GOC: Globular & Open Clusters

Hello, we are GOC! We are looking at globular and open clusters in our very own galaxy with the hope of plotting Hertzsprung-Russell (HR) diagrams that will show how the properties of stars vary between the two types of cluster. We will determine the properties, ages and metallicities of stars.

GOC Research team:

Harry Baker, Hamish Child (Coordinator), Matthew Hodge (Administrator), Emma Dodd, Alexander Hackett-Evans & Thomas Harrison.


Weekly Research Updates:

Result of the week #1:

It shows an unreduced (left) then a reduced image of the open cluster M67 (g-band), made using our code written by Emma and Harry.


A globular cluster describes a collection of stars that are bound by gravity, these clusters typically reside in the halo of a galaxy and are much older than an open cluster. One cluster at the focus of our report, M71 (Messier 71), is a much younger globular cluster. We can observe this difference in age through how metal rich a cluster is – the younger ones will be much more metal rich than a typical example of this object.

Open clusters contain far fewer stars and are loosely bound by their gravitational attraction. Since they also orbit much closer to the galactic centre, the shorter lived open clusters interact with gas clouds and other open clusters making them a crucial part of stellar evolution. In our project we aim to plot Hertzsprung-Russell diagrams (scatter graph relating a stars brightness to its surface temperature) of these types of clusters with the intention to learn about the unique properties that globular and open clusters have, as well as the ones they share.

In our first week we begun manual photometry on the 4 clusters (2 open and 2 globular) we have chosen to study. Photometry measures the variations in brightness of an object over time to plot and analyse data, in our case the object is the cluster and the stars contained within it. Once manual photometry is done, we can test our Hertzsprung-Russell diagram scripts, coded by Harry and Emma. Hopefully, all will go well and we can begin plotting the data of thousands of stars across 4 different clusters with help from the INT (Isaac Newton Telescope) and Hubble.

Matthew Hodge

Week 2

Week 3

Week 4

Week 5

Alternatively, read all the update posts in one place.