A planet blacker than coal? That’s what astronomers say they've discovered in our home galaxy with NASA’s Kepler telescope. Orbiting only about three million miles out from its star, the Jupiter-size gas giant planet ~ named TrES-2b ~ reflects almost none of the starlight that shines on it, according to a new study.
"Being 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."
The Kepler spacecraft was specifically designed to find planets outside our solar system. But at such distances ~TrES-2b, for instance, is 750 light-years from us ~ it's not as simple as snapping pictures of alien worlds. Instead, Kepler uses light sensors called photometers that continuously monitor tens of thousands of stars as it looks for the regular dimming of stars.
Such dips in stellar brightness may indicate that a planet is transiting, or passing in front of a star, relative to Earth, blocking some of the star's light. In the case of the coal-black planet, blocking surprisingly little of that light.
Image shows TrES-2b, mostly black with a reddish glow.