Epsilon Octantis

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Epsilon Octantis (ε Octantis) is a faint red giant star in the southern, circumpolar constellation Octans. With an apparent magnitude of about 4.6 to 5.3, it is barely visible to the naked eye. Based on its parallax of 11.22 milliarcseconds, it lies roughly 291 light-years from the Sun. It is moving away from us at about 11.7 km/s, with proper motion of +56.8 mas/yr in right ascension and −43.5 mas/yr in declination.

This star is classified as M5III, a cool red giant. It has about 1.3 solar masses and has expanded to roughly 112 solar radii. It shines with around 1,800 times the Sun’s luminosity and has an effective temperature near 3,560 K.

Epsilon Octantis is a semiregular variable star, varying in brightness from magnitude 4.58 to 5.30 with a loosely defined period of about 55 days. It was identified as variable in a Bamberg Observatory survey in 1966. In 1972 it was briefly called BO Octantis, but that designation is no longer used since Bayer-designated stars do not receive separate variable-star names.