by neufer » Fri Sep 25, 2015 8:30 pm
Ironsides wrote:
I have a question regarding the expanding shock wave from Supernovas such as what created the Veil Nebula. Assuming the shock wave expands in a spherical pattern, can anyone tell me how fast that shock wave is moving? And considering how massive these nebula appear, would such an expanding cloud pose a danger to any planetary systems in nearby star systems?
The Veil Nebula is traveling at less than 1% the speed of light and should reach the Earth no sooner than 150,000 years.
https://en.wikipedia.org/wiki/Veil_Nebula wrote:
<<The Veil Nebula is a [~100 light-year wide] cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop (radio source W78, or Sharpless 103), a large but relatively faint supernova remnant. The source [Type II] supernova exploded some 5,000 to 8,000 years ago, and the remnants have since expanded to cover an area roughly 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full moon). Far Ultraviolet Spectroscopic Explorer data supports a distance of about 1,470 light-years.>>
Ironsides wrote:
NASA is constantly reminding us there is no chance of any fair-sized asteroids impacting the Earth but what are the chances of any nearby stars exploding into a supernova? What would be the danger to our solar system?
https://en.wikipedia.org/wiki/Near-Earth_supernova wrote:
<<On average, a ["
dangerously close"] supernova explosion occurs within 10 parsecs of the Earth every 240 million years.
Gamma rays are responsible for most of the adverse effects a supernova can have on a living terrestrial planet. In Earth's case, gamma rays induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. Phytoplankton and reef communities would be particularly affected, which could severely deplete the base of the marine food chain. In 2009, researchers have found nitrates in ice cores from Antarctica at depths corresponding to the known supernovae of 1006 and 1054 CE, as well as from around 1060 CE. The nitrates were apparently formed from nitrogen oxides created by gamma rays from the supernovae. This technique should be able to detect supernovae going back several thousand years.
Speculation as to the effects of a nearby supernova on Earth often focuses on large stars as Type II supernova candidates. Several prominent stars within a few hundred light years from the Sun are candidates for becoming supernovae in as little as a millennium. In 1996, astronomers at the University of Illinois at Urbana-Champaign theorized that traces of past [Type II] supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata. Subsequently, iron-60 enrichment has been reported in deep-sea rock of the Pacific Ocean by researchers from the Technical University of Munich. 23 atoms of this iron isotope were found in the top 2 cm of crust, and these date from the last 13 million years or so. It is estimated that the supernova must have occurred in the last 5 million years or else it would have had to happen very close to the solar system to account for so much iron-60 still being here. A supernova occurring so close would have probably caused a mass extinction, which didn't happen in that time frame. The quantity of iron seems to indicate that the supernova was less than 30 parsecs away.
Adrian L. Melott et al. estimated that gamma ray bursts from "dangerously close" supernova explosions occur two or more times per billion years, and this has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth.>>
[quote="Ironsides"]
I have a question regarding the expanding shock wave from Supernovas such as what created the Veil Nebula. Assuming the shock wave expands in a spherical pattern, can anyone tell me how fast that shock wave is moving? And considering how massive these nebula appear, would such an expanding cloud pose a danger to any planetary systems in nearby star systems?[/quote]
The Veil Nebula is traveling at less than 1% the speed of light and should reach the Earth no sooner than 150,000 years.
[quote=" https://en.wikipedia.org/wiki/Veil_Nebula"]
<<The Veil Nebula is a [~100 light-year wide] cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop (radio source W78, or Sharpless 103), a large but relatively faint supernova remnant. The source [Type II] supernova exploded some 5,000 to 8,000 years ago, and the remnants have since expanded to cover an area roughly 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full moon). Far Ultraviolet Spectroscopic Explorer data supports a distance of about 1,470 light-years.>>[/quote][quote="Ironsides"]
NASA is constantly reminding us there is no chance of any fair-sized asteroids impacting the Earth but what are the chances of any nearby stars exploding into a supernova? What would be the danger to our solar system?[/quote][quote=" https://en.wikipedia.org/wiki/Near-Earth_supernova"]
<<On average, a ["[b][i][color=#FF0000]dangerously close[/color][/i][/b]"] supernova explosion occurs within 10 parsecs of the Earth every 240 million years. [b][color=#FF0000]Gamma rays are responsible for most of the adverse effects a supernova can have on a living terrestrial planet[/color][/b]. In Earth's case, gamma rays induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. Phytoplankton and reef communities would be particularly affected, which could severely deplete the base of the marine food chain. In 2009, researchers have found nitrates in ice cores from Antarctica at depths corresponding to the known supernovae of 1006 and 1054 CE, as well as from around 1060 CE. The nitrates were apparently formed from nitrogen oxides created by gamma rays from the supernovae. This technique should be able to detect supernovae going back several thousand years.
Speculation as to the effects of a nearby supernova on Earth often focuses on large stars as Type II supernova candidates. Several prominent stars within a few hundred light years from the Sun are candidates for becoming supernovae in as little as a millennium. In 1996, astronomers at the University of Illinois at Urbana-Champaign theorized that traces of past [Type II] supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata. Subsequently, iron-60 enrichment has been reported in deep-sea rock of the Pacific Ocean by researchers from the Technical University of Munich. 23 atoms of this iron isotope were found in the top 2 cm of crust, and these date from the last 13 million years or so. It is estimated that the supernova must have occurred in the last 5 million years or else it would have had to happen very close to the solar system to account for so much iron-60 still being here. A supernova occurring so close would have probably caused a mass extinction, which didn't happen in that time frame. The quantity of iron seems to indicate that the supernova was less than 30 parsecs away.
Adrian L. Melott et al. estimated that gamma ray bursts from "dangerously close" supernova explosions occur two or more times per billion years, and this has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth.>>[/quote]