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| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cancer[1] |
| Right ascension | 08h 31m 35.730s[2] |
| Declination | +18° 05′ 39.91″[2] |
| Apparent magnitude (V) | +5.323[3] |
| Characteristics | |
| Evolutionary stage | red giant branch[2] |
| Spectral type | K5 III[4] |
| U−B color index | +1.949[3] |
| B−V color index | +1.565[3] |
| Astrometry | |
| Radial velocity (Rv) | +44.47±0.19[5] km/s |
| Proper motion (μ) | RA: −59.639 mas/yr[2] Dec.: −56.615 mas/yr[2] |
| Parallax (π) | 7.5577±0.1008 mas[2] |
| Distance | 432 ± 6 ly (132 ± 2 pc) |
| Absolute magnitude (MV) | −0.19[1] |
| Details | |
| Mass | 1.3[6] M☉ |
| Radius | 67[2] R☉ |
| Luminosity | 949[2] L☉ |
| Surface gravity (log g) | 1.82[6] cgs |
| Temperature | 3,998[6] K |
| Metallicity [Fe/H] | −0.19[6] dex |
| Other designations | |
| θ Cnc, 31 Cancri, BD+18°1963, FK5 2667, HD 72094, HIP 41822, HR 3357, SAO 97881[7] | |
| Database references | |
| SIMBAD | data |
Theta Cancri, is a multiple star[8][4] system in the zodiac constellation of Cancer. Its name is a Bayer designation that is Latinised from θ Cancri, and abbreviated Theta Cnc or θ Cnc. This star is visible to the naked eye as a dim point of light with an apparent visual magnitude of +5.32.[3] The system is located at a distance of approximately 432 light-years (132 pc) from the Sun, based on parallax,[2] and is drifting further away with a radial velocity of +44 km/s.[5] Since it is near the ecliptic, it can be occulted by the Moon[9] and, very rarely, by planets.
The primary, designated component A, is K-type giant star with a stellar classification of K5 III,[4] having exhausted the supply of hydrogen at its core, then cooled and expanded. At present it has 67 times the girth of the Sun. It is radiating 949[2] times the luminosity of the Sun at an effective temperature of 3,998 K.[6]
In Chinese astronomy, Ghost (Chinese: 鬼宿; pinyin: Guǐ Xiù) refers to an asterism consisting of Theta Cancri, Eta Cancri, Gamma Cancri and Delta Cancri.[10] Theta Cancri is the first star of Ghost (Chinese: 鬼宿一; pinyin: Guǐ Xiù yī), as it is also the determinative star for that asterism.[11]
