Fhirinne
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User ID: 1063055 United Kingdom 06/03/2012 05:28 PM Report Abusive Post Report Copyright Violation | Was Sirius B responsible for mass extinctions on Earth? The Age and Progenitor Mass of Sirius B
The Sirius AB binary system has masses that are well determined from many decades of astrometric measurements. Because of the well-measured radius and luminosity of Sirius A, we employed the TYCHO stellar evolution code to determine the age of the Sirius A,B binary system accurately, at 225-250 Myr. Note that this fit requires the assumption of solar abundance, and the use of the new Asplund et al. primordial solar metallicity. No fit to Sirius A's position is possible using the old Grevesse & Sauval scale. Because the Sirius B white dwarf parameters have also been determined accurately from space observations, the cooling age could be determined from recent calculations by Fontaine et al. or Wood to be 124 +/- 10 Myr. The difference of the two ages yields the nuclear lifetime and mass of the original primary star, 5.056 +0.374/-0.276 solar masses. This result yields in principle the most accurate data point at relatively high masses for the initial-final mass relation. However, the analysis relies on the assumption that the primordial abundance of the Sirius stars was solar, based on membership in the Sirius supercluster. A recent study suggests that its membership in the group is by no means certain. [ link to arxiv.org] "With a mass nearly equal to the Sun's, Sirius B is one of the more massive white dwarfs known (0.98 solar masses[81]); it is almost double the 0.5–0.6 solar-mass average." Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago [ link to en.wikipedia.org] At the time Sirius B was at red giant stage the Permian–Triassic (P–Tr) extinction event (The Great Dying) took place [ link to en.wikipedia.org] The Permian-Triassic (P-T) event, 250 My ago Before the T-J event came ‘the great dying’, the worst mass extinction since Cambrian explosion. It was the one that separated the Permian from the Triassic period. Ninety five percent and sixty six of land animal species went extinct. By contrast the plant kingdom suffered much less. [ link to www.bevpease.force9.co.uk] The P-T extinction was another long drawn-out event. It lasted 160,000 years. [ link to www.sciencedaily.com] The Early Aptian (120 million years ago) was an age of intense volcanic activity on Earth. I've had a little to drink but this makes some sense to me. You are the CEO of your own wellness. You need to take back your health from the disease-care system |
Anonymous Coward User ID: 17300783 Romania 06/03/2012 05:44 PM Report Abusive Post Report Copyright Violation | Re: Was Sirius B responsible for mass extinctions on Earth? The Sirius system is 8.6 light years away ! I'm no astronomer but I don't think that Sirius B going nova could affect us from that distance !
If Antares was at that distance and it would go nova...that would be a different story ! |
Fhirinne
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User ID: 1063055 United Kingdom 06/03/2012 06:00 PM Report Abusive Post Report Copyright Violation | Re: Was Sirius B responsible for mass extinctions on Earth? The Sirius system is 8.6 light years away ! I'm no astronomer but I don't think that Sirius B going nova could affect us from that distance !
If Antares was at that distance and it would go nova...that would be a different story !
Quoting: subzero86 They say the minimum safe distance from a supernova is and this changes somewhat but 50 to 100 light years away from us. Like you say Sirius is currently 8.6 ly away. You are the CEO of your own wellness. You need to take back your health from the disease-care system |
SnowballSolarSystem
User ID: 21357207 United States 11/25/2012 09:32 PM Report Abusive Post Report Copyright Violation | Re: Was Sirius B responsible for mass extinctions on Earth?
Fhirinne, I think you're on to something here, and of course the more significant event is the P-Tr extinction, 251 Ma, possibly the result of a stellar-merger luminous red nova (LRN), predating the more recent white-dwarf nova (but of course any hypothesized terrestrial connection assumes that Sirius formed in our stellar neighborhood). I suspect we're looking at a degenerate, quadruple star system with two close-binary stellar mergers, forming the present-day wide-binary pair of Sirius A and Sirius B. And secular core-collapse perturbation of the close-binary pairs created the 7.5 AU wide-binary separation. Was the connection your idea or did you glean it from elsewhere? "Orthodoxy means not thinking"—Eric Blair |