Look! This Strange Cosmic Cloud Looks Like a Dinosaur
This striking image of CG4 was captured by a telescope instrument originally built to study dark energy.
This strange cosmic cloud is called “the hand of God,” but it looks more like a Tyrannosaurus rex to us.
The reddish aura surrounding the cloud of gas and dust called CG4 comes from hydrogen gas, heated and ionized (electrically charged) by the radiation from massive nearby stars. That powerful bombardment of radiation is probably what eroded and stretched CG4 into its distinctive shape.
Astronomers call clouds like CG4 cometary globules, because their long, dust-shrouded tails look a bit like comets, even though they form completely different ways and on drastically different scales (one cometary globule probably contains a few star systems’ worth of actual comets). This one, CG4, is an especially dense patch of gas and dust within the larger Gum Nebula, which is home to the Vela Supernova Remnant and the Vela Pulsar.
Once you see it, you can’t unsee it.
Cometary globules like CG4 are just one form of a type of cosmic cloud called a Bok Globule. These clouds of gas and dust are so dense that visible and ultraviolet light can’t pass through them, making them appear as dark shadows in telescope images (when we can see them at all). The best way to see a Bok Globule is with an infrared telescope, like the Dark Energy Camera: an instrument mounted on the Victor Blanco Telescope on a mountaintop in Chile.
Weirdly, all of the 32 cometary globules in the Gum Nebula have their heads pointed toward the center of the nebula, where the fast-spinning Vela Pulsar lurks at the heart of the Vela Supernova Remnant; the pulsar and the expanding cloud of stellar debris around it are all that’s left of a massive star that exploded in a supernova about 1 million years ago. That explosion, along with radiation and charged particles from nearby massive stars in the Gum Nebula, may have shaped CG4 and other cometary globules into their streamlined shapes.
If you’d like a sense of scale, CG4 is about 1300 light years away. Its head is about 1.5 light-years wide, and its faint tail stretches across 8 light years.
