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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Tue Jan 26, 2010 11:06 pm 
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If planets rotate and move along a specific axis could the mass of the planets matter not be sufficiently massive to effect gravity and cause the movement of a star? if i understand it correctly a sufficiently large amount of matter effects gravity then wouldnt black holes have enough pull to "suck" or pull the stars towards them. I cant remember where i read it but i remember something along the lines of how our galaxy was not originally part of the milky way but is a dwarf galaxy being consumed by the milky way so can galaxies also have an effect on the movement of stars? a whole lot or random thoughts sorry :doh:

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 1:01 am 
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Lovely stuff this ... it's moving into realms and dimensions I never even considered ...
Would love to hear others' opinions - it doesn't even have to make much sense to you ... as long as you think about the question and tell us what you believe to be the case.

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 7:34 am 
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What about the "Big Bang" Theory - Everything is supposed to be moving away from a central point - Expanding universe? Or is that just for planets or the Earth only?

:?

Really rambling here - At Hartebeesfontein they use radio telescopes which gives a colour picture? "Things coming closer are HOT and therefore the waves are RED picture and moving away - COLD and a BLUE colour?

:huh:

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 9:31 am 
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Thanks for that JJ! Just wondering ... weren't the objects moving away the red ones and the ones coming towards us the blue ones?

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 9:42 am 
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Wonderful ideas and response! Any last inputs from the beginners' club before I summarise and give a suitable answer!

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 9:51 am 
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Jungle Junkie wrote:
Really rambling here - At Hartebeesfontein they use radio telescopes which gives a colour picture? "Things coming closer are HOT and therefore the waves are RED picture and moving away - COLD and a BLUE colour?
:huh:


onewithnature wrote:
Thanks for that JJ! Just wondering ... weren't the objects moving away the red ones and the ones coming towards us the blue ones?


I also have it as when they are moving away they appear red and it's called the Redshift effect!?


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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 9:57 am 
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I am sure you are right, I just know they are different colours in different directions.

I'm no expert.. Just thinking as usual, and putting an idea forward. :hmz:

Okay ready for the answer OWN :D

PS Found this on the web - :D
a star whose motion in its orbit is taking it further from the earth is redshifted.
Conversely, a decrease in wavelength is called blue shift, and generally seen where the source has orbital motion toward the Earth.

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Last edited by Jungle Junkie on Wed Jan 27, 2010 10:11 am, edited 1 time in total.

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 5:08 pm 
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Jungle Junkie wrote:
I am sure you are right, I just know they are different colours in different directions.

I'm no expert.. Just thinking as usual, and putting an idea forward. :hmz:

Okay ready for the answer OWN :D [/b].


Fantastic: keep thinking and putting forward ideas, JJ ... :thumbs_up: :thumbs_up:

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 5:12 pm 
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Okay, because this is such an interesting topic, I'm going to invite some of the more advanced and advanced mites to post their thoughts here. Just to remind you of the question:

Are the stars stationary, or do they move?

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 5:16 pm 
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Move relative to what? :)

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 5:25 pm 
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joshilewis wrote:
Move relative to what? :)


THAT'S EXACTLY THE POINT, JOSHILEWIS! :wink: :wink:

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 5:30 pm 
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oddesy wrote:
looking forward to the synthesized answer OWN :thumbs_up: and thoroughly enjoying this quiz, i like the asking questions almost discussion type format :D


Glad you like it, Oddesy! To ensure that this quiz goes along in the direction that I would like it to, I will generally follow a process of practical star-gazing information, followed by periods where I will open up the floor for discussions like we're having now. It will not be all the time, but there will be a good mix of both practiacl stargazing and discussions to enhance the practical aspects.

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Wed Jan 27, 2010 9:06 pm 
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onewithnature wrote:
joshilewis wrote:
Move relative to what? :)


THAT'S EXACTLY THE POINT, JOSHILEWIS! :wink: :wink:


Yup, that's exactly the point. Everything is moving relative to everything else! :mrgreen:

Accordng to the Big Bang theory everything is moving outwards from a central point - thus all galaxies as a whole are moving away from one another. Within the galaxies, the galaxy itself is also spinning around a central point. Or is that only some galaxies? :doh: Been too long since I really read up on these things, can't remember it any more... :tongue: And of course the stars also spin - it is this spinning effect that helps/causes the birth of the star in the first place.

I've got an old Reader's Digest Atlas here (1964) that shows the difference in the Plough between what it is now, what is is thought to have been like 200,000 years ago, and what it is thought it will look like in 200,000 years. Of course the stars in many such constellations don't have anything to do with one another and may be millions of light years apart - we just see them in a grouping as we essentially see a sky in a single plane.

OWN, I do remember sorta correctly don't I? Or did I just type a load of Taurus? :huh:

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Thu Jan 28, 2010 10:00 am 
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Thanks for the invite OWN :lol:

Quote:
Are the stars stationary, or do they move?


The answers given so far have been excellent :thumbs_up: Simply put the stars move. Take our star (good old Sol) for example, we are in a spiral galaxy in which our star wonders around at a speed of roughly 200 km/s making one orbit every (number could be high or low here) 230 odd million years. So, stars rotate within their own galaxies, and believe it or not, there are some stars wondering between galaxies - ours potentially could be heading in that direction in a few billion years, give or take a couple of million :whistle: .

Ah ha, he says, but a little bit more movement occurs (I LIKE your question joshilewis :thumbs_up: ) In addition to the movement within our own galaxy, the galaxies themselves, as a whole, are in motion. For example, our galaxy (the Milky Way Galaxy) and the Andromeda Galaxy are moving towards each other and will likely merge in 4 to 6 billion years. So, the stars as a whole in a galaxy are in motion, not just orbitally within the galaxy but as the galaxy moves. The estimated velocities of this movement are in the region of 600km/s for our galaxy and about 110 km/s for the Andromeda galaxy. I say estimated because of the peculiarities of requiring a frame of reference for measuring velocity of which there really is'nt for galactic movement.

For all we know there may be multiple universes and these universes are moving around each other providing yet another motion.

So, as I said, simply put, stars do move but at such a slow rate that for all intents and purposes, as Siobain said, in our lifetime we could consider them stationary for observational purposes.

For further information there are two methods of "seeing" star motion – the movement along the plane of the sky called "proper motion" and the movement along our line of sight called "radial motion". Previously discussed was redshift / blueshift which is the change in wavelength of the object. This is the measurement of radial motion. Proper motion is measured by taking the movement of an object relative to another distant "fixed" object. (JJ's initial statement :thumbs up: ). The "fastest" moving object visible to us is Barnard's Star (4th nearest star to Earth) which moves at a relative speed of about 10 arcseconds per YEAR) (1 arcsecond is approximately 0.0003 degrees – therefore 10 arcseconds is approximately 0.003 degrees). That's NOT a lot of motion – how many years before it has moved 1 degree?! I think that most stellar objects have a proper motion in the region of 0.1 arcseconds per year, ie. 0.00003 degrees per year!

I may be off a little in the figures I've given but that's as close as I can remember them. :huh:

Sorry if I've gone further than you required OWN but it's a lovely topic :redface: :?

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 Post subject: Re: BEGINNERS' STARGAZING QUIZ (QM)
Unread postPosted: Thu Jan 28, 2010 10:38 am 
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Timepilot wrote:
Ah ha, he says, but a little bit more movement occurs (I LIKE your question joshilewis :thumbs_up: )

Thanks :)

Timepilot wrote:
I say estimated because of the peculiarities of requiring a frame of reference for measuring velocity of which there really is'nt for galactic movement.

Exactly, that's my point. The notion of 'movement' or 'velocity' is meaningless unless there's a fixed frame of reference. That's the point of Newtonian and Einsteinian physics (trying not to go overboard here).

Timepilot wrote:
So, as I said, simply put, stars do move but at such a slow rate that for all intents and purposes, as Siobain said, in our lifetime we could consider them stationary for observational purposes.

To paraphrase, these objects are moving very quickly (as Timepilot said on the order of 100km per second), but the distances involved (light years, parsecs etc) are so big that even this fast speed seems non-existent.

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