Question about distant planets?

Question

Ok, I was reading an article the other day, that astronomers have found earth and mars like planets 400000 light years away, or something like that.

I am new to this so someone kind of explain this to me. So it take 400,000 light years for the light to reach us, so we can see it here from earth. So there is a possibility that those planets could have evolved, and be bearing intelligent life right now but since the great distance, we are just seeing the beginnings of it. Just want someone to say if I am on the right page. It is mind boggling

Answer 1

Light travels at a finite speed. It takes 8 minutes to reach us from the sun and four years to reach us from the nearest stars. We see stars as they were when the light left them. If a star is 40,000 light years away, we see it with light that left it 40,000 years ago. We see the Andromeda galaxy as it was about two million years ago. We see the farthest galaxies in the universe as they were over 10 billion years ago.
So, yes, if we look at stars and planets outside our own solar system, significant differences could have taken place since the time that light left those stars and planets, including evolution, supernovas, etc.

Answer 2

You are correct about the speed of light and seeing things far away as the were years ago.

But now more practical considerations. 400,000 years is like 30 seconds in the time scale of the universe. Planets and stars are millions or billions of years old, so seeing them with a 400,000 year delay is no big deal. Also, none of the planets discovered so far is as far away as 400,000 light years because that would be outside the galaxy, which is only 100,000 light years wide. Many are quite close, like a few hundred light years or less. Most are a few thousand light years away I think, but I don't know off the top of my head. Also, we have not seen these planets at all. They are hidden by the glare of the stars they orbit. We only know they exist based on measurements of very slight changes in the light of the star they are orbiting; changes that these planets cause. It is very extremely highly indirect evidence that a planet exists and not an actual observation of the planet itself.

Answer 3

It's far more complicated than that. The majority of the planets we have found are not planets for which we have visual confirmation. They are detected by their gravitational influence on the movement of the stars in their environment.

The ones we do have visual confirmation are not so much earthlike as they are a similar distance from their star and of about the same temperature as the earth. The size of these planets and their material composition vary greatly, and as a result, their mass and thus their gravity, make them far less hospitable than the temperature would have us expect.

As for life, we don't know what life is possible in a universe that is for all intents and purpose, infinite. However, the chemical composition of the atmospheres of the earthlike planets is similar enough to ours that we can imagine that they can sustain earthlike life. As yet, we have no publicly available concrete evidence of these planets actually containing life at all, let alone intelligent life.

To be sure, we're basing our information on data that is reaching us years, decades, hundreds, thousands, millions, or billions of years after the fact.

But it would seem pretty arrogant to assume that we're the only smart ones in an infinite universe. Assuming they'd even think of us as smart. ;-)

Answer 4

You're right - we're seeing those planets as they were 400,000 years ago - however, we haven't actually detected planets that far away - that would put them outside the milkyway. I believe the most distant planet we've discovered was on the order of 1000 light years away, but most are within the neighborhood - within a few dozen light years.

Answer 5

I think you've got the distance wrong. The furthest planets we have found are something like 17,000 light years away. They are not like Earth or Mars. They are gas giants similar to Jupiter except larger.

The rest of what you say is spot on.

Answer 6

Yes. Man. You are saying is absolutely true.
So, astronomers do not expect signals from life. They expect to see the planet with elements which lead to life.

4,00,000 light years..... It is a very funny number.
The diameter of our galaxy is 1,00,000 light years.

Anyways,

It is 40 light years.
So, We should try to get signals from those,
because,
40 years before, Human was trying to send signals.
So,
Based of example of us, We can get signals from it.....
no signal is found.