A stunning new image from the Dark Energy Camera (DECam) shows the glowing structures of the Gum Nebula illuminated by the hot, massive stars studded throughout this cloud of dust and gas. Located 1,300 light-years away in the constellation of Puppis, this image highlights an unusually shaped structure in the nebula that looks like a hand reaching out into space. Nicknamed “God’s Hand,” the structure is a type of object called a cometary globule.
A cometary globule is a particularly dense cloud of dust and gas with an unusual comet-like shape. They tend to have a compact head, with a long trailing tail, like the comets from which they get their name. But while comets are made of rock and ice, and have tails due to ice sublimating as the comet approaches a warm star, the cometary globules get their tails through a different process. They are also much, much larger. In this case, the God’s Hand globule has a huge head that is 1.5 light-years across, and its tail is eight light-years long.
Technically known as CG 4, this cometry globule is in fact on the smaller size for membership in a group called Bok globules. The (relatively) small size compared to whole nebulae or galaxies makes the globules hard to spot, as they tend to be quite faint. “With its special Hydrogen-alpha filter, DECam can pick up the faint red glow of ionized hydrogen present within CG 4’s head and around its outer rim,” NOIRLab explains. “This light is produced when hydrogen becomes excited after being bombarded by radiation from nearby hot, massive stars.”
Scientists are still figuring out what processes create cometary globules, but they have noticed that there are many of them within this nebula in particular. Researchers think either they could have been formed after starting life as spherical nebulae. They were then disrupted by the supernova that created the Gum Nebula. Or they could be shaped by winds and radiation from nearby hot stars.
