Top Story: August 18, 2011

Dark, Hot Exoplanet

DarkExoplanet

Kepler is proving that exoplanets can be weird and unusual. Now the mission has discovered a hot, new planet that is dark-- really dark.

750 light-years away, TrES-2b is the size of Jupiter and reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system.

“TrES-2b is considerably less reflective than black acrylic paint, so it's truly an alien world,” explains astronomer David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author on the paper reporting the research.

In our solar system, Jupiter is swathed in bright clouds of ammonia that reflect more than a third of the sunlight reaching it. In contrast, TrES-2b lacks reflective clouds due to its high temperature.

TrES-2b orbits its star at a distance of only three million miles (Mercury, at its closest, is 28.5 million miles from our Sun). The star’s intense light heats TrES-2b to a temperature of more than 1,800° Fahrenheit—much too hot for ammonia clouds. Instead, its exotic atmosphere contains light-absorbing chemicals like vaporized sodium and potassium, or gaseous titanium oxide. Yet none of these chemicals fully explain the extreme blackness of TrES-2b.

The planet is leaving scientists in the dark.

“It's not clear what is responsible for making this planet so extraordinarily dark,” states co-author David Spiegel of Princeton University. “However, it's not completely pitch black. It's so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove.”

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