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Messier 83

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Messier 83 is a massive barred spiral galaxy. It is also known as the Southern Pinwheel Galaxy or NGC 5236. This galaxy is one of the closest and brightest barred spiral galaxies in our sky. It is located approximately 15 million light-years away. You can find it near the borders of the Hydra and Centaurus constellations. Because it is so bright, you can even see it using binoculars.

M83 - Southern Pinwheel
M83 - Southern Pinwheel

The structure of M83 is quite specific. Astronomers use the De Vaucouleurs system to classify its shape. M83 is classified as SAB(s)c. The 'SAB' label means it is a weak-barred spiral. This means it has a bar-shaped center, but the bar is not very strong. The '(s)' part indicates it is a pure spiral structure without a ring. Finally, the 'c' means the spiral arms are loosely wound. This shape gives it the nickname of the Southern Pinwheel.

M83 - Southern Pinwheel
M83 - Southern Pinwheel

Many interesting processes happen within the arms of this galaxy. According to density wave theory, star formation happens more quickly along the leading edge of the spiral arms. This means new stars are born in specific patterns as the arms move. In 2008, NASA's Galaxy Evolution Explorer project found something surprising. It reported large numbers of new stars in the outer reaches of the galaxy. These stars were far from the center. Scientists previously thought these outer areas lacked the materials needed to make stars.

M83 - Southern Pinwheel
M83 - Southern Pinwheel

Gravity also plays a huge role in the history of M83. A peculiar dwarf galaxy called NGC 5253 lies near M83. It is likely that these two galaxies interacted within the last billion years. This interaction caused starburst activity in their central regions. Starburst activity is a period of intense star formation. Additionally, researchers found first clues in April 2025 regarding a possible supermassive black hole. This black hole might exist at the very center of M83.

M83 - Southern Pinwheel
M83 - Southern Pinwheel

Humans have been observing M83 for centuries. Nicolas-Louis de Lacaille discovered the galaxy on 17 February 1752. He made this discovery at the Cape of Good Hope. Later, Charles Messier added it to his famous Messier Catalogue in March 1781. Since then, astronomers have recorded many important events. They have observed six different supernovae, which are massive explosions of dying stars. These explosions help us learn about the life cycles of stars within the galaxy.

M83 - Southern Pinwheel
M83 - Southern Pinwheel

One supernova, named SN 1983N, was particularly significant. It was discovered by Robert Evans from Australia on 3 July 1983. On 6 July, scientists observed it with the Very Large Array. This was the first time radio emissions were detected from a Type I supernova. The explosion reached its peak optical brightness on 17 July. About one year after the explosion, scientists discovered a large amount of iron in the ejecta. This was the first time such a large amount of iron was clearly detected from a supernova.

M83 - Southern Pinwheel
M83 - Southern Pinwheel

M83 is part of a larger cosmic neighborhood. It sits at the center of one of two subgroups in the Centaurus A/M83 Group. Centaurus A is at the center of the other subgroup. These two subgroups are physically close to each other. They do not appear to be moving relative to one another. By studying M83, scientists can better understand how galaxy groups and star formation work across the universe.

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File:M83 - Southern Pinwheel.jpg
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