McGill University students discover pitch-dark planet with NASA’s Hubble telescope News, Sci/Tech

WASP -12b the black planet that absorbs light. (NASA, ESA, G. Bacon)

By Junisha Dama

A group of students from McGill University observed the planet WASP-12b using NASA’s Hubble Space Telescope and found that it looks as black as fresh asphalt.

McGill student and lead researcher Taylor Bell carried out the study to observe how much light was reflected by WASP-12b.  Bell observed the planet for over five hours and studied the light reflected when WASP-12b passed behind the star and came to the deduction that the planet was black.

“There was barely any to no light that was reflected,” Bell said. He suggested that as WASP-12b is mostly made of hydrogen, the high temperatures cause it to be opaque. However, he added that the group did not expect it to be as dark as they found it.

McGill Professor, Nicolas Cowan, who is a researcher of the climate of planets outside our galaxy said, “What’s amazing with this planet is that we know from previous measurements that it’s got water vapour and probably clouds, yet our new observations show that the dayside is intensely black, so black that it probably has precious few molecules, let alone clouds.”

The study has revealed that the planet absorbs 94 per cent of visible starlight falling into its atmosphere, compared to other hot Jupiter planets that absorb 40 per cent of the light.

Artist’s impression of WASP-12b — as black as fresh asphalt, orbiting a star like our Sun. (NASA, ESA and G. Bacon)

This isn’t the first time the planet has fascinated astronomers. WASP-12b is unique for multiple reasons. When it was first discovered in 2008, NASA researches characterized it as a “hot Jupiter” planet, which is a class of planets that are as big as Jupiter or bigger than any planet in our solar system. The planet has been studied and observed by NASA often and has a reputation as one of the hottest Jupiters, with daytime temperatures that are half of the sun’s, and nighttime temperatures close to the melting point of iron.

According to NASA, the planet is so close to its host star that it is tidally locked, which means that it is perpetually daytime on the side facing the host star and night on the other, but this hasn’t been proved. The planet’s proximity to its host star is causing it to be eaten away by the star and scientists predict that the planet is likely to be destroyed in 10 million years. These unique characteristics are some of the reasons that attracted Bell, to study the planet.

 “We were fascinated by the idea of a planet so dark that it absorbs light. There are so many stars and planets with so much diversity in space,” said Ray Villard, Director of Media Relations at the Space Telescope Science Institute, Baltimore.

Villard also points out that it was only 20 years ago when astronomers began discovering “hot Jupiters” but thanks to the Hubble telescope, astronomers can now determine the characteristics of the planets as well.

 For astronomers and space enthusiasts, Bell’s research helps understand the climate of the planet. In particular, it gives a peak into what the winds are like on WASP-12b. “We expect that the winds don’t carry the heat to the night side of the planet,” said Bell.

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