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Author | Topic: How big is our Galaxy. | |||||||||||||||||||||||||||
jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
One step in determining some minimum age for our universe would be to find out how big our local neighborhood is.
Our solar system, the backyard, is only one yard in the neighborhood of our galaxy, so how big is the galaxy? Once we know the size of the neighborhood, the next question is "Where are we in relation to the center of the neighborhood?" Suggested for Bible A&I
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AdminWounded Inactive Member |
As it stands this seems to be a perfect candidate for the Big bang and Cosmology forum to me. If you feel this is particularly relevant to the Accuracy and inerrancy forum could you try and frame your OP with that in mind?
TTFN, AW
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
Nah,I can accept that.
Aslan is not a Tame Lion
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AdminWounded Inactive Member |
Thread moved here from the Proposed New Topics forum.
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
I know a song about this
Our galaxy itself contains 100 billion stars It's 100,000 light years side to side, It bulges in the middle, 16,000 light years thick But out by us it's just 3,000 light years wide Admittedly I'm not sure of the accuracy or derivation of these figures. *ABE* Here is a page addressing the accuracy of the 'Galaxy song'. TTFN, WK This message has been edited by Wounded King, 13-Jan-2006 05:17 PM
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Son Goku Inactive Member |
The Galaxy and the Local group are absolutely gigantic, is the easiest way of putting it.
For an analogy the distance between the Sun and pluto is about 3.6 billion miles. If we then say that this distance is equivalent to the width of a blood cell, the galaxy is the size of a 10 meter diameter disk and the local group a sphere of 1 kilometer in diameter. We are moderatly displaced to the bottom right of the local group if you were looking at the centre head on.
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Clark Inactive Member |
Where are we in relation to the center of the neighborhood? 26,000 light years away from the center of the galaxy. From today's Astronomy Picture of the Day: APOD: 2006 January 13 - Stars of the Galactic Center
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
And this is an image we can actually see?
Aslan is not a Tame Lion
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
Only if you can see in infrared.
TTFN, WK
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
Well, while we cannot see in infrared, we can detect in infrared.
How do we determine that the galactic center is 26,000 light years away? Aslan is not a Tame Lion
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Clark Inactive Member |
How do we determine that the galactic center is 26,000 light years away? I don't know. Geometry? This message has been edited by Clark, 01-13-2006 12:36 PM
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
I assume it is some sort of triangulation based upon our own relative motion compared to some reference objects and the galactic center.
Apparently som eearly estimates were base upon observing the motions of stars and using these observations to try and calculate their center of rotation.
Here we go, apparently efforts are in place to use 'Trigonometric Parallax' to measure the distance. TTFN, WK
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Matt P Member (Idle past 4805 days) Posts: 106 From: Tampa FL Joined: |
In the 1780s William Herschel observed all of the stars around our solar system and determined their distances. From this, he determined that we were at the center of the galaxy, as stellar density seemed to be homogeneous throughout the sky. Unfortunately, Herschel didn't realize that there was a large cloud of dark dust blocking our view of the center of the galaxy. Once infrared and radio astronomy became available, scientists in the 1960s penetrated this cloud and saw a slew of stars at the galactic center.
The distance to the galactic center was determined mostly by use of Cepheid variable stars, through the work of R.J.Trumpler:Cepheid variable - Wikipedia which are a "standard candle" for astronomy. To summarize this article, cepheid variables have a specific periodicity to their variance in luminosity, and by determining the period of a Cepheid variable, astronomers determine its suspected luminosity. Since luminosity correlates with distance, one can determine the distance to a Cepheid variable through this method. Trumpler used Cepheid variable stars to determine the distance to globular clusters surrounding the galaxy and saw that they weren't distributed in the pattern we would expect if we were at the center of the galaxy, but were consistent with being off the center. Later work with other wavelengths of life confirmed this.
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
Later work with other wavelengths of life confirmed this. I assume you mean light not life. So currently, how accurate would you say the 26,000 light year distance to the Galactic Center and 100,000 Light year diameter figure for the local Galaxy is? Aslan is not a Tame Lion
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Son Goku Inactive Member |
Very accurate. Its consistent across the whole structure, even when a shift is made to different methods for measuring distance.
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