Pluto, Planet Nine and Other Backyard Worlds cover

Pluto, Planet Nine and Other Backyard Worlds


If you're interested in playing a part in discovering a new Planet Nine you're in luck - no scientific background necessary. Introducing a citizen science project called Backyard Worlds: Planet 9: a new search for moving objects in the realm beyond Neptune.
PLoS Blogs
CC BY 4.0

NoteStream NoteStream

NoteStreams are readable online but they’re even better in the free App!

The NoteStream™ app is for learning about things that interest you: from music to history, to classic literature or cocktails. NoteStreams are truly easy to read on your smartphone—so you can learn more about the world around you and start a fresh conversation.

For a list of all authors on NoteStream, click here.

Read the NoteStream below, or download the app and read it on the go!

Save to App

Pluto, Planet Nine and Other Backyard Worlds

Eighty-seven years ago, Clyde Tombaugh was poring over a pair of photographic plates, hoping to change the world. He was staring hard into an arcane device called a blink comparator, which allowed him to rapidly switch from viewing one image to the next. In those days before computers, that was the best tool he had for finding the faint, moving dot he was seeking, a new planet in our solar system.

When Tombaugh discovered Pluto in those photographic plates on February 18, 1930, the news made headlines all around the globe. “In the little cluster of orbs which scampers across the sidereal abyss under the name of the solar system there are, be it known, nine instead of a mere eight, worlds,” said the New York Times. It was a victory for Tombaugh, and for astronomy.

The astronomer Clyde Tombaugh, discoverer of Pluto here shown with his homemade 9-inch telescope.

Times have changed since that big day. Computers and the internet have changed the way we handle large data sets and interact with one another.

Telescopes are bigger, and some fly in space, giving us access to wavelengths of light that astronomers in the 1930s could only dream of seeing one day. Pluto is no longer considered a planet, but a dwarf planet, the king of the Kuiper belt, which is a collection of icy bodies orbiting the sun beyond the orbit of Neptune.

But the quest to understand the outskirts of our solar system has only picked up speed. Now evidence for a new planet in the outer solar system has surfaced, one more distant than Pluto.

Artist’s concept of the Planet Nine, cold and massive, orbiting hundreds of times farther from the Sun than Earth. Credit: NASA

A pattern in the orbits of Kuiper belt objects points to a large perturber—possibly a new Planet Nine. This hypothesized planet could be as massive as Neptune, or even larger, but it has escaped detection because it is so cold and faint.

Moreover, images of moving objects from NASA’s Wide-field Infrared Explorer (WISE) mission point to a population of ultracool brown dwarfs, or rogue planets, whizzing by the solar system beyond Neptune. Some of these nearby worlds may even lurk between us and the closest known star, Proxima Centari. These brown dwarfs hold keys to understanding how stars and planets form and how planetary atmospheres behave.

So today we’re announcing a new search for moving objects in the realm beyond Neptune: a citizen science project called Backyard Worlds: Planet 9. Hosted by Zooniverse, the project invites you to follow in the bold footsteps of Clyde Tombaugh by combing images from NASA’s WISE telescope to find objects that move, like brown dwarfs and planets. Participants will share the credit for their discoveries in any scientific publications that result from the project.

You won’t need a blink comparator like Tombaugh’s, just a laptop or cell phone. You’ll view animated images of the sky, in color, and simply click on interesting candidates when you spot them.

You’ll join thousands of other citizen astronomers, whom you can chat with on the “TALK” social network, and a team of astrophysicists from NASA, the American Museum of Natural History, Arizona State University, and the University of California – Berkeley.

Making a big discovery these days still takes hard work. But it can be a lot more fun, thanks to citizen science.

Before Tombaugh made his big discovery, Percival Lowell, the astronomer for whom Pluto is named, searched for Pluto for ten years, to no avail. Perhaps if he had help from citizen scientists, he might have lived to see its discovery. He might have made thousands of new friends as well.

When you log into Backyard Worlds: Planet 9, you’ll see images of the sky taken at four different times, one after another, from the WISE telescope. Planet Nine is expected to look like a blue dot, hopping and jumping all the way across the images. Brown dwarfs will be redder, and slower moving. Some moving objects will appear as “dipoles”, pairs of bright and dark images. You’ll also learn how to search other catalogs to see if someone else has already discovered the object you’ve found – or if you’ve made a new discovery.

Backyard Worlds: Planet 9 shows you animated images of the sky taken at four different times. To participate in the search, click on the moving objects. Credit: Zooniverse

Join this historic quest at and check out thousands of other citizen science projects at SciStarter!