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NASA's Swift Observatory  (Source: NASA)
Gamma burst reported as most powerful on record.

NASA scientists have identified a violent cosmic eruption that temporarily blinded a NASA satellite in June.  An X-ray telescope that tracks gamma rays on board the NASA Swift satellite captured a record-breaking burst of rays that had left scientists mystified about its massive brightness and point of origin.  

At it's peak the gamma-ray explosion – documented as the most powerful emission on record -- produced between 143,000 and 145,000 X-ray protons per second, which is about 10 to 15 times brighter than previous bursts captured by the telescope.   

After weeks of analysis, researchers are now indicating that the astounding blast was produced by a massive star collapsing into a black hole.  

According to 
Astronomy.com and Space.com, although the Swift satellite was designed specifically to study gamma-ray bursts, the instrument was not designed to handle an X-ray blast this bright.

"The intensity of these X-rays was unexpected and unprecedented," said Neil Gehrels from NASA's Goddard Space Flight Center in Greenbelt, Maryland. He said the burst, named GRB 100621A, is the brightest X-ray source that Swift has detected since the observatory began X-ray observation in early 2005. "Just when we were beginning to think that we had seen everything that gamma-ray bursts could throw at us, this burst came along to challenge our assumptions about how powerful their X-ray emissions can be.”

The event was so powerful, it disrupted the telescope's data-analysis capabilities.

"The burst was so bright when it first erupted that our data-analysis software shut down," said Phil Evans from the University of Leicester in the United Kingdom. "So many photons were bombarding the detector each second that it just couldn't count them quickly enough. It was like trying to use a rain gauge and a bucket to measure the flow rate of a tsunami."

The X-rays had been traveling for over 5 billion years before being detected by the Swift satellite.

The burst lasted for about one minute and was about 200 times brighter than the Crab Nebula, an X-ray radiation benchmark for astronomers. 

The X-ray blast is the brightest ever detected from outside of the Milky Way galaxy. 



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Huh?
By docawolff on 7/19/2010 9:09:30 AM , Rating: -1
They have the Crab Nebula as a known benchmark and they designed a detector that couldn't handle a source that was only 200x brighter? I guess I don't know a lot about how these detectors are designed. I would have thought that when the designers sat down to spec out the detector they would have looked at the Crab Nebula source and said "How much brighter a source should we design for? A thousand? Ten thousand?"

Perhaps they were more interested in designing for much less bright sources?

Interesting what the limits of technology are/were.




RE: Huh?
By DanNeely on 7/19/2010 9:21:12 AM , Rating: 5
You're designing a scale to weigh people. You know Michael Jordan weighs 216lbs which you decide to use as a benchmark; and that the heaviest known people weight about half a ton. How many tons do you design your scale to read.

Remember that the higher your maximum goes the less accurately you can measure differences between small values...


RE: Huh?
By docawolff on 7/19/2010 11:14:20 AM , Rating: 2
There is a difference between designing an instrument to measure a population that is well-understood, i.e.: a scale to measure the weight of humans, and designing an instrument to observe previously unknown or poorly understood events.

However, as you point out, the higher the maximum, the less accuracy and the larger the minimum event required for detection. As I said, I didn't really understand the trade-offs on designing this instrument.


RE: Huh?
By DanNeely on 7/19/2010 11:59:38 AM , Rating: 2
that's true. In this case the impact of guessing low for where to place the maximum sensitivity is relatively low. The firmware can be updated to change the level of signal it interprets as a hardware failure, and as was done with smaller events that partially saturated the detector the total signal strength can be estimated from the size of the area just outside the saturation zone because the falloff in strength of a point source follows a well known pattern. (Google Airy Disk for more details.)


RE: Huh?
By Veerappan on 7/19/2010 3:01:42 PM , Rating: 2
When designing a telescope, you usually have a specific type of target group in mind. With X-Rays, you can point at something like the Sun, which will give you a LOT of photons in a short period of time, or you can design a telescope to point at far-away objects which will bring in many fewer photons in a given period of time.

Often, the sensitivity level of the CCD which is taking the images is hand-tailored for the luminosity of the target. If you point at an object which is much brighter (in X-Rays) than what your instrument is designed for, you can damage your instruments.

Example:
Pointing an X-Ray telescope like Chandra/Fermi at the Sun would destroy the CCDs within seconds, but at the same time, we've got other telescopes that are designed to spend their entire lives staring at the sun.

In the case of the Crab Nebula, it is one of the most well-studied X-Ray objects, and so therefore it is used as a benchmark for testing X-Ray telescopes. Generally, you can design your instrument to either look at really bright things, really dim things, or somewhere in the middle, but you can't design one instrument that will work well for all classes of objects.


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