Astronomers will use a $70 million instrument designed by the University of Colorado at Boulder now set for installation on the Hubble Space Telescope in mid-October to probe the "fossil record" of gases in the early universe for clues to the formation and evolution of galaxies, stars and planets.

The telephone-booth-sized instrument known as the Cosmic Origins Spectrograph, or COS, should help scientists better understand the "cosmic web" of material believed to permeate the universe, said CU-Boulder Professor James Green, COS science team leader.

COS will gather information from ultraviolet light emanating from distant objects, allowing scientists to look back in time and space and reconstruct the physical condition and evolution of the early universe, said Green.

"Light traveling from quasars billions of light-years away is altered as it passes through the material between galaxies, allowing us to see fingerprints of different gases," said Green of CU-Boulder's Center for Astrophysics and Space Astronomy.

"By choosing hundreds of targets in many directions, we can build up a picture of the way matter is organized in the universe on the grandest of scales."

While matter is thought to have been distributed uniformly throughout space just after the Big Bang, gravity has collapsed the universe into its present structures, said Green.

"The Cosmic Origins Spectrograph is 10 times more sensitive than any instrument of its kind, which opens up a whole new vista of scientific opportunities for Hubble," he said. "That's why we are so excited to get it into orbit."

The spectrograph will break light into its individual components -- similar to the way raindrops break sunlight into the colors of the rainbow -- revealing information about the temperature, density, velocity, distance and chemical composition of galaxies, stars and gas clouds. COS will be able to peer back in time to 10 billion years ago when the first galaxies and chemical elements were forming, Green said.

The COS team will use distant quasars as "lighthouses" to track light as it passes through the cosmic web, believed to be made up of long, narrow filaments of galaxies and intergalactic gas separated by enormous voids. Astrophysicists have theorized that a single cosmic web filament may stretch for hundreds of millions of light-years, an eye-popping length considering a single light-year is about 5.9 trillion miles.

"The gases in between the galaxies contain the fossil record of the first stars and galaxies," said CU-Boulder Professor Michael Shull, a co-investigator for COS and a professor in CU-Boulder's astrophysical and planetary sciences department along with Green.

"Light passing through this material in the cosmic web illuminates fingerprints of elements like carbon, oxygen, silicon and iron, the building blocks of life that were made billions of years ago inside young, hot stars."

COS was built primarily by CU-Boulder's industrial partner, Ball Aerospace and Technology Corp. of Boulder. Other participating co-investigators on COS are from Ball Aerospace, the Southwest Research Institute in Boulder, the University of Wisconsin-Madison, the University of California, Berkeley, NASA's Goddard Space Flight Center in Greenbelt, Md., and the Space Telescope Science Institute in Baltimore, Green said.

"I think of the cosmic web as the backbone of the universe," said Shull. "To really understand it, we need to look at hundreds of different targets, which will allow us to take a CAT scan of the universe. And with the Cosmic Origins Spectrograph, we can make observations 10 times faster than before."

COS also will be used to detect young hot stars shrouded in the thick dust clouds they formed in, providing new information on star birth, said CASA Senior Research Associate Cynthia Froning, deputy principal investigator for COS. Scientists also will point COS at gas surrounding the outer planets of the solar system to glean new clues about planetary evolution, Froning said.

Green and his COS science team, which is made up of 14 CU-Boulder scientists and engineers and 10 scientists from other institutions, have been allotted 552 orbits of observing time on Hubble. CU-Boulder's CASA is in the process of hiring several dozen postdoctoral researchers, graduate students and undergraduates to work on the project in the coming years, Green said.