Epsilon Indi

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Epsilon Indi
Stellar characteristics
Right ascension (Epoch J2000)22h 03m 21.66s
Declination (Epoch J2000)-56° 47' 09.51"
Spectral typeK4-5 Ve
Distance from Sol11.8 ly
Other designationsEps Ind, HR 8387, Gl 845, Hip 108870, HD 209100, CP(D)-57 10015, SAO 247287, FK5 825, LHS 67, LTT 8813, LFT 1677.
PlanetsAlice (E Indi A I)
Mad Hatter (E Indi A II)
Queen of Hearts (E Indi A III)
Cheshire (E Indi A IV)
Walrus (E Indi A V)
Doormouse (E Indi A VI)
Jabberwock (E Indi A VII)
Tenniel (E Indi Bb I)
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Epsilon Indi is a orange-red main sequence dwarf star of spectral and luminosity type K4-5 Ve. The star has about 70 to 77 percent of Sol's mass[1], 68 to 76 percent of its diameter[2], and about 14.7 percent of its visual luminosity and 20.4 percent of its theoretical bolometric luminosity, correcting for infrared output[3]. According to a 2006 study, it appears to be around 87 percent as enriched as Sol with elements heavier than hydrogen ("metallicity") based on its abundance of iron, although earlier studies found a range of 59 to 110 percent of Sol's metallicity[4]. The star has a rotational period of 22 days[5].

This star system is located about 11.8 light-years (ly) away from our Sun, Sol, at the northwestern edge of Constellation Indus, the Indian -- southeast of Delta Indi and northwest of Alpha Tucanae. The fifth brightest star in Indus, this star is the title member of the Epsilon Indi stellar moving group. Although smaller and dimmer than Sol, it is clearly visible with the naked eye.

On January 13, 2003, astronomers announced the discovery of a methane brown dwarf companion to this nearby star[6]. In August 2003, the same team (as well as another team) of astronomers discovered that the brown dwarf had its own brown dwarf companion[7]. As of late 2003, the two substellar objects are the closest known brown dwarfs to the Solar System.

(Boilerplate from SolStation.com)

Epsilon Indi System

The Epsilon Indi system was first explored in 2011 by the Soviet Air Force.

Epsilon Indi A

The Soviets discovered seven planets around the K4 primary E Indi A (Alice, Mad Hatter, Queen of Hearts, Cheshire, Walrus, Doormouse and Jabberwock). Alice, the innermost planet, turned out to be a wet-Mars analogue, somewhat cooler than Earth but warm enough to have liquid water on the surface. No life was found at the Soviet landing sites, though there may be extremophile bacteria hiding in the deeper parts of Alice's oceans. The planet seems like a good terraforming candidate.

Epsilon Indi B

The pair of brown dwarfs that compose the unit known as E Indi B (Tweedledee and Tweedledum) were also surveyed by the VVS. To everyone's surprise, Tweedledum actually sported a planet of its own; earlier models suggested that gravity disruption would keep planets from forming around either dwarf. The small gas giant Tenniel orbits very close to Tweedledum, in what would be a heliosphere-grazing orbit in a brighter star.


  1. RECONS; and NASA Star and Exoplanet Database, from David F. Gray, 1992
  2. Johnson and Wright, 1983, page 701; and NASA Star and Exoplanet Database, from Kenneth R. Lang, 1980
  3. NASA Star and Exoplanet Database, from Kenneth R. Lang, 1980
  4. Santos et al, 2006, page 7 for HD 209100; and Cayrel de Strobel et al, 1991, page 310
  5. NASA Star and Exoplanet Database
  6. ESO and AIP joint press release and API press release
  7. Gemini press release