HOW short can a planet's year be? That's the question raised by a planet orbiting its star in less than an Earth day.
The planet, named 55 Cancri e, was discovered years ago. It is a "super-Earth" – a world with a mass several times that of Earth – and orbits a star like our sun.
Now Rebekah Dawson and Daniel Fabrycky at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, say gaps in the observational record meant the planet's orbital period – originally thought to be about three days – was miscalculated.
Their analysis shows that the planet's true year is 17 hours and 41 minutes. There may be a planet around the star SWEEPS-10 with an even shorter year, but its existence is unconfirmed.
"We expect that 55 Cancri e will not hold the status of shortest orbital period for long," says Dawson.
If a planet could orbit our sun at a distance equivalent to the sun's radius without burning up, its year would be about 3 hours.
Planets orbiting more compact objects, such as white dwarfs, pulsars and black holes, might have even shorter years since they can get closer in. However, no confirmed planets have so far been found around white dwarfs or black holes.
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