Our Milky Way galaxy may be much bigger than previously thought, a new study has found. Spiral galaxies like the Milky Way appear to be much larger and more massive than believed earlier, according to a new University of Colorado Boulder study by researchers using the Hubble Space Telescope.
Professor John Stocke, study leader, said new observations with Hubble's USD 70 million Cosmic Origins Spectrograph, or COS, show that normal spiral galaxies are surrounded by halos of gas that can extend to over one million light-years in diameter. The current estimated diameter of the Milky Way, for example, is about 100,000 light-years. One light-year is roughly 6 trillion miles.
The material for galaxy halos detected by the researchers originally was ejected from galaxies by exploding stars known as supernovae, a product of the star formation process, said Stocke. "This gas is stored and then recycled through an extended galaxy halo, falling back onto the galaxies to reinvigorate a new generation of star formation," he said.
"In many ways this is the 'missing link' in galaxy evolution that we need to understand in detail in order to have a complete picture of the process," said Stocke. Building on earlier studies identifying oxygen-rich gas clouds around spiral galaxies by scientists, Stocke and his
colleagues determined that such clouds contain almost as much mass as all the stars in their respective galaxies.
"This was a big surprise. The new findings have significant consequences for how spiral galaxies change over time," said Stocke. Researchers discovered giant reservoirs of gas estimated to be millions of degrees Fahrenheit that were enshrouding the spiral galaxies and halos under study. The halos of the spiral galaxies were relatively cool by comparison - just tens of thousands of degrees - said Stocke.