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MarymommyP

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Message 2278 - Posted: 15 Mar 2008, 19:12:47 UTC
Last modified: 15 Mar 2008, 19:13:16 UTC

How many stars are there in the Milkyway?
What are the dementions of the Milkyway?
How many Constillations are there in the Milkyway?
Question by Josh age 9
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Odysseus

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Message 2283 - Posted: 16 Mar 2008, 4:14:45 UTC - in response to Message 2278.  
Last modified: 16 Mar 2008, 4:15:50 UTC

How many stars are there in the Milkyway?
What are the dementions of the Milkyway?

The Galaxy contains about two hundred billion stars. It’s in the form of a disc, nearly a hundred thousand light-years across and a couple of thousand light-years thick, bulging in the middle. (A light-year is about ten trillion kilometres, or six trillion miles.) Here's a picture of what it might look like from a distance: The Milky Way Galaxy. There’s lots more information on that page, and links to other maps.

How many Constillations are there in the Milkyway?

All of the stars we can see are in the Milky Way Galaxy; most of them are comparatively very near to us. Astronomers have divided the sky into 88 official constellations. Many are based on traditional patterns from ancient Mesopotamia and Greece, but there are also recent additions to fill in gaps and to cover parts of the sky that couldn't be seen from those places.

The band of the Milky Way as seen encircling the sky is what the spiral arms look like from inside. The centre of the Galaxy is in the direction of Sagittarius. A Galactic Chart shows the other constellations that it passes through.
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MarymommyP

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Message 2569 - Posted: 23 Mar 2008, 20:10:49 UTC
Last modified: 23 Mar 2008, 20:11:54 UTC

Why are the constillation not connect to look like the name of the constillation? Such as Hercules?
How did the constillations get there names?
why are there characters in the stars?
All questions by Alexis Age 8
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vraa

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Message 2819 - Posted: 25 Mar 2008, 10:04:05 UTC
Last modified: 25 Mar 2008, 10:07:17 UTC

Constellations only reflect what society sees at the time, in a sense psychologically projecting itself onto the stars.

Remember different cultures call certain Constellations different things (in different languages too).

I would most positively get "Cosmos" by Carl Sagan (book or the tv series) for a kid who has even the smallest inkling of curiosity.

http://www.amazon.com/s/ref=nb_ss_gw/105-3878210-5376436?url=search-alias%3Daps&field-keywords=cosmos+carl+sagan&x=0&y=0

Also Hawking's "A Brief History of Time" is amazing as well.
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Emanuel

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Message 2923 - Posted: 31 Mar 2008, 19:52:58 UTC - in response to Message 2819.  

And perhaps for yourself, The Science of Discworld, by Terry Pratchett - he discusses the very questions your children are asking in a witty and easily accessible way :) Not that it's all about cosmology, mind you, it goes though loads of things.
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MarymommyP

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Message 2934 - Posted: 1 Apr 2008, 21:11:17 UTC

Thank you for all you smart suggestions. I will look into them. MarymommyP

Why are all the stars in the night sky different sizes?
Why do some stars twinkle and others don't?
Why is the galaxy so big?
Questions by Alexis age 8
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Odysseus

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Message 2936 - Posted: 2 Apr 2008, 2:25:58 UTC - in response to Message 2934.  
Last modified: 2 Apr 2008, 2:36:15 UTC

Why are all the stars in the night sky different sizes?

Good question! Theories of how stars form are still quite speculative. Areas of space where this is believed to be happening are known (the Great Orion Nebula, M42, for example, is one of the nearest), but they’re all very far away and the processes involved take millions of years, so it’s hard to tell just what’s going on. I believe this is quite an active area of research, as today’s giant telescopes are just beginning to see sufficient detail to investigate. I guess the size of a star is generally determined by conditions in the cloud of gas and dust in which it forms: the distribution of mass, how many stars have already been created in the region, shocks and flows created by supernovae, and so on.

Most of the stars we can see are bigger and brighter than the Sun, but on the other hand most of the stars in any given region of space are smaller and fainter—although there are a great many red dwarfs around, we can only see the nearest ones because they’re so dim (and even so we need to use telescopes; infra-red instruments are better at detecting these objects than optical ones are). The largest stars are thought to have very short lives, in astronomical terms, only a few million years, but they can be thousands of times brighter than the Sun and therefore visible for great distances. Medium-sized stars like the Sun last for billions of years, but small ones can be expected to keep burning much longer than the Universe has existed so far.

Why do some stars twinkle and others don't?

Twinkling (the technical term is “scintillation”) is caused by unsteadiness in the atmosphere. Since stars are far enough away to be effectively point-sources of light, it only takes a small deviation in the path of a ray to your eye for the image to be dispersed. It’s most evident near the horizon, because toward a low altitude you have to look through a lot more air than where your target is high overhead. If you look straight up and see twinkling stars, the air must be very turbulent; you might be near a source of heat that’s creating local currents. But low, bright stars are very often seen to twinkle—sometimes in multiple colours, as different wavelengths of starlight are refracted by varying amounts.

Why is the galaxy so big?

I don’t think anybody knows for sure. The question is similar to that of star sizes, but all on a much larger scale, with events unfolding even more slowly. Our Galaxy is one member of a cluster of galaxies of widely varying sizes—it’s one of the bigger ones—called the Local Group, which in turn is an outlying part of a super-cluster containing thousands of galaxies. It appears that the early universe was slightly uneven in consistency, and as it expanded the density variations developed into a froth-like pattern, with galaxies distributed in sheets and strands surrounding ‘bubbles’ of mostly empty space.

