Pluto may have a replacement soon — astronomers are searching for a hypothetical ninth planet in the solar system. They haven't found it yet, but the search has uncovered three smaller worlds hiding out on the edge of the solar system, according to new research that will be published in the Astronomical Journal.
Small new worlds: These kinds of tiny, distant objects are known as trans-Neptunian objects, often abbreviated TNOs. While searching for Planet Nine, astronomers Scott Sheppard and Chadwick Trujillo discovered three of them tumbling around beyond Neptune.
One of the newly discovered TNOs is called 2014 SR349, and it has an orbital pattern that might be influenced by Planet Nine, according to the research. The other two, called 2013 FT28 and 2014 FE72, have unusual orbits, but might not be controlled by Planet Nine.
Still, the more TNOs astronomers find, the more they'll be able to narrow down the position of Planet Nine.
"Objects found far beyond Neptune hold the key to unlocking our Solar System's origins and evolution," Sheppard explained in a statement. "Though we believe there are thousands of these small objects, we haven't found very many of them yet, because they are so far away. The smaller objects can lead us to the much bigger planet we think exists out there."
Sheppard, Trujillo and astronomer David Tholen have already scanned nearly 10% of the sky for Planet Nine, but there's more work to be done.
A long search: Sheppard and Trujillo discovered an unusual TNO back in 2014 and predicted there was a ninth planet lurking out there, herding the orbital paths of smaller TNOs. Then in 2016, researchers Mike Brown and Konstantin Batygin created a mathematical model that suggested Planet Nine is real. The research has sparked an all out man-hunt for the possible planet. No one has found it yet, but the evidence keeps piling up.
If it exists at all, Planet Nine must be mind-bogglingly far away compared to the other planets, so it will take some time to track it down.