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NMSU astronomers who use Hubble Space Telescope hope for its rescue

New Mexico State University astronomer Tom Harrison is working on a project that will make the measurement of distances to astronomical objects more precise than ever before.


Vogt looks far back in time to study the formation and evolution of galaxies. She and her collaborators have shown that galaxies were forming at least 10 billion years ago - much earlier than was thought just a decade ago.

Chris Churchill is focused on the gases in and around galaxies, and the chemical evolution that occurs in these gas clouds over time. It's a field of astronomy that "has revolutionized our understanding of the large-scale structure of the universe," he said.

In all three cases, the research depends on data from the Hubble Space Telescope, an orbiting observatory that has allowed scientists to look deeper into space than ever before. Like many astronomers, the NMSU researchers are concerned about the loss of this unique tool if NASA sticks by its decision to pull the plug on the 14-year-old observatory.

Harrison's latest efforts are part of a research project that was rated as the highest priority out of 1,100 proposals in the latest cycle of competition for the HST's time. A team led by Fritz Benedict of the University of Texas at Austin will measure the distance to 10 pulsating stars known as Cepheid variables with unprecedented precision.

The result, said Harrison, will affect the measurement of distances to virtually all astronomical objects, as well as calculations of the expansion of the universe. That's because astronomers often use Cepheids as benchmarks for determining the distance to other objects, so the more precisely they can pin down the relationship between the Cepheids' pulsating luminosity and their distance, the more accurate the benchmark will be.

"All the calculations depend on how well we know this, and we are going to calibrate it to a precision no one has done before," he said.

Without Hubble's high resolution, this project would not have been possible. Similarly, the space telescope's resolving power makes it possible for Vogt to study both the luminosity and the mass and structure of galaxies at different stages in their evolution.

As astronomers look farther into space, they are essentially looking back in time. But at greater distances, only the brightest galaxies are visible to ground-based telescopes. A galaxy's luminosity changes and can be deceiving, while its mass remains relatively constant, Vogt noted. Hubble's ability to see deeper into space has provided data on the structure and mass of galaxies as they were billions of years ago.

If Hubble ceased to be available, "we'd be in big trouble," Vogt said. "We would do as best we could with ground-based telescopes but it wouldn't be as good."

Hubble's ability to capture ultraviolet light makes Churchill's work possible. He studies how clouds of gases affect the formation and evolution of galaxies. Using quasars, some of the brightest objects in the universe, as "beacons," Churchill can capture a wealth of information about these gases with Hubble's spectroscope, which breaks light down into a spectrum.

"Every time the light from a quasar intersects with the gas cloud of a galaxy, a very sensitive and clear-cut fingerprint is created," he said. "Every chemical element that is present absorbs light in a unique way. We have a unique technique to go way, way back in time to measure chemical evolution."

The challenge is that "all these chemical fingerprints hang out in the ultraviolet" portion of the light spectrum, he said, and ultraviolet light is absorbed by the Earth's atmosphere before it reaches ground-based telescopes.

"Hubble is an unbelievably unique resource," Churchill said. "The next generation of telescope (the James Webb Space Telescope scheduled for launch in 2011) is not a better version of HST -- that telescope is optimized for different kinds of science."

Churchill is not ready to mourn the demise of Hubble, however.

"My gut feeling is Hubble will get resuscitated," he said. "It will get another servicing mission. The pressure from the scientific community is going to be so great, (NASA administrator) Sean O'Keefe is going to come around."

O'Keefe, concerned about safety after the Columbia disaster, has cancelled a 2006 space shuttle mission to service the Hubble and install new instruments. Two key senators - Sen. Barbara Mikulski, D-Md., and Sen. Sam Brownback, R-Kans. - have introduced a Senate resolution, S. Res. 324, calling on NASA to continue preparations for the shuttle mission while an independent panel of scientists and engineers examines options.