Beta Gruis
 Location of β Gruis (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Grus |
| Right ascension | 22h 42m 40.05027s |
| Declination | −46° 53′ 04.4752″ |
| Apparent magnitude (V) | 2.146(2.0 - 2.3) |
| Characteristics | |
| Spectral type | M5 III |
| U−B color index | +1.757 |
| B−V color index | +1.620 |
| Variable type | SRb |
| Astrometry | |
| Radial velocity (Rv) | +1.6 km/s |
| Proper motion (μ) |
RA: +135.16 mas/yr Dec.: −4.38 mas/yr |
| Parallax (π) | 18.43 ± 0.42mas |
| Distance | 177 ± 4 ly (54 ± 1 pc) |
| Details | |
| Mass | 2.4 M☉ |
| Radius | 180 R☉ |
| Luminosity | 2,500 L☉ |
| Surface gravity (log g) | 0.4 cgs |
| Temperature | 3,480 K |
| Metallicity [Fe/H] | 0.0 dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
Beta Gruis (β Gruis, β Gru) is the second brightest star in the southern constellation of Grus. It was once considered the rear star in the tail of the constellation of the (Southern) Fish: it, with α, δ, θ. ι, and λ Gru, belonged to Piscis Austrinus in medieval Arabic astronomy.
This is a red giant star with an estimated mass of about 2.4 times that of the Sun and a surface temperature of approximately 3,480 K, just over half the surface temperature of the Sun. This low temperature accounts for the dull red color of an M-type star. The total luminosity is about 2,500 times that of the Sun, and it has estimated 180 times the Sun's radius.
Beta Gruis is a type semiregular variable (SRb) star that varies in magnitude by about 0.4. It varies between intervals when it displays regular changes with a 37-day periodicity and times when it undergoes slow irregular variability.
Beta Gruis played a crucial part in Perth Observatory's tracking of comet 2000 WM1 LINEAR in December 2001.
Coordinates: 
22h 42m 40.1s, −46° 53′ 05″
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