The race is on to discover the hidden ninth planet in our solar system
Astronomers from Caltech have discovered compelling evidence that there is a ninth planet hidden on the far edges of the solar system, and the hunt is on to find it.
The researchers, Dr. Konstantin Batygin and Dr. Mike Brown, believe that the object, which they are calling simply “Planet Nine” for the moment, has about 10 times the mass of Earth, and it is believed to orbit the sun at about 20 times the distance that Neptune orbits the sun. It is so far from the sun that it takes somewhere between 10,000 and 20,000 years to complete a single orbit.
By comparison, Pluto takes around 248 years to orbit the sun.
“This would be a real ninth planet,” Brown said. “There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting.”
It’s somewhat fitting that the discovery comes from Brown and Batygin. The two were instrumental in stripping Pluto of its classification as a planet, leaving it instead designated as a dwarf planet. They helped to take away our first ninth planet, and now they may help to replace it.
The pair’s new findings will be published in The Astronomical Journal, partly to spread the news of their discovery, and partly to gain the help of the astronomical community.
Although Planet Nine hasn’t officially been spotted yet, when it is, it shouldn’t have any problem passing the test to be classified as a planet. Planet Nine is roughly 5,000 times larger than Pluto, and it dominates the other objects in its neighborhood – in this case the Kuiper Belt.
Astronomers have spent years exploring and mapping the remote Kuiper Belt, and new discoveries are frequently being made – like the dwarf planet Sedna, which Brown also helped to discover. Recently, astronomers found evidence of what may be two more planets in the Kuiper Belt. It’s not clear if Planet Nine could be one of those planets, but there is plenty of reason to think the Kuiper Belt holds many secrets.
The origins of Planet Nine are still unknown, but one theory is that it may have started with the core of a gas giant. During the formation fo the solar system, a run in with Jupiter may have forced it out of the known solar system and into the Kuiper Belt, where it took up an irregular orbit after freezing.
Brown and Batygin only discovered the planet because of the unusual orbits of six other objects in the Kuiper Belt. The bodies were moving in a strange direction, all pointed in the same direction. Neither Brown nor Batygin even considered the possibility of a full planet at first. They tested several ideas using computer models, including dwarf planets exerting their gravitational pull.
It was almost by accident that the astronomers stumbled upon the correct answer. They tried simulations with a planet in a more traditional orbit, but it didn’t work. They then tried a model with a planet in a strange orbit. They didn’t believe that was the answer, but they wanted to rule out all other possibilities.
The problem was the orbits of the objects. No one could imagine a body moving perpendicularly to the plane of the planets. After several tests though, Brown finally realized the truth.
“Suddenly I realized there are objects like that,” recalls Brown. “We plotted up the positions of those objects and their orbits, and they matched the simulations exactly,” says Brown. “When we found that, my jaw sort of hit the floor.”
Now that Planet Nine has been theoretically proven to exist, the race is on to find it using a telescope and by examining older images of the sky. Depending on where it is in its orbit – and where Earth is at the time – it may be able to be seen with a relatively standard telescope. If it is at its most distant, it may require something larger, like the massive telescope at the Mauna Kea Observatory.
Brown began looking for Planet Nine over a year ago, and at the time he predicted that it would be discovered within five years. With astronomers around the world looking, it may take far less time than that.