Despite the small probabilities involved, the vast number of red dwarfs out there mean that the existence of a Krypton-like planet is still a possibility.
The search for exoplanets, worlds orbiting stars other than our own, has become a major field of research in the last decade – with nearly 2,000 such planets discovered to date. So the release of Batman v. Superman: Dawn of Justice got me thinking: does Superman’s home planet of Krypton actually exist? Or at least a planet very much like it?
We don’t know a huge amount about Krypton. Since the very earliest Superman comic strips, it has been depicted as a rocky planet similar to Earth, but much older. In the film Man of Steel, it was said to be about 8.7 billion years old with intelligent life, Kryptonians, having existed for hundreds of thousands of years – comparable to the amount of time humans have existed on Earth.
Start with the red stars
In order to find Krypton, the first thing we’d need to do is identify its star, or at least its type. For a long time, all we knew was that, unlike the sun, Krypton’s star Rao is red. There are three classes of stars which are red in colour: red dwarfs, red giants and red super giants. While they are very different in size, their red colour tells us that they are some of the coolest stars in existence, with surface temperatures of only just over 3,200°C, about half that of the Sun.
Red dwarfs are by far the most common stars – around 75% of the stars in the vicinity of the solar system are of this type. As the name suggests, they are quite small compared to the sun, being between 7.5% and 50% of the sun’s mass.
Meanwhile, our sun will one day become a red giant, as it runs out of its hydrogen fuel – ballooning in size so that it consumes the orbit of the Earth. But that’s nothing compared to a red supergiant – stars which would extend all the way out to the orbit of Saturn.
While depictions of Krypton’s star have varied between these three types over the years, what we see of Rao in Man of Steel points towards it being a red dwarf.
Destination LHS 2520
In 2012, it seemed that the matter was settled when astrophysicist Neil deGrasse Tyson was invited to choose Rao’s real location. He picked a star known as LHS 2520, a red dwarf star in the southern constellation of Corvus. Our searches for planets around this star have so far proved fruitless, but that doesn’t mean it’s not there.
To find an Earth-like exoplanet around a red dwarf star, a good approach would be to use the radial velocity method or the doppler technique, measuring the small movement a star makes as it responds to the gravitational tug of an orbiting planet.