Question About the Universe

I'm having a tough time understanding this.This story just came out recently. Star 13 Billion Light Years AwayI'm told that the universe is about 13 billion years old, and here we have a star that is observed by us to be 13 billion light years away.1/ Doesn't this mean that what we are now seeing is that star as it was at a time very shortly after the Big Bang?2/ I also understood that there is an "event horizon" because of the expansion of the universe that has moved galaxies beyond our ability to perceive them. However here we have a star that has been here since nearly T=0 and we're still able to view it. Why is that?3/ Using the penny on the balloon analogy shouldn't this mean that we are looking virtually all the way around the balloon, (the universe), and if we looked in another direction that we could see the same star very much closer?I'm only suggesting this as a topic of discussion for my own information. I don't pretend to have the knowledge to actually debate it.

Thread moved here from the Proposed New Topics forum.

First of all, let's do a little math. The current consensus on the age of the universe is somewhere around 13.73 billion years, with an error margin of about 120 million years.What's important to keep in mind is the vastness of time periods we're talking about. While 120 million years may seem like small change when comparing it to the total age of the universe, realize that a lot can happen in the way of cosmological evolution during the course of 120 million years.This is from your article itself: Seeing as how a billion (1,000,000,000) is one thousand million (1,000,000), this gives plenty of time for this star to have appeared sometime after the Big Bang.In any case, someone else on this forum can probably explain it with greater detail than I can. Cosmology isn't my forte; I'm a biology major. Edited by RDK, : No reason given.Edited by RDK, : No reason given.

Hi GDR, Yes (on the order of several hundred million years after the BB) We are seeing the "star" before the cosmological expansion carries it over the cosmological horizon. If we continue to observe it over time, we will see it receed and redden to the point that it fades from view. No - even if the Universe is closed as in the balloon analogy, this is on a scale unimaginably larger than the distance to the "star", because of inflation. In an inflated closed universe, the observable universe is a tiny fraction of the whole universe. Edited by cavediver, : No reason given.

Stephen Hawking write that after 1,000 million, (an American billion), years after the BB "Clusters of matter form quasars, stars and proto-galaxies". If as RDK says, the universe is 13.87 billion years old, wouldn't this make it among the very first stars to be formed? As I understand it, we are seeing the light that left that star 13 billion years ago even though, from our perspective, that star has since that time inflated beyond the cosmological horizon. If then, we can look out into space and see things as they were 13 billion ago then what is left to have inflated beyond our ability to perceive?

Hello, GDR.I'm not even going to pretend I can answer your question. Rather, I'm going to add to it, to make it more confusing. If the universe has been expanding since the Big Bang, wouldn't this mean that a star 13 billion lightyears away was less than 13 billion lightyears away at a time closer to the Big Bang?So, would it still have taken the light 13 billion years to get here from there?
Or, if it was 10 billion lightyears closer at the time of its formation, would the light have reached here 10 billion years earlier?

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-Bluejay/Mantis/ThylacosmilusDarwin loves you.

Hi BluejayI believe, that although the star would have been closer in the past it doesn't change the fact that the light from that star that was recently viewed left it 13 billion years ago. I would imagine that if we could see that star as things are right now it would likely have burned itself out, but if it still existed it would be much further away than 13 billion light years.

Hi, GDR. If the expansion of the universe is slower than the speed of light, shouldn't it have been able to shave off at least a little bit of the transit time?

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-Bluejay/Mantis/ThylacosmilusDarwin loves you.

Hi Bluejay, The space in between galaxies is expanding at a rate that is faster than light speed. That does not mean that the objects in space are traveling at a rate faster than lightspeed, in fact, they are barely moving at all - in comparison to (c).That's why eventually we won't be able to see objects that we could once see, their light will not be able to reach us since the space between us and them, so to speak, is expanding at a rate faster than that of (c).... as I understand it.- OniEdited by onifre, : No reason given.

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"I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks"I never knew there was another option other than to question everything"--Noam Chomsky

Hi GDR,In an attempt to better help me understand it too, I'll try to answer this so if I get it wrong cavediver will be able to correct my understanding of it as well. What is left to "inflate beyond our ability to see it" is what we can currently see.With time, billions of years of course, from our point in space, we will not be able to see anything more than the clusters near us. Everything else will be out of our "sight" due to the expansion rate being faster than light can travel.... as I understand it.- Oni

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"I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks"I never knew there was another option other than to question everything"--Noam Chomsky

Aboslutely - unless we have something very wrong! Not "inflated" - inflation is reserved for what happened in the first 10^-34sec of the Universe - but "carried by the expansion of the Universe" would be fine. I'm not sure I understand your question. Most of the Universe has never been visible to us and never will. This "star" was relatively very close to us for it to be visible at all.

Yes - much much closer. If you imagine the sphere on the sky centred on us with surface so far away that it contains this star, the actual surface area of that sphere is relatively quite small - much smaller than many of the concentric spheres that are much closer to us! Think of standing on the North Pole, and being surrounded by the lines of latitude. The Arctic Circle is obviously smaller than the Tropic of Capricorn, and the Equator, but by the time we reach the Tropic of Cancer, the surrounding circles are growing smller, down past the Antarctic Circle and finally we reach the South Pole as a point.

Doesn't make sense. Expansion is measured in how much distance appears in so much time in so much existing distance. So, 10m/sec per km is an expansion rate. Every second, any distance of 1km becomes 1.01km. This is not a speed or velocity. You could say that across 1km, space is expanding at 10m/sec and you'd sort of have a point. Is this faster than light? Of course not. But what about this same expansion across 5x10⁸km? Across that distance, you could say that space is expanding at 5x10⁹m/sec, which is significantly faster than light. Any uniform expansion rate, over a sufficient distance, creates a "superluminal" expansion.

Hi, Cavediver. Okay. So, is the expansion rate uniform, or close enough to it to get away with saying it is?It also seems that, if each kilometer is thought of as expanding over a period of time, wouldn't much of the expansion between us and the other star be happening behind the light as it traveled? To my mind, this means that any light we're seeing didn't actually travel the entire distance from there to here.Am I leaving something out?
It seems like I'm making it harder than it needs to be.

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-Bluejay (a.k.a. Mantis, Thylacosmilus)Darwin loves you.

I think it's the opposite. The expansion behind the light doesn't affect the light itself, so we don't see it. The expansion in front of the light, however, makes it travel longer than it would have to without any expansion, meaning the star was closer when the light was released than the total distance the light actually has to travel to reach us.