Observations of a Milky Way look-alike
BY DR EMILY BALDWIN
ASTRONOMY NOW

Posted: September 04, 2008

ESO's Wide Field Imager (WFI), attached to the 2.2 metre Max-Planck Society/ESO telescope in Chile, has captured the intricate swirls of the barred spiral galaxy Messier 83, a smaller version of our own Milky Way.

Colour-composite image of M83, as seen by ESO's Wide Field Imager (WFI), attached to the 2.2-metre Max-Planck Society/ESO telescope in Chile. The brighter stars in the foreground are stars in our own Galaxy, whilst behind M83 the darkness is peppered with the faint smudges of distant galaxies. Image: ESO.

M83, often nicknamed the Southern Pinwheel because of its spectacular spiral arms, lies roughly 15 million light-years away towards the huge southern constellation of Hydra, and spans a distance of over 40,000 light-years, making it roughly 2.5 times smaller than our own Milky Way. Despite the difference in size however, M83 shares some familiar traits with the Milky Way; both possess a bar across their galactic nucleus, and a dense pool of stars packed into their centres.

The new image was composed by training the WFI on the galaxy for around 100 minutes, which brought out the exquisite details in the galaxy’s arms and the ruby red glow of hydrogen gas marking the sites of newly born massive stars. These stellar newborns are bathed in thick ultraviolet radiation which ionises the galaxy’s gas clouds, producing the red glow. These star forming regions are contrasted dramatically against the ethereal glow of older yellow stars towards the galaxy's central hub, and the delicate dust streams waving throughout the arms.

Other recent observations of M83 in ultraviolet light and radio waves have shown that even the far reaches of the galaxy – further than revealed in this image – are populated with baby stars, while X-ray observations of the heart of M83 reveal an oven of frenetic star formation within a cloud of gas superheated to seven million degrees Celsius.

Messier 83 is also one of the most prolific producers of supernovae and is one of two galaxies which has witnessed six supernovae in the past 100 years. One of these, SN 1957D was observable for 30 years.

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