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Fraser
2005-Apr-07, 06:15 PM
SUMMARY: Gamma ray busts are the most powerful known explosions in the Universe, so if one went off in our galactic back yard, it could be bad for life on Earth. Researchers working with NASA think that a massive extinction hundreds of millions of years ago could have been started by such an explosion. If a GRB went off only 6,000 light-years away, it would strip away much of the Earth's ozone layer, and expose all surface life to deadly levels of ultraviolet radiation from the Sun.

View full article (http://www.universetoday.com/am/publish/grb_extinctions.html)

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greenone
2005-Apr-07, 07:06 PM
i would think they'd be looking for the culprit star, there must still be a reminant from the explosion. maybe there are just too many stars within 6,000 light years.

Don Alexander
2005-Apr-08, 10:35 AM
i would think they'd be looking for the culprit star, there must still be a reminant from the explosion. maybe there are just too many stars within 6,000 light years.


It's long gone.

Supernova remnants last only a few million years, then dissipate into the interstellar medium.

Furthermore, in 450 million years, the complete Galaxy has revolved about twice, and the stars surrounding the sun have completely changed.

But such a blast could leave traces in ices, an extreme future prospect is ice cores from comets or the frozen outer moons.

David Alexander Kann
Thueringer Landessternwarte Tautenburg, Germany

Guest
2005-Apr-08, 11:43 AM
I thought we knew this. wasn't this one of the possible explanations for the dinos long goodbye

Greg
2005-Apr-08, 01:26 PM
This gives us yet another reasaon to get humanity and life off this planet and on some others. After a few hundred million years due to the different speed of rotation of stars around the galaxy we will be sufficiently dispersed such that one burst would not kill all of our civilizations at once.
If this theory is correct then you would think that there should be evidence in the geologic record to confirm it. However, since the event would only last 10 years, that might not be so easy to find.

SCHNECK
2005-Apr-11, 11:42 AM
The Ordovician extinction is usually related to a glaciation after a drop of CO2 from a value 17 times to present (Berner&Crowley)

The Precambrian Cambrian boundary sharp negative excursion in carbon isotopes has a duration less than 1 Ma.The carbonates clastic and evaporites of Infracambrian 542 Ma deposited within the rift salt basins of the Huqf group of Oman record an unusual enrichment of Uranium. Th/U has show a positive correlation with d13C variation across the Precambrian Cambrian boundary(1).Patterns of distribution of redox sensitive trace metals in contact with the oxygen minimum zone are significantly higher in interglacial stage sediments compared to glacial stage(2).The study of the Uranium interactions with pure Fe-mineral phase have focused on the Uranium pH dependent absorption(3).The 57Fe mossbauer spectroscopy of a metamict gadolinite sample from Ytterby(Sweden) reveal only Fe2+ ions located definitely in octahedral coordinations,similar to the crystalline structure of gadolinite(4).Pu-244 was found in Precambrian age phosphate.

Each 240 Ma years and at the Kretaceous Tertiary event,the sun appeared to be in the Sagittarius Carina spiral arm(5).Actually,Kr/H abundance ratios within the orion spur are remarkably uniform(6)Oxygen is predominently produced in massive star evolution ,which also contributes the majority krypton nucleosynthesis.Models producing the light element depletion trends observed, can reproduced observed Li and Be abundances in the Hyades:at 70 Myr, the Lithium depletion edge should occur at 0.09M Sun(7).Light fluctuations beginning after the onset of intense Helium flares on the Hyades were reported(8).Parahydrogen induced polarization to Iridium reveal both 31P and natural abundance 13CO ligation in very short time
During the Cretaceous tertiary solar moderate conditions(9)Helium 3 could concentrate in the topside ionosphere .Hydroxyl Radical trails appears to be general features in the luminosities lifetimes and define the oxidative capacity of the atmosphere.
In some experiment,amorphous nonhydrogenated carbon possess photoluminescent properties analogous to those of hydrogenated amorphous carbon films with a high hydrogen content(10).

Ref:(1) Hiroto Kimura,Yoshio Watanabe Oceanic Anoxia at the Precambrian Cambrian boundary.
(2)T.J.Nameroff,S.E.Calvert,J.W.Murray Glacial Interglacial variability in the Eastern tropical North Pacific oxygen minimum zone recorded by redox sensitive trace metals.
(3)M.O.Barnett,P.M.Jardine,S.C.Brooks and H.M.Selim Absorption and Transport of Uranium
(4)Malczewski D. Structural analysis of radiation damage in Precambrian gadolinite.
(5)Shin Yabu****a The Sun encounter with the Spiral arms as the causes of Cretaceous-Tertiary and Permian Triassic boundary events.
(6)S.I.B.Cartledge The element Abundance Homegeneity of the interstellar Medium
R.Rebolo Beryllium,Lithium and Oxygen abundances in F-type stars
(7)V.V. Zaitsev:LRC-circuit analog of current-carrying magnetic loop:diagnostic of electric parameters.
(8)Luminescent Iridium Diethyldithiocarbamate Complexes:Synthesis,Structure,and Reactivity Including Stereoselective Hydrogen Oxidative Addition J.Am Ceem Soc 1997,119,7716-7725
(9)M.P.Sulzer Detection of He+layering in the topside ionosphere over Arecibo During Equinox Solar Minimum Conditions
(10)A.V.Vasin,L.A.Matveeva,and V.A.Yuhimchuk The photoluminescence of Amorphous carbon in a C:C60 Films obtained by Fullerenes C60 Deposition