to say "Pictures or it didn't happen!"
Provocative title for this Caltech press release.<p>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".<p>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).<p>The quotes given at the time (<a href="http://www.space.com/2791-pluto-demoted-longer-planet-highly-controversial-definition.html" rel="nofollow">http://www.space.com/2791-pluto-demoted-longer-planet-highly...</a>) are revealing:<p>"Pluto is dead." -- Mike Brown<p>"This definition stinks, for technical reasons...It's a farce." -- Alan Stern<p>For more: <a href="http://www.space.com/12709-pluto-dwarf-planet-decision-5-years-anniversary-iau.html" rel="nofollow">http://www.space.com/12709-pluto-dwarf-planet-decision-5-yea...</a><p>Stern is visiting Pasadena on a New Horizons victory lap next week. Should be interesting.
This how Qigong found the Clone Planet in Star Wars 2. Although the planet had be erased from the galactic database, it left a gravitational signature on nearby systems.