If it isn’t already evident to you, the question is a bit misleading. How can you see something old through a telescope? Should you not be seeing something far with a telescope? After all, that is why we use a telescope right? You definitely get an enlarged image of the moon and the planets with you garden variety telescope so then why should we not ask as to what is the farthest thing we have observed with our telescope?
The thing is, the farther out you see with a telescope into space, the older things you observe. This is true for when your telescope is in space and you are an astronomer. See, light speed is the fastest possible speed in the world and we measure all astronomical distances with this unit of measurements. However, what most folks fail to understand with the term light speed is that it also happens to be the speed at which light travels and so if you are seeing an object one light year away, it means the light from that object has also taken one entire year to reach you. This means you are seeing a year old image of that object. Get it now?
Hence, the farthest out object you see in your telescope is also the oldest object in view. For those who haven’t yet understood the concept take the sun for example and the time it takes for light from the sun to reach us. It is approximately 8 minutes, which means what we see in real time is an 8-minute delay of how the sun was. So when we catch a glimpse of some star 20 light years away we are seeing it as it was 20 years back.
Before you start asking more questions, any star system or galaxy that is 100 million light years away is basically a snapshot of how that object was 100 of millions of years ago, when dinosaurs roamed our own Earth!
With this out of the way, lets now get back to the question at hand – how old is the oldest object we have seen with out space telescopes? The answer is 13 billion years old. The Hubble Space Telescope managed to peer through all the layers and see total of seven galaxies that are 13 billion light-years away. These galaxies were born just 400 million years after the universe came into existence.
To achieve this spectacular feat, Hubble space telescope basically spent hours and hours peering at a specific spot until it managed to capture a complete image of the object in that field of view. While the actual distance or age isn’t yet certain, what is certain is that it ranges anywhere from 13 to 13.3 billion years.
The James Webb Space Telescope takes things one step further as with infrared lenses, it can actually go as far as 200 million years closer to the Big Bang. This telescope will launch somewhere in 2018.