ASTRON 2B03 Lecture Notes - Lecture 6: Blueshift, Redshift, Edwin Hubble
1 Dec 2016
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Document Summary
Has galaxies changed at all when we take pictures of it by receiving its light? (lookback time) Tiny details are different, but galaxy movements occur through billions of years. However, if lookback time is over billions of years, then galaxies can combine and look much different. Some galaxies are 12 million light years away means we see it as it was 12 million year ago. When we observe stars near center of the milky way galaxy, we detect light that was emitted from those stars about: 12,000 years away. Distance of milky way is about 100k light years. You can use this to look back into the past. 1930s, it was discovered that galaxies are getting farther away from each other. 2 things needed to be measured: distances b/w galaxies. We can"t use parallax method (only inside milky way; local) Instead, we can find recognizable, familiar objects in a galaxy (e. g. stars or nebula) whose properties we already known.
