While many children are taught that planets orbit a star, the way the Earth and the other planets in our Solar System orbit the Sun, that’s not strictly true. There are planets drifting out in space that are known as rogue planets, or starless planets.
Rogue planets orbit a galaxy after either having been ejected from the planetary system in which they formed or having never been gravitationally bound to any star. Recently, the largest known rogue planet, known as 2MASS J2126, was discovered to have a star after all. The planet orbits 600 billion miles from its host star, which makes its solar system the largest one known, according to Space.com. The planet completes one orbit every 900,000 years or so.
“This is the widest planet system found so far and both the members of it have been known for eight years, but nobody had made the link between the objects before,” Dr. Niall Deacon of the University of Hertfordshire, who lead the team of researchers that discovered the connection, said in a statement. “The planet is not quite as lonely as we first thought, but it’s certainly in a very long distance relationship.”
According to the Royal Astronomical Society, there is unlikely to be aby life on the planet, but if there were, they would see their sun as just a bright star in the sky and probably wouldn’t even know they were connected to it all.
The closest rogue planet to Earth is WISE 0855-0714, which is still roughly 7 light years away. Rogue planets are difficult to be detected since astronomers usually rely on the planet’s orbit around a host star. However, there are 2 other methods of detecting rogue planets: gravitational microlensing and direct imaging.
There are 8 known rogue planets, discovered within the last 6 years. As of yet, there is no way of knowing whether these planets were ejected from orbiting a star or originally formed on their own.
In Cosmos: A Spacetime Odyssey, Neil deGrasse Tyson introduced viewers to the concept of lonely, interstellar planets. Tyson said that the galaxy has billions of these rogue planets. In fact, it’s possible that our own Solar System has cast out a planet that is now drifting along in space. National Geographic reported that most theories describing the early Solar System don’t work unless there had been another fifth giant planet present at the start and that this fifth giant was kicked out of the Solar System.