a)a galaxy in the Local Group
b) a galaxy observed at a distance of 5 billion light-years
c)a galaxy observed at a distance of 10 billion light-years
2007-03-20 15:25:28 · 8 answers · asked by Jason G 1 in Science & Mathematics ➔ Astronomy & Space
A light year is the distance light moves in one earth year. The greater the light years, the further back in time you are seeing. So a galaxy at 10 billion light-years is 10 billion years younger and a galaxy at 5 billion light-years is 5 billion years younger. The oldest would be a galaxy you see that is part of the Local Group because it would be closer than 5 or 10 billion light-years.
2007-03-20 15:37:13 · answer #1 · answered by Twizard113 5 · 0⤊ 1⤋
Actually all the answers above are completly wrong.
A galaxy that is 10 Billions light-years away, had just about 3 billions years to evolve, since the Universe is about 13 Billions years old. The Galaxy exists somewhere beyond the visible universe as an old object but we don't see it as it is now but how it was 10 billions ago, so it is young from our point of view. What is now in physics is what the observer observes now (in his frame). It is a tricky question and as the question is asked it is absolutely true that the oldest galaxies are in the local group because we see them more or less as they are now (well, within few millions of years, that in terms of a galaxy life is almost nothing). The galaxies in the local group have very old stars, 3rd generations stars, and had almost the entire life of universe to evolve so they are the oldest.
2007-03-20 15:42:38 · answer #2 · answered by santostasigio 1 · 0⤊ 2⤋
a) Local Group
Simply because the galaxy you're seeing at 10 or 15 billion light years is as it appears 10 or 15 billion years ago. A very young galaxy, and quite different from our "modern" galaxies that we observe "only" a few million of light years away.
2007-03-20 16:16:04 · answer #3 · answered by Anonymous · 0⤊ 1⤋
Well basic astronomy here.
1. Light moves at a finite speed.
2. The distance light travels in one year is called a light-year.
3. The more light-years something is away from us, the longer the light had to travel to get to your eyes, so the further back in time you are looking.
So the closest galaxy to us would be the oldest, which would be (a) a galaxy in the Local Group.
2007-03-20 18:10:50 · answer #4 · answered by Roman Soldier 5 · 0⤊ 1⤋
c.
The light we see is ALREADY 10By (Billion Years) old.
(Light travels one Light Year in One year).
Another issue here, though, is the red shift, or the measurement in the difference in velocity of Galaxies at a distance. One of the ways astronomers determine the distance to an object is by measuring the red shift and comparing it to standards. Astronomers assume that the higher an object's red shift, the further away it is because red shift is relative to velocity. A VERY good explaination of this can be found at the web site listed below.
2007-03-20 16:19:16 · answer #5 · answered by edward_otto@sbcglobal.net 5 · 0⤊ 0⤋
c)a galaxy observed at a distance of 10 billion light-years
We see it as it was 10 billion years ago.
2007-03-20 15:28:15 · answer #6 · answered by novangelis 7 · 1⤊ 2⤋
It says the galaxy that IS the oldest, morons, not which one LOOKS oldest. Therefore it is the one which is farthest away.
2007-03-20 16:28:16 · answer #7 · answered by Anonymous · 0⤊ 0⤋
Is this a trick question??? The answer is in your question! which do you think is older?
2007-03-20 15:29:18 · answer #8 · answered by Scarp 3 · 0⤊ 0⤋