Messier 83, also known as the Southern Pinwheel Galaxy, is one of the most prominent spiral galaxies in the night sky. It’s named for its resemblance to the Pinwheel Galaxy and spans around 50,000 light-years, making it much smaller than the Milky Way galaxy, although it has a higher rate of star formation, as evidenced by the striking bursts of pink throughout its spiral arms. This display of intense starburst activity likely results from a past merger with another galaxy.
This image was captured with the Department of Energy-fabricated Dark Energy Camera (DECam), mounted on the U.S. National Science Foundation Víctor M. Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF NOIRLab.
Between 1750 and 1754, French astronomer Nicolas-Louis de Lacaille was studying the night sky with the aim of determining the distances to the planets. During this period he observed and cataloged 10,000 stars and identified 42 nebulous objects, including Messier 83, which he discovered in 1752 during his expedition to the Cape of Good Hope.
In 1781 Charles Messier added it to his famous catalog, describing it as a “nebula without stars,” reflecting the limited knowledge of galaxies at the time. It wasn’t until the 20th century, through the work of Edwin Hubble, that astronomers realized objects like Messier 83 are actually other galaxies far outside the Milky Way.
This image shows Messier 83’s well-defined spiral arms, filled with pink clouds of hydrogen gas where new stars are forming. Interspersed amongst these pink regions are bright blue clusters of hot, young stars whose ultraviolet radiation has blown away the surrounding gas. At the galaxy’s core, a yellow central bulge is composed of older stars, and a weak bar connects the spiral arms through the center, funneling gas from the outer regions toward the core. DECam’s high sensitivity captures Messier 83’s extended halo, and myriad more distant galaxies in the background.
Just as Messier 83 is filled with countless newly formed stars, the galaxy is also host to many dying stars. In the past century, astronomers have witnessed a total of six stellar explosions, called supernovae, in Messier 83 — a number matched by only two other galaxies. And while we have only detected these six stellar deaths, the galaxy is estimated to be filled with hundreds of thousands of ‘ghosts’ of dead stars called supernova remnants.
In 2006 a mysterious feature of Messier 83 was discovered by NSF NOIRLab astronomer Ruben Diaz and an international team of astronomers using the Gemini South telescope, one half of the International Gemini Observatory, funded in part by the NSF and operated by NSF NOIRLab. At the heart of this galaxy, they discovered a previously unseen concentration of mass resembling a second nucleus, likely the remnant of another galaxy that is being consumed by Messier 83 in an ongoing collision — possibly the same collision responsible for the starburst activity. The two nuclei, which likely contain black holes, are expected to merge to form a single nucleus in another 60 million years.
