SWEEPS-10 is, as of June 2007, the planet candidate with the shortest orbital period yet found. It completes an orbit of its star (designated SWEEPS J175902.00−291323.7) in just 10 hours. Located only 1.2 million kilometers from its star (roughly three times the distance between the Earth and the Moon), the planet is among the hottest ever detected; its estimated temperature is approximately 1650 degrees Celsius. "This star-hugging planet must be at least 1.6 times the mass of Jupiter, otherwise the star's gravitational muscle would pull the planet apart," said team leader Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland. Such ultra-short period planets (USPPs) seem to occur only around dwarf stars.
The small star's relatively low temperature allows the planet to exist. "USPPs occur preferentially around normal red dwarf stars that are smaller and cooler than our Sun," Sahu said.