55 Cancri
 Location of 55 Cancri (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Cancer |
| 55 Cancri A | |
| Right ascension | 08h 52m 35.81s |
| Declination | +28° 19′ 51.0″ |
| Apparent magnitude (V) | 5.95 |
| 55 Cancri B | |
| Right ascension | 08h 52m 40.9s |
| Declination | +28° 19′ 59″ |
| Apparent magnitude (V) | 13.15 |
| Characteristics | |
| Spectral type | G8V / M3.5-4V |
| U−B color index | 0.65 / 1.66 |
| B−V color index | 0.86 / 1.21 |
| Astrometry | |
| Radial velocity (Rv) | 27.3 km/s |
| Proper motion (μ) |
RA: -485.80 ± 0.97 mas/yr Dec.: -234.05 ± 0.68 mas/yr |
| Parallax (π) | 81.03 ± 0.75mas |
| Distance | 40.3 ± 0.4 ly (12.3 ± 0.1 pc) |
| Absolute magnitude (MV) | 5.46 / 12.66 |
| Details | |
| Mass | 0.95 ± 0.1 / 0.13 M☉ |
| Radius | 1.152 ± 0.035 / 0.30 R☉ |
| Luminosity | 0.57 ± 0.01 L☉ |
| Luminosity (bolometric) | 0.63 / 0.0076 L☉ |
| Temperature | 5373 ± 9.7 K |
| Metallicity [Fe/H] | +0.27 dex |
| Rotation | 42.2 d |
| Age | (7.4–8.7) × 109 years |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| ARICNS | data |
| Extrasolar Planets Encyclopaedia |
data |
55 Cancri (/ˈkæŋkraɪ/ or /ˈkæŋkriː/) (abbreviated 55 Cnc) is a binary star approximately 41 light-years away from the Sun in the constellation of Cancer. The system consists of a G-type star (designated 55 Cancri A, also named Copernicus) and a smaller red dwarf (55 Cancri B).
As of 2015[update], five extrasolar planets (designated 55 Cancri b, c, d, e and f; named Galileo, Brahe, Lipperhey, Janssen and Harriot, respectively) are believed to orbit 55 Cancri A.
55 Cancri is the system's Flamsteed designation. It also bears the Bayer designation ρ¹ Cancri (Latinised to Rho¹ Cancri) and the Bright Star Catalogue designation HR 3522. The two components are designated A and B, though A is itself sometimes referred to as 55 Cancri. The first planet discovered orbiting 55 Cancri A was designated HR 3522b by its discoverers, though it is more commonly referred to as 55 Cancri b. Under the rules for naming objects in binary star systems it should be named 55 Cancri Ab and this more formal form is occasionally used to avoid confusion with the secondary star 55 Cancri B. The other planets discovered were designated 55 Cancri c, d, e and f, in order of their discovery.
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