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Ullsokk
2009-Aug-17, 06:34 AM
I stumbled across this picture on digg a while ago, and it just blew my mind. I have always been fairly interested in astronomy, and knew that the sun was a relatively small star, and that the universe is really really big.

But does anyone know where this picture comes from, and if it is accurate?

Here's the link:
http://img19.imageshack.us/img19/2706/spaceb.jpg

tusenfem
2009-Aug-17, 06:55 AM
Dear Ullsokk,

Welcome to BAUT, please take some time to read the rules of the board (http://www.bautforum.com/forum-rules-faqs-information/32864-rules-posting-board.html#post564845) (as you already violated one in the title of your thread, but I took it out).

Have fun here!


For the rest, I think the picture is correct. I have seen it before, but I don't know the origin of the pic. Most likely someone here on the board will know.

Jens
2009-Aug-17, 06:56 AM
Yes, it's accurate AFAIK. You can see an article about VY Canis Majoris (http://en.wikipedia.org/wiki/VY_Canis_Majoris) on Wikipedia.

AndreasJ
2009-Aug-17, 07:38 AM
the sun was a relatively small star

Remember, tho, that while the Sun is tiny compared to truly great stars, most stars are smaller still. By number, the Sun is in the top tenth of stars.

Frog march
2009-Aug-17, 08:28 AM
I wouldn't mind that as a poster.

astromark
2009-Aug-17, 09:06 AM
Are we that small ? YES.

Those size images are correct. But wait there's more, distances..

I like to use the speed of light when talking of this subject of relative size and distances., and no. I am not stealing your thread.

Compared to our sun the earth is tiny. Compared to the super massive but rare stars sol is small. Sol, our sun is actually larger than the average star.

The small distance to the sun from Earth is 150,000,000km or 93,000,000 miles. It takes light just 8.5 minutes to reach us from there.

The next closest star is Proxima Centarie and it is 4.2 light years away. That's four and a bit years at the speed of light.

Just this Milkyway Galaxy is hundreds of times that distance across ....

So when I see 'Are we that small ?' I get a little wound up... cos the answer is Oh ya, small.

and then I could drag into this the fact that humanity it is thought has not yet attained two million years of evolutionary development. The local Solar system is about four billion years old. That's a small fraction of that time line... and that's only part of this story.... 13.7 billion years ago..but that's another story.

Small, Yes. Very very small.

slang
2009-Aug-17, 09:39 AM
Hi Ullsokk. You should be able to find each of the listed stars in Wikipedia, and get an estimated size from there. It should be an easy exercise to get a piece of paper and draw lines of that length, to scale. Wiki may not be the most trustworthy reference for star data, but I think it will do to get a quick verification. Also, there are several videos on youtube that make similar comparisons. Unfortunately I don't have youtube access right now, but perhaps another member has one bookmarked.

matthewota
2009-Aug-17, 04:07 PM
Most stars are smaller and dimmer than the sun. The diagram shows unusually large stars.

JohnBStone
2009-Aug-18, 12:10 AM
It doesn't even begin to do it justice.

The youtube version of the Hubble discovery is here
http://www.youtube.com/watch?v=oAVjF_7ensg&feature=player_embedded.

I applaud these attempts to try and create glimpses of the Total Perspective Vortex (http://en.wikipedia.org/wiki/Technology_in_The_Hitchhiker%27s_Guide_to_the_Gala xy#Total_Perspective_Vortex).

novaderrik
2009-Aug-18, 12:34 AM
Are we that small ? YES.

Those size images are correct. But wait there's more, distances..

I like to use the speed of light when talking of this subject of relative size and distances., and no. I am not stealing your thread.

Compared to our sun the earth is tiny. Compared to the super massive but rare stars sol is small. Sol, our sun is actually larger than the average star.

The small distance to the sun from Earth is 150,000,000km or 93,000,000 miles. It takes light just 8.5 minutes to reach us from there.

The next closest star is Proxima Centarie and it is 4.2 light years away. That's four and a bit years at the speed of light.

Just this Milkyway Galaxy is hundreds of times that distance across ....

So when I see 'Are we that small ?' I get a little wound up... cos the answer is Oh ya, small.

and then I could drag into this the fact that humanity it is thought has not yet attained two million years of evolutionary development. The local Solar system is about four billion years old. That's a small fraction of that time line... and that's only part of this story.... 13.7 billion years ago..but that's another story.

Small, Yes. Very very small.

i think the galaxy is hundreds of thousands of times bigger than that distance..

neilzero
2009-Aug-18, 03:43 AM
I suppose there are a few stars that orbit our galaxy 210,000 light years from the center. but a considerably smaller radius is typically suggested for the radius of our galaxy. Can someone tell us the current main stream radius or diameter? Neil

Cougar
2009-Aug-18, 04:26 AM
I suppose there are a few stars that orbit our galaxy 210,000 light years from the center. but a considerably smaller radius is typically suggested for the radius of our galaxy. Can someone tell us the current main stream radius or diameter? Neil

Unless there's a new estimate, for quite a while the literature has had it as roughly 100,000 ly in diameter. That's the luminous disk (the edge of which I imagine would be a bit difficult to establish precisely). Judging from the orbital speed of gas beyond the disk, the galactic disk is apparently spinning inside a big snow globe (http://en.wikipedia.org/wiki/Snow_globe) of dark matter.

Caelus
2009-Aug-18, 04:26 AM
According to Wikipedia, 100,000 light years in diameter. Milky Way (http://en.wikipedia.org/wiki/Milky_Way)

WayneFrancis
2009-Aug-18, 06:22 AM
Hi Ullsokk. You should be able to find each of the listed stars in Wikipedia