Darkest exoplanet spotted by astronomers

A dark alien world, blacker than coal, has been spotted by astronomers.

TrES-2b is literally darker, on average, than coal
TrES-2b is literally darker, on average, than coal

 

The Jupiter-sized planet is orbiting its star at a distance of just five million km, and is likely to be at a temperature of some 1200C.

The planet may be too hot to support reflective clouds like those we see in our own Solar System, but even that would not explain why it is so dark.

The research will be published in the journal Monthly Notices of the Royal Astronomical Society.

The planet, called TrES-2b, is so named because it was first spotted by the Trans-Atlantic Exoplanet Survey in 2006. It is about 750 light-years away, in the Draco constellation.

It also lies in the field of view of the Kepler space telescope, whose primary mission is to spot exoplanets using extremely sensitive brightness measurements as far-flung worlds pass in front of their host stars.

Using the first four months’ worth of data from Kepler, David Kipping of the Center for Astrophysics at Harvard University and David Spiegel from Princeton University, looked at the amount of light coming directly from TrES-2b itself.

They measured the amount of light coming from the planet’s “night side” – when it is directly in front of its star. They compared that to the light coming from its “day side”, just before it passes behind its star and Kepler sees it bathed in light.

The difference between the two gives a measure of how much light the planet reflects – or its albedo.

In our Solar System, clouds on Jupiter give it an albedo of 52%; Earth’s is about 37%. But it appears that TrES-2b reflects less than 1% of its star’s light.

“This albedo is darker than that of black acrylic paint or coal – it’s weird,” Dr Kipping told BBC News.

Read more on this story via BBC News – Darkest exoplanet spotted by astronomers.





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