Viewing Stars

Hi all,

just another thing that found its way into my imagination

When we look at the stars from our backyard we see them from millions of years ago, now some people say that these stars may not exist now, so if that was the case what would happen if one of these said stars exploded from us viewing it, what type of effect would that have on us here at earth ?

would it just disappear or would there be a brilliant flash of light ? people say that they may not exist now but what would happen if one of these stars time was up ? say for example the middle star in orions belt was to explode, would we see that in real time or would it take an age for it to disappear ?

There have been supernova realtively often in the sky. One of the more famous ones was back in ancient times, lit up the sky for weeks. (night was day)

It would take the same time as the light we see to get here. Why? Because it's light. And if happens right now and is 6 million light years away, that light has to travel 6 million light years to get here.

The farther the object in the sky is away from us, the more we are seeing into the past, so by the time the supernova "flash" is visible to us, it might allready be a cooled down white dwarf with bits of its egecta around it.

A supernova has to be within 10 parsecs (30 light years) or so to be dangerous to life on Earth. This is because the atmosphere shields us from most dangerous radiations. Astronauts in orbit may be in danger if a supernova is within 1000 parsecs or so.

No stars currently within 20 parsecs will go supernova (as far as we can tell) within the next few million years.

There are some indirect effects, though, which are harder to evaluate: the possible effects on the Earth ozone layer. Additionally, according to one calculation, the neutrino flux from a nearby supernova might heat up the Sun.

there is some more detailed technical info here:
stupendous.rit.edu...

[edit on 5/7/2005 by Jehosephat]

Originally posted by Jehosephat
A supernova has to be within 10 parsecs (30 light years) or so to be dangerous to life on Earth. This is because the atmosphere shields us from most dangerous radiations. Astronauts in orbit may be in danger if a supernova is within 1000 parsecs or so.

It seems that GRBs are associated to supernovas and these beams of radiation are dangerous to much farther distance.


Also magnetars are capable to causing very powerful radiation bursts.
www.astronet.ru...
www.nasa.gov...

Originally posted by Scaart
say for example the middle star in orions belt was to explode, would we see that in real time or would it take an age for it to disappear ?

Better example would be Betelgeuse which might blow any second...
or might have done it hundreds years ago, it's distance is ~400 LY.
It would be propably as bright as full moon and at its brightest for (few) weeks-month and after that it would start become dimmer so that after something like many months/half year it would be barely visible anymore.
Saying anything more specific would be hard because all except few oberved supernova's have been so far that there haven't been any knowledge about star itself which exploded or process.