It may be hard to imagine a planet blacker than coal, but that's what astronomers say they've discovered in our home galaxy with NASA's Kepler space telescope. the Jupiter-size gas giant planet, dubbed TrES-2b, is heated to 1,800 degrees Fahrenheit (980 degrees Cels!
Yet the apparently inky world appears to reflect almost none of the starlight that shines on it, according to a new studyBeing less reflective than coal or even the blackest acrylic paint—this makes it by far the darkest planet ever discovered," lead study author David Kipping said. If we could see it up close it would look like a near-black ball of gas, with a slight glowing red tinge to it—a true exotic amongst exoplanets," added Kipping, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
The Dark Mystery of TrES-2b
Current computer models predict that hot-Jupiter planets—gas giants that orbit very close to their stars—could be only as dark as Mercury, which reflects about 10 percent of the sunlight that hits it.
But TrES-2b is so dark that it reflects only one percent of the starlight that strikes it, suggesting that the current models may need tweaking, Kipping said.
Assuming the new study's measurements are sound, what exactly is making the new planet's atmosphere so dark?
"Some have proposed that this darkness may be caused by a huge abundance of gaseous sodium and titanium oxide," Kipping said. "But more likely there is something exotic there that we have not thought of before.
"It's this mystery that I find so exciting about this discovery."
TrES-2b may even represent a whole new class of exoplanet—a possibility Kipping and company hope to put to the test with Kepler, which has so far detected hundreds of planets outside our solar system.
"As Kepler discovers more and more planets by the day, we can hopefully scan through those and work out if this is unique or if all hot Jupiters are very dark," Kipping said.
Meanwhile, the very darkness of the new exoplanet suggests perhaps a catchier moniker for TrES-2b, Kipping said. "Maybe an appropriate nickname would be Erebus"—ancient Greece's god of darkness.
