It is science fiction made fact: Astronomers have discovered two alien planets around the same star whose orbits come so close together that each rises in the night sky of its sister world like an ...

Few nighttime sights offer more drama than the full Moon rising over the horizon. Now imagine that instead of the Moon, a gas giant planet spanning three times more sky loomed over the molten ...

Two planets with very different densities and compositions are locked in surprisingly close orbits around their host star, according to astronomers working with NASA’s Kepler mission. One planet is a ...

The two planets circling Kepler-36, a sun-like star in its senior years, are as different as Earth and Neptune. But unlike the hundreds of millions of miles that separate our solar system's rocky ...

In this artist's conception, a "hot Neptune" known as Kepler-36c looms in the sky of its neighbor, the rocky world Kepler-36b. The two planets have repeated close encounters, experiencing a ...

(CNN) — The discovery of a planetary “odd couple” is broadening the way scientists think about planetary migration. Scientists at the Harvard Smithsonian Center for Astrophysics and University of ...