Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Indus [1] |
Right ascension | 22h 24m 36.88539s [2] |
Declination | −72° 15′ 19.4882″ [2] |
Apparent magnitude (V) | 5.278±0.005 [3] |
Characteristics | |
Evolutionary stage | Subgiant [4] [5] [6] [7] [8] |
Spectral type | G9V Fe-3.1CH-1.5 [9] |
Astrometry | |
Radial velocity (Rv) | +32.51±0.16 [10] km/s |
Proper motion (μ) | RA: +1,303.872 mas/yr [2] Dec.: −674.186 mas/yr [2] |
Parallax (π) | 35.1281±0.0640 mas [2] |
Distance | 92.8 ± 0.2 ly (28.47 ± 0.05 pc) [2] |
Absolute magnitude (MV) | +2.70±0.05 [6] |
Details | |
Mass | 0.85±0.04 [4] M☉ |
Radius | 2.95±0.12 [6] R☉ |
Luminosity | 6.28±0.23 [5] L☉ |
Surface gravity (log g) | 3.43±0.10 [6] cgs |
Temperature | 5,318±80 [6] K |
Metallicity [Fe/H] | −1.54±0.07 [6] dex |
Rotational velocity (v sin i) | 2.67 [11] km/s |
Age | 11.0±0.7 [4] Gyr |
Other designations | |
ν Indi, CD−72°1742, GJ 855.1, HD 211998, HIP 110618, HR 8515 | |
Database references | |
SIMBAD | data |
Nu Indi is a star in the southern constellation of Indus. With an apparent visual magnitude of +5.278, it is faintly visible to the naked eye in sufficiently dark skies. Based upon parallax measurements, the star is 92.8 light-years distant.
The spectrum of this star matches a classification of G9V Fe-3.1CH-1.5, [9] with the notation G9V suggesting it is a late-type G-type main sequence star. However, it is actually a subgiant, [4] [5] [6] [7] [8] a star which is running out of hydrogen in its core and expanding in size. The "Fe-3.1CH-1.5" indicate an underabundance of methylidyne radical and iron. The star has an overabundance of alpha elements, that is, elements heavier than carbon produced by nuclear reactions involving helium. [4] The metallicity indicators classify it as a Population II star. [6]
Nu Indi has been a target of asteroseismic studies since it displays solar-like oscillations. [7] [8] [4] It was the first metal-poor star of which asteroseismology has been applied. [8] Using this method, its mass and age have been measured at 0.85 solar masses and 11 billion years. [4] As a subgiant, it has expanded in size and become brighter, with a current radius of three solar radii [6] and a luminosity 6.3 times that of the Sun. [5] The effective temperature is 5,318 K , [6] giving it the yellow hue typical of G-type stars. [12]
It is a native member of the galactic halo which is currently crossing the galactic disk. The orbital eccentricity is somewhat high, at 0.60. It reaches a minimum distance of 8,000 light-years from the Galactic Center, and its distance relative to the galactic plane is no more than 4,900 ly. [4] It does not make part of any stellar association or moving group. [13]
Nu Indi was once thought to be a binary star whose components have spectral types of A3V and F9V, but this claim has since been disproven. [14] However, there is evidence it may be an astrometric binary. [6]