Jul 7, 2020 - Science

The race to find Planet X heats up

Illustration of flashlight revealing a semi-hidden planet
Illustration: Eniola Odetunde/Axios

Teams of scientists are vying to be the first to spot a large, hypothetical planet that might be lurking in the outer reaches of our solar system.

Why it matters: Astronomers have found thousands of planets orbiting other stars, but the hunt for this possible planet orbiting our own Sun — called Planet X or Planet 9 by some — is showing just how little we know about our solar system.

What's happening: Teams of scientists are racing to find the possible planet using telescopes trained on distant parts of the solar system before a more powerful telescope comes online in the coming years.

  • They've lost months of observation time due to the coronavirus pandemic as many telescopes have been shut down because of restrictions placed on observatories in various parts of the world to contain the pandemic.
  • Astronomers hope to start observing again, at least remotely, in the coming months in order to beat out a new telescope and potentially be first to spot the theoretical planet.
  • "It's a friendly competition. I mean, it's a race. It's something that you want to find. It's a pretty amazing thing," astronomer Scott Sheppard told Axios.

The ground-based Rubin Observatory is expected to make its first science observations by next year and reach full operation in 2022.

  • It will then likely be able to quickly figure out whether or not Planet X is out there thanks to its sensitivity to objects in the distant solar system.
  • "The timescale for us or for anybody else really to find it is closing because once LSST [the Rubin Observatory] comes online, it's going to be the new game — perhaps the only game — in town," astronomer Konstantin Batygin, one of the first to propose the existence of Planet X, told Axios.

Details: The existence of Planet X could help explain some of the odd orbits seen among objects in the Kuiper Belt, far past Pluto.

  • Scientists who think Planet X is out there expect it's about 5 to 10 times Earth's mass and orbits the Sun once every 10,000 to 20,000 Earth years.
  • Even though it's thought to be relatively large, the planet would be particularly difficult to see because of its extreme distance from Earth, potentially small size and possibly dark color, making it harder to see any light reflected off of it.
  • The possibility of Planet X was boosted in 2015 when researchers produced new models and simulations showing the world could be out there.

The intrigue: Everyone wants to be first to find proof-positive of the new planet using their own techniques and telescope parameters, but the best way to actually find the world is through collaboration, a fact the scientists hunting for it know all too well.

  • "There is an understanding — or at least I hope — there is an understanding that collectively we will get there faster if we all do the work," Batygin said.

Yes, but: It's not a sure thing that Planet X is out there at all.

  • Theoretical research has been mounting that may explain the odd orbits on the edge of the solar system without the need for an extra, large planet orbiting far from the Sun.
  • New data suggests the samples of observations being used to claim Planet X may be out there are actually biased in part due to the small number of objects in the distant reaches of the solar system detected so far.
  • "I would be delighted if Planet Nine existed. That would be so cool," physicist Samantha Lawler told Axios. "But I don't think the evidence is there."
Go deeper