One of the reasons I like looking at the night sky is that when you look up you are looking into the past. The sky is a map of what things used to look like. The objects you see have moved from their apparent location due to gravitational forces and the expansion of the universe. Some/many/most? may no longer exist at all!

Those objects close to us such as Alpha Centauri(a mear 4.3 light years away) are showing us an image of what they looked like about 4.3 years ago. So in theory we would not know if it exploded until the light from that explosion reached us 4.3 year after the fact.

What this means is that the further away we see an object, the further back into the past we are observing. This is where our telescopes come in. The further away an object is, the longer it has taken for that light to reach us, so the older the object.  Most things we observe are moving away due to the expansion of the universe.  This is seen as light changing color or being red shifted. As telescopes improve we get to see things further and further away. The furthest thing now observed is shown below (the red dot in the middle).

This is GRB (Gamma Ray Burst) 090423 which occured over 13 billion years after the big bang, and is likely to be the explosion of one of the earliest stars in the universe. That makes it only about 670 million years after the big bang. The age of the universe is approximately 13.7 Billion years old.

In an interview, Edo Berger with the Gemini Telescope was reported to say “This happened a little more than 13 billion years ago. We’ve essentially been able to find gamma ray bursts throughout the Universe. The nearest ones are only about 100 million light years away, and this most distant one is 13 billion light years away, so it seems that they populate the entire universe. This most distant one demonstrates for the first time that massive stars exist at those very high red shifts. This is something people have suspected for a long time, but there was no direct observational proof. So that is one of the cool results from this observation.”

So just how far back are we going to see?