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]

References

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