| News

How messy are your globular clusters? Messier?

A globular cluster, slightly bulging at the midriff. Named 'Messier 9'

How quickly we become jaded to astronomical discovery. A globular cluster. Sounds a bit like something you find in your nose on a hay fever day. Stars, thousands of them, dragged into a slightly wider-than-sperical shape by the cluster's proximity to the Milky Way's dead centre. The image brought to us by the in-orbit Hubble Space Telescope, allows us to see individual stars for the first time, in a cluster that has been known since 1764. Celestial beauty, worthy of a much more lofty title than 'globular cluster'.

IMAGE: This image from the NASA/ESA Hubble Space Telescope shows the globular cluster Messier 9.



In particular, the elements crucial to life on Earth, like oxygen and carbon, and the iron that makes up our planet's core, are very scarce in Messier 9 and clusters like it. This is because the Universe's heavier elements were gradually formed in the cores of stars, and in supernova explosions. When the stars of Messier 9 formed, there were far smaller quantities of these elements in existence.


The contrast between Messier's equipment and the tools at the disposal of today's astronomers is stark. Hubble's image, the highest resolution image yet made of Messier 9, is able to resolve individual stars, right into the crowded centre of the cluster. Over 250 000 of them are neatly focused on the detector of Hubble's Advanced Camera for Surveys, in an image which covers an area no bigger than the size of the head of a pin held at arm's length.

As well as showing the individual stars, Hubble's image clearly shows the different colours of the stars. A star's colour is directly related to its temperature — counter-intuitively, perhaps, the redder it is, the cooler it is; and the bluer it is, the hotter. The wide range of stellar temperatures here is clearly displayed by the broad palette of colours visible in Hubble's image of Messier 9.


Source: NASA/ESA

Comments are closed.

Our weekly newsletter

Sign up to get updates on articles, interviews and events.