Epsilon Indi
Epsilon Indi, Latinized from ε Indi, is a star system located at a distance of approximately 12 light-years from Earth in the southern constellation of Indus. The star has an orange hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.83. It consists 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.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Indus |
| Right ascension | 22h 03m 21.65363s |
| Declination | −56° 47′ 09.5228″ |
| 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 | |
| ε Ind A | |
| Radial velocity (Rv) | −40.43±0.13 km/s |
| Proper motion (μ) | RA: 3,966.661(86) mas/yr Dec.: −2,536.192(92) mas/yr |
| Parallax (π) | 274.8431 ± 0.0956 mas |
| Distance | 11.867 ± 0.004 ly (3.638 ± 0.001 pc) |
| Absolute magnitude (MV) | 6.89 |
| ε Ind Ba/Bb | |
| Parallax (π) | 270.6580 ± 0.6896 mas |
| Distance | 12.05 ± 0.03 ly (3.695 ± 0.009 pc) |
| Orbit | |
| Primary | ε Ind Ba |
| Companion | ε Ind Bb |
| Period (P) | 11.0197 ± 0.0076 yr |
| Semi-major axis (a) | 661.58 ± 0.37 mas (2.4058 ± 0.0040 au) |
| Eccentricity (e) | 0.54042 ± 0.00063 |
| Inclination (i) | 77.082 ± 0.032° |
| Longitude of the node (Ω) | 147.959 ± 0.023° |
| Argument of periastron (ω) (secondary) | 328.27 ± 0.12° |
| Details | |
| ε Ind A | |
| Mass | 0.762±0.038 M☉ |
| Radius | 0.711±0.005 R☉ |
| Luminosity | 0.21±0.02 L☉ |
| Surface gravity (log g) | 4.63±0.01 cgs |
| Temperature | 4,649±84 K |
| Metallicity [Fe/H] | −0.13±0.06 dex |
| Rotation | 35.732+0.006 −0.003 days |
| Rotational velocity (v sin i) | 2.00 km/s |
| Age | 3.5+0.8 −1.0 Gyr |
| ε Ind Ba/Bb | |
| Mass | Ba: 66.92±0.36 MJup Bb: 53.25±0.29 MJup |
| Radius | Ba: ~0.080–0.081 R☉ Bb: ~0.082–0.083 R☉ |
| Luminosity | Ba: 0.00002037(81) L☉ Bb: 0.00000597(27) L☉ |
| Surface gravity (log g) | Ba: 5.43–5.45 Bb: 5.27–5.33 cgs |
| Temperature | Ba: 1,352–1,385 K Bb: 976–1,011 K |
| Other designations | |
| Database references | |
| SIMBAD | The system |
| A | |
| Bab | |
| Bab (as X-ray source) | |
ε Indi A has one known planet, ε Indi Ab, with a mass of 3.3 Jupiter masses in an elliptical orbit with a period of about 45 years. ε Indi Ab is the second-closest Jovian exoplanet, after ε Eridani b. The ε Indi system provides a benchmark case for the study of the formation of gas giants and brown dwarfs.