Collinder 229

Collinder 229 is a young, bright open star cluster in the constellation Carina, also known as IC 2602, Caldwell 102, the Southern Pleiades and the Theta Carinae Cluster. It is one of the nearest open clusters, about 150 parsecs (roughly 480 to 490 light-years) away. It spans about 50 arcminutes, and Gaia studies identify 308 members within one tidal radius and 451 candidate members in a Gaia DR2 study. It stands out as one of the youngest benchmark clusters, with a Pleiades-like appearance, and it is the fifth-brightest open cluster in the sky. Its age is about 35 to 46 million years. It is also a near twin of the northern Pleiades. The bright star Theta Carinae (magnitude 2.7) dominates the view, though some sources doubt that it is a true member. At a combined magnitude of 1.9 it is a naked-eye object, best seen in binoculars, and Nicolas-Louis de Lacaille discovered it in 1751 from South Africa.