by Ann » Wed Dec 03, 2014 11:40 am
molechaser wrote:I'm not an astronomer or astrophysicist, but something doesn't sound right about the distances mentioned in todays description. If the light of the supernova reached earth 30,000 years ago then it must have been 30,000 light years away. Now it is only 5000 light years away? It has moved a distance of 25,000 light years in the time span of 30,000 years, which means the nebula/neutron star remnant has been moving toward earth at 83% of the speed of light! Am I in left field on this one?
The fact that the light of the supernova that created the Jellyfish Nebula reached the Earth 30,000 years ago doesn't mean that the supernova had to be 30,000 light-years away at the time when it exploded.
Consider
Supernova 1987A in the Large Magellanic Cloud. This supernova was discovered on February 24, 1987, almost 28 years ago. The fact that it was discovered almost 28 years ago doesn't mean it was 28 light-years away when it exploded. In fact, it was about 160,000 light-years away, since it was located in the Large Magellanic Cloud.
A supernova that was relatively nearby when it was discovered on the Earth 30,000 years ago can be much closer than 30,000 light-years away - or rather, its remnants can be much closer than 30,000 light-years.
Ann
[quote="molechaser"]I'm not an astronomer or astrophysicist, but something doesn't sound right about the distances mentioned in todays description. If the light of the supernova reached earth 30,000 years ago then it must have been 30,000 light years away. Now it is only 5000 light years away? It has moved a distance of 25,000 light years in the time span of 30,000 years, which means the nebula/neutron star remnant has been moving toward earth at 83% of the speed of light! Am I in left field on this one?[/quote]
The fact that the light of the supernova that created the Jellyfish Nebula reached the Earth 30,000 years ago doesn't mean that the supernova had to be 30,000 light-years away at the time when it exploded.
Consider [url=http://en.wikipedia.org/wiki/SN_1987A]Supernova 1987A[/url] in the Large Magellanic Cloud. This supernova was discovered on February 24, 1987, almost 28 years ago. The fact that it was discovered almost 28 years ago doesn't mean it was 28 light-years away when it exploded. In fact, it was about 160,000 light-years away, since it was located in the Large Magellanic Cloud.
A supernova that was relatively nearby when it was discovered on the Earth 30,000 years ago can be much closer than 30,000 light-years away - or rather, its remnants can be much closer than 30,000 light-years.
Ann