NASA’s Hubble Space Telescope has found that a previously discovered exoplanet is almost completely black. The planet was found to absorb 94 percent of light falling upon it, making it very unusual.
The exoplanet is called WASP-12b, located 1,400 light-years from Earth. It’s a “hot Jupiter”, which is a gas giant that orbits incredibly close to its host star. This planet is thought to have a temperature of 2,500°C (4,600°F) on its day side. On its night side, it’s about half as hot.
Using Hubble, a team of scientists led by McGill University, Canada, and the University of Exeter, UK, found that the planet had an albedo – or reflectivity – of just 0.064. This is darker than asphalt, and makes the planet two times less reflective than our own Moon, which has an albedo of 0.12.
WASP-12b was discovered back in 2008, orbiting its Sun-like star towards the constellation of Auriga. It has since been studied numerous times, but this is the first time we’ve got a grasp on what it looks like.
"We did not expect to find such a dark exoplanet," said lead researcher Taylor Bell of McGill University and the Institute for Research on Exoplanets in Montreal, Quebec, Canada, in a statement. "Most hot Jupiters reflect about 40 percent of starlight."
The planet is tidally locked to its star, so one side is in perpetual daylight and the other endless darkness. Astronomers deduced its color by watching as the planet passed behind the star. This lets them spot how much light is being reflected by the day side, but observations showed there was essentially no reflected light. This means the day side is absorbing all the starlight hitting it.
The cause of this is thought to be that clouds cannot form on the day side of the planet. It gets so hot that hydrogen molecules are broken down into atomic hydrogen, which absorbs more of the incoming light.
WASP-12b orbits just 2 million miles away from its star, completing an orbit in a day. Its proximity not only makes it extremely hot, but it has also stretched the planet into an egg shape. If you could see the planet up close, it would appear red because of its high temperature, similar to a glowing metal.