Astronomers Find 2.6 Million-Light-Year Long Hydrogen Gas Bridge

Astronomers have found a stream of hydrogen gas that is around 2.6 million light years long. The gas bridge connects two galaxies, 500 million light years away.

Czech Academy of Sciences researchers and students found the cosmic bridge using the William E. Gordon Telescope at the Arecibo Observatory.

The researchers discovered the gas stream in data, taken between 2008 and 2011 for the Arecibo Galaxy Environment Survey (AGES),

"This was totally unexpected. 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," said Dr Rhys Taylor, a researcher at the Czech Academy of Sciences and lead author of the paper, according to a news release.

The researchers said that the length as well as the amount of gas in the bridge is quite surprising.

"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 Roberto Rodriguez, from the University of Puerto Rico in Humacao.  That's far more than in the Milky Way and Andromeda galaxies combined!"

The team isn't sure how the gas stream was formed. One theory is that one of the galaxies in the pair moved close to the other, resulting in the gas stream. The other explanation is that one of the galaxies ploughed through the other one, pushing a tail of hydrogen gas from the galaxy. The researchers said that they plan on using computer simulations to find which of the theories best explains the gas bridge formation.

The study results are published in the Monthly Notices of the Royal Astronomical Society.