Astronomers think the Universe has been around for about 13.7 billion years. Well, they just spotted an object about 13 billion years old: http://news.yahoo.com/s/afp/20091028/sc … 1028233220
The object was an exploding mega-star that occurred about 13 billion years ago. The light from this explosion just reached us, here on Earth.
To people who may not be good with astronomy and space, the light you see from the nearest stars started many years ago and you are seeing the light from the past. For example, the Sun's light takes about 8 minutes to reach Earth. So the light you see from the Sun is actually 8 minutes old. The light from the nearest star to Earth takes about a year to get here. So, the light you see from that star is a year old.
That is why we can see light that is billions of years old (from the beginning of the Universe) still today. When there is a big explosion, we don't see that explosion for "x" number of years, depending on how far away that object is to us.
This May be a silly question,but I am not miss science gal,exactly how do they know the actual distance to something that far away if they are seeing it through a 2 dimensional lens?
They use math and physics. Light travels at a set speed (except in or near black holes). They also use the "known" distances of nearby objects in the Universe to further gauge how far something is.
I don't know the exact formula, as I'm not an astronomer of physicist, but it's a lot of math and I believe they use radar to measure X-rays and radiation of the object, as well.
Now, with this explosion, only 2 people saw it appear and by the time all the telescopes turned to that object, everyone saw the after-glow of the explosion.
If those 2 people weren't looking in that exact spot at that exact time, everyone would've missed the explosion.
So I'm sure we've missed thousands of other explosions, over time, because no one was looking in that exact part of space when the light finally hit us.
They use concepts called red shifts and blue shifts. It's related to the doppler effect (the pitch of an ambulance siren, for instance, goes up as it approaches you). Objects emitting radiation that are far away and drifting further away as the universe expands will redshift, and like Tim says, math can calculate the distance and age of the object.
If you want to get crazy:
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