What is behind GRB 971214?
May 14, 1998
to this forum's introduction.
in this forum:
May 7, 1998
Dr. David Helfand of Columbia University discusses GRB 971214
February 27, 1998
The rapidly-expanding universe.
December 31, 1997
The Hubble Space Telescope dazzling imagery.
February 11, 1997:
The success of the Hubble Space Telescope.
Browse the NewsHour's coverage of science.
NASA's page on GRB 971214.
The CalTech page on GRB 971214.
NASA's Hubble Space Telescope
Dan Olson of Tinley Park, IL, asks:
Is it possible a GRB could occur in our galaxy and, if so, what effects if any would it have on our planet?
Dr. David Helfand of Columbia University responds:
While we still don't have what I consider a convincing model for these events, it is hard to be certain if they occur in our galaxy. But most of the things we can think of (see my answer on other models) most certainly do occur in our Milky Way. In fact, to account for the total number of these gamma ray flashes that we see, we require one to happen in every galaxy in the universe once every 10 million years or so.
If the burst occurred clear across the galaxy, 50,000 light years away, its visible afterglow would still shine 100 times more brightly than Venus at its brightest, and would takes weeks to fade from view. The energy we receive in invisible gamma rays during the ten seconds of the burst would equal the total energy received from the Sun in the same interval. This would cause some destruction of atmospheric molecules, but at such a distance, would not likely cause permanent damage. However, as outlined in an entertaining article in the February issue of Sky and Telescope, a burst only a thousand light years away could devastate the Earth. The gamma rays would dissociate the nitrogen and oxygen molecules in much of the atmosphere, allowing them to recombine as various nitrogen oxides which would destroy the ozone layer and darken the sky for years. The blast of high energy cosmic rays that would arrive a few days later would kill almost all life on Earth and make the surface radioactive for thousands of years. The authors of the scientific journal article which prompted the Sky and Telescope story estimate that such a nearby burst might occur once every one hundred million years -- about the interval between mass extinctions we find in the fossil record (although I believe this estimated rate to be somewhat high).
To end this gloom and doom on a light note however, Steve Thorsett of Princeton has noted that one of the most common compounds formed from the dissociated nitrogen and oxygen molecules will be nitrous oxide (the chemical name for laughing gas) -- so at least we'd all die laughing!
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