Habitable Zone
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The planet OGLE-2005-BLG-390, nicknamed Hoth, is a cold super-Earth that might be a failed Jupiter. Although icy, the planet appears red because of the red star it orbits. Unable to grow large enough, it had to settle for a mass five times that of Earth and a surface locked in the deepest of deep freezes, with a surface temperature estimated at minus 364 degrees Fahrenheit (minus 220 Celsius). Astronomers used an extraordinary planet-finding technique known as microlensing to find this world in 2005, one of the early demonstrations of this technique’s ability to reveal exoplanets. In microlensing, back light from a distant star is used to reveal planets around a star closer to us.

The planet lies toward the heart of the Milky Way, where a greater density of stars makes microlensing events more likely. The onetime event revealing the distant Hoth was captured by the Optical Gravitational Lensing Experiment, or OGLE, and confirmed by other instruments.

PLANET TYPE
Super-earth
DISCOVERY DATE
January 2006
MASS
5.5 x Earth
PLANET RADIUS
Unknown
ORBITAL RADIUS
2.6 AU
ORBITAL PERIOD
3285.0 days
ECCENTRICITY
Unknown
DETECTION METHOD
Microlensing