To modern eyes, the brightest stars of the constellation Sagittarius form the outline of a teapot, with the handle to the left and the spout to the right. To ancient eyes, though, it was the archer — a centaur holding a bow and arrow. It’s tough to pick out the centaur, but the bow is easy. It’s traced by an arc of three stars in the teapot, including the brightest star in the whole constellation.

The stars are Kaus Borealis, Kaus Media, and Kaus Australis — names that mean the northern, middle, and southern points of the bow. Kaus Borealis forms the top of the teapot. Kaus Australis is at the teapot’s bottom right, and is the brightest member of the constellation. And Kaus Media bows outward between them.

All three stars are giants — they’re much bigger and brighter than the Sun. And even though they’re much younger than the Sun, they’re much later in life. That’s because they’re all more massive than the Sun. Heavy stars consume their nuclear fuel quickly, so they burn out in a hurry. That process causes their outer layers to puff up, which makes them much brighter.

Kaus Media is the farthest member of the bow, which means that it’s actually the most impressive of the three stars — it’s more than a thousand times brighter than the Sun.

And if there’s a bow, there must be an arrow as well. It forms the outer point of the spout of the teapot — one more giant star that’s near the end of its life.
 

Script by Damond Benningfield

Support McDonald Observatory