It is quite likely that part of the Galaxy’s bulk, especially that of the disc, came from smaller neighbours that it absorbed in the past. The Magellanic Clouds, two small nearby galaxies, seem to be undergoing such a process at the moment, trailing streamers of stars and gas as tidal forces gradually pull them apart. It’s thought by some that the formation of the spiral arms that characterize galaxies like the Milky Way can be promoted by collisions with other galaxies.
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MarymommyP

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Message 2996 - Posted: 4 Apr 2008, 3:38:00 UTC
Last modified: 4 Apr 2008, 3:54:09 UTC

Alexis says, Thank you for your answers. She was able to see the big dipper tonight. She was so excited.

Are all stars the same temperature?
Are there any cold stars?
All questions by Josh 9 years old.

What is the closest star after the sun?
Do you think any of the planets will become a star?
All questions by Bonnie 11 years old.

Do you ever think that people will every get farther than the moon?
If they can send space probes to other planet, why can't they send people?
question by Alexis 8 years old
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ProfileJayargh
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Message 3003 - Posted: 4 Apr 2008, 5:09:29 UTC - in response to Message 2996.  
Last modified: 4 Apr 2008, 5:55:52 UTC

Great Questions! I will try to answer:
Alexis says, Thank you for your answers. She was able to see the big dipper tonight. She was so excited.

Are all stars the same temperature?


no. the blue stars are the hottest,white then the yellow and the coldest are red.

Are there any cold stars?


Yes there are cold/dark stars because fusion is so low the light is invisible at great distances.Some think because of minor disturbances in the solar systems orbits currently unexplained that the sun has a dark twin.(theoretically possible.) Most stars are double stars.....stars that revolve around a common center.

All questions by Josh 9 years old.


What is the closest star after the sun?
Alpha centauri ...approx 4 light years away that is easily visible(I believe Barnards star is closer but very faint)
Do you think any of the planets will become a star?
No.Not even mighty Jupiter has the mass to ignite into a star.Stellar mass is critical in starting the fusion neccesary to become a star.
All questions by Bonnie 11 years old.


Do you ever think that people will every get farther than the moon?
Some of us think man already has in past civilizations or that we come from the stars...but in the future I think/hope so.

If they can send space probes to other planet, why can't they send people?
question by Alexis 8 years old

Its not a matter of can't through technology but a matter of cost...$$$.

Regards -Jeff :)
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Odysseus

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Message 3005 - Posted: 4 Apr 2008, 6:54:57 UTC - in response to Message 3003.  

Are there any cold stars?

Yes there are cold/dark stars because fusion is so low the light is invisible at great distances. […]

What’s “cold” for a star is still pretty hot as far as we are concerned. Consider the element on a stove: although it’s hottest when it’s on “high” and glowing red, when it’s on “medium” and quite dark you still wouldn’t want to touch it!

The coldest known ‘living’ stars are of the type called “brown dwarfs”: their temperatures range from about 750 K to 2200 K (825°F to 3400°F), and they cool as they age.

—What is the closest star after the sun?

Alpha centauri ...approx 4 light years away that is easily visible(I believe Barnards star is closer but very faint)

You must be thinking of Proxima Centauri (also called Alpha Centauri C or V645 Centauri). This faint star is a member of the Rigil Kent system, which comprises a pair of rather sunlike stars (you guessed it: Alpha Centauri A & B), 4.4 LY from here, and their red-dwarf companion, just a bit closer to us at 4.2 LY. Barnard’s Star (V2500 Ophiuchi), another red dwarf, is famous for having the greatest “proper motion” of any star, but it’s about 5.9 LY from here, making it only the fourth closest to the Sun.
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Emanuel

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Message 3046 - Posted: 6 Apr 2008, 15:59:10 UTC - in response to Message 3005.  

I'd like to add that '1 light year' means the distance that light can travel in a year. In a vacuum, this is 299792458 (about 300 million) meters per second, or 670616629.38 miles per hour. That means that, to get to the nearest star outside the solar system, it would take us 4.2 years -even if- we could travel at the speed of light. We can't even get close to that speed, but alternative methods of propulsion, such as fusion or anti-matter based, might just get us there within a lifetime. Of course, we'd have to wait another 4.2 years just to get a signal from them if they did make it :)
There are some exotic possibilities that have been proposed, such as generating a wormhole large enough to transport us, or somehow traveling through a pocket dimension in which the distance between earth and some distant point happens to be much smaller. But time (and the LHC, among other such projects) will have to tell if such theories have any basis in reality.
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Odysseus

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Message 3050 - Posted: 6 Apr 2008, 20:23:49 UTC - in response to Message 3046.  
Last modified: 6 Apr 2008, 20:24:44 UTC

I'd like to add that '1 light year' means the distance that light can travel in a year. In a vacuum, this is 299792458 (about 300 million) meters per second, or 670616629.38 miles per hour. […]

Where “this” refers to the speed of light, symbolized by c: multiplying the above figures by the number of seconds in a year gives the distance of 9.46 trillion kilometres, or 5.88 trillion miles, that I mentioned (less precisely) upthread.

Some appreciation of interstellar distances may be obtained by observing that our Moon averages about 1.5 light-seconds from Earth, the Sun 8.3 light-minutes, Neptune 4.2 light-hours, and the distant dwarf planet 90377 Sedna 7.2 light-days, while examples of bright stars include Alpha Centauri at 4.4 light-years, as mentioned above, Arcturus (Alpha Boötis) at 3.7 light-decades, Polaris (Alpha Ursae Minoris, the North Star) at 4.3 light-centuries, and Deneb (Alpha Cygni) at 3 light-millennia.
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