The galaxy M83 was discovered by a French astronomer by the name of Nicolas Louis de Lacaille in 1752. Its stunning spiral shape earned it the nickname of the Southern Pinwheel. It was the first galaxy discovered beyond our local group of galaxies and is best seen from southern locations. Charles Messier cataloged the galaxy; it is the most southern galaxy on his famous list.
M83 Compared to the Milky Way
M83 has a similar overall look to what we know of the Milky Way. M83 is a barred spiral galaxy, meaning that across its center is a large and somewhat straight region of stars before the curl of the spiral arms begins. M83, however, is quite a bit smaller than the Milky Way. It spans more than 40,000 light-years wide, whereas the Milky Way is approximately two and a half times larger than that.
The Image of M83, the Southern Pinwheel
This image of M83 was taken by the European Southern Observatory's Wide Field Imager (WFI), situated in the dry Atacama Desert in Chile. The WFI captured M83 over the course of 100 minutes. Billions of stars reside in the galaxy. Gigantic clouds of hydrogen gas glow red due to ultraviolet radiation from newly born, massive stars ionizing the gas in these clouds. The yellow glow at center is from older stars, while the dark webs winding through the arms are collections of dust. Besides the Southern Pinwheel's environs, the image also captures bright foreground stars from our galaxy and fainter, smaller swirls of more distant galaxies.
Research on M83
Recent observations of the galaxy show that the outer regions, not seen in this image, are pooulated with young stars. X-ray observations have revealed vigorous star formation hiding in the nucleus deep within a cloud of gas heated to 7 million degrees Celsius. M83 has also added much to the study of supernovae. Over the past 100 years, six supernovae have been located here, tying it with another galaxy as the most prolific supernova producer known. One of M83's supernovae, SN 1957D, was visible for 30 years.
Seeing M83
To observe M83, a southerly location is ideal. The Southern Hemisphere is the best spot, but northerners can also see M83 during late spring and early summer. M83 lies in the constellation Hydra, some 15 million light-years away. M83 may most easily be spotted by looking 19 degrees south of the bright star Spica in Virgo. M83 shines at magnitude 7.6.
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