Cometary globules have nothing to do with comets. They are nebulae with long tails of gas and dust being shaped and stripped by the hot ionized material around them – and the Dark Energy Camera has found a spectacular example of one.
Located in the constellation of Puppis – translating in Latin to “poop deck” – the cometary globule has been given the name CG 4. It extends for about eight light-years and its head is 1.5 light-years across – we are saying “head” because we are seeing a resemblance to Shai-Hulud, the giant worms from Dune, but the astronomers in the team are calling this formation God’s Hand.
Cometary globules are a special type of Bok Globules that have been known since 1976. But even after 50 years, they remain extremely difficult to observe. The reason for this is that the gas and dust are very dark. Your standard telescope gets these dark nebulae confused with the darkness of the universe – but a filter can reveal it.
The Dark Energy Camera has a Hydrogen-alpha filter which picks the faint glow of ionized hydrogen. This emission is the red glow surrounding the cometary globule, the more distant background field, and the main nebula from which the globule is extending. Hydrogen atoms get excited by the energetic light of a hot massive star or stellar object. This energy can make them glow with the emission of a specific light
The light of those stars is not only ionizing the hydrogen, but it is also sculpting the cometary globule. In particular, it is destroying the head/hand portion of it. There is enough material in the head to form several new Sun-sized stars, but it is a race against time as to whether that many will form before the head is destroyed as the head is being destroyed and heated but to make new stars you need a cool stable cloud.
The cometary globules are found throughout the Milky Way, but this special region known as the Gum Nebula has 32 cometary globules. This is believed to be the expanding remains of a supernova explosion that took place about a million years ago. And it is a famous one: the Vela pulsar. All the cometary globules appear to have tails pointing away from it, probably sculpted by its intense radiation.
Near the mouth of the giant worm, there is a distant galaxy that looks like it is about to be eaten. In reality, ESO 257-19 (PGC 21338) is more than 100 million light-years away from CG 4. The gum nebula is 1,470 light-years away.
Source Link: God’s Hand Or Giant Worm? Dark Energy Camera Spots Cometary Globule In Space
