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Epsilon Eridani, a young Sun-like star, has a confirmed exoplanet and a possible second planet detected through lumps in its gas and dust disk. It is a leading candidate for extraterrestrial life and a target for future space missions.
Epsilon Eridani is a Sun-like star, located about 10.5 light-years from Earth. Epsilon Eridani is slightly smaller than the Sun, with about one-quarter the luminosity of the Sun. A large disk of gas and dust still surrounds the star, and Epsilon Eridani is thought to be quite young, at around eight hundred million years old. A planet has already been confirmed orbiting the star, at a distance of about three AU; at ten light-years away, it is the closest confirmed exoplanet. Lumps of gas and dust in the star’s disk suggest a second, much more distant planet. Many scientists believe Earth-like terrestrial planets could be orbiting Epsilon Eridani, and the star is a leading candidate in the search for extraterrestrial life.
In 1998, a team of astronomers detected a planet orbiting the star using the Doppler shift of Epsilon Eridani, which indicates how fast the star is approaching or receding from Earth. Doppler shift analysis is the most common planetary search technique; if a large planet is present, its gravity will pull the star in different directions as the planet moves along its orbit. Because Epsilon Eridani is so young, the star’s surface is still quite volatile, and this has been proposed as an alternative explanation for the data, however, further analyzes have confirmed the presence of a planet, now named Epsilon Eridani b. The planet itself is probably gaseous and is too far from its star to support liquid water; however, its presence could be indicative of other, closer planets.
Epsilon Eridani is surrounded by a large disk of gas and dust, at a distance of about 30-100 AU, left over from the formation of the star. Strange lumps in the disk indicate the presence of a second planet, Epsilon Eridani c, which is much less massive than Jupiter and orbits at a distance of about 40 AU. While it currently cannot be detected using traditional techniques due to its long and slow orbit, if confirmed, it will be one of the largest orbiting planets ever detected, with an orbit longer than that of Pluto in our solar system.
If life exists in the Epsilon Eridani system, it is likely on a small planet closer to the star, which has not yet been detected. Epsilon Eridani b itself is too cold to have liquid water moons and has a highly eccentric orbit that would disrupt any organic chemical reactions. The planet’s gravitational influence could help protect the terrestrial planets from incoming comets, which are still abundant due to the system’s youth; it could also interfere with the planetary formation process, preventing any other planet from growing beyond the size of an asteroid.
Microwave emissions from water molecules have been detected, but no one knows where they are coming from within the system, and they may have been emitted by the star itself. Several proposed space missions hope to block light from host stars, to view their planets directly; Epsilon Eridani is one of the primary targets, and this analysis could hunt down other planets or find chemical signs of life.
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