Gas Bridge Between Galaxies is the Longest Ever Discovered: 2.6 Million Light-Years

Astronomers have spotted a stream of gas that's a staggering 2.6 million light years long with the help of the William E. Gordon Telescope. The new findings reveal a bit more about the two galaxies connected by this gas, located about 500 million light-years away.

This bridge of atomic hydrogen gas is actually the largest known to date. In fact, it's a million light-years longer than a gas tail found in the Virgo Cluster just a few years ago. And it's not just the length that has astronomers awed; it's also the amount of gas found within it.

"We normally find gas inside galaxies, but here half of the gas-15 billion times the mass of the sun-is in the bridge," said Robert Rodriguez, one of the researchers, in a news release. "That's far more than in the Milky Way and Andromeda galaxies combined!"

Currently, the researchers are still investigating the origin of this massive stream of gas, though there are a few theories. It's possible that the large galaxy at one end of the bridge passed close to the group of smaller galaxies at the other end in the past, and that the stream of gas was drawn out as they moved apart. It's also possible that the large galaxy plowed through the middle of the group, pushing gas out of it. The scientists plan to used computer simulations in order to find out which of these ideas best fits the shape of the bridge currently seen.

"This was totally unexpected," admits Rhys Taylor, lead author of the new study. "We frequently see gas streams in galaxy clusters, where there are lots of galaxies close together, but to find something this long and not in a cluster is unprecedented."

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.