hubble capture

Astronomers find a pitch-black planet

hubble capture
Image via HubbleSite.

The Hubble Space Telescope has observed an exoplanet — or planet orbiting a distant star — that seems as black as fresh asphalt. The planet is named WASP-12b, and it is one of a class of so-called hot Jupiters, colossal, gaseous planets orbiting close to their host stars and therefore heated to extreme temperatures. The astronomers say this planet is so black as it absorbs some 94 percent of the visible starlight falling into its own air, as opposed to reflecting it back into space. A statement from HubbleSite stated:

The planet’s atmosphere is so hot that many molecules are not able to survive on the blistering day side of Earth, where the temperature is 4,600 degrees Fahrenheit. Therefore, clouds probably cannot form to reflect light back into space. Rather, incoming light penetrates deep into the world’s atmosphere where it’s absorbed by hydrogen atoms and converted into heat energy.

This planet is about 1,400 light-years away. It contrasts a sunlike star, situated in our skies in the direction of the constellation Auriga the Charioteer. He said:

We didn’t expect to find this type of dark exoplanet.

WASP-12b is about 2 million kilometers (3 million kilometers) from its star. It’s a fixed day side and nighttime side; this is, it orbits so near its star that it is tidally locked to the star, much as our moon is tidally locked to Earth and thus keeps one face turned perpetually toward our world. Water vapor is present in the air on the night side, and clouds do form. Previous Hubble observations of this day/night border uncovered evidence of water vapor and potentially clouds and hazes in the atmosphere. Bell said:

This new Hubble research further shows the huge diversity among the odd population of hot Jupiters. You can have planets like WASP-12b which are 4,600 degrees Fahrenheit and a few which are 2,200 degrees Fahrenheit, and they are both called hot Jupiters. This prior study suggests that more heat is being pumped to the day side of Earth, but the procedures, like winds, that carry the heat to the night side of the planet do not maintain the pace.

These astronomers used the Hubble’s Space Telescope Imaging Spectrograph to hunt in largely visible light to get a very small dip in starlight as the world passed directly behind the celebrity. The amount of dimming tells astronomers how much reflected light is given off from the planet. However, the observations didn’t detect reflected light, meaning that the day side of the planet is absorbing almost all of the starlight falling onto it.

Bottom line: Astronomers used the Hubble Space Telescope to study the exoplanet WASP-12b and discovered that’s absorbs most starlight falling onto it, so that it’s “as black as fresh asphalt.”

From HubbleSite