Deepest X-rays Ever Reveal Universe Teeming With Black Holes
For the first time, astronomers believe they have proof
black holes of all sizes once ruled the Universe. NASA's
Chandra X-ray Observatory provided the deepest X-ray images
ever recorded, and those pictures deliver a novel look at the
past 12 billion years of black holes.
Two independent teams of astronomers today presented images
that contain the faintest X-ray sources ever detected, which
include an abundance of active super-massive black holes.
This image, known as the "Chandra Deep Field South" since it is located in the Southern Hemisphere constellation of Fornax, is the deepest X-ray exposure every achieved.
"The Chandra data show us that giant black holes were much
more active in the past than at present," said Riccardo
Giacconi, of Johns Hopkins University, Baltimore, MD, and
Associated Universities, Inc., Washington, DC. The exposure is
known as "Chandra Deep Field South" since it is located in the
Southern Hemisphere constellation of Fornax. "In this million-
second image, we also detect relatively faint X-ray emission
from galaxies, groups, and clusters of galaxies."
The images, known as the Chandra Deep Fields, were obtained
during many long exposures over the course of more than a
year. Data from the Chandra Deep Field South will be placed in
a public archive for scientists beginning today.
"For the first time, we are able to use X-rays to look back to
a time when normal galaxies were several billion years
younger," said Ann Hornschemeier, Pennsylvania State
University, University Park. The group's 500,000-second
exposure included the Hubble Deep Field North, allowing
scientists the opportunity to combine the power of Chandra and
the Hubble Space Telescope, two of NASA's Great Observatories.
The Penn State team recently acquired an additional 500,000
seconds of data, creating another one-million-second Chandra
Deep Field, located in the constellation of Ursa Major.
The images are called Chandra Deep Fields because they are
comparable to the famous Hubble Deep Field in being able to
see further and fainter objects than any image of the universe
taken at X-ray wavelengths. Both Chandra Deep Fields are
comparable in observation time to the Hubble Deep Fields, but
cover a much larger area of the sky.
"In essence, it is like seeing galaxies similar to our own
Milky Way at much earlier times in their lives," Hornschemeier
added. "These data will help scientists better understand star
formation and how stellar-sized black holes evolve." Combining
infrared and X-ray observations, the Penn State team also
found veils of dust and gas are common around young black
Another discovery to emerge from the Chandra Deep Field South
is the detection of an extremely distant X-ray quasar,
shrouded in gas and dust. "The discovery of this object, some
12 billion light years away, is key to understanding how dense
clouds of gas form galaxies, with massive black holes at their
centers," said Colin Norman of Johns Hopkins University.
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