University Helps NASA Study Cosmic Explosions

Article ID: 541210

Released: 29-May-2008 8:50 AM EDT

Source Newsroom: University of Alabama Huntsville

  • Dr. William Paciesas of The University of Alabama in Huntsville

  • The rapidly fading source of a 1999 gamma ray burst from a galaxy more than 100 million light years from Earth.

Newswise — The most powerful explosions in the cosmos still hide a few secrets, despite decades of intensive study.

Scientists at UAHuntsville helped design (and will lead the ground team keeping track of) NASA's new GLAST Burst Monitor, an instrument scheduled to be rocketed into orbit next month to help astrophysicists learn more about the star crushing (or merging?) explosions that create gamma ray bursts.

"The UAH contingent is responsible for most of the software, as well as much of the calibration testing and system integration," said Dr. Bill Paciesas, a UAHuntsville physics research professor and the GRM ground system manager. "We will support the GBM Instrument Operations Center here in Cramer Hall, where we will do all the planning for operating the instrument. We will do the first stage data analysis, determining some of the parameters and putting the data in a form that can be studied by other scientists."

UAHuntsville teamed with NASA's Marshall Space Flight Center and the Max Planck Institute for Extraterrestrial Physics in Germany in proposing and developing the burst monitor, which is a secondary instrument on board NASA's Gamma-ray Large Area Space Telescope (GLAST).

Gamma ray bursts are flashes of the most powerful energy in the electromagnetic spectrum -- stronger than X-rays and at least 1,000 times as powerful as visible light.

Paciesas and the UAH team are veterans of the group that developed and operated the Burst and Transient Source Experiment (BATSE) that flew aboard the Compton Gamma Ray Observatory. When CGRO was launched little was known about gamma ray bursts, except that they were apparently caused by the most powerful explosions in the universe.

One of the unanswered questions for BATSE was whether the sources of these blasts of energy were "local" or out of the fringes of the universe. Surely, some suggested, waves of energy could not travel billions of light years and still be that ... energetic.

Well, yeah, they can.

"BATSE proved that (gamma ray burst sources) are some of the most distant objects we can see in the universe," Paciesas said. When other telescopes look at the sky where the bursts come from they see evidence of rapidly-dimming explosions or stars often billions of light years from Earth, meaning the events the orbiting detectors record happened billions of years ago when the universe was much younger.

While the BATSE data solved some mysteries, it found others. One of the most puzzling is the apparent two-faced nature of bursts. Some are short, more often about one second in duration, and less powerful, while others seem to cluster around the ten second length and are much more powerful.

"It has long been speculated that there is some fundamental difference between these two types burst," said Paciesas, who is also associate director of UAHuntsville's Center for Space Plasma and Aeronomic Research (CSPAR).

The study of gamma ray bursts is rife with superlatives: The most powerful. The highest energy. New theories about the longer and stronger bursts push the hyperbole to new heights. Not content with mere supernovae exploding stars, astrophysicists theorize, says Paciesas, that the longer, more powerful bursts might come from "hypernovae, the collapse of super massive stars."

At the same time, the shorter and less powerful bursts might come from something as relatively mundane and routine as the collision -- or merger -- of two neutron stars or a neutron star and a black hole.

One of the problems with these theories is that gamma rays, because they have such small wavelengths, are easily blocked. Earth's atmosphere stops most incoming gamma rays from reaching the ground, which is why gamma ray detectors have to be above the atmosphere. If gamma rays are so easily blocked, how do bursts of them escape from events as inherently messy as star collisions?

While the X-ray, ultraviolet and optical after glows of these events can often be tracked for weeks as they fade away, "there are many things we don't understand about the mechanism that produces these early gamma rays," Paciesas said.

A new theory says the gamma rays escape from a column of energy at a collapsing megastar's axes, similar to the energy jets seen on quasars. If that model turns out to be accurate, it would mean there are many, many more gamma ray bursts in the universe than we are counting, said Paciesas, "because we only detect the jets that are pointing in our direction."

The other members of UAH's GBM team are Dr. Robert Preece, an assistant research professor in physics, Dr. Valerie Connaughton, a CSPAR research scientist, Dr. Michael Briggs, a research scientist in physics, and Dr. Narayana Bhat, a CSPAR senior research associate.

GLAST is scheduled for launch no earlier than June 3 atop a Delta II Heavy launch vehicle built in Decatur, Ala.


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