Epsilon Eridani

From Conservapedia

Epsilon Eridani is a nearby K2 class star some 10.5 light years away in the constellation of Eridanus. In addition to being one of the nearest Sun-like stars, it is the closest known star with a planetary companion, which was discovered in 2000. Because of Epsilon Eridani's proximity to our solar system, the star has been an object of high interest among astronomers, and is a "Tier 1" target for NASA's optical Space Interferometry Mission.

Contents 1 The Star 2 Planetary System 2.1 Planets 2.2 Dust Disk 3 References 4 Links

The Star

Epsilon Eridani is a main sequence, orange-red dwarf star of spectral class K2 V^[1], which is estimated to have an age of around 850 million years but may be as young as 500 million years and as old as a billion years^[2]. Its high level of chromospheric activity, strong magnetic field, and relatively fast rotation rate of only 11 days (less then half the rotation period of the Sun) indicate this age. However, the star also has a low metallicity, estimated at only 49 to 74 of the Sun's abundance of iron, which is more typical of older stars.

The star is smaller then our Sun, with an estimated 85 percent of its mass^[3], and 84 percent of the Sun's radius^[4]. But even with nearly the size of the Sun, Epsilon Eridani only is 27.8 percent as luminous^[5].

From Earth, Epsilon Eridani has an apparent magnitude of 3.73, making it the third closest star (after Alpha Centauri AB and Sirius) that can be viewed with the unaided eye.

Planetary System

Epsilon Eridani has one confirmed planet orbiting the star, with a possible but unconfirmed second world that possibly shepherds Epsilon Eridani's dust disk.

Planets

Using long term radical velocity observations, scientists announced the discovery of a planet orbiting Epsilon Eridani in August of 2000^[6]. The planet is believed to be a gas giant with an estimated mass 1.55 times that of Jupiter, with a mean orbital distance of 3.3 AU, taking 6.9 years to complete one orbit^[7].

A second unconfirmed planet is believed to be possibly orbiting Epsilon Eridani some 35 AU away. A planet is proposed as the most likely candidate to explain the "lumpiness" observed in the star's broad, outer belt of icy particles as such action is typically caused by perturbations by one or more planetary bodies.^[8]. If the planet exists, it is believed to be some 30 times the mass of the Earth (or about a tenth of Jupiter's mass).

A possible third world is also hypothesized due to the discovery of a second asteroid belt between the inner asteroid belt and the broad outer belt of icy bodies, comet-type bodies. Such a world would most likely be a Jupiter-class planet orbiting at roughly 20 AUs around Epsilon Eridani, which would be "shepherding" the icy, rocky bodies at the outer rim of the second asteroid belt, just as Epsilon Eridani b shepherds the inner asteroid belt^[9].

Dust Disk

Epsilon Eridani has a large dust disk made up of tiny particles of ice and dust that orbits in a ring that generally stretches between 35 and 90 AU from the star, being densest around 60 AU that was first detected in 1998. The total mass of the dust disk is estimated to be around 1000 times greater then the amount of similar material in our own inner solar system. Inside of 35 AU the dust is depleted. It is believed that this is due to the formation of planets that has cleared out the dust in the region.

In 2008, using the Spitzer Space Telescope, NASA revealed there are two asteroid belts in the system in addition to the outer dust disk. Made of rocky and metallic debris, the closer belt is estimated to be approximately the same distance from Epsilon Eridani as the asteroid belt in our Solar System is from the Sun, while the second belt orbits at a mean distance of around 20 AU^[10].

References

Links

• Extrasolar Planets Encyclopaedia
• ExoPlanets