  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 31m 35.73082s[1] |
| Declination | +18° 05′ 39.9166″[1] |
| Apparent magnitude (V) | +5.323[2] |
| Characteristics | |
| Spectral type | K5 III[3] |
| U−B color index | +1.949[2] |
| B−V color index | +1.565[2] |
| Astrometry | |
| Radial velocity (Rv) | +44.47±0.19[4] km/s |
| Proper motion (μ) | RA: −60.438[1] mas/yr Dec.: −57.331[1] mas/yr |
| Parallax (π) | 7.3204 ± 0.1826 mas[1] |
| Distance | 450 ± 10 ly (137 ± 3 pc) |
| Absolute magnitude (MV) | −0.19[5] |
| Details | |
| Radius | 40.02+2.22 −2.35[1] R☉ |
| Luminosity | 353.1±10.1[1] L☉ |
| Temperature | 3,955+121 −105[1] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Theta Cancri, Latinised from θ Cancri, is a multiple star[7][3] system in the zodiac constellation of Cancer. It is visible to the naked eye as a dim point of light with an apparent visual magnitude of +5.32.[2] The system is located at a distance of approximately 450 light-years away from the Sun, based on parallax,[1] and is drifting further away with a radial velocity of +44 km/s.[4] Since it is near the ecliptic, it can be occulted by the Moon[8] and, very rarely, by planets.
The primary, designated component A, is K-type giant star with a stellar classification of K5 III,[3] having exhausted the supply of hydrogen at its core, then cooled and expanded. At present it has 40[1] times the girth of the Sun. It is radiating 353[1] times the luminosity of the Sun at an effective temperature of 3,955 K.[1]
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.[9] 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.[10]
