A team of astronomers using ESO’s MPG/ESO 2.2-m telescope has captured a colorful view of the open star cluster NGC 3532.
This image of the bright star cluster NGC 3532 was captured by the Wide Field Imager instrument at La Silla Observatory in 2013; some of the stars still shine with a hot bluish color, but many of the more massive ones have become red giants and glow with a rich orange hue. Image credit: ESO / G. Beccari.
NGC 3532, also known as Caldwell 91, the Wishing Well Cluster or Football Cluster, lies in the constellation Carina, some 1,300 light-years from the Sun.
Discovered by French astronomer Nicolas Louis de Lacaille in 1752, the cluster is easily seen with the naked eye from the southern hemisphere. It was described as a binary-rich cluster by John Herschel who observed ‘several elegant double stars’ during his stay in southern Africa in the 1830s.
The cluster was the first target to be observed by NASA’s Hubble Space Telescope in 1990.
It contains about 400 stars and covers an area of the sky that is almost twice the size of the full Moon.
NGC 3532 is about 300 million years old. The cluster stars that started off with moderate masses are still shining brightly with blue-white colors, but the more massive ones have already exhausted their supplies of hydrogen fuel and have become red giant stars.
As a result the cluster appears rich in both blue and orange stars. The most massive stars in the original cluster will have already run through their brief but brilliant lives and exploded as supernovae long ago.
There are also numerous less conspicuous fainter stars of lower mass that have longer lives and shine with yellow or red hues.
The background sky here in a rich part of the Milky Way is very crowded with stars.
Some glowing red gas is also apparent, as well as subtle lanes of dust that block the view of more distant stars. These are probably not connected to the cluster itself, which is old enough to have cleared away any material in its surroundings long ago.
