Beta Caeli
Binary star in the constellation Caelum
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Beta Caeli is a star with an orbiting companion in the southern constellation of Caelum. Its name is a Bayer designation that is Latinized from β Caeli, and abbreviated Beta Cae or β Cae. This star is dimly visible to the naked eye, having an apparent visual magnitude of 5.04.[2] Based upon an annual parallax shift of 34.6 mas as seen from Earth,[1] it is located at a distance of 94 light-years (29 pc). The star is moving away from the Sun with a radial velocity of +27.5 km/s.[1]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Caelum |
| Right ascension | 04h 42m 03.482s[1] |
| Declination | −37° 08′ 39.59″[1] |
| Apparent magnitude (V) | 5.04[2] |
| Characteristics | |
| Spectral type | F3 V[3] or F3 IV[4] |
| U−B color index | +0.01[2] |
| B−V color index | +0.38[2] |
| Astrometry | |
| Radial velocity (Rv) | 27.47±0.24[1] km/s |
| Proper motion (μ) | RA: +42.561 mas/yr[1] Dec.: +212.705 mas/yr[1] |
| Parallax (π) | 34.6088±0.0531 mas[1] |
| Distance | 94.2 ± 0.1 ly (28.89 ± 0.04 pc) |
| Absolute magnitude (MV) | +2.64[5] |
| Orbit[6] | |
| Primary | A |
| Name | B |
| Period (P) | 7.5 yr |
| Semi-major axis (a) | 4.6 AU |
| Eccentricity (e) | 0.6 |
| Inclination (i) | 27 or 153° |
| Longitude of the node (Ω) | 151° |
| Argument of periastron (ω) (secondary) | 38° |
| Details | |
| β Cae A | |
| Mass | 1.482±0.040[1] M☉ |
| Radius | 1.902+0.001 −0.004[1] R☉ |
| Luminosity | 6.615+0.020 −0.019[1] L☉ |
| Surface gravity (log g) | 3.981+0.003 −0.002[1] cgs |
| Temperature | 6,665.7+1.6 −1.4[1] K |
| Metallicity | = −0.12[3] |
| Rotation | 0.8669±0.0013[6] days |
| Rotational velocity (v sin i) | 97.5±4.9[5] km/s |
| Age | 0.2 or 1.17[6] Gyr 1.941±0.307[1] Gyr |
| β Cae B | |
| Mass | 0.08 or 0.2[6] M☉ |
| Temperature | 3,593±160[6] K |
| Other designations | |
| β Cae, CD−37°1867, FK5 1130, GJ 176.1, GJ 9165, HD 29992, HIP 21861, HR 1503, SAO 195239[7] | |
| Database references | |
| SIMBAD | data |
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Characteristics
Beta Caeli is a probable single-lined spectroscopic binary system, meaning only the spectral lines of the visible component can be seen.[8] This primary component has a stellar classification of F3 V[3] or F3 IV,[4] indicating it is either an F-type main-sequence star or a somewhat more evolved subgiant star, respectively. It has an estimated 1.5 times the mass of the Sun and about 1.9 times the Sun's radius.[1] The star is 200 million[6] to two billion years old[1] and has a high rate of spin with a projected rotational velocity of around 97.5 km/s.[5] It is radiating 6.6 times the luminosity of the Sun from its photosphere[1] at an effective temperature of 6,666 K.[1] Based on the amount of iron detected, the abundance of elements with mass greater than helium is lower than in the Sun.[3]
The low-mass companion is orbiting about 5 AU from the primary, with an orbital period of around seven years. Its exact mass is uncertain; an orbital solution suggest it is close to the brown dwarf regime at around 0.08 M☉, but models of stellar atmospheres suggest a higher mass of 0.2 M☉.[6] It was first detected in 2017 and was believed to be either a brown dwarf or a star with minimum mass around 40 Jupiter masses.[8] In 2022, Beta Caeli was imaged with the Gemini Planet Imager, with a point source that very likely is β Caeli B being detected.[6] This object may be the source of the X-ray emission coming from the same location, which suggests the companion could be a late-type star.[8]
The existence of additional companions beyond 55 astronomical units is ruled out.[8]