Mass, radius and temperature The planet is estimated to be about five times Earth's mass (5.5 ). Some astronomers have speculated that it may have a rocky
core like Earth, with a thin
atmosphere. Its distance from the star, and the star's relatively low temperature, means that the planet's likely surface temperature is around , making it one of the coldest known. If it is a rocky world, this temperature would make it likely that the surface would be made of frozen
volatiles, substances which would be liquids or gases on Earth: water,
ammonia,
methane and
nitrogen would all be frozen solid. If it is
not a rocky planet, it would more closely resemble an icy gas planet like
Uranus, although much smaller.
Host star OGLE-2005-BLG-390L (located in the constellation
Scorpius,
RA 17:54:19.2,
Dec −30°2238,
J2000, 6.6 ± 1.0
kpc distance) is thought to likely be a cool
red dwarf (95% probability), or a
white dwarf (4% probability), with a
very slight chance that it is a
neutron star or
black hole (<1% probability). Regardless of the star's classification, its
radiant energy output would be significantly less than that of the
Sun. It has a mass of 0.22 , but an unknown radius. If it is a red dwarf, it would likely have a radius of 0.17 . The age is estimated to be around 9.587 billion years old.
Orbit OGLE-2005-BLG-390Lb
orbits its star every 3,500 days (about 10 years) at an average distance of , or an orbit that would fall between the orbits of
Mars and
Jupiter in the Solar System (This range of distances is the range of error in measurement and calculation; it does not represent the planet's
orbital eccentricity, as its orbital elements are not known, other than its orbital period). Until this discovery, no small exoplanet had been found farther than from a
main-sequence star. ==Discovery==