Fw: Re: Space Explosion to Blame for Tree Ring Mystery, Astronomers Say - 775 Tree Ring C-14 Spike

This is a post of mine on another group.

--- On Thu, 24/1/13, John W <[email protected]> wrote:
From: John W <[email protected]>
Subject: Re: [ArtBellTalk] Space Explosion to Blame for Tree Ring Mystery, Astronomers Say | 775 Tree Ring Spike | Space.com
To: [email protected]
Date: Thursday, 24, January, 2013, 10:26 AM

Gamma-ray bursts, which would probably mostly emanate at very long intervals from the vicinity of the Galactic Center, located close to the ecliptic (latitude 7º South) and at a longitude (tropical) of about 27º Sagittarius, would probably mostly result from stars the orbits of which around the Galactic Center bring them too close to the immense black hole (which has a mass of the order of billions of solar masses) located there. The tidal force (due to a steep gradient in gravitational field force) in the vicinity of the black hole tears the stars apart, with some of their matter falling into the black hole, and the rest remaining in orbit about it. 

Another, mostly closer, possible source of gamma ray bursts would be mergers of stars in a binary system with unseen non-luminous companion black holes or neutron stars, which however would have a mass of
 only a few to several tens of solar masses, especially where both stars are black holes or neutron stars. Such mergers occur as the result of the orbits around each other of a close pair of very massive binary stars steadily decaying over many millions of years, as the result of slow loss of kinetic energy though the emission of gravitational radiation (which is emitted by massive bodies that undergo relativistic acceleration).

Because of the multiplicity of other galaxies, all gamma-ray bursts that have so far been observed since their discovery a few decades ago occurred in other galaxies, typically billions of light-years away. They are very rare, on average a few per galaxy per million years, and last only a few minutes..

The effects of such cosmic events on the growth of trees and production of C-14 in carbon dioxide in the atmosphere could only occur if there were a most unusual and unprecedented spate of many such gamma ray bursts
 in this galaxy, in view of the distance, rarity, and the short duration of the bursts. A MUCH more likely explanation of the C-14 spike found in tree rings dating from about the year 775 would, instead, be a major Type II (core-collapse) supernova explosion relatively near Earth, resulting in much more intense and long-lasting radiation (several weeks to months) reaching Earth. Supernovae are MUCH more common than gamma-ray bursts, as well as lasting much longer. A Type II supernova results from the rapid collapse and violent explosion of a massive star, throwing off its outer layers to leave a white dwarf star, when its core is exhausted of fusionable elements, of which the heaviest are iron, cobalt, and nickel. It must have at least 8 times (the Chandrasekhar Limit), and no more than 40–50 times, the mass of the Sun, for it to occur. A star with between about 20 and 40 solar masses will firstly go supernova  and then its core will collapse into
 a black hole, while a star more massive than 40 solar masses (very rare) will collapse directly into a black hole.

The main effect (besides a spike in creation of C-14) of a close gamma-ray burst, or more likely supernova, would be to heavily deplete the ozone layer. This would let in much more short ultra-violet light, with its damaging biological effects. It would also result in global cooling, and in the formation of a large amount  of nitrogen oxides, causing acid rain after they form nitric acid.

It is thought that only a Type II supernova within 50 light-years of Earth could significantly affect life on Earth. Recent estimates predict that a Type II supernova would have to be closer than 26 light-years to destroy half of the Earth's ozone layer. 

The white-dwarf companion, Sirius B, of Sirius, 8½ light-years away, must have gotten that way as the result of such a supernova, about 120 million years ago during the
 Cretaceous period, at which time there apparently were no mass extinctions of dinosaurs or plants. It is the white-dwarf star nearest to Earth. Sirius itself, the brightest star in the night sky and the nearest really massive star, with 2.02 times the mass of the Sun, and only about 300 million years old (compared to the 4.5 billion years of the Sun), is much too small to go supernova, but it will evolve off the "main sequence" to become an even brighter red/orange giant in about 900 million years when its core is exhausted.

However, the second-brightest star in the night sky, Canopus, has a mass estimated at between 9 and 10.6 solar masses (more than 8), being the most intrinsically-bright star within 700 light-years. Having already substantially evolved off the "main sequence" to a yellow-white giant, it will go supernova in only a few million years time. Being 310 light-years away, it is too distant for this to affect Earth, but the sight of
 its going supernova would be highly spectacular. A star of about that mass has a main-sequence life of only about 23 million years.

See: 

http://en.wikipedia.org/wiki/Gamma-ray_burst

http://en.wikipedia.org/wiki/Fermi_Gamma-ray_Burst_Monitor

http://www.wheretosurvive2012.com/gamma-ray-burst-2012/

http://gizmodo.com/gamma_ray-burst/

http://imagine.gsfc.nasa.gov/docs/science/know_l1/bursts.html

http://www.history.com/shows/armageddon/videos/gamma-ray-burst

http://earthsky.org/science-wire/did-an-8th-century-gamma-ray-burst-irradiate-the-earth

http://www.astro.psu.edu/users/nnp/grbphys.html

http://www.pbs.org/wgbh/nova/gamma/milkyway.html

http://au.news.yahoo.com/thewest/a/-/business/15893306/gamma-ray-burst-blasted-earth-in-8th-century-study/

http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction..html

In support of my opposing view in favor of a supernova explanation:

http://en.wikipedia.org/wiki/Supernova

http://en.wikipedia.org/wiki/Type_II_supernova

http://www.britannica.com/EBchecked/topic/611660/Type-II-supernova

http://cse.ssl.berkeley.edu/bmendez/ay10/2000/cycle/snII.html

http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html

http://www.space.com/6638-supernova.html

http://www.tutorgigpedia.com/ed/Type_II_supernova

http://en.wikipedia.org/wiki/Sirius_(star)

http://en.wikipedia.org/?title=Canopus

Also S Chandrasekhar's books on astrophysics, which are downloadable online somewhere, especially  "Stellar Interiors".

John W.


--- On Wed, 23/1/13, [email protected] <[email protected]> wrote:
From: [email protected] <[email protected]>
Subject: [ArtBellTalk] Space Explosion to Blame for Tree Ring Mystery, Astronomers Say | 775 Tree Ring Spike | Space.com
To: [email protected]
Date: Wednesday, 23, January, 2013, 4:02 AM
















 



  


    
      
      
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