An open cluster (sometimes called a Galactic Cluster) is a group of 10s or 100s of stars that were born from the same initial cloud of gas (mainly Hydrogen) and dust. When they are young (a few million or tens of millions of years old), these clusters contain some very large, bright stars (called O or B-type stars). The very youngest clusters (usually less than 10 million years old) often still contain the remains of the gas cloud from which the stars were born – this is seen as nebulosity.

Cluster stars are very useful as they were all formed from the same giant cloud (so they have the same chemistry), and they are all at about the same distance from us (although they are typically hundreds or thousands of light years away!). By observing a group of stars in a cluster, we can assume they are all made of the same stuff, and they are all the same distance away from us – so any differences between them are really caused by their different mass.

In this project you will be shown how to use Faulkes Telescope data to measure the intensity of light from the stars in a cluster (a process known as photometry), through different filters, and plot the colours of the stars on a 'colour-magnitude diagram'. Once a measure of how “red” or “blue” the stars are is made, more informtion about them can be obtained– massive stars are usually very blue (hot), intermediate mass stars (like the Sun) are yellow, and the very lowest mass stars are red (cool).

Getting Started