Even though the galaxy ‘may look serene and peaceful as it swirls in the vast, silent emptiness of space,’ Hubble scientists write on a blog post, ‘don’t be fooled — it keeps a violent secret. It is believed that this galaxy consumed another smaller galaxy to become the large and beautiful spiral that we observe today.’
It is believed that a while ago, a smaller dwarf satellite galaxy rotated around a larger galaxy, but the dwarf object came too close to the more massive body, which caused it to break apart by gravitational forces. The smaller galaxy, therefore, got consumed by the larger cosmic body.
How NGC 4651 Got Its Shape
The galaxy that currently exists is known as the Umbrella Galaxy because it has a dim umbrella-shaped form that spreads outward from the main body. That shape cannot be seen in the image captured by Hubble Space Telescope, but it can be seen in this older image of the same object.
The massive structure expands 100,000 light-years out from the galactic nuclei and is comprised of the debris left behind by bare stars. The umbrella form was formed after the galaxy consumed its neighbor, and as the smaller body got torn apart in a process known as ‘gravitational stripping,’ it structured into a long, thin shape called a ‘tidal stream.’
It is believed that these streams, made out of stars and gas, can ultimately shape prolonged disks, such as the one the Andromeda galaxy has. However, in the case of the NGC 4651, the stream was pulled away from the central galactic disk, and it then extended to form the umbrella structure.
“Although only a telescope like the NASA/ESA Hubble Space Telescope, which captured this image, could give us a picture this clear, NGC 4651 can also be observed with an amateur telescope — so if you have a telescope at home and a star-gazing eye, look out for this glittering carnivorous spiral,” the Hubble astronomers explained.