Free Astronomy Magazine May-June 2016

SPACE CHRONICLES The wilds of the Local Group by ESO T his image, captured by ESO’s OmegaCAM on the VLT Survey Telescope, shows a lonely gal- axy known as Wolf-Lundmark-Melot- te, or WLM for short. Although con- sidered part of our Local Group of dozens of galaxies, WLM stands alone at the group’s outer edges as one of its most remote mem- bers. In fact, the gal- axy is so small and secluded that it may never have interact- ed with any other Local Group galaxy — or perhaps even any other galaxy in the history of the Universe. Rather like an uncontacted tribe living deep in the Amazon rainforest or on an island in Oceania, WLM offers a rare insight into the primordial na- ture of galaxies that have been little dis- turbed by their envi- ronment. WLMwas discovered in 1909 by German astronomer Max Wolf, and identified as a galaxy some fif- teen years later by astronomers Knut Lundmark and Phili- bert Jacques Melotte T his image, captured by ESO’s OmegaCAM on the VLT Survey Telescope, shows a lonely galaxy known as Wolf-Lundmark-Melotte, or WLM for short. Although considered part of our Local Group of dozens of 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. [ESO] 8000 light-years at its greatest ex- tent, a measurement that includes a halo of extremely old stars discover- ed in 1996. Astronomers 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 — explaining the galaxy’s unusual moniker. The dim galaxy is located in the constellation of Cetus (The Sea Monster) about three million light- years away from the Milky Way, which is one of the three dominant spiral galaxies in the Local Group. WLM is quite small and lacks struc- ture, hence its classification as a dwarf irregular galaxy. WLM spans about