Rates and Potential Effects On Life On Earth
All the bursts astronomers have recorded so far have come from distant galaxies and have been harmless to Earth, but if one occurred within our galaxy and were aimed straight at us, the effects could be devastating. Currently orbiting satellites detect an average of about one gamma-ray burst per day. The closest known GRB so far was GRB 031203.
Measuring the exact rate is difficult, but for a galaxy of approximately the same size as the Milky Way, the expected rate (for long GRBs) is about one burst every 100,000 to 1,000,000 years . Only a small percentage of these would be beamed towards Earth. Estimates of rates of short GRBs are even more uncertain because of the unknown degree of collimation, but are probably comparable.
Gamma-ray bursts are thought to emerge mainly from the poles of a collapsing star. This creates two oppositely-shining beams of radiation shaped like narrow cones. Planets not lying in these cones would be comparatively safe; the chief worry is for those that do.
Depending on distance, a gamma flash and its ultraviolet radiation could damage even the most radiation resistant organism known, the bacterium Deinococcus radiodurans. These bacteria can endure 2,000 times more radiation than humans. Life surviving an initial onslaught would have to contend with a potentially lethal aftereffect, depletion of the atmosphere's protective ozone layer by the burst.
Read more about this topic: Gamma-ray Burst
Famous quotes containing the words rates, potential, effects, life and/or earth:
“[The] elderly and timid single gentleman in Paris ... never drove down the Champs Elysees without expecting an accident, and commonly witnessing one; or found himself in the neighborhood of an official without calculating the chances of a bomb. So long as the rates of progress held good, these bombs would double in force and number every ten years.”
—Henry Brooks Adams (1838–1918)
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—Elizabeth Debold (20th century)
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—Henry David Thoreau (1817–1862)
“It is not growing like a tree
In bulk, doth make man better be,
Or standing long an oak, three hundred year,
To fall a log at last, dry, bald, and sere:
A lily of a day
Is fairer far in May
Although it fall and die that night;
It was the plant and flower of light.
In small proportions we just beauties see,
And in short measures life may perfect be.”
—Ben Jonson (1572–1637)
““Our earth is degenerate in these latter days. Bribery and corruption are common. Children no longer obey their parents. . . . The end of the world is evidently approaching.” Sound familiar? It is, in fact, the lament of a scribe in one of the earliest inscriptions to be unearthed in Mesopotamia, where Western civilization was born.”
—C. John Sommerville (20th century)