Free Astronomy Magazine July-August 2024

52 JULY-AUGUST 2024 ASTRO PUBLISHING Remnant and Vela Pulsar are lo- cated. The Vela Pulsar is a rapidly spinning neutron star that was formed when a massive star col- lapsed, and it’s possible that its stellar winds and radiation pressure are shaping the nearby globules. Also in this image it looks as if CG 4 is about to devour the edge-on spi- ral galaxy ESO 257-19 (PGC 21338), which appears to be placed so de- fenselessly in front of it. But in real- ity, this galaxy is more than a hundred million light-years beyond CG 4 and only appears to be close because of a chance alignment. T his excerpt shows a close-up of CG 4 seemingly about to devour the edge-on spiral galaxy ESO 257- 19 (PGC 21338). But in reality, this galaxy is more than a hundred million light-years be- yond CG 4 and only appears to be close because of a chance alignment. Near the head of the cometary glob- ule are two young stellar ob- jects (YSOs). YSOs are stars in their early stage of evolution, before they be- come main-se- quence stars, that often ex- hibit characteris- tics such as jets, bipolar out- flows, proto- planetary discs, and other indicators of a new star being born. [CTIO/NOIRLab/DOE/NSF/AURA. Image Processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), D. de Martin & M. Zamani (NSF’s NOIRLab)] served these structures throughout the Milky Way, the overwhelming majority of them, including CG 4, are found within a huge patch of glowing gas called the Gum Nebula. Believed to be the expanding re- mains of a supernova that took place about a million years ago, the Gum Nebula is currently known to contain at least 31 cometary glob- ules in addition to CG 4. The mechanism by which these comet-like objects get their distinct shape is not entirely known, but as- tronomers have developed two main ideas about their origins. The first idea is that they could have originally been spherical nebulae — like the well-known Ring Nebula — which were then disrupted by a nearby supernova explosion, possi- bly the original explosion that cre- ated the Gum Nebula. The second idea is that cometary globules are shaped by a combina- tion of stellar winds and radiation pressure from nearby hot, massive stars. In fact, all of the cometary globules found within the Gum Neb- ula appear to have tails pointing away from the center of the nebula, which is where the Vela Supernova !