| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 40m 11.45280s[1] |
| Declination | +19° 58′ 16.0852″[1] |
| Apparent magnitude (V) | 6.61[2] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | A1 V[3] |
| B−V color index | 0.006±0.005[2] |
| Astrometry | |
| Radial velocity (Rv) | +34.4±0.6[2] km/s |
| Proper motion (μ) | RA: −35.312[1] mas/yr Dec.: −13.595[1] mas/yr |
| Parallax (π) | 5.2065 ± 0.0713 mas[1] |
| Distance | 626 ± 9 ly (192 ± 3 pc) |
| Absolute magnitude (MV) | 0.32[2] |
| Details | |
| Mass | 2.46±0.12[4] M☉ |
| Radius | 2.72±0.12[4] R☉ |
| Luminosity | 73.68[2] L☉ |
| Surface gravity (log g) | 3.78[5] cgs |
| Temperature | 9,382[5] K |
| Rotational velocity (v sin i) | 10[5] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
40 Cancri is a binary star[4] system in the zodiac constellation of Cancer, located about 614[1] light years from the Sun in the Beehive Cluster (NGC 2632).[4] It is a challenge to view with the naked eye, having an apparent visual magnitude of 6.61.[2] The system is moving further from the Earth with a heliocentric radial velocity of 34 km/s.[2]
The primary component appears to be a normal A-type main-sequence star with a stellar classification of A1 V,[3] showing neither an organized magnetic field nor a chemical peculiarity.[5] However, it has an excessive temperature for its luminosity, and thus is considered an extreme[4] blue straggler.[7] This is a second generation star formed through a collision of two low mass stars some 5–350 million years ago. The collision was either between two separate cluster members or the coalescence of a binary star system.[4]
With an effective temperature of 9,382[5] K, this is the hottest star in the cluster[7] by about 1,200 K. It has 2.46 times the mass of the Sun and 2.72 times the Sun's radius. The star has an unusually slow rotation for an A1V star,[4] with a projected rotational velocity of 10 km/s.[5] It is radiating 74[2] times the Sun's luminosity from its photosphere.
40 Cancri has a common proper motion companion, located at an angular separation of 0.425″±0.009″ along a position angle of 127.6°±0.5°, as of 1983. This object is about 2.5±0.5 magnitudes dimmer than the primary, and is most likely an F-type star with a mass of about 1.5 M☉. The projected separation between the pair is 80 AU, so their orbital period is 450 years or greater.[4]
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