IC 2602

Lore & Background

IC 2602 was first discovered by French astronomer and abbot Nicolas-Louis de Lacaille on March 3, 1751 while at the Cape of Good Hope, South Africa. In his initial discovery, Lacaille classified Theta Carinae (referred to as 'Theta Navis' or 'Theta Argus') as a third magnitude star, while citing the cluster's resemblance to the northern Pleiades. The cluster is thought to form part of the Lower Scorpius–Centaurus association.

The cluster contains about 75 stars. Theta Carinae, the brightest member, is part of the asterism known as the Diamond Cross, which is often mistaken for the Southern Cross asterism in Crux. Another third-magnitude member, p Carinae (PP Carinae), lies well outside the main visible grouping and exhibits a variable apparent magnitude ranging from 3.22 to 3.55. All other members are of the fifth magnitude and fainter, but several are naked-eye objects, including HR 4196 (V518 Car), HR 4204, HD 93194, HR 4219, HR 4220, HR 4222, HD 92536, HD 93738, and V364 Carinae. An exoplanet has been found orbiting the star TOI-837 in this cluster.

Reader's Guide

IC 2602 is notable as one of the nearest and brightest open clusters, easily spotted without optical aid from the southern hemisphere. Its position at a declination of -64° makes it circumpolar from southern subtropics and temperate climates, while only observable from limited tropical regions in the north. The cluster is identifiable a few degrees south of the southern Milky Way, surrounded by various fifth and sixth magnitude stars. To the unaided eye, several faint stars are distinguishable to the east of the blue Theta Carinae. Its age is uncertain, with estimates ranging from about 50 million years (based on lithium depletion boundary age of similar cluster IC 2391) to about 13.7 million years (from its Hertzsprung-Russell diagram). The cluster's membership in the Lower Scorpius–Centaurus association places it within a larger stellar context. The presence of an exoplanet around TOI-837 adds to its scientific interest.

Did You Know?

• IC 2602 is the third-brightest open cluster in the sky, after the Hyades and the Pleiades.
• Its brightest star, Theta Carinae, is part of the Diamond Cross asterism, often mistaken for the Southern Cross.
• The cluster was discovered by Nicolas-Louis de Lacaille on March 3, 1751 from South Africa.