Although its name may not be all that memorable, the recently discovered planet 131399Ab is one for the record books.
It’s unique in a number of ways. At four times the size of Jupiter and a temperature of 580 degrees Celsius, it is one of the smallest and coldest planets that we’ve been able to directly image. Usually when we find a planet, we do so by looking at the what parts of the light spectrum it blocks when it passes in front of a star. In addition, 131399Ab is also only about 16 million years old, making it not only one of the youngest planets ever observed, but just overall pretty young. In comparison, our Earth is estimated to be about 4.5 billion years old.
But the most interesting thing about this planet is the fact that it resides in a solar system with three stars. We’ve been aware of binary star systems for a while now, and those are almost as common as single systems with a single star. But nobody expected to find a planet in a solar system with three stars, because its orbit would probably be so erratic that the planet would be fired out of the system after a very short time.
But 131399Ab has a very stable orbit, about 80 AU from the largest sun in the system. An AU, or astronomical unit, is the distance from the Earth to the Sun–so this planet is about 80 times further away from its sun as Earth is from our sun, or twice as far as Pluto. The other two stars are about 300 AU away from the largest sun and orbit each other about 10 AU apart. The main star is also about 80% bigger than our Sun.
All told, 131399Ab is pretty spectacular, and astronomers are excited about it, especially because studying it could tell us a lot about how gravity works in similar complex systems. We can also likely learn more about how planets form in the first place, since there are some very strong forces at work in this solar system.