The discovery of a pitch-black planet darker than hot asphalt

Hubble observes pitch black planet — an alien world as black as fresh asphalt, orbiting a star like our Sun.

Astronomers have discovered that the well-studied exoplanet WASP-12b reflects almost no light, making it appear essentially pitch black. This discovery sheds new light on the atmospheric composition of the planet.

Author Taylor Bell: “The measured albedo of WASP-12b is 0.064 at most. This is an extremely low value, making the planet darker than fresh asphalt!” This makes WASP-12b two times less reflective than our Moon which has an albedo of 0.12. Bell adds: “The low albedo shows we still have a lot to learn about WASP-12b and other similar exoplanets.”

WASP-12b orbits the Sun-like star WASP-12A, about 1400 light-years away, and since its discovery in 2008 it has become one of the best studied exoplanets.

With a radius almost twice that of Jupiter and a year of just over one Earth day, WASP-12b is categorised as a hot Jupiter.

Because it is so close to its parent star, the gravitational pull of the star has stretched WASP-12b into an egg shape and raised the surface temperature of its daylight side to 2600 degrees Celsius.

The high temperature is also the most likely explanation for WASP-12b’s low albedo.

The daylight side of WASP-12b is so hot that clouds cannot form and alkali metals are ionised. It is even hot enough to break up hydrogen molecules into atomic hydrogen which causes the atmosphere to act more like the atmosphere of a low-mass star than like a planetary atmosphere.

This leads to the low albedo of the exoplanet.

The new data indicate that the WASP-12b does, however, emit light because of its high temperature, giving it a red hue similar to a hot glowing metal.

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Source: Hubble captures blistering pitch-black planet