Note: this topic is from 1/09/2002.
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Posted on 01/09/2002 7:14:03 AM PST by blam
Supernova "smoking gun" linked to mass extinctions
15:07 09 January 02
Eugenie Samuel, Washington DC
Evidence of an astronomical "smoking gun" has been discovered that supports the idea that cosmic rays from a nearby supernova triggered at least one of the six mass extinctions on Earth. Luckily for us, the astronomers say, there is very little danger of it happening again anytime soon.
Narcisco Benítez at John Hopkins University in Baltimore, Maryland and Jesús Maíz Appellániz of the Space Telescope Science Institute in Virginia traced the motion of a cluster of young, short lived stars formed from the debris of around 20 supernova which have exploded over the last 20 million years.
The cluster, called the Scorpius-Centaurus OB association, is now positioned a safe 350 light-years from Earth. But the group says it passed within 130 light-years of Earth about two million years ago.
This puts it in the right place at the right time to explain evidence uncovered on Earth by German researchers in 1999. They found atoms of a very rare isotope of iron, 60Fe, in cores taken from the ocean floor. 60Fe is rare in the solar system because it has a half-life of 1.5 million years. The German group suggested that the iron arrived on Earth as fallout from a nearby supernova about two million years ago. This is about the time that fossil records indicate that many marine molluscs went extinct.
Ozone hole
Donald Clayton, an astronomer at Clemson University, says the story appears consistent: "The amount of 60Fe found in deposits is about what you might expect from a supernova going off about 100 light-years away." Clayton says 60Fe would be blasted towards Earth when high energy neutrons from the supernova core smack into iron atoms in its outer shell.
Benítez argues that high energy cosmic rays caused by particles from a supernova 100 to 130 light-years from Earth would generate enough ions in the Earth's atmosphere to oxidise the ozone layer that usually protects life on Earth from damaging ultraviolet B radiation.
He estimates the damage could last between 100 and 1000 years, long enough to wipe out susceptible species on Earth.
So far, astronomers have not found any evidence of stars about to go supernova in our immediate vicinity. The next star due to explode in the Scorpius-Centaurus OB association is a safe 500 light-years away.
The new research was presented at the American Astronomical Society meeting in Washington DC.
15:07 09 January 02
I guess its sorta like not riding on airplanes all your life, only to trip and fall down a flight of stairs to your death..
They did a pretty good job of cramming in the last 30 years of Cosmology into a 1 hour, understandable program.
Last night's show was a good one. The section on "A Bad Day in the Milky Way" is the relative section, I believe.
'Fireworks' greeted early star birth
Astronomers say there may have been a cosmic firework display when the first stars burst into being.
Information from the Hubble telescope suggests many of the universe's first stars appeared at around the same time.
Scientists say there was a 'torrential firestorm of star birth' a few hundred million years after the Big Bang.
They now hope the clues Hubble has given them about this early firework display will let them see it for themselves with the next generation of telescopes.
When astronomers use the most powerful telescopes, they are looking at events which happened millions of years ago because light from these objects takes so long to get here.
As part of a study published in the Astrophysical Journal, Kenneth Lanzetta, from the State University of New York at Stony Brook, makes the preliminary conclusion that the universe was lit up all at once.
Though stars are still being born, their birth rate may only be a trickle compared to the number in those early times.
Dr Anne Kinney, director of the astronomy and physics division at Nasa headquarters in Washington, says: "Because stars are the building blocks of galaxies and the birthplace of solar systems, proving that countless numbers of stars began forming so early after the birth of the universe could cause us to rethink a lot of our theories."
Story filed: 10:50 Wednesday 9th January 2002
Note: this topic is from 1/09/2002.
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Note: this topic is from 1/09/2002.
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