45 Cancri
Star in the constellation Cancer
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45 Cancri is a binary star[4] system in the zodiac constellation of Cancer, located 680 light-years away from the Sun.[1] It has the Bayer designation A1 Cancri;[7] 45 Cancri is the Flamsteed designation. It is visible to the naked eye as a faint, white-hued star at an apparent visual magnitude of 5.62.[2] The pair form a double-lined spectroscopic binary with an orbital period of 2.76 years and an eccentricity of 0.46.[4] They are drifting closer to the Earth with a heliocentric radial velocity of −6 km/s.[2]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 43m 12.32940s[1] |
| Declination | +12° 40′ 51.1486″[1] |
| Apparent magnitude (V) | 5.62[2] |
| Characteristics | |
| Spectral type | G8 III and A3 III[3] |
| B−V color index | 0.435±0.005[2] |
| Astrometry | |
| Radial velocity (Rv) | −6.2±2.3[2] km/s |
| Proper motion (μ) | RA: −9.828[1] mas/yr Dec.: +0.916[1] mas/yr |
| Parallax (π) | 4.7700±0.1025 mas[1] |
| Distance | 680 ± 10 ly (210 ± 5 pc) |
| Absolute magnitude (MV) | −1.62[2] |
| Orbit[4] | |
| Period (P) | 1,009.36±0.12 d |
| Eccentricity (e) | 0.461±0.002 |
| Semi-amplitude (K1) (primary) | 20.04±0.06 km/s |
| Semi-amplitude (K2) (secondary) | 20.75±0.02 km/s |
| Details | |
| 45 Cnc A | |
| Mass | 3.11±0.10[3] M☉ |
| Radius | 13.86+5.03 −1.73[1] R☉ |
| Luminosity | 210.3±5.4[1] L☉ |
| Surface gravity (log g) | 2.72[5] cgs |
| Temperature | 5,058[5] K |
| Metallicity [Fe/H] | −0.69±0.22[5] dex |
| Rotational velocity (v sin i) | 5.3[6] km/s |
| 45 Cnc B | |
| Mass | 3.00±0.10[3] M☉ |
| Luminosity | 190.5+43.9 −35.6[3] L☉ |
| Other designations | |
| A1 Cnc,[7], 45 Cnc, BD+13°1972, FK5 2686, HD 74228, HIP 42795, HR 3450, SAO 98069[8] | |
| Database references | |
| SIMBAD | data |
The primary, designated component A, is an aging giant star with a stellar classification of G8 III,[9] but has most likely not yet made multiple ascents up the red giant branch.[3] It has 3.11[3] times the mass of the Sun and has expanded to 14[1] times the Sun's radius. The star is radiating 210[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 5,058 K.[5] The less evolved secondary, component B is likewise a giant star, having a class of A3 III. It has three times the mass of the Sun and shines with 191 times the Sun's luminosity.[3]