Eta Chamaeleontis

Eta Chamaeleontis (η Cha, η Chamaeleontis) is a star in the constellation Chamaeleon. It has an apparent magnitude of about 5.5, meaning that it is just barely visible to the naked eye. Based upon parallax measurements made by the Hipparcos spacecraft, this star is located some 310 light years (95 parsecs) away from the Sun.

Eta Chamaeleontis has a spectral type of B8V, meaning it is an B-type main sequence star. These types of stars are a few times more massive than the Sun, and are have effective temperatures of about 10,000 to 30,000 K. Eta Chamaeleontis is just over 3 times more massive than the Sun and has a temperature of about about 12,000 K.

Eta Chamaeleontis is the brightest and most massive member of the eponymous Eta Chamaeleontis Cluster (or Mamajek 1), a very nearby (316 light years), and young (8 million years old) open cluster discovered in 1999. The cluster contains nearly 20 stellar members spread out over a 40-arcminute diameter region of sky, including the neighboring A-type star HD 75505 and the eclipsing binary RS Cha. All of the low-mass members (including RS Cha) are pre-main sequence, and several of them appear to still be accreting from protoplanetary disks.