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:
“One of the most important findings to come out of our research is that being where you want to be is good for you. We found a very strong correlation between preferring the role you are in and well-being. The homemaker who is at home because she likes that “job,” because it meets her own desires and needs, tends to feel good about her life. The woman at work who wants to be there also rates high in well-being.”
—Grace Baruch (20th century)
“A child is born with the potential ability to learn Chinese or Swahili, play a kazoo, climb a tree, make a strudel or a birdhouse, take pleasure in finding the coordinates of a star. Genetic inheritance determines a child’s abilities and weaknesses. But those who raise a child call forth from that matrix the traits and talents they consider important.”
—Emilie Buchwald (20th century)
“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)
“My life has crept so long on a broken wing
Through cells of madness, haunts of horror and fear,
That I come to be grateful at last for a little thing.”
—Alfred Tennyson (1809–1892)
“As a man-of-war that sails through the sea, so this earth that sails through the air. We mortals are all on board a fast-sailing, never-sinking world-frigate, of which God was the shipwright; and she is but one craft in a Milky-Way fleet, of which God is the Lord High Admiral.”
—Herman Melville (1819–1891)