If the nearest star is 100 million light years away, how do we know it is still there?

Answer 1

The nearest star is far less than 100 million Ly away. M31, the Andromeda Galaxy isn't our closest neighboring star, but it is only 2.5 million LY away. Other stars in our own Milky Way galaxy are closer.
Your question is correct, however. Stars at a distance of more than 4.65 billion LY away from Earth may no longer exist, since they may have turned supernova in the time it takes for their light to reach Earth. Astronomers today are beginning to study a phenomenon called "afterglow" to learn more about these far away stars. It is the study of the remnants of the supernova explosion.

Answer 2

The nearest star to us is the Sun. Light takes about 8 1/2 minutes to get to us from the Sun. If anything happened there, we'd know pretty quickly.

The next nearest star to us, after the Sun, is Proxima Centauri. That's about 4 light years away. Since our galaxy (the Milky Way) is estimated to be 100 light years across, your figure of 100 million light years will relate to a star in another galaxy rather than the nearest star (or even the closest galaxy).

Anyway - to answer the question, for a star that is say, 2000 light years away, the light we are seeing started its journey 2000 years ago. It is quite possible the original star no longer exists. When we see stars explode catastrophically (supernovae) we are watching an event that actually happened long ago and the original star does, indeed, no longer exist.

It is also worth bearing in mind that everything in the Universe is moving. This means that the light arriving at our eyes shows the position of the celestial body (be it star, planet or galaxy) at the time the light started its journey towards us. So for any star we're seeing in the sky, it has actually no longer in that position relative to us. Let's say we look at a star which is 1000 light years away and is travelling Eastwards (by our frame of reference) at 1000 miles per year. Although we see it in a certain position in the sky - that is where it was 1000 years ago. It is now actually 1000x1000 (i.e. 1 million) mile east of that position. So I suppose the most accurate answer to your question is that nothing is still where we are seeing it.

Answer 3

Good point, we don't know its still there. What we are seeing is the light that has been travelling for 100 million light years, the star could have burned out by now.

However, I don't think the nearest star is anywhere that far away--proxima centauri is the nearest star to the solar system, only 4.3 light years away.

Answer 4

we can never tell that the star is still there.
What we are seeing is the light that the star send out 100 million years ago. Right now we are seeing how the star was 100 million years ago

Answer 5

I think the nearest star is a lot closer than that. It's Alpha Centauri which really consists of 3 stars. Just more than 4 light years away. So we know it's still there, at least it was 4 years ago and likely to still be there now.

Of course for stars much farther out we have uncertainty since we can't know for sure what has happened at their location since their light reaches us. But from history, we know stars can be stable for billions of years.

Answer 6

It isn't. The nearest star is not 100 million light years away. It is only 4.3 light years away. And both of them will not be there because we are seeing the light which left them 4.3 or 100 million years ago.

Regards.

Answer 7

Well we don't really, the light that we are getting is 100 million years old. For all we know that star is gone. But it's kinda cool, if you think of it as time travelling....we're seeing something that happened 100 million years ago.

Answer 8

The nearest star is Proxima Cenurai and its less than 4 light years away.

But its true that we do not know whether very distant stars still exist, their light has been travelling so long.

Answer 9

The nearest star is still there.... the sun. But for the part of the question, some peole think some of the stars are gone maybe.

Answer 10

Well, it's rather simple - that star that's nearest us is called "the sun". If it went super nova I'm sure we'd know about it, at least for a few hours.