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Science and Astronomy Questions
neutronium76Date: Friday, 28.10.2011, 09:14 | Message # 1
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Hi. I just thought that plenty of us (myself at least) although fascinated by SE, have little/limited knowledge about facts and figures in real astronomy. So I am starting this thread with a couple of (probably stupid) questions and awaiting the answers from the pro's: cool

1. Why are there no stars with excotic colors like green, turqoise, violet? What is responsible for the color of a star? Is it impurities in its composition i.e the stars do not contain only hydrogen and helium (biproduct from the fusion process) but ()probably) contain other elements like iron, aluminium, sulphur etc.. or is it because of its size and/or mass/volume=density ratio?

2. How do we know the exact/approximate position of our sun in the galaxy? And of stars in the galaxy in general..

3. How do we measure distances of celestial objects? How do we know if a star, that appears to be close to another star in the sky, is in fact thousands of parsecs closer/farther away?

4. How do we detect free floating planets in between stars? It must be really really hard I guess wacko .

5. Why galaxies have such a huge variation in their shapes and sizes? What gives a galaxy its unique appearance? How do we know the shape/size of our galaxy? What laws govern the motion of stars, star clusters, nebulaes, free floating planets, dark matter etc.. inside the galaxy? What is non-newtonian physics and how is it related to newtonian and relativistic physics?

6. Are there any lonely stars, star clusters, planets, nebulaes outside galaxies and in between them? (I ve been wondering about this for years wacko )

7. Why is the universe sooo huge? Why are the distances in between objects sooo big? If distances were smaller than interstellar and maybe intergalactic travel would have been possible..

and many more that I leave for others to post (and answer wink )

Sorry if some questions are so childish and for my bad English sad

PS: it would be greatly appreciated if the answers were not just a link to an wikipedia article - Just an as simple as possible answer would be great plus a link to wikipedia or other source (NASA, ESA, space/astronomy related sites) for further in depth reading wink





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SpaceEngineerDate: Friday, 28.10.2011, 15:05 | Message # 2
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Quote (neutronium76)
1. Why are there no stars with excotic colors like green, turqoise, violet? What is responsible for the color of a star? Is it impurities in its composition i.e the stars do not contain only hydrogen and helium (biproduct from the fusion process) but ()probably) contain other elements like iron, aluminium, sulphur etc.. or is it because of its size and/or mass/volume=density ratio?


Stars consists 99% of hydrogen and helium in the form of plasma. Nearly all electrmagnrtic radiation is emitted by stars as thermal radiation. The color of the star is determined by thermal radiation spectrum and is close to black body color. The spectrum is formed by free-free radiation of huge ensemble of atoms moving with different velocities according to Maxwell–Boltzmann distribution. Some deviations in spectrum is caused by free-bound and bound-bound radiation (recombination radiation from ionized atoms and radiation from transitions between atomic levels) - it forms so-called spectrum lines, but its contribution in spectrum is negligible. For example, incandescent lamp emits thermal radiation from hot filament (continuous black body spectrum), while fluorescent or neon lamp emits bound-bound radiation of cool gas or luminophore (a line spectrum). Such line spectrum (generated from atoms) have greater contribution in cool stars (the hot stars have no atoms at all - they are so hot so all atoms are fully ionized). in addition cool stars have an absorption spectrum lines caused by relatively cool gas floating in their atmospheres. But only some brown dwarfs have noticeble color caused by line absorption or emission.

*





 
SpaceEngineerDate: Friday, 28.10.2011, 15:24 | Message # 3
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Quote (neutronium76)
2. How do we know the exact/approximate position of our sun in the galaxy? And of stars in the galaxy in general..


Quote (neutronium76)
3. How do we measure distances of celestial objects? How do we know if a star, that appears to be close to another star in the sky, is in fact thousands of parsecs closer/farther away?


We know not the Sun's position, but only the position of the galactic center relative to the Sun smile There are many methods of locating the galaxy center's position: Concentration of globular clusters at the center, moving of Sun relative to other stars, etc. The first measurment of distance to the galactic center was made by Harlow Shapley. He found globular clusters distribution, he measured distance to the clusters (using Cepheid variable method) and obtained 8 kpc or 25000 ly.

The positions of other stars are determined relative to the Sun. There are many methods, but all of them are quite approximate. The mist precise method is a parallax method, used by HIPPARCOS satellite to obtain precise positions of 120,000 stars. All other cataloged stars have very approximate distance values (like by spectroscopic parallax method). The next space mission GAIA will obtain very precise parallaxes of over 2 billion stars.

Read this article for more detail about cosmic distance measuring methods.



*





 
SpaceEngineerDate: Friday, 28.10.2011, 15:38 | Message # 4
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Quote (neutronium76)
5. Why galaxies have such a huge variation in their shapes and sizes? What gives a galaxy its unique appearance? How do we know the shape/size of our galaxy? What laws govern the motion of stars, star clusters, nebulaes, free floating planets, dark matter etc.. inside the galaxy? What is non-newtonian physics and how is it related to newtonian and relativistic physics?


All is determined by gravity. Take a powerful supercomputer, make a globular distribution of 200-300 billions particles, give them some random velocities, and run N-body simulation - you'll obtain an elliptical galaxy. If you give them velocities with some global rotation and add 1% of gas and dust, you obtain a spiral galaxy - a flat disk with density waves in the form of spirals. The appearance of a galaxy is determained not only by star distribution, but by the stars too. The gas and dust concentrates along the spiral arms, and star formation begun in dense gas clouds, resulting in new very bright blue stars born there - they make the spiral arms so sharp. If a galaxy is very small, it has no sharp spiral arms and star formation in random places make its appearance irregular - it is an irregular galaxy. Some galaxies may approach each other close enough to begin merging.

