· The cometary globule, also known as CG4, is powered by the leftover, dense core of a star
· The head of CG4, which is the part visible in this ESO image, has a diameter of 1.5 light-years
· Why CG4 and other cometary globules have their distinct form is still unknown by astronomers
· One theory is cometary globules are shaped by stellar winds and radiation from hot, massive stars
The cometary globule, also known as CG4, shines brightly in this spectacular image, and looks as though it is about to grab at stars.
Although it appears vivid in this picture, this is in fact a faint nebula, which makes it very hard for amateur sky watchers to spot.
Astronomers believe it is powered by the leftover, dense core of a star that blew up in a supernova explosion. But its exact nature remains a mystery.
In 1976 several elongated comet-like objects were discovered on pictures taken with the UK Schmidt Telescope in Australia.
Because of their appearance, they became known as cometary globules even though they have nothing in common with comets.
They had dense, dark, dusty heads and long, faint tails, which were generally pointing away from the Vela supernova remnant located at the centre of the Gum Nebula.
Although these objects are relatively close by, it took astronomers a long time to find them as they glow very dimly and are therefore hard to detect.
The object shown in this latest picture, CG4, which is also sometimes referred to as the Mouth of the Beast, is one of these cometary globules.
The fist of 'God's Hand', which is the part visible on this image and resembles the head of the gigantic beast, has a diameter of 1.5 light-years.
The tail of the globule — which extends downwards and is not visible in the image — is about eight light-years long. By astronomical standards this makes it a comparatively small cloud.
The relatively small size is a general feature of cometary globules.
All of the cometary globules found so far are isolated, relatively small clouds of neutral gas and dust within the Milky Way, which are surrounded by hot ionised material.
The head part of CG4 is a thick cloud of gas and dust, which is only visible because it is illuminated by the light from nearby stars.
The radiation emitted by these stars is gradually destroying the head of the globule and eroding away the tiny particles that scatter the starlight.
However, the dusty cloud of CG4, captured by the European Southern Observatory's Very Large Telescope, still contains enough gas to make several sun-sized stars.
Why CG4 and other cometary globules have their distinct form is still a matter of debate among astronomers and two theories have developed.
Cometary globules could originally have been spherical nebulae, which were disrupted and acquired their new, unusual form because of the effects of a nearby supernova explosion.
Other astronomers suggest, that cometary globules are shaped by stellar winds and ionising radiation from hot, massive stars.
These effects could first lead to the bizarrely named formations known as elephant trunks and then eventually cometary globules.
To find out more, astronomers need to find out the mass, density, temperature, and velocities of the material in the globules.
These can be determined by the measurements of molecular spectral lines which are most easily accessible at millimetre wavelengths — wavelengths at which telescopes like the Atacama Large Millimeter/submillimeter Array (Alma) operate.
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