An excessive amount of gas flowing into the Milky Way galaxy has been discovered by astronomers—though the reason behind the phenomenon remains a mystery.
According to a news release from NASA's Hubblesite, about 10 years' worth of data from the Hubble Space Telescope shows there has been more gas coming in than out, said Andrew Fox, an astronomer and lead author of a forthcoming study for The Astrophysical Journal.
When employing Cosmic Origins Spectrograph (COS) technology through the telescope, gas heading away from the galaxy appears redder, while gas coming toward it appears bluer. This led to the unexpected realization that the amount of gas coming into to the Milky Way is far greater than that which is escaping.
"Our Milky Way is a frugal galaxy," Hubblesite explained. "Supernovas and violent stellar winds blow gas out of the galactic disk, but that gas falls back onto the galaxy to form new generations of stars."
The process itself—which has occurred for billions of years—does not explain why there is a surplus of gas in the galaxy rather than equilibrium.
Hubblesite said the study offers that one theoretical source behind the Milky Way's "unbalanced books" is the intergalactic medium—a mass of hydrogen gas believed to exist in between different galaxies.
However, Fox, an astronomer for the Space Telescope Science Institute (which performs science operations for Hubble), believes that the Milky Way is able to use its gravitational pull to steal gas reserves from smaller, nearby galaxies.
The study's co-author, Rongmon Bordoloi of North Carolina State University, added: "The original Hubble COS observations were taken to study the universe far beyond our galaxy, but we went back to them and analyzed the Milky Way gas in the foreground. It's a credit to the Hubble archive that we can use the same observations to study both the near and the more distant universe. Hubble's resolution allows us to simultaneously study local and remote celestial objects."
The Hubble Space Telescope first launched in on April 24, 1990, and has made more than a million observations since then. Using two 25-foot solar panels, it gets its energy from the sun and sends out roughly 120 gigabytes of data once a week.
Experts say as of right now, the Milky Way is the only galaxy we are able to monitor this closely with the telescope.
