THE VIVID RED CLOUD in this new image from the European Southern Observatory’s (ESO) Very Large Telescope is a region of glowing gas surrounding the star cluster NGC 371.
NGC 371 is an example of a mature ‘star birth’ region. The red cloud is made of ionised hydrogen—an HII region in astronomers’ jargon—surrounding a place that has experienced high rates of recent star birth, leading to the formation of an ‘open star cluster’.
An open star cluster is group of stars that formed together and are all in the same vicinity, but with a random scattering (unlike ‘globular’ star clusters, which form into a ball shape).
Stars in open clusters all originate from the same diffuse HII region. Over time the majority of the hydrogen is used up to form the stars, leaving behind just a leftover shell of hydrogen such as the one in this image.
NGC 371’s home, the Small Magellanic Cloud (SMC), is a dwarf galaxy a mere 200,000 light-years away, which makes it one of the closest galaxies to the Milky Way.
Watch a video that zooms into the SMC and NGC 371:
The SMC contains stars at all stages of their evolution…from the highly luminous young stars found in NGC 371 to supernova remnants of dead stars.
The energetic young stars emit copious amounts of ultraviolet radiation, making the surrounding gas light up with a colourful glow that extends for hundreds of light-years in every direction.
NGC 371 is of particular interest due to the unexpectedly large number of variable stars it contains. These are stars that change in brightness over time.
A particularly interesting type of variable star, known as slowly pulsating B stars, can also be used to study the internal working of stars through a technique known as asteroseismology, and several of these have been confirmed in this cluster.
Variable stars play a pivotal role in astronomy—some types are invaluable for determining distances to far-off galaxies and the age of the Universe.
The data for this image were selected from the ESO archive by Manu Mejias as part of the Hidden Treasures competition.
Adapted from information issued by ESO / Manu Mejias.
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