*





 
SpaceEngineerDate: Friday, 28.10.2011, 15:49 | Message # 5
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Quote (neutronium76)
6. Are there any lonely stars, star clusters, planets, nebulaes outside galaxies and in between them? (I ve been wondering about this for years )


Intergalactic globular clusters are already found. BTW, spherical dwarf galaxies are very similar to giant globular clusters - so maybe all globular clusters are ancient dwarf galaxies consumed by our galaxy (and other galaxies), that are prevented from full destruction because of its high density.

Intergalactic stars may form by ejection of a star in supernovae explosion in binary system or close approaching of a third star in a binary system. This processes gives a big velocity to a star, which allows it to fly away from the galaxy. Another process is a collision (merging) of galaxies - up to 50% of stars may be spreaded out in a huge expanding cloud of stars, but too dim to be observable by modern telescopes.

Intergalactic planets of course must exist too, formed by the same mechanism as intergalactic stars, but we have only one method to bind them - microsensing.

*





 
SpaceEngineerDate: Friday, 28.10.2011, 15:51 | Message # 6
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Quote (neutronium76)
7. Why is the universe sooo huge? Why are the distances in between objects sooo big? If distances were smaller than interstellar and maybe intergalactic travel would have been possible..


This is like the question "Why are atoms so small?" - This is more of a philosophical question, rather than an astronomical one:)

*





 
neutronium76Date: Friday, 28.10.2011, 17:26 | Message # 7
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Wow! Space Engineer you are a trully remarkable person! Now I have plenty of reading to do wacko ...




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RobbieDate: Friday, 28.10.2011, 17:59 | Message # 8
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rolleyes Trust SpaceEngineer to write a book on the OP questions. I saw this coming... I know how his mind works.... biggrin ..and he knows how I'm feeling about this post....and I haven't even read it yet!... but I will do so....eventually.... smile

pretty please, please tell me you used the grammar/spell checker on this occasion, yes?
only google to find typos =)





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neutronium76Date: Friday, 28.10.2011, 21:39 | Message # 9
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Quote
Trust SpaceEngineer to write a book on the OP questions. I saw this coming... I know how his mind works.... ..and he knows how I'm feeling about this post....and I haven't even read it yet!... but I will do so....eventually....


What is OP??





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RobbieDate: Saturday, 29.10.2011, 05:23 | Message # 10
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When used on a forum 'OP' is an abbreviation of 'opening post' or 'original poster.' The first post is the opening post.




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neutronium76Date: Saturday, 29.10.2011, 08:18 | Message # 11
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Oh allright thanks for the info - I am not good at acronyms and abbreviations - too many for my little brain %). I wish I had more RAM/ROM installed in my head wink .

So where can I find this book from Space Engineer?





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RobbieDate: Saturday, 29.10.2011, 08:30 | Message # 12
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Quote (neutronium76)
Oh allright thanks for the info - I am not good at acronyms and abbreviations - too many for my little brain %). I wish I had more RAM/ROM installed in my head.


I wish I had a neural networked brain too, plugged directly into Google. I don't trust my brain functions at time, it doesn't always access the right information when I need it most... biggrin

Quote (neutronium76)
So where can I find this book from Space Engineer?


That was my poor attempt at being ironic, smile basically I was stating that if anyone asks SpaceEngineer a set of questions, you can be sure to get many in-depth replies; hence the "book," so to speak smile





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neutronium76Date: Saturday, 29.10.2011, 09:12 | Message # 13
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Oups. And that was me with my autism - can't detect irony or sarcasm really biggrin . But I was not expecting answers only from space engineer. I didn't want to distract him from his creation wink - but it seems I did distact him sad . Ok so I set a rule to my FAQ: No answers from Space Engineer unless the answer from another poster is totally wrong and Space Engineer wants to correct it wink biggrin




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RobbieDate: Saturday, 29.10.2011, 11:22 | Message # 14
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hi again neutronium76, Your post is perfectly fine here. You haven't done anything wrong.... smile the fact that SpaceEngine replied makes your post even more valid to be here. And like you said, it's not just for SpaceEngineer to reply, any one can.

One thing I try to do as a moderator, is get people to use the new search function to find answers to existing questions first, because the new search engine is brillant compared to the old search engine. We can now actually find stuff that we want!

What I tend to do with newcomers is to point them to this thread here, then that way it helps to keep SpaceEngineer more focused on coding the engine, and of course I and others here will alway try our best to answer questions, if we can. smile

Anyway, I KNEW he was going to reply to this post... he loves talking about this kind of stuff...I wonder why? wink





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HardtsDate: Thursday, 17.11.2011, 00:47 | Message # 15
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This is the perfect thread for my boatload of astronomy and physics questions smile For now, I just have a few;

- Q1: Is there any place in the cosmos we know of where the temperature is lower than 0 K ?

- Q2: Is it possible to have liquid water below 0 C (excluding water current as a factor), and would atm. pressure have any say in this ?

- Q3: how would you calculate the terminal velocity of a spherical object (to simplify), given you have 'g' (gravity) and atmospheric pressure ? Can we (or is this perhaps the only option) ignore the makings of a given atmosphere (ie. procentage of different gasses) and just consider density as a multiplier to increasing friction? - How would we go about doing this calculation biggrin ?
Sorry for messyness of the question wink .





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Edited by Hardts - Thursday, 17.11.2011, 00:48
 
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