Published: Sun, September 17, 2017
Life&Culture | By Rose Hansen

A pitch black planet? NASA's Hubble observes exoplanet reflecting nearly no light

A pitch black planet? NASA's Hubble observes exoplanet reflecting nearly no light

According to the European Space Agency, it took an eclipse of the planet to measure its brightness - scientists fired up the Hubble Space Telescope and waited for WASP-12b to pass behind its star, then measured how much light it reflected back into space, a quality known as its albedo. What they soon realized was that the planet is so impossibly dark that it nearly completely blends in to the darkness of space.

This high temperature is the most likely explanation for WASP-12b's low albedo. It circles a Sun-like star residing 1,400 light-years away in the constellation Auriga.

WASP-12b was observed by the scientists because they were very keen to know the reason behind it being so dark as well as hot. Previous observations by Hubble's Cosmic Origins Spectrograph (COS) revealed that WASP-12b may be downsizing. Its atmosphere it so hot that it starts to mimic the atmosphere of a small star.

The full results of the study, performed to observe WASP-12b's atmosphere, are available in the Thursday's issue of "The Astrophysical Journal Letters". It's called Wasp-12b, and it is known as a hot jupiter, or a gas giant that orbits very close to its host star. From this, researchers found out that the exoplanet's albedo is only 0.064 and defined it to be darker than fresh asphalt.

This makes WASP-12b two times less reflective than our Moon which has an albedo of 0.12. "This is in contrast to the Bond albedo, which describes the total amount of energy reflected across all wavelengths and always falls in the range of 0 to 1", the researchers explained.

"The low albedo shows we still have a lot to learn about WASP-12b and other similar exoplanets", Bell added.

The new Hubble data indicate that the exoplanet's atmosphere is composed of atomic hydrogen and helium.

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"After we measured the albedo we compared it to spectral models of previously suggested atmospheric models of WASP-12b", Nikolay Nikolov (University of Exeter, UK), co-author of the study, said.

"There are other hot Jupiters that have been found to be remarkably black, but they are much cooler than WASP-12b", Bell said. The planet's atmosphere is so hot that most molecules are unable to survive on the blistering day side of the planet, where the temperature is 4,600 degrees Fahrenheit.

But the planet's nighttime side is a different story.

Scientists believed that the excess high temperature of the planet might have resulted in its low albedo because there is no chance of formation of hot clouds due to the extremely high temperatures and also the alkali metal get ionized. It is 2,400 degrees Fahrenheit (1,340 degrees Celsius) cooler, which allows water vapor and clouds to form.

An global team of astronomers from McGill University, Canada and the University of Exeter, UK measured how much light is reflected by the exoplanet, otherwise known as its 'albedo, ' in order to better understand the chemical makeup of the planet's atmosphere. Researchers said that WASP-12b does not appear to show a color preference in the light that it reflects and rather glows red like a hot glowing metal because of its heat.

Taylor Bell, lead researcher of the study says, "This new Hubble research further demonstrates the vast diversity among the unusual population of hot Jupiters".

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