CG 4: The Globule and the Galaxy

Explanation: Is this a cosmic monster ready to devour an unsuspecting galaxy? Thankfully, that is not the case. The red “monster” shown in the featured image is Cometary Globule CG 4 , 1,300 light-years away in the Constellation Puppis . CG 4 is a molecular cloud , where hydrogen becomes cold enough to form molecules that can be brought together by gravity to create stars . The shape of CG 4 resembles that of a comet , but its head is 1.5 light-year in diameter and its tail is 8 light-years long; for comparison, the distance from the Earth to the sun is only 8 light-minutes . Astronomers believe that the tail of a cometary globule could have been shaped by a nearby supernova explosion or by irradiation from hot, massive stars. Indeed, CG 4 and other nearby globules point away from the Vela Supernova Remnant , at the center of the Gum Nebula . The edge-on spiral galaxy , ESO 257-19, is more than a hundred million light-years beyond CG 4, and is completely safe from the “ monster ”.