CENTAURUS (the "Centaur"), in astronomy, a southern constellation (invisible in northern lands) rich in bright stars and globular clusters. The two stars a, (3 are known as the southern Pointers since they point to the Southern Cross. One of these, a Centauri, is the third brightest star in the sky, and it is found to be our nearest neighbour; the distance is 4 light years (parallax It is a double star of which the brighter component is almost a replica of the sun, having nearly the same brightness and mass but slightly lower surface temperature ; there is also a third widely separated faint companion called Proxima Centauri, be cause it is slightly nearer to us than the main star. The constella tion also contains co Centauri which is the finest example of a globular star-cluster; it is probably the nearest object of this class, but the distance is no less than 20,000 light years. Photo graphs of it show more than 6,000 stars within a circle of 20' diameter, but the number must be much greater. (A. S. E.)