  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (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−Bcolor index | +1.949[2] |
| B−Vcolor 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 | |
| θ Cnc,31 Cancri,BD+18° 1963,FK5 2667,HD 72094,HIP 41822,HR 3357,SAO 97881[6] | |
| Database references | |
| SIMBAD | data |
Theta Cancri,Latinised from θ Cancri, is amultiple star[7][3] system in thezodiacconstellation ofCancer. It is visible to the naked eye as a dim point of light with anapparent visual magnitude of +5.32.[2] The system is located at a distance of approximately 450 light-years away from the Sun, based onparallax,[1] and is drifting further away with aradial velocity of +44 km/s.[4] Since it is near theecliptic, it can beocculted by theMoon[8] and, very rarely, byplanets.
The primary, designated component A, isK-typegiant star with astellar classification of K5 III,[3] having exhausted the supply of hydrogen at itscore, then cooled and expanded. At present it has 40[1] times the girth of the Sun. It is radiating 353[1] times theluminosity of the Sun at aneffective temperature of3,955 K.[1]
InChinese astronomy,Ghost (Chinese:鬼宿;pinyin:Guǐ Xiù) refers to anasterism consisting of Theta Cancri,Eta Cancri,Gamma Cancri andDelta 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]
