This week’s Hubble image is, appropriately enough, a star cluster called NGC 330 which glitters in shades of red, white, and blue. Stars appear different colors because of the differences in their temperatures and ages, with the hottest stars glowing blue and the coolest glowing red. There is a huge difference in the range of temperatures stars can be, with the hottest blue stars having a temperature of over 40,000 Kelvin, while the coolest red stars can be as low as 2,500 K.
At a distance of around 180,000 light-years away, this star cluster is located inside the Small Magellanic Cloud. The Small Magellanic Cloud or SMC is a satellite galaxy of the Milky Way, meaning it is a smaller companion galaxy which orbits our own galaxy. The SMC is tiny compared to the Milky Way, at just 7,000 light-years across, and contains hundreds of millions of stars. It is one of a pair of satellite galaxies along with its companion, the Large Magellanic Cloud.
As well as being beautiful to look out, observing star clusters can be a handy way to learn about the lifecycle of stars. As the Hubble scientists explain, “Because star clusters form from a single primordial cloud of gas and dust, all the stars they contain are roughly the same age. This makes them useful natural laboratories for astronomers to learn how stars form and evolve.”
In order to create this image, the Hubble scientists combined two sets of observations which both targeted this particular region of space. “This image uses observations from Hubble’s Wide Field Camera 3 and incorporates data from two very different astronomical investigations,” they write.
“The first aimed to understand why stars in star clusters appear to evolve differently from stars elsewhere, a peculiarity first observed with Hubble. The second aimed to determine how large stars can be before they become doomed to end their lives in cataclysmic supernova explosions.”