Home » Technology News » 2011 » August » August 12, 2011

Jupiter-sized 'alien' planet that's blacker than coal discovered

August 12, 2011 - Washington

Astronomers have discovered the darkest known exoplanet in the galaxy that is blacker than coal or any planet or moon in our solar system.

Known as TrES-2b, the distant, Jupiter-sized gas giant reflects less than one percent of the sunlight falling on it.

Scientists used NASA's Kepler spacecraft to make the observations.

"TrES-2b is considerably less reflective than black acrylic paint, so it's truly an alien world," said lead researcher David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA).

TrES-2b, discovered in 2006 by the Trans-Atlantic Exoplanet Survey, or TrES, lacks reflective clouds due to its high temperature.

It orbits its star at a distance of only three million miles. The star's intense light heats TrES-2b to a temperature of more than 1,800 degrees Fahrenheit.

The researchers propose that light-absorbing chemicals such as vaporized sodium and potassium or gaseous titanium oxide in the planet's atmosphere could help explain why it is so dark. Yet none of these chemicals fully explain the extreme blackness of TrES-2b.

"It's not clear what is responsible for making this planet so extraordinarily dark," stated 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," he added.

TrES-2b is believed to be tidally locked like our moon, so one side of the planet always faces the star. And like our moon, the planet shows changing phases as it orbits its star. This causes the total brightness of the star plus planet to vary slightly.

"By combining the impressive precision from Kepler with observations of over 50 orbits, we detected the smallest-ever change in brightness from an exoplanet: just 6 parts per million," said Kipping.

"In other words, Kepler was able to directly detect visible light coming from the planet itself."

The extremely small fluctuations proved that TrES-2b is incredibly dark.

TrES-2b orbits the star GSC 03549-02811, which is located about 750 light-years away in the direction of the constellation Draco.


Comment on this story