67 Cancri

Lore & Background

The binary nature of 67 Cancri was discovered by James South and John Herschel. As of 2007, the two components have an angular separation of 103.9″, corresponding to a projected separation of 6,100 AU. They are moving further from Earth with a heliocentric radial velocity of +12 km/s.

The primary, designated component A, is an A-type main-sequence star with a stellar classification of A8 Vn. The 'n' notation indicates 'nebulous' lines due to rapid rotation. It is a shell star, with weak shell lines of singly-ionized titanium being detected in the near ultraviolet in 1970. These may have come from a sporadic mass loss event. Uesugi and Fukuda (1970) gave a projected rotational velocity estimate of 105 km/s for the star, although Abt et al. (1997) suggested it could be as high as 205 km/s.

67 Cancri A is about 867 million years old with 1.89 times the mass of the Sun and 1.9 times the Sun's radius. It is radiating 10.4 times the Sun's luminosity from its photosphere at an effective temperature of 7,982 K.

Reader's Guide

67 Cancri is notable as a wide binary system discovered by the pioneering astronomers James South and John Herschel. Its primary component is an A-type main-sequence star with a rapid rotation, indicated by the 'n' suffix in its spectral classification and by conflicting projected rotational velocity estimates of 105 km/s and 205 km/s. The star is also a shell star, showing weak shell lines of singly-ionized titanium in the near ultraviolet, possibly from a sporadic mass loss event. The system's wide separation of 103.9″ (6,100 AU) and its heliocentric radial velocity of +12 km/s provide context for its motion and structure. The primary's physical parameters—mass 1.89 solar masses, radius 1.9 solar radii, luminosity 10.4 solar luminosities, and effective temperature 7,982 K—are well-characterized, with an age of 867 million years. The system's faint combined magnitude of 6.07 makes it just visible to the naked eye, and its location 185 light years away in Cancer adds to its interest as a nearby binary.

Did You Know?

• 67 Cancri is a wide binary system discovered by James South and John Herschel.
• The primary component is a shell star with weak lines of singly-ionized titanium detected in 1970.
• The projected rotational velocity of the primary is disputed, with estimates of 105 km/s and 205 km/s.
• The two components have a projected separation of 6,100 AU as of 2007.