Few night-time 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 landscape of a lava world.
This alien vista exists in the newly discovered two-planet system of Kepler-36.
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| Planetrise: In this artist's impressions, 'hot Neptune' Kepler-36c looms in the sky of its neighbour, the rocky world Kepler-36b. The two planets have repeated close encounters, experiencing a conjunction every 97 days on average |
The new-found system contains two planets circling a sub-giant star, which is much like the Sun except several billion years older.
The inner world, Kepler-36b, is a rocky planet 1.5 times the size of Earth and weighing 4.5 times as much. It orbits about every 14 days at an average distance of less than 11million miles.
The outer world, Kepler-36c, is a gaseous planet 3.7 times the size of Earth and weighing 8 times as much. This 'hot Neptune' orbits once each 16 days at a distance of 12 million miles.
The two planets experience a conjunction every 97 days on average. At that time, they are separated by less than 5 Earth-Moon distances.
Since Kepler-36c is much larger than the Moon, it presents a spectacular view in its neighbor's sky and such close approaches stir up tremendous gravitational tides that squeeze and stretch both planets.
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