The observable universe boundary has been placed at 13.7-billion light years. But the most distant object observed so far lies at only 13.2-billion light years (en.wikipedia.org/wiki/UDFj-39546284) Why the 500,000,000 light year difference? Is the 13.7-billion light year boundary actually based on when the CMBR first emerged from the opacity following the Big Bang?
-
First off, let me make a small note about distances in cosmology. That 13.7 billion light year distance to the edge of the observable universe is not actually 13.7 billion light years distant. That is the distance where if we were to see light from that boundary today, the light would have traveled 13.7 billion light years. However, the boundary would have continued to move away from us during that whole time period. This means the boundary is now at a distance of 46 billion light years away.
That also means that while the light from this object traveled 13.2 billion light years to get to us, the object is now actually 30 billion light years away from us.
However, you ask why the most distance object ever observed is still not as far as we can technically see. The reason is partially because there isn't much to see that far out. You have to realize that in the early early universe (which is what we're talking about at these distances) there wasn't even that much to shine brightly for us to even see.
Not to mention the fact that we are actually limited to only theoretically seeing 300,000 years after the big bang. This is because, as you suggested, the universe was opaque before that. Essentially no light could travel anywhere because the universe was too dense.
If we want to see any farther, we just have to stare into the vastness of space with a hugely powerful telescope and hope we catch a flash of some form of light from an object that actually existed that early.
Hope that helped.
That also means that while the light from this object traveled 13.2 billion light years to get to us, the object is now actually 30 billion light years away from us.
However, you ask why the most distance object ever observed is still not as far as we can technically see. The reason is partially because there isn't much to see that far out. You have to realize that in the early early universe (which is what we're talking about at these distances) there wasn't even that much to shine brightly for us to even see.
Not to mention the fact that we are actually limited to only theoretically seeing 300,000 years after the big bang. This is because, as you suggested, the universe was opaque before that. Essentially no light could travel anywhere because the universe was too dense.
If we want to see any farther, we just have to stare into the vastness of space with a hugely powerful telescope and hope we catch a flash of some form of light from an object that actually existed that early.
Hope that helped.
-
partly it's just because distant objects are so faint, it's very hard to spot them and determine their distance accurately. also, after the CMBR was emitted, there was nothing else around to emit light. it's expected that there will be a gap of several hundred million years before we see the first stars and quasars forming.
-
The observable universe is so small, it is probably minuscule as to the actual whole! Some galaxies are so big, it takes 6 million light years to cross! Good luck on your question.
-
Scientist used math to calculate the speed of the universe expansion. The fartherest object observe doesn't mean it's the boundaries.