Whether you call it Planet Nine or Planet X or Nibiru, there are a lot of people looking for an alleged large planet in our solar system far beyond the orbit of Neptune which may or may not explain the odd orbits of trans-Neptunian objects and may or may not collide with Earth someday. Speculation among planetary scientists about the existence of a Planet X began after the discovery of Neptune in 1846, but the general public became interested in 2016 when astronomers Konstantin Batygin and Michael E. Brown suggested that Planet Nine could be the core of a giant planet that was ejected from its original orbit by Jupiter during the early days of the Solar System. Brown’s involvement was key because he was primarily responsible for downgrading Pluto from its planetary status, thus freeing up ‘nine’ for the next new planet. Now, Brown and Batygin are at it again – they’ve created a map of the probable location of Planet Nine. Should you grab your telescope and the map and start looking? Is there a prize – other than a laurel and hearty handshake?
“A suite of numerical simulations shows that the orbital distribution of the distant KBOs is strongly influenced by the mass and orbital elements of P9 and thus can be used to infer these parameters. Combining the biases with these numerical simulations, we calculate likelihood values for discrete set of P9 parameters, which we then use as input into a Gaussian Process emulator that allows a likelihood computation for arbitrary values of all parameters. We use this emulator in a Markov Chain Monte Carlo analysis to estimate parameters of P9.”
The scientific jargon gets more complicated after this in Brown and Batygin’s new paper, “The Orbit of Planet Nine.” In essence, as explained in SyFy Wire, they took previous data on Kuiper Belt Object (KBO) orbits and ran over a hundred physical simulations of tens of thousands of KBOs, allowing their orbits to be affected by Planet Nine for 200 million years. They varied the values for the mass of Planet Nine and changed its orbital shape and orientation to see how those affected the simulations.
The end result of all of those simulations was a map that’s understandable to astronomers and planetary scientists, but doesn’t look like any treasure, road or constellation map you’ve ever seen. (See it here). It’s shaped like an ellipse and called a Mollweide projection of the entire sky, with left-to-right being east-to-west, the top being the north celestial pole and the equator in the middle. A curved black line shows the plane of the solar system (called the ecliptic) and two solid black lines are the plane of the Milky Way galaxy. The probable locations of Planet Nine are a blue wavy ribbon across the map and the area of highest probability is in red. That red spot puts Planet Nine’s probable location near the Taurus constellation!
Before you go running for your telescope, they emphasize ‘probable’ and there are some caveats. The most probable magnitude for Planet Nine is about 20.5 – the faintest star you can see by eye at night is over 600,000 times brighter. That magnitude would require an 8 to 10-meter class telescope to find it -- the Vera Rubin Telescope will be an 8.4-meter and there are a few others available. Brown and Batygin got a head start and are searching for Planet Nine using the Subaru telescope.
Is this map from Brown and Batygin the smoking telescope for finding Planet Nine? Only time will tell. If someone discovers it using the map, will people stop complaining to Brown about Pluto? Probably not. Can squinting through your home telescope at Taurus help? There’s only one way to find out.
Happy Planet Nine hunting!