How can Astronomers measure such huge distances from Earth to the most distant stars?

Question

They say some stars are 12 Billion light years away, how or earth can you measure that? Light traveling at 150,000 Miles/second for 12 billion years, amazing but how could you know such a huge distance?

Is there a possibility that they are wrong?

How can they even say the galaxy is 100,000 light years across?

Answer 1

special methods... the trick is seeing how the object moves as earth moves.

Answer 2

There are three methods that are used most frequently:

1. Parallax - For nearby stars, they can measure the angle that the star appears to move through as the earth swings from one side of the sun to the other - this is the most direct and probably the most accurate method, but it only works for stars in the local region.

2. Cepheid variables. - For more distant stars and nearby galaxies, there is a certain type of variable star known as a Cepheid variable that has a predictable range of intensity. Since we know that distance and intensity are related, then wherever we see these stars we can obtain a reasonable measure of the distance to them by measuring the intensity. When this is done with a large number of these stars, the distances to nearby galaxies can be found with reasonable accuracy.

3. Redshift - For the most distant galaxies, we can use the observation that the universe is expanding in order to measure the relative distances to really distant objects. The further away these objects are, the faster thay are receding from us (ADDED: and the deeper the redshift of the spectrum from that object due to the Doppler effect). This is true in all directions that we look, and for all but a few galaxies. This method is perhaps subject to the most questions, but makes sense for the really distant objects until someone suggests a better idea.

There is always a possibility that we are wrong. That is why it is called science, and not religion, where questions about original assumptions are rarely allowed. If you have a better approach, please provide it. (ADDED - don't mean to sound strident - but I'm serious - we are always open to new ideas) In the meantime, the numbers that are available make perfect sense with the observations that we see.

Answer 3

There are many different methods. Some methods overlap, which is good for verification, but mostly we have to use a number of different methods, each appropriate to a certain range of distances, in order to calibrate distances further and further away from earth. See this article on the cosmic distance ladder.

There is certainly the possibility of error, but science involves both an ongoing process of self-correction and of estimation of uncertainties for measured quantities.

Answer 4

i've heard some method but ones i understand well is by x-ray diffraction and x-ray difference wave lenght (after travelling such long space and time dimension there are a difference in X-ray wave lenght between the source and the receiver(us))

Answer 5

There are many methods ,one of them is by calculating the time of reaching the light to the earth from the object from where they need