宇宙还在不断膨胀?

tin1098tin

宇宙还在不断膨胀?
From NASA: < http://www.nasa.gov/mission_page ... e/young_bright.html >

...
A1689-zD1 appears as a grayish-white smudge in the close-up view takenwith NICMOS [image at center, right], and as a whitish blob in theSpitzer close-up view [image at bottom, right]. The galaxy is brimmingwith star birth. It is one of the youngest and brightest galaxies everdiscovered. Astronomers estimate that the galaxy is 12.8 billionlight-years away. Abell 1689 is 2.2 billion light-years away.

So it is 128亿光年 away. Forget 2400...

[ 本帖最後由 tin1098tin 於 2008-2-20 17:02 編輯 ]

tin1098tin

http://www.nasa.gov/mission_page ... e/young_bright.html

[ 本帖最後由 tin1098tin 於 2008-2-20 17:03 編輯 ]

tin1098tin

http://www.nasa.gov/mission_page ... e/young_bright.html

[ 本帖最後由 tin1098tin 於 2008-2-20 17:04 編輯 ]

mca

This observational news gives us some insight:

1.   Distance of galaxy (A1689-zD1) = 12.8 billion light years.
2.   Age of galaxy = born 0.7 billion years after the Big Bang.
3.   The Big Bang happened 12.8 + 0.7 = 13.5 billion years ago.
4.   We cannot see the "universe" farther than 13.5 billion light years.

5.   Assuming the universe is expanding linearly (Hubble’s law), this galaxy is receding from us at 12.8 / 13.5 = 0.948 light speed, equivalent to a red shift amount of 5.1

AC

C.L.Chan

Hi, tin,
看不到你指示的網頁.請用兩個引號 <....>  把網頁藏在中央.例如
<http://zh.wikipedia.org/w/index. ... 6&variant=zh-hk>

tin1098tin

宇宙还在不断膨胀?

[ 本帖最後由 tin1098tin 於 2008-2-20 17:00 編輯 ]

tin1098tin

宇宙还在不断膨胀?

<     http://www.nasa.gov/mission_page ... e/young_bright.html    >

mca

其實這個網頁不是大新聞，也沒有說明 「宇宙仍然在膨脹與否」，它只是報導了一個極遠的星系 (A1689-zD1) 在 Big Bang 之後 7 億年誕生而已。這類新聞久不久出現。 A1689-zD1 不算是已知最遠的星體，有幾個類星體 (星系核) 比 A1689=zD1還要遠少少。

mca

記得在 ~7 年前，「宇宙是否不斷膨脹」是熱門話題:
<http://www.alanchuhk.com/Supernova_1997ff.doc>

那時 SN1997ff 被認為是宇宙膨脹的証據，因為它的光度在理論曲線之下 (曲線的垂軸 = 視星等，橫軸 = 紅移) 。

當年還提及一顆 SNAP 衛星預算在 2020 年發射，但近年它的報導又靜下來了。

AC