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:
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—Gloria Steinem (20th century)
“Most days I feel like an acrobat high above a crowd out of which my own parents, my in-laws, potential employers, phantoms of “other women who do it” and a thousand faceless eyes stare up.”
—Anonymous Mother. Ourselves and Our Children, by Boston Women’s Health Book Collective, ch. 2 (1978)
“If one judges love according to the greatest part of the effects it produces, it would appear to resemble rather hatred than kindness.”
—François, Duc De La Rochefoucauld (1613–1680)
“After I discovered the real life of mothers bore little resemblance to the plot outlined in most of the books and articles I’d read, I started relying on the expert advice of other mothers—especially those with sons a few years older than mine. This great body of knowledge is essentially an oral history, because anyone engaged in motherhood on a daily basis has no time to write an advice book about it.”
—Mary Kay Blakely (20th century)
“There were ghosts that returned to earth to hear his phrases,
As he sat there reading, aloud, the great blue tabulae.
They were those from the wilderness of stars that had expected more.
There were those that returned to hear him read from the poem of life,
Of the pans above the stove, the pots on the table, the tulips among them.
They were those that would have wept to step barefoot into reality....”
—Wallace Stevens (1879–1955)