Friday, October 8, 2010
WASHINGTON -- During a period of universal warming 11 billion years ago, quasars -- the brilliant core of active galaxies -- produced fierce radiation blasts that stunted the growth of some dwarf galaxies for approximately 500 million years.
This important conclusion comes from a team of astronomers that used the new capabilities of NASA's Hubble Space Telescope to probe the invisible, remote universe. The team's results will be published in the October 10, 2010 issue of The Astrophysical Journal.
Using Hubble's Cosmic Origins Spectrograph (COS), the astronomers identified this era, from 11.7 to 11.3 billion years ago, when the ultraviolet light emitted by active galaxies stripped electrons off helium atoms. The process, known as ionization, heated the intergalactic helium from 18,000 degrees Fahrenheit to nearly 40,000 degrees. This inhibited the gas from gravitationally collapsing to form new generations of stars in some small galaxies.
Because of its greatly improved sensitivity and lower background "noise" compared to previous spectrographs in space, the COS observations were ground-breaking. The observations allowed scientists to produce more detailed measurements of the intergalactic helium than previously possible.
Posted by .Sheila at 5:44 PM