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Swift Sees the Light


If we were able to see Gamma-Ray Bursts (GRBs) with the naked eye, they would look as though the universe were taking daily flash photos of us from different parts of the sky.

Never occurring in the same spot twice, GRBs are totally unpredictable. We never know where or when the next one will happen, and they fade so quickly that trying to get follow-up observations is extremely difficult. It wasn't until 1999 that a telescope, operating robotically, caught a GRB in action. Even then, the few seconds it took to find the burst meant precious data were lost.

Chart showing occurrence of grbs taken by BATSE The first notice about GRBs comes from space-based gamma-ray observatories, above the Earth's atmosphere which absorbs gamma rays. Unfortunately, even in 1999, the alerts from these observatories weren't fast enough for astronomers to pinpoint their telescopes while the rapidly-fading afterglows were still visible.

Image Right: This map shows the locations of a total of 2704 gamma-ray bursts recorded with the Burst and Transient Source Experiment on board NASA's Compton Gamma-Ray Observatory during its nine-year mission. Image credit: NASA

Large space-based observatories like Hubble can't be redirected quickly enough to catch the fleeting bursts. But a global network of astronomers, both professional and amateur could monitor these erratic, heavenly flash-bulbs with a moment's notice, if they only knew where to find them.

After many years of GRB observations, scientists at NASA's Goddard Space Flight Center established a program called the Gamma-ray burst Coordinates Network (GCN), designed to notify observers of the GRB coordinates within seconds after they're received.

In October 2000, NASA launched a burst observatory entirely devoted to the study of GRBs, called the High Energy Transient Explorer-2 (HETE-2 for short). It was able to relay the accurate location of each burst within minutes and transmit that information through the Internet.

In coordination with several other GRB-observing spacecraft, HETE-2 has improved the ability of astronomers to spot and study these brief, brilliant, and mysterious flashes of light.

Schematic drawing of gamma-ray burst detection satellites transmitting data through the GCN NASA is now preparing for the launch of a next-generation spacecraft to observe gamma-ray bursts, due to launch in October from Cape Canaveral Air Force Station, Florida. This new satellite is called Swift, named for a small, nimble bird that quickly darts from one direction to another.

Image Left: GCN is a system that distributes locations of GRBs detected by spacecraft (some in real-time while the burst is still bursting and distributes reports follow-up observations made by ground-based optical and radio observers. These two functions provide a one-stop shopping network for follow-up sites and GRB researchers. Click on image for larger view. Image credit: NASA

Using the largest of its three onboard telescopes, Swift will patrol about 1/6th of the sky at a time, vigilantly watching for the next GRB to appear. When it catches one, the satellite "swiftly" turns to the point of origin of the burst to get a better look with its two smaller, focusing telescopes. It also relays a message within seconds to the GCN, providing the location of the burst.

Professional telescopes can then be commanded to turn in the direction of the event and amateur astronomers may be able to experience this incredible event from their own backyards.

Swift will work in conjunction with other NASA and internationally-built burst-observing spacecraft, allowing pro and rookie astronomers alike a glimpse into the mysterious and powerful phenomenon of gamma-ray bursts.

For further information, visit:
Goddard Space Flight Center's Swift site.

Elaine M. Marconi
NASA's John F. Kennedy Space Center and Goddard Space Flight Center

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Last Updated: May 26, 2010
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