A new study of a mysterious hot exoplanet called WASP-12b has revealed it to be a pitch-black, light-eating oddity. The revelation surprised scientists as they discovered the gigantic planet has a unique ability to absorb almost all the light that hits it, making it appear "black as fresh asphalt."
WASP-12b was discovered back in 2008 orbiting the WASP-12 star, around 1400 light-years from our solar system. The exoplanet is almost twice the size of Jupiter and sits extremely close to to its parent star, only 2 million miles (3.2 million km), meaning an orbital year takes just over one Earth day to complete.
The strange exoplanet belongs to a class of planets called "hot Jupiters" that resemble our gas giant neighbor, but which sit in extremely close proximity to their stars. These "hot Jupiters" have high temperatures and the tidally locked WASP-12b is no exception, with the atmosphere on the daylight side reaching 4,600° F (2,600° C).
The amount of light a planet reflects is known as its albedo, and in recent years scientists have studied some exoplanets with extraordinarily low albedo. WASP-12b was found to have an albedo of 0.064 which translates into reflecting as little as 6 percent of the light that hits its surface. This makes it one of the darkest planetary objects ever identified, but it isn't the darkest. That title is still held by a "hot Jupiter" named TrES-2b, which was discovered in 2011 to reflect as little as 1 percent of the light that falls on it.
"There are other hot Jupiters that have been found to be remarkably black, but they are much cooler than WASP-12b," explains lead author on the new research, Taylor Bell. "For those planets, it is suggested that things like clouds and alkali metals are the reason for the absorption of light, but those don't work for WASP-12b because it is so incredibly hot."
WASP-12b is around 2,800° F (1,500° C) hotter than TrES-2b, making its strange light-eating ability a mystery to scientists. The current hypothesis behind the low albedo of this super-hot planet is that the atmosphere of the side facing the star is so hot that it breaks hydrogen molecules into atomic hydrogen. This means the atmosphere ultimately resembles something closer to that of a low-mass star instead of any known planetary atmosphere.
"This new Hubble research further demonstrates the vast diversity among the strange population of hot Jupiters," says Bell. "You can have planets like WASP-12b that are 4,600 degrees Fahrenheit and some that are 2,200 degrees Fahrenheit, and they're both called hot Jupiters."
The new research was published in the journal The Astrophysical Journal Letters.
Source: Hubble Space Telescope
