An odd couple lives some 100 million light years away with spiral galaxy, NGC 2276 shown on the left, and its neighbor NGC 2300 on the right. There are quite a few intriguing questions concerning this pair. First of all NGC 2276 displays a perturbed spiral structure yet astronomers seem to agree that NGC 2300 is not the source of the angst. Instead, astronomers have learned that there is an abundance of gas (not shown in this picture) surrounding these galaxies. It could be that NGC 2276's motion through the gas affects its morphology.
Finally, recent studies have revealed that the common envelope of gas that surrounds these two galaxies is very massive and hot (emitting X-ray radiation). Yet there isn't enough luminous mass from these two galaxies alone to gravitationally hold on to the gas. This is one of many observations that lends credence to "dark matter" and its ubiquitous nature in our Universe. Please visit the following link to learn more about the NGC 2300 group of galaxies and dark matter.
The Daily Galaxy via NRAO