Epsilon Indi
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One of the nearest stars to the Sun; a dwarf K star, somewhat cooler than and about one-seventh as luminous as the Sun, it lies in the constellation Indus. Around it, at an average distance of 1.46 AU (220 million km), orbits our nearest known brown dwarf. Discovered in 2003, this brown dwarf has a mass of 40 to 60 times the mass of Jupiter and a surface temperature of about 1,260 K. Epsilon Indi has the tenth highest proper motion of any known star.
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This star system is located about 11.8 light-years (ly) away from our Sun, Sol, at the northwestern edge (22:03:21.66-56:47:09.51, ICRS 2000.0) of Constellation Indus, the Indian -- southeast of Delta Indi and northwest of Alpha Tucanae. The fifth brightest star in Indus, the 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. Epsilon Indi has such a high proper motion that, within a few thousand years, it will have moved out of Constellation Indus constellation and into neighbouring Constellation Tucana, the Toucan.
Epsilon Indi is a orange-red main sequence dwarf star of spectral and luminosity type K5 Ve. The star has about 77 percent of Sol's mass (RECONS), 76 percent of its diameter (Johnson and Wright, 1983, page 701), and about 14.7 percent of its luminosity. It appears to be about 59 to 110 percent as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (Cayrel de Strobel et al, 1991, page 310).
Epsilon Indi Ba
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Epsilon Indi Ba Statistics
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While brown dwarfs have too little mass to fuse "regular" hydrogen (which has a single proton nucleus), virtually all of the ones discovered until 1999 were too hot -- that is "young" -- to show evidence of methane which is destroyed by stellar temperatures. In fact, while methane is a atmospheric characteristic of giant gas planets like Jupiter, the only brown dwarf found to even have a trace of methane was Gliese 229 b. In Spring 1999, however, two very dim and reddish brown dwarfs were found as solitary objects (one 30 light-years away in Ophiuchus and another also relatively nearby in Virgo). Analysis of their spectra indicated that both have atmospheres that are rich in methane. In addition, four similar objects that are too cool to be observed in visible light were found using near-infrared telescopes also to have the methane fingerprint of extremely cool (that is "old") brown dwarfs. |
These discoveries represent strong evidence that, although hard for astronomers to detect, faint brown dwarfs which have had billions of years to cool may represent a significant population of the universe. Some astronomers speculate that these objects may well be as numerous as the stars, reviving theories of stellar formation that suggest the existence of uncountably numerous brown dwarfs, rather than the relatively few easy-to-detect, bright ones found thus far.
Epsilon Indi Bb
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Epsilon Indi Bb Statistics
| Object Type: | Brown Dwarf |
| Parent Star: | epsilon Indi Ba (T1) |
| Discovery Status: | Imaged |
| Mass : | 28 Jupiters |
| Mean Distance: | 2.65 AU |
| Orbital Period: | 15 Years |
| Estimated Radius: | 0.932 Jupiters |
| Temp from Internal Heating : | 792.477 Kelvins |
| Mean Angular Star Size: | 0.152 Degrees |
| Year Discovered: | 2003 |
| Discovered By: | Optical and Infrared Imaging |
Planetary Orbit Of Epsilon Indi
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