astrophotography - How can we take pictures of something billion of light years away?

I have had this question in my mind for a long time, I thought you guys might enlighten me easily.

I am confused about some space photographs and claims like "this galaxy is 13 billions light years away from us.": how we can take the photograph of something that far, if it is 13 billion light years away wouldn't it take 26 billion light years to take those pictures?

today this post led me to ask this question, at last: a space picture

There certainly is something I don't know about photography or light years; if you could tell me the logic behind this, I would appreciate it.

I am not a physicist or any science guy, so please tolerate my ignorance.

Answer

The error is probably in this statement

if it is 13 billion light years away wouldn't it take 26 billion light years to take those pictures?

I think you are imagining that cameras send out light to the objects, and when this light comes back records the light as an image. Not really. Cameras merely record the light they see from that area. So if that area is 13 billion light years away (not sure how credible source is) then all that means is that the light you are capturing today is the light that galaxy emitted 13 billion years ago.

Imagine for instance Anna and Bob are playing catch with a ball. Anna throws the ball to Bob. Bob receives the ball, and says the ball came at 3:00pm sharp. But the ball was in the air for 1 minute (anna is a slow thrower). That means Anna threw the ball at 2:59, even if Bob recorded it at 3:00. In this scenario, Bob is acting much like a camera acts, by receiving information (in this case a ball, in a camera's case it would be light from galaxies) The reason that Hubble took photos for 4 months (this might be wrong, I'm no good with photography) is that the longer it receives the information, the more 'background' light that we don't want to capture can be removed.

Hoped this makes sense.

P.S. may have misunderstood the question. You say

if it is 13 billion light years away wouldn't it take 26 billion light years to take those pictures?

as if light years are a measure of time. A light year is a measure of distance, the distance light travels in a year in a vacuum.