Lambda Centauri

After the small constellation of Crux was separated from the larger Centaurus, the constellation of the Centaur was left with a narrow stretch in the southwest that runs southward between Crux and Carina. Third magnitude Lambda Centauri is the brightest star in this small segment of the larger constellation. It stands out against the backdrop of the Running Chicken Nebula and its clusters, though the nebula in fact lies more than ten times farther from Earth than Lambda Centauri itself. The most recent parallax data places Lambda Centauri at a distance of some 394 light years (though other estimates suggest a slightly more distant value).

Lambda Centauri belongs to the Scorpius-Centaurus Association, a group of more than four hundred hot O-type and B-type stars that share a common origin in the far past, but are now spread across a wide region of the southern skies.

This is a binary star, with the primary being a blue giant, probably rotating rapidly enough to deform itself into an oblate form. The giant has a smaller companion with about a fifth its mass, orbiting the primary over a period of centuries at a distance of some 100 AU. There are some indications that the system may have a third component in a more distant orbit still, though this is unconfirmed.