"We expected to find the Milky Way's books balanced, with an equilibrium of gas inflow and outflow, but 10 years of Hubble ultraviolet data has shown there is more coming in than going out," said astronomer Andrew Fox of the Space Telescope Science Institute, Baltimore, Maryland, lead author of the study to be published in the Astrophysical Journal.
Fox said that, for now, the source of the excess inflowing gas remains a mystery.
Explanation - Gas - Medium - Fox - Milky
One possible explanation is that new gas could be coming from the intergalactic medium. But Fox suspects the Milky Way is also raiding the gas "bank accounts" of its small satellite galaxies, using its considerably greater gravitational pull to siphon away their resources. Additionally, this survey, while galaxy-wide, looked only at cool gas, and hotter gas could play a role, too.
The new study reports the best measurements yet for how fast gas flows in and out of the Milky Way. Prior to this study, astronomers knew that the galactic gas reserves are replenished by inflow and depleted by outflow, but they did not know the relative amounts of gas coming in compared to going out. The balance between these two processes is important because it regulates the formation of new generations of stars and planets.
Astronomers - Survey - Observations - Hubble - Cosmic
Astronomers accomplished this survey by collecting archival observations from Hubble's Cosmic Origins Spectrograph (COS), which was installed on the telescope by astronauts in 2009 during its last servicing mission. Researchers combed through the Hubble archives, analyzing 200 past ultraviolet observations of the diffuse halo that surrounds the disk of our galaxy. The decade's worth of detailed ultraviolet data provided an unprecedented look at gas flow across the galaxy and allowed for the first galaxy-wide inventory. The gas clouds of the galactic halo are only detectable in ultraviolet light, and Hubble is specialized to collect detailed...
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