Epsilon Indi
 Location of ε Indi (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Indus |
| Right ascension | 22h 03m 21.658s ± 2.11 |
| Declination | −56° 47′ 09.52″ ± 1.50 |
| Apparent magnitude (V) | 4.8310 ± 0.0005 |
| Characteristics | |
| Spectral type | K5V + T1 + T6 |
| U−B color index | 1.00 |
| B−V color index | 1.056 ± 0.016 |
| Astrometry | |
| Radial velocity (Rv) | −40.4 km/s |
| Proper motion (μ) |
RA: 3960.93 ± 0.24 mas/yr Dec.: −2539.23 ± 0.17 mas/yr |
| Parallax (π) | 276.06 ± 0.28mas |
| Distance | 11.81 ± 0.01 ly (3.622 ± 0.004 pc) |
| Absolute magnitude (MV) | 6.89 |
| Details | |
| ε Ind A | |
| Mass | 0.762 ± 0.038 M☉ |
| Radius | 0.732 ± 0.006 R☉ |
| Luminosity (bolometric) | 0.22 L☉ |
| Surface gravity (log g) | 4.65 ± 0.15 cgs |
| Temperature | 4,630 K |
| Metallicity [Fe/H] | −0.06 dex |
| Rotation | 23 days |
| Rotational velocity (v sin i) | 1.46 km/s |
| Age | 1.3 Gyr |
| ε Ind Ba/Bb | |
| Mass | Ba: 0.066 M☉ Bb: 0.047 M☉ |
| Radius | Ba: 0.08 R☉ Bb: 0.08 R☉ |
| Other designations | |
| Database references | |
| SIMBAD | The system |
| A | |
| Bab | |
| Bab (as X-ray source) | |
Epsilon Indi (ε Indi, ε Ind) is a star system approximately 12 light-years from Earth in the constellation of Indus consisting of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf (T1) and ε Indi Bb a late T dwarf (T6) separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.
The constellation Indus (the Indian) first appeared in Johann Bayer's celestial atlas Uranometria in 1603. The 1801 star atlas Uranographia, by German astronomer Johann Elert Bode, places Epsilon Indi as one of the arrows being held in the left hand of the Indian.
In 1847, Heinrich Louis d'Arrest compared the position of this star in several catalogues dating back to 1750, and discovered that it possessed a measureable proper motion. That is, he found that the star had changed position across the celestial sphere over time. In 1882–3, the parallax of Epsilon Indi was measured by astronomers David Gill and William L. Elkin at the Cape of Good Hope. They derived a parallax estimate of 0.22 ± 0.03 arcseconds. In 1923, Harlow Shapley of the Harvard Observatory derived a parallax of 0.45 arcseconds.
During Project Ozma in 1960, this star was examined for artificial radio signals, but none were found. In 1972, the Copernicus satellite was used to examine this star for the emission of ultraviolet laser signals. Again, the result was negative. Epsilon Indi leads a list, compiled by Margaret Turnbull and Jill Tarter of the Carnegie Institution in Washington, of 17,129 nearby stars most likely to have planets that could support complex life.
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