Using the OmegaCAM wide-field imager, a large camera mounted on ESO’s VLT Survey Telescope, astronomers have captured this vivid image of a small galaxy known as Wolf-Lundmark-Melotte.
This image shows the dwarf irregular galaxy Wolf-Lundmark-Melotte. Image credit: ESO / VST / Omegacam Local Group Survey.
Wolf-Lundmark-Melotte (WLM for short) is a dwarf irregular galaxy located in the constellation Cetus, approximately 3.1 million light-years away.
This small galaxy was first discovered in 1909 by German astronomer Max Wolf. Its nature as a galaxy was only established in 1926 by Knut Lundmark and Philibert Jacques Melotte.
Also known as DDO 221 and LEDA 143, the galaxy spans about 8,000 light-years at its greatest extent, a measurement that includes a halo of extremely old stars discovered in 1996.
Although considered part of Local Group of galaxies – the collection of galaxies that includes the Milky Way, the Magellanic Clouds, Andromeda, M33, and dozens of smaller galaxies, WLM stands alone at the group’s outer edges as one of its most remote members.
In fact, the galaxy is so small and secluded that it may never have interacted with any other Local Group galaxy – or perhaps even any other galaxy in the history of the Universe.
Scientists think that comparatively small primeval galaxies gravitationally interacted with each other and in many cases merged, building up into larger composite galaxies. Over billions of years, this merging process assembled the large spiral and elliptical galaxies that now appear to be common in the modern Universe.
WLM has instead developed on its own, away from the influence of other galaxies and their stellar populations.
Accordingly, WLM represents a relatively unperturbed ‘state of nature,’ where any changes occurring over its lifetime have taken place largely independent of activity elsewhere.
This small galaxy features an extended halo of very dim red stars, which stretches out into the inky blackness of the surrounding space.
This reddish hue is indicative of advanced stellar age.
It is likely that the halo dates back to the original formation of the galaxy itself, helpfully offering clues about the mechanisms that spawned the very first galaxies.
The stars at the center of WLM, meanwhile, appear younger and bluer in color.
In this image, pinkish clouds highlight areas where the intense light from young stars has ionized ambient hydrogen gas, making it glow in a characteristic shade of red.
