Astronomy Picture of the Day

Explanation: Stars come in all different colours. The colour of a star indicates its surface temperature, an important property used to assign each star a spectral type. Most stars in the above Sagittarius Star Cloud are orange or red and relatively faint, as our Sun would appear. The blue and greenish stars are hotter, many being relatively young and massive. The bright red stars are cool Red Giants, bloated stars once similar to our Sun that have entered a more advanced stage of evolution. Stars of the Sagittarius Cloud lie towards the centre of our Galaxy - tantalizing cosmic jewels viewed through a rift in the dark, pervasive, interstellar dust. This famous stellar grouping houses some of the oldest stars known.