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Epsilon Indi is the also known as HR 8387, Gl 845, and HD 209100. Second nearest single sunlike star to the Sun. Orange dwarf with a binary brown dwarf orbiting it. The smaller of the two is the closest thing to an "extrasolar moon" found so far. The constellation "Indus" first appeared in 1603 in the Uranometria. Epsilon Indi appeared as one of the Indian's arrows in Bode's 1801 atlas, the Uranographia. The star's high proper motion was first discovered by Gill in 1882, which was improved upon by Shapley in 1923. During 1960, the star was observed for radio signals, but none was found. In 1972, it was searched for ultraviolet laser signals. It leads a Carnegie list of stars most likely to have an earth-like planet. The star's age has been controversial, at first thought to be older than the sun, then younger, then even older than originally thought, all based on studies regarding the brown dwarf's nature and the rotation rate of the star.

Epsilon Indi Web Pages[]

Epsilon Indi Artwork[]

Stellar Winds Detected (1995)[]

Discovery of First Brown Dwarf "B" (Jan 2003)[]

Discovery of Second Brown Dwarf "Bb" (Sep 2003)[]

Follow-ups on Brown Dwarves (2003-2005)[]

Proposed Imaging of Unconfirmed Planet b (2005)[]

Fun Links[]

  • Epsilon Indi Band - ha ha, there's an italian band called "Epsilon Indi"
  • Sci Fi Web Page
  • Battletech
  • Star Gen - I'm sure these made up planets won't fit the system anymore, gotta update it!
  • Eridanus League - hey, it's the x-box league of planets
  • MSpace - hey, this sci-fi site actually includes the brown dwarves in it. I say we all start referring to them as Sagan (Bb) and Copernicus (B) from now on =)
  • Rogues Gallery of the Andorians - Epsilon Indi was once considered the homeworld of the Andorians of Star Trek (back in 1975). It may well be an Andorian colony world.
  • Bughunters
  • Starship Exeter - The fan produced Star Trek show has them going to Andoria in the Epsilon Indi system
  • Grandmasters - An ebook about descendents of chess masters from Earth and Epsilon Indi going to war
  • Memory Alpha - Star Trek Wiki

Epsilon Indi (System) Factoids[]

  • Composed of three parts, a methane brown dwarf orbiting a methane brown dwarf (narrow binary) orbiting an orange dwarf (wide separation). First triple star systems containing binary brown dwarves.
  • System has a very high proper motion. Travels a full moon diameter through the sky in only 400 years.
  • Second "fastest" moving visible star system after 61 Cygni.
  • Brown dwarves Ba and Bb orbit their common gravitational center once every 15 years.
  • Epsilon Indi is the second nearest wide-separation multi-star system known after Alpha Centauri.
  • Since the Brown Dwarves orbit over a thousand au from the primary star, a full planetary system could easily still fit around Epsilon Indi A, including its habitable zone.
  • If Epsilon Indi has an Oort Cloud similar to the Sun's, the the Brown Dwarves plough right through it, possibly sending comets inwards.
  • System is about a third as old as the Sun (1.3 GY)
  • The Sun seen from this system would appear near the bowl of the Big Dipper.
  • This star is leading the list of 17,129 nearby stars most likely to have planets that could support complex life, compiled by Margaret Turnbull and Jill Tarter of the Carnegie Institution in Washington [1].
  • A prime target for the Terrestrial Planet Finder.
  • Since the period of the two dwarves around each other is short (15 years), the mass of the Brown Dwarves can be determined with great accuracy, which can help calibrate brown dwarf evolutionary models [2]

Epsilon Indi (Star) Factoids[]

(Most info from [3])

  • Barely a magnitude 5 naked-eye visible star (4.69)
  • It is the eastern-most reasonably bright star in the Indus constellation
  • Class K4.5 star
  • One of the intrinsically least-luminous stars visible to the naked-eye
  • Temperature is 4620 K
  • Has 22% of the Sun's Luminosity, and has 75% the Sun's radius.

Brown Dwarf B (or Ba) Factoids[]

  • T-1 V Class Star (Methane Brown Dwarf). This is about the brightest a methane brown dwarf can get.
  • When discovered in 2003, it was the brightest T-Dwarf known. I'm not sure if it still is.
  • Found to have methane and water steam in its atmosphere, which classified it as a T-Dwarf. As such, it radiates mostly in the infrared and does not undergo nuclear fusion.
  • Orbits at the very large distance of 1469 au away from primary star
  • Discovered by its high proper motion against the sky. This was found out to be identical Epsilon Indi's, so the association was made between the two.
  • Mass of 47 Jupiters [4]
  • Like all Methane Brown Dwarves, its diameter is about the same as Jupiter's.
  • Measured Temperature = 1276 K. This is the same temperature as a Dark Hot Jupiter. I wonder how it would compare? Many hot jupiters are hotter than this though. They get their heat from without rather than within though.
  • Luminosity = 0.02% Sol

Brown Dwarf Bb Factoids[]

  • T6 Type Star (Methane Brown Dwarf)
  • Orbits Primary Brown Dwarf Ba 2.65 au away, completing an orbit about every 15 years
  • Mass is 28 Jupiters (about 40% of the mass in the binary system) [5]
  • Radius is similar to primary brown dwarf and Jupiter (0.932 RJ)
  • A lot "cooler" than Ba, at 854 Kelvin. This is similar to the temperature of the hottest clarified giants.
  • Discovered using Adaptive Optics
  • Not detected earlier because it was invisible at the bands use to detect Epsilon Indi B.

Epsilon Indi Stellar Moving Group[]

Epsilon Indi is the title member of the Epsilon Indi Moving Group (identified 1958 by Eggen). Some other members include[6]

  • HD 40409
  • Lambda Aur
  • HD 102365

Other nearby Brown Dwarves[]

There are seven other brown dwarves known within 20 light years. Four of them are also Methane Brown Dwarves, while the other three are younger and brighter M Class brown dwarves. Gliese 229 was the first of this bunch to be discovered back in 1996. (list courtesy of Sol Station

  • 11.8 ly- Epsilon Indi ba (T1 V) 0.043 MS
  • 11.8 ly- Epsilon Indi bb (T6 V) 0.028 MS
  • 13.2 ly DENIS 1048-39 [2000] (M8.5 V) 0.08 MS - possibly a red dwarf?
  • 16.3 ly- LP 944-20 [1975/1998] (M9.0 V) 0.060 MS - flares
  • 18.5 ly- 2MASS 1835+3259 (M8.5 V) 0.07 MS
  • 18.7 ly- 2MASS 0415-0935 (T8 V) ? MS - faintest known Methane Dwarf
  • 18.8 ly- Gliese 229 b [1996] (T6.5 V) 0.025 MS - first brown dwarf discovered, orbits a red dwarf
  • 19.3 ly- Gliese 570 d [2000] (T7-8 V ) 0.05 MS - orbits a triple (K-M-M spectrums) star system
  • 20.0 ly- 2MASS 0937+2931 (T6 V) <0.08 MS

T-Dwarf Reference[]

Here is a great link on the nature of Methane Brown Dwarves worth mentioning:

See Also[]