The Devourer of Worlds
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 were all located in a huge patch of glowing gas called the Gum Nebula. 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 new picture, CG4, also sometimes referred as God’s Hand, is one of these cometary globules. It is located about 1300 light-years from Earth in the constellation of Puppis.
The head of CG4, 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 still contains enough gas to make several Sun-sized stars and indeed, CG4 is actively forming new stars, perhaps triggered as radiation from the stars powering the Gum Nebula reached CG4.
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, and therefore also CG4, 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 OB stars. These effects could first lead to the bizarrely (but appropriately!) named formations known as elephant trunks and then eventually cometary globules.
instead of God’s Hand, I personally think it looks like a were-worm (from The Hobbit) about to swallow a galaxy :)
This picture is a composite between data acquired by two telescopes in 2018 & 2021:
- Riccardi Honders 305mm f3.8 for the wide field
- Planewave 17“ CDK @ F6.8 for the high res of CG 4
RA: 07h 34m 22.7s
DEC: -46° 54’ 06.7“
Size: 70 x 48.8 arcmin
Orientation: Up is 0.6 degrees E of N
Distance: 1.3 kly
Acquisition December 2018 & February 2021
Total acquisition time of 38.3 hours.
Data acquisition: Martin PUGH
Processing: Nicolas ROLLAND
Telescope 1 (17.3 hours):
Location: Heaven's Mirror Observatory, Australia
L 8 x 1200 sec
R 9 x 1200 sec
G 9 x 1200 sec
B 8 x 1200 sec
Ha 12 x 1800 sec
Optics: Riccardi Honders 305mm f3.8
Mount: Paramount ME II
CCD: SBIG STXL-16200
Telescope 2 (21 hours):
Location: El Sauce Observatory, Rio Hurtado, Chile
L 27 x 1200 sec
R 12 x 1200 sec
G 12 x 1200 sec
B 12 x 1200 sec
Optics: Planewave 17“ CDK @ F6.8
Mount: Paramount ME
CCD: SBIG STXL-11002 (AOX)
Pre Processing: CCDstack & Pixinsight
Post Processing: Photoshop CC