It even seems as if the grasping hand wants to grab an entire galaxy out of the sky. But appearances are deceiving; In reality, the galaxy is approximately 100 million light years away – and therefore far out of reach – from the ‘hand’.
But of course it remains a great recording. This was taken by the Dark Energy Camera, located on the Victor M. Blanco 4-meter Telescope in Chile.
Eraser Nebula
For the shot, the camera focused on the Gum Nebula, which is located about 1,300 light-years from Earth. In the center of it we find CG 4, an object that looks strikingly like a grasping hand.
Ball cloud
In reality, however, CG 4 is nothing more than a spherical cloud: a dense cloud of gas and dust in which star formation takes place. Some of these globular clouds – such as CG 4 – are somehow stripped of some of their material (see box), giving them a long tail and – with a little imagination – looking something like a comet.
It is unclear why some globular clouds take on a comet-like shape. Astronomers have two theories about it. One states that spherical clouds such as CG 4 were initially round, but were subsequently disrupted by a nearby supernova explosion. The second theory states that the remarkably shaped globular clouds owe their shape to a combination of stellar winds and radiation from nearby hot, massive stars. We don’t know exactly how it works. In the case of CG 4, both theories hold water; At the heart of the Gum Nebula is a supernova remnant – meaning CG 4 could have been affected by a supernova explosion. But a pulsar can also be found in the nebula; this is a rapidly spinning neutron star that, with its stellar winds and radiation pressure, could also influence the shape of CG 4. By the way, CG 4 is not the only comet-shaped globular cloud in the Gum Nebula; At least 31 of these globular clouds can still be found in the nebula.
Tail
So CG 4 is a spherical cloud with a tail. That tail is about 8 light-years long – which means that light takes 8 years to travel from one end of the tail to the other. On the tail there is a somewhat spherical gas and dust cloud that is about 1.5 light-years wide.
Glow
Globular clouds with a tail – such as CG 4 – have not been known for very long; astronomers only spotted them for the first time in 1976. This has everything to do with the fact that the gas and dust that they are made of has a fairly high density and allows virtually no light to pass through. The fact that such a beautiful image of a spherical cloud has been obtained with the Dark Energy Camera is thanks to a special filter that this camera has, which allows it to detect the weak red glow of ionized hydrogen in the ‘hand’ and along the ‘arm’. of CG 4 can detect. This glow is caused by the hydrogen being bombarded by radiation from nearby hot, massive stars.
Those stars make CG 4 visible. But with their intense radiation they also destroy the spherical cloud very gradually. However, this does not prevent the CG 4, which is still richly filled with dust and gas, from currently producing several new stars the size of our sun.
