NASA’s Hubble Space telescope has discovered a huge halo of gas surrounding Andromeda galaxy, the closest galactic neighbor. Andromeda is about 25 percent brighter than the Milky Way, contains twice as many stars, and is the largest galactic member in the group of 45 galaxies.
The research team was led by Nicolas Lehner at the University of Notre Dame, and they spent five years to study the halo using the Hubble Space telescope.
They determined that the halo extended approximately one million light years outwards from Andromeda, nearly half the distance to the Milky Way. The halo contains at least the mass as half of Andromeda’s trillion stars. Though Hubble has discovered similar halos in other galaxies beyond the Milky Way, the new discovery is the closest to Earth.
‘The properties of these gaseous halos control the rate at which stars form in galaxies,” said Lehner.
Hubble’s high-resolution spectroscope was used to detect the halo in ultraviolet light. the team used 18 different quasars at different distances, to probe the extent and distance of the halo. When the light from the quasar passes through the halo, it becomes distorted, and makes them dimmer in various range of wavelengths.The measurement of the dimming reveals the volume of gas in between the quasars and Earth’s vantage point.
So far, Hubble Cosmic Origins Spectrograph (COS) program has studied 44 distant galaxies, but Andromeda is the closest massive galaxy till date. The program is an international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland controls the telescope while the science operations are conducted by Space Telescope Science Institute (STScl) in Baltimore. STScl works on behalf of the Association of Universities Research in Astronomy for NASA.[ Source ]