Hubble Telescope Picture Shows Gorgeous Star Cluster

Another impressive Hubble telescope picture shows a large star cluster, made possible by combining ultraviolet, visible and infrared observations made by Hubble's Wide Field Camera 3 into a composite image. Such a filter set lets the telescope "see" colors slightly further beyond red and the violet ends of the spectrum.

This sphere of stars looks exactly like one of the 150 globular clusters, which are roughly spherical collections of extremely old stars, and are scattered around our galaxy. Hubble is one of the best telescopes for studying these, as its extremely high resolution lets astronomers see individual stars, even in the crowded center. The clusters all look very similar, and in Hubble's images it can be quite hard to tell them apart.

But the cluster pictured here, NGC 411, is not even one of the globular clusters, it consists of young stars instead of old stars, and is not even in the Milky Way.  NGC 411 is instead classified as an open cluster, where stars tend to drift apart over time as they age, whereas globular clusters have survived for well over 10 billion years of galactic history. NGC 411 is a relative youngster - not much more than a tenth of this age. Far from being a relic of the early years of the Universe, the stars in NGC 411 are in fact a fraction of the age of the Sun.

This can be generalized, since the stars in NGC 411 are all about the same age, having formed in one go from one giant cloud of gas. They are not all the same size though. Hubble's image shows a wide range of colours and brightnesses in the cluster's stars. These tell astronomers many facts about the stars, including their mass, temperature and evolutionary phase, with the latter depending on the first parameter.