May 8, 2013
Surprise Clouds Of Hydrogen Discovered In Our Galactic Neighborhood
Watch the video “Intergalactic Clouds Lurk Between Nearby Galaxies"
John P. Millis, PhD for redOrbit.com — Your Universe OnlineAs we gaze into space beyond the confines of our own Milky Way, we see a Universe filled with galaxies. But what scientists have come to realize is that the emptiness that spans between these giant pools of stars is not empty at all, but rather is filled with massive amounts of gas. In fact, these gas reservoirs can sometimes outweigh the galaxies themselves.
Closer to home, however, we have not observed such massive rivers of gas — until now.
Using the NSF´s Green Bank Telescope (GBT), researchers studying the galaxies that surround the Milky Way, known as the Local Group, have noticed that there are significant clouds of hydrogen gas lurking between some of our nearest neighbors: The Andromeda (M31) and Triangulum (M33) galaxies.
"We have known for some time that many seemingly empty stretches of the Universe contain vast but diffuse patches of hot, ionized hydrogen," said Spencer Wolfe of West Virginia University in Morgantown.
"Earlier observations of the area between M31 and M33 suggested the presence of colder, neutral hydrogen, but we couldn't see any details to determine if it had a definitive structure or represented a new type of cosmic feature. Now, with high-resolution images from the GBT, we were able to detect discrete concentrations of neutral hydrogen emerging out of what was thought to be a mainly featureless field of gas."
Initially, researchers speculated that streams of hydrogen gas might exist between the two galaxies. Given their close proximity to each other, gravitational interactions between the objects could have torn the gas from either spiral disk. However, if that had been the case, then the gas would appear as a smear of gas in the region. According to the research team, however, the gas appears in clumps.
"These observations suggest that they are independent entities and not the far-flung suburbs of either galaxy," said Felix J. Lockman, an astronomer at the National Radio Astronomy Observatory (NRAO) in Green Bank. "Their clustered orientation is equally compelling and may be the result of a filament of dark matter. The speculation is that a dark-matter filament, if it exists, could provide the gravitational scaffolding upon which clouds could condense from a surrounding field of hot gas."
These findings may just be the beginning. Researchers with the BGT and other radio observatories may now search the rest of the Local Group, looking for additional reserves of hydrogen gas.
"The region we have studied is only a fraction of the area around M31 reported to have diffuse hydrogen gas," said D.J. Pisano of West Virginia University. "The clouds observed here may be just the tip of a larger population out there waiting to be discovered."