1
$\begingroup$

I don't know much about the astronomy or the universe but enjoy reading articles from time to time as they pop up. Just finished reading an article on CNN that discussed how a South African telescope has discovered hundreds of galaxies, some 200 million light years away.

This got me thinking: Are these galaxies and or some of their stars we see in telescopes still there? Let's say STAR X is confirmed to be 200 million light years away. What if it completely exploded 1 million years ago? Wouldn't we need to wait 199 million years before we could detect that?

$\endgroup$
  • $\begingroup$ You're precisely correct. If for some reason it exploded 1million years ago, we'd need to wait 199 million years to see that. $\endgroup$ – Fattie Jul 18 '16 at 13:10
0
$\begingroup$

Simple answer is yes. It will take light from an explosion that happened 1 mya at a distance of 200 Mly, about 199 million years to reach "us" - not that any of "us" will be around then. The speed of light is the fastest speed we can get information from anywhere in the Universe. There's nothing special in asking about what happens to that star after that light starts out on its journey here. The fact is, we can't know, until we are able to gather more light from that same source. So, that star would appear to explode if you were looking up at it 199 million years from now (keeping in mind that both the Solar System and the Milky Way are also moving through space, so the exact time it takes the light to get here will be different than the time it took the light we are now seeing from that star to have gotten here.)

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.