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Offline cuso4

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About the Milkyway...
« on: 21/04/2004 08:27:57 »
How come we can see the Milkyway using an astronomical telescope when the Earth is actually in the Milkyway?

Of course the 'Milkyway' I'm referring to is the galaxy and not the chocolate bar! ;)

Angel


 

Offline chris

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Re: About the Milkyway...
« Reply #1 on: 21/04/2004 10:16:16 »
I went camping in the Bush the other day. By night there is total blackout and the night sky looks incredible.

You can clearly see the Milky Way with the naked eye, no need for a telescope. It appears as a lightish band studded with brighter stars stretching across the sky.

The reason we can see it is because the Milky Way galaxy is planar. All of the stars and systems it contains lie on the same plane and so viewed from our perspective (on the edge of it) you see all of the stars stacked up on top of each other producing a lighter hue.

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Offline cuso4

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Re: About the Milkyway...
« Reply #2 on: 21/04/2004 12:53:21 »
Wow, seeing the Milky Way with the naked eye. It must be some amazing sight.

Thanks Chris for the explanation.


Angel
 

Offline chris

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Re: About the Milkyway...
« Reply #3 on: 21/04/2004 23:54:46 »
quote:
Originally posted by MayoFlyFarmer

You don't even have to be in that dark of a region to be able to see it, its pretty easy, as long as you're not standing in the middle of downtown tokyo or something.


Actually the light pollution in the UK is now so bad that the view of the night sky is heavily obscured. When I looked at the milky way from the bush last week I suddenly understood how early astronomers made their measurements - because everything was so easy to see. I also realised how beautiful the night sky really is and how much people back home are missing out...

Chris

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Offline roberth

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Re: About the Milkyway...
« Reply #4 on: 23/04/2004 01:33:57 »
Also, the southern hemisphere faces towards the centre of the milky way and the northern half points away from it. You can see many more stars from here than there.
 

Offline Ultima

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Re: About the Milkyway...
« Reply #5 on: 27/04/2004 17:31:26 »
If we were orbiting a star in the halo of the Milky Way could we see the whole galactic-plane at once (edge to edge) face on, with the spiral viewable, or would it just fill the sky? Though if we were in the halo we would most likely be made of dark matter ;) how would that effect our view?

wOw the world spins?
« Last Edit: 27/04/2004 17:36:07 by Ultima »
 

Offline tweener

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Re: About the Milkyway...
« Reply #6 on: 27/04/2004 18:53:24 »
It would depend on where in the halo we were, but overall the view would look pretty much like it does now.  The reason for this is that we are already most of the way out on one of the spiral arms and being farther out wouldn't add very many stars between us and the galactic center.  If we were far enough out in the halo, it would probably make the "milky way" strip in the sky narrower and probably dimmer because there would be more dust in the way, but I don't think it would be a huge difference.

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Offline tweener

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Re: About the Milkyway...
« Reply #7 on: 28/04/2004 03:12:40 »
quote:
Originally posted by cuso4

How come we can see the Milkyway using an astronomical telescope when the Earth is actually in the Milkyway?

Of course the 'Milkyway' I'm referring to is the galaxy and not the chocolate bar! ;)

Angel



Angel, I don't think anyone ever answered your question, so I'll give it a shot.

When you look at the "Milky Way" on a really dark night, like Chris is talking about in the Austrailian outback, you see what looks like a blotchy patch of light across the sky.  You are looking into the galaxy from a vantage point about 2/3 of the way out from the center.  What you are actually seeing are individual stars, but they are so many and so far away they look like an almost solid patch.  If you look the other way, you don't see this because there aren't very many stars between us and intergalactic space.

By the way, any individual star you see is definitely a member of the milky way galaxy, and rather close to us at that (by galactic standards anyway).  If you get a pair of binoculars or a small telescope, the Andromeda galaxy is spectacular, but you can't pick out individual stars - just a hazy disk with streaks.

On a really dark night or with binoculars or a telescope, you can even see dark patches in the milky way, which are dust clouds that obscure much of the center of the galaxy.  Here is a picture that shows this pretty well:

http://zebu.uoregon.edu/~imamura/209/mar31/milkyway.gif

So, in reality, you can't really see the galaxy for what it is.  Astronomers finally got a map of the galaxy in the 1950's and 60's with the advent of infra-red and radio astronomy that could see through the dust clouds.  What they did was build up a 3-D map of the density of stars and presto! it looked like a spiral galaxy.

I hope this helps.

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Offline gsmollin

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Re: About the Milkyway...
« Reply #8 on: 28/04/2004 03:40:40 »
Nice pic, tweener. I like the satellite multiple-exposing down the right side. It was good night for meteors too.
 

Offline tweener

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Re: About the Milkyway...
« Reply #9 on: 28/04/2004 04:18:05 »
I assumed the spots down the side were a plane with a blinking light.  A satellite would make a solid streak (I think).  And the meteor in the center is neat.  I don't know how long the exposure was, but I'd guess at least several minutes if not an hour or more.

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Offline Dan B

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Re: About the Milkyway...
« Reply #10 on: 29/04/2004 15:50:52 »
quote:
Originally posted by roberth

Also, the southern hemisphere faces towards the centre of the milky way and the northern half points away from it. You can see many more stars from here than there.



The Earth rotates. SagA* is at 19H-25deg.... It can be viewed in the northern hemisphere.
 

Offline gsmollin

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Re: About the Milkyway...
« Reply #11 on: 30/04/2004 02:00:41 »
quote:
Originally posted by tweener

I assumed the spots down the side were a plane with a blinking light.  A satellite would make a solid streak (I think).  And the meteor in the center is neat.  I don't know how long the exposure was, but I'd guess at least several minutes if not an hour or more.

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John - The Eternal Pessimist.



It doesn't look like a plane. The spots are caused by multiple exposures of ~ 1 sec each. This prevents star trails from forming. Then the exposures are stacked up and aligned with an astronomical photo program, integrated to reduce noise, and unsharp-masked.
 

Offline Radrook

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Re: About the Milkyway...
« Reply #12 on: 11/06/2004 11:57:01 »
quote:
Originally posted by cuso4

How come we can see the Milkyway using an astronomical telescope when the Earth is actually in the Milkyway?

Of course the 'Milkyway' I'm referring to is the galaxy and not the chocolate bar! ;)

Angel




You cannot see the Milky Way from an outsider's perspective.
What you have probably seen are artistic renditions of how the Milky Way would appear to us if we were to view it from a distance. Since we are limited to viewing it from the insider's perspective, and that view is often obstructed by clouds of dust,our galaxy's true shape remained a mystery for many years. It was only by gathering bits and pieces of observational data that the Milky Way's true form
eventually became known.




« Last Edit: 11/06/2004 11:59:17 by Radrook »
 

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Re: About the Milkyway...
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