Are the spaces between galaxies filled with stars or gas?
Intergalactic space, the space between galaxies, can be filled with a hot gas that emits X-rays, but this is only found within clusters of galaxies. Sensitive searches have been made for a variety of forms of hot and cold gas in the intergalactic space outside clusters of galaxies. Some indications are that, long ago, there once were vast clouds of hydrogen gas, but we do not know where these clouds went because they can no longer be detected except as ‘absorption features’ in the light from very distant quasars. It is believed that many if not all of these clouds were ultimately ‘eaten’ by galaxies. THE INTERGALACTIC MEDIUM (IGM) MAY HAVE BEEN DETECTED , at least that part of it consisting of singly ionized helium. Using the Hubble Space Telescope (HST), a Dutch- British-French-US team of astronomers have sampled the light coming from the quasar Q0302- 003 (redshift of 3.286). They notice that ultraviolet light at a wavelength of 304 angstroms is being absorbed along the way, supposed
