Due to the particular nature of its atmosphere, which absorbs the vast majority of light it receives instead of reflecting it, this planet appeared pitch black when observed by the Hubble team.
The exoplanet, called WASP-12b, is one of a class of so-called "hot Jupiters", huge, gaseous planets that orbit very close to their host star and are heated to extreme temperatures.
Researchers from the McGill University, Canada, and the University of Exeter in the United Kingdom discovered the approximate amount of light that the planet reflects by using the Hubble Space Telescope, in the NASA/ESA Space Telescope Imaging Spectrograph (STIS).
The results were surprising, explains lead author Taylor Bell, a Master's student in astronomy at McGill University who is affiliated with the Institute for Research on Exoplanets: "The measured albedo of WASP-12b is 0.064 at most".
WASP-12b is only the second planet to have spectrally resolved albedo measurements, the first being HD 189733b, another hot Jupiter. "The low albedo shows we still have a lot to learn about WASP-12b and other similar exoplanets".
WASP-12b is about two million miles away from its star and completes an orbit once a day.
The planet reflects just 6.4% of the total light but darker planets have been found which reflects only one percent of the total light back in 2011. That short distance means that the planet's surface could top 2600 degrees Celsius, which may mean its atmosphere is actually responsible for absorbing so much of the light that hits the planet. A single Earth day is equal to a year at WASP-12b.
With a mass 1.4 times that of Jupiter, a radius nearly twice that of Jupiter and a year of just over one Earth day, WASP-12b is categorized as a hot Jupiter.
"There are other hot Jupiters that have been found to be remarkably black, but they are much cooler than WASP-12b", he said in the same statement. "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", said Bell.
The daylight side of WASP-12b is so hot that clouds can not form and alkali metals are ionized.
It's so hot, in fact, that molecular hydrogen - the familiar H2 - gets broken apart into atomic hydrogen in WASP-12b's skies. These type phenomena make the albedo very low. On this side, temperatures are about 1366 K (1093 °C; 2000 °F) cooler, which allows water vapor and clouds to form. This Hot-Jupiter, located in a star system 1400 light years from Earth in the direction of the Auriga constellation, was recently studied by a team of astronomers using the Hubble Space Telescope.
But the planet's nighttime side is a different story. There is evidence that the night side has water vapour in the atmosphere.
Scientists measured the exoplanet's albedo during an eclipse in October 2016 when it passed behind its star. Scientists revealed that the WASP-did not show any color preference and looked like a red hot glowing planet because of excess heat. Past observations of hot Jupiters indicate that the temperature difference between the day and night sides of the planet increases with hotter day sides.