By Patricia Daukantas
The Hubble Space Telescope (HST) has helped astronomers find some of the “missing matter” that they have been seeking in the vast spaces between galaxies.
A team headed by two University of Colorado astronomers found the about half of the missing baryonic (normal) matter in regions between the galaxies, otherwise known as the intergalactic medium. The scientists made observations along sight-lines to 28 quasars—which are some of the most distant objects in the universe—and used the light from the quasars to examine the stuff in between them and us.
The analysis combined data from the HST’s Space Telescope Imaging Spectrograph (STIS) and a separate astronomical satellite, NASA’s Far Ultraviolet Spectroscopic Explorer, to find filaments of hydrogen and highly ionized oxygen in the intergalactic regions. This matter is too hot to glow in the visible spectrum but too cool to give off X-rays.
More information is at HubbleSite, a multimedia Web site for educating the public about the many astronomical discoveries that have resulted from HST images and data since the space telescope’s launch in 1990.
Incidentally, the Colorado astronomers collected their STIS data before power problems shut that instrument down in August 2004. Later this year, the astronauts on the final HST servicing mission will attempt to repair the spectrograph’s electronics so that it can go back into service for several more years. A future issue of OPN will describe the servicing mission in more detail.