WhatsUP! --What is Red Shift?
One of the questions we always get at public star parties is, "How far away is that star?"
Those of us with a computer controlled scope just punch in a few codes and get the answer displayed on the hand controller screen. Yes I know it's CHEATING!-- but this does not bother me at all. Ha!
Real Astronomers on the other hand calculate stellar distances using several different methods: Parrallex, AU (Astronomical Unit), Type 1a Supernova luminance, and Red Shift. Today let's talk about Red Shift. You can Google the other calculation methods and learn how they are used to measure distance.
Definition:
Red Shift is proportional to distance using a Z parameter, and the amount of wavelenght (red or blue) Shift. Let's take a few minutes and try to explain that in simple terms.
A. The Universe is expanding-- so distant galaxies are moving AWAY from us and their light is shifted to the red end of the spectrum. If they were moving toward us it would be shifted toward the BLUE end of the spectrum. This is similar to the Doppler Effect which occurs as a moving object passes us --- the sound frequency changes-- or the WAVE-length of the sound changes -- it is compressed in the front and stretched out in the back. Light waves do the same thing.
B. An object coming towards us will have a blue shifted (compressed) wavelenght; while objects going away from us have RED (stretched out)) wavelenghts. The farther it is away the more RED SHIFTED the light--seems like the SPEED of expansion is increasing the further out into space that we look!
C. The most distant objects that we can observe are moving away from us at almost the speed of light! It is notable that our nearest galaxy neighbor Andromeda, is blue shifted -- as it is coming towards us for an eventual collision with our galaxy the Milky Way. Dark Energy-- or whatever the heck that force is that is pushing the galaxies away from us-- just cannot overcome the GRAVITY in the local group of galaxies nearby us. So the Local Group is still gravitationally attached to each other. Not so for far away galaxies!
D. The Z parameter is a measurement of how much the light has shifted -- here is a link that shows the math!!!
http://hyperphysics.phy-astr.gsu.edu/Hbase/astro/redshf.html#c2
F. Finally we note again "that distance is proportional to the amount of Red Shift". Since the Universe is expanding we see all distant galaxies as highly RED SHIFTED and moving away from us at great speeds!
I have posted a short video on NeighborsGo that discusses Red Shift using a COW and a Flying Saucer for examples. Take a few minutes and watch it.
http://www.neighborsgo.com/video/1329
The Universe is stranger than you can imagine! It's even stranger than Stephen King can imagine!
http://www.arachnoid.com/sky/redshift.html
Clear Skies !
TelescopeMan
