Hubble spots black, super hot exoplanet

Sept. 14 (UPI) -- New analysis of an oft-studied exoplanet suggests the alien world reflect almost no light -- it's surface is pitch black, making it nearly invisible.

A surface's reflectivity is known as its albedo. Researchers measured the albedo of WASP-12b using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope.

"The measured albedo of WASP-12b is 0.064 at most," Taylor Bell, a grad student in astronomy at McGill University in Montreal, said in a news release. "This is an extremely low value, making the planet darker than fresh asphalt!"

And like asphalt on a sunny summer day, WASP-12b gets extremely hot. The exoplanet is also about twice the size of Jupiter. Thus, scientists categorize the exoplanet as a "hot Jupiter."

Few hot Jupiters are as hot as WASP-12b, which orbits a sun-like star located 1,400 light-years from Earth. The exoplanet is so hot that few clouds can form and alkali metals are ionized. Its atmosphere behaves more like that of a small star.

WASP-12b is only the second exoplanet to have its albedo measured. The other, HD 189733b, also a hot Jupiter, glowed a cool blue. The spectral data showed WASP-12b reflects neither end of the spectrum, but likely glows red from light radiated by its intense heat.

The new spectral data also suggests the alien world boasts a thin atmosphere of atomic hydrogen and helium.

"The fact that the first two exoplanets with measured spectral albedo exhibit significant differences demonstrates the importance of these types of spectral observations and highlights the great diversity among hot Jupiters," said Bell.

Researchers described the analysis of the new spectral data this week in the Astrophysical Journal Letters.