How do we see stars now when what we are seeing on earth is the light from millions of years ago?
OK, dumb question I m sure, however,

When we see the stars in the sky, it s light arriving here that left millions of years previously right? So how do we actually know what s out there now, what do those planets look like NOW. Presumably we are only see what the used to look like?
-------------------------------------------------------

answers:
Clive say: Not at all dumb, except that stars millions of light years away are too dim for us to see without a telescope. Any individual star you can actually see with your own eyes is hundreds of light years away at most, maybe a thousand or two in the case of the very brightest. But yes, you're still seeing it as it was that many years ago when the light left it, and as nothing can travel any faster, there's no way of knowing what has happened to the star since.

You can't see any planets without a telescope except the ones in our own solar system, and the light was reflected from those at most a few hours ago. And even if I look at you from across the room, I can still only see you as you were a tiny fraction of a second ago.

Anyway, over that amount of time it probably still looks the same now. The only chance of a star looking significantly different now from what it did when the light left it is if something very fast and big happened to it, which basically means a supernova. This happens when a big star can no longer keep up nuclear fusion to keep it shining steadily, so in a fraction of a second its own gravity makes it collapse, now it's even hotter and even more unstable and it blows itself to bits, leaving behind a neutron star or a black hole.

The usual example of which star we can see might go supernova next is Betelgeuse, as it's a pretty old giant so it could go boom at any time. It's difficult to measure distances this long with accuracy but it's somewhere in the range of 600-650 light years off. Let's say 650. Then all we can say about it is as of 650 years ago, it hadn't gone boom yet. It might have done since, but the light of the explosion hasn't had time to get here yet.

Now that would be a sight to see. At that distance it would be so bright that it might even be visible in daytime in the parts of the world where Betelgeuse is above the horizon. And it would take days or weeks to fade away.
-
Jeffrey K say: It is not possible to see what stars look like right now. Nothing can travel faster than light to show us.
In fact, even the concept of NOW is not the same everywhere. The very definition of NOW demands on where you are and how you are moving.
-
tham153 say: no star millions of LY away are visible, most of the stars in the night sky are within 60 LY. 60 years in the life of a star is trivial and will show no changes
-
ryan say: Simple... We don’t!

We can’t pred where things are from there trajectory but unless they are stars that are only a few light years away (a year for light to travel), we don’t really know what they look like now, or even if they are still there.
-
Ronald 7 say: Actually Billions a lot of them
it is true we see them as they were when the light left them
What has happen in the meantime between then and now is really anybodies guess
In Relativity everything moves including us here on Earth in our Solar System
There is no reason either it or us has moved a little or a lot
From there we might even have ceased to exist at all
13.8 Billion Light years is the consensus for the Radius of the Universe right now
But some Stars have been detected even our own Galaxy are estimated to be more than 14 Billion years old
Surely there is something wrong there
The Universe must be older than we think, hence even larger
-
jehen say: The stars we see unaided in the night sky are much closer - but still up to 25,000 light years away. On a really good clear night well away from light pollution you may spot the Andromeda galaxy about 2.5 million light years away. Yes, it is entirely possible that some of the stars (very few, and only those known to be unstable) in the night sky no longer exists and we won't know for several hundred to several thousand years depending on how far away they are. But most of what we see is quite stable and it is a sure bet that they pretty much exist as we see them. But the most distant galaxies that we can see at the edge of the visible universe with our most powerful telescopes probably don't exist as we see them now.
-
Climate Realist say: Most of the stars that you see are much closer than Earth than millions of light years. Alpha Centauri is 4.5 light years away. Even Betelgeuse is only about 600 light years away.

But, through telescopes, astronomers do see galaxies that are millions and even billions of light years away. Light does not age when it moves.
-
Pearl L say: i think theyre still there or we wouldnt be able to see thenn
-
John say: Pretty fascinating, isn't it?
-
billrussell42 say: stars are mostly closer than that, as close as a few light years.

We can't see planets around other stars, only the stars themselves, and you are correct, what we are seeing is what was there years in the past. In the case of galaxies, millions or even billions of years in the past.

But even the light from the sun takes 8 minutes to reach us. The sun could go out and we would not know it for 8 minutes.
-
CarolOklaNola say: Most stars are a lot close to us than that. Sirius is only a little over 8 light years away. The planets like Jupiter are a lot closer. Vega is a little more than 25 light years away. Altair is 16.7 light years. Betelgeuse is 642.5 light years away. Betelgeuse has been shrinking for 30 years. It may already have gone supernova and we will not know it for more than 500 years.
-
duke_of_urls say: You can't.

In fact, you can't even see how you look Now when looking in a mirror. There is a non-zero amount of time for light to reflect off of your face, travel to the surface of a mirror, and then travel from the mirror to your eyes.
-
Luca say: The point is that the "now" isn't their now. In special relativity present isn't a flat constant time-plane, we can only see and interact with everything that is in our light-cone.
If the star explode, we're still gonna see its sign only after years have passed, both optically and gravitationally, so that's the present, that's what is there now from our PoV.
-
Lone Cat say: You seem to understand just fine. Everything we know about the universe is based on the light we get from stars.
-