How do astronomers learn about distant objects in the universe?

Answer 1

Mass spectography, xray detectors, infrared detectors, and just visible light allow scientists to differentiate between planets, stars, solar systems, coets, galaxies and cluster galaxies. Each one has it's own fingerprint and like people, it's own traits.

Answer 2

Yes. Because they are so far away that it takes light billions of years to travel from the distant galaxy to earth.

I just thought of this analogy:

One day the mailman delivers a letter from your good friend in Central Asia. You're happy to hear from him, since you haven't spoken to him in a long time, and you'd like to know how things are going for him and his family and his herd of yaks. Quickly and with trembling hands, you tear open the letter, and begin to read.

He starts out: "My dear American friend i am happy today because today is my birthday and my children have given me a new sheep."

Now ... is today his birthday, on the day when you're reading his letter ? What's the next thing you do ? Don't you immediately look on the outside of the envelope, to see if there's a postmark on it, so you can try and figure out how long it took for his letter to get to you, and then maybe you can figure out when his birthday actually was ?

Same with stars and galaxies. It takes a while for their letters to reach us ... like billions of years in some cases. All we know is what they looked like when they mailed the letter.

Answer 3

The further something is away form us the longer the light from it has been travelling to reach us. Thus when we look at very distant objects (galaxies) we see them as they were in the distant past when they were young. The more distant they are the younger/earlier they are. This effect is enhanced by the expansion of the universe which also makes the light from distant objects shift towards the red end of the spectrum.

Answer 4

Light has a finite and constant speed. It always takes time to travel from the object to our eyes. When we look out at the sun moon and stars we see into the past.

We see the moon as it was 1.29 seconds ago. It takes light 1.29 seconds to travel the 384,000 km to the earth. It is 1.29 light seconds away.

We see the sun as it was 8 minutes ago. If it were to explode suddenly then we would be unaware for 8 minutes. It is 8 light minutes away.

We see Proxima Centuri our nearest stellar neighbour as it was 4.2 years ago. 4.2 ly

We see the center of the Galaxy as it was 26,000 years ago. It is 26 Kly

We see Andromeda Galaxy as it was 2.5 million years ago. 2.5 Mly

and so on.

The more distant the object the further into the past we see.

The most distant galaxy group we have seen was the cluster JKCS041 which is 10.1Gly away only some 3.63 billion years after the Big bang.

The most distant object we have seen was a gamma ray burst 13.1 Gly. This massive explosion took place only 630 million years after the big bang.

Answer 5

There are many stars in each stage of development, so the obvious assumption is that they represent similar stars, with similar stages, except that they began their existence at different times.

Imagine you knew nothing of people. You were then given millions of pictures of people in varying states of aging. Different people, each one in a different stage of development. Would you be able to figure out that the tiny ones were young ones and that the wrinkly ones were old ones? Maybe. It is in that way that studying the pictures of the distant galaxies, and for that matter, stars, that human beings can guess at how these inter-stellar bodies age.

Answer 6

Depending upon how distant the galaxies are, in some cases it takes light billions of years to reach our planet from distant galaxies, which means that we are not seeing those galaxies as they are now, but we are instead seeing them as they were, billions of years ago. The more distant a galaxy is, the longer it takes for its light to reach us, and therefore the earlier the galaxy that we are observing.

Answer 7

We cannot see the entire Milky Way, because we're INSIDE it; our Sun is part of the Milky Way. We observe other galaxies where we can see the whole thing hoping to learn about where we are, and how our galaxy may have evolved - and where it may evolve next.

And we humans don't live long enough to watch how a galaxy is formed, or what happens to it as it grows old. We can study other galaxies that are younger and older than ours, and try to learn how our galaxy formed and what may happen to it later on.

Right now, there is an interest in studying what happens when galaxies collide with each other. We don't have to worry about this any time soon, but the Milky Way galaxy will probably collide with the Andromeda galaxy in about 3.5 billion years.

Answer 8

Images of distant galaxies are taken from powerful telescope. By studying its redshift, its distance is measured and we came to know about it.

Answer 9

They look at far-away galaxies. When they watch the far-away galaxies, they see the Universe in its early stages.

Answer 10

Light from distant galaxies took billions of years to reach us. Therefore, we are looking at the far past of the Universe.