Free Astronomy Magazine May-June 2016

SPACE CHRONICLES T his wide-field view shows the sky around the dwarf galaxy WLM in the constellation of Cetus (The Sea Monster). This picture was cre- ated from images forming part of the Digitized Sky Survey 2. The galaxy appears near the centre of the picture as an irregu- larly shaped clump of faint stars. [ESO/Digi- tized Sky Survey 2] spiral and elliptical gal- axies that now appear to be common in the modern Universe. Galaxies congregating in this manner is similar to the way in which hu- man populations have shifted over thousands of years and intermixed into larger settlements, eventually giving rise to today’s megacities. WLM has instead devel- oped on its own, away from the influence of other galaxies and their stellar populations. Ac- cordingly, like a hidden human po- pulation with limited contact with outsiders, WLM represents a rela- tively unperturbed “state of na- ture”, where any changes oc- curring over its lifetime have taken place largely indepen- dent 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 red- dish hue is indicative of ad- vanced stellar age. It is likely that the halo dates back to the original formation of the galaxy itself, helpfully offer- ing clues about the mech- anisms that spawned the very T his close-up video pan sequence, captured by ESO’s OmegaCAM on the VLT Survey Tele- scope, shows a lonely galaxy known as Wolf- Lundmark-Melotte, or WLM for short. [ESO] first galaxies. The stars at the centre of WLM, meanwhile, appear youn- ger and bluer in colour. In the image (previous page), pinkish clouds high- light areas where the intense light from young stars has ionised am- bient hydrogen gas, making it glow in a characteristic shade of red. This detailed image was captured by the OmegaCAM wide-field imager, a huge camera mounted on ESO’s VLT Survey Telescope (VST) in Chile — a 2.6-metre telescope exclusively de- signed to survey the night sky in visible light. OmegaCAM’s 32 CCD detectors create 256-megapixel im- ages, offering a very detailed wide- field view of the cosmos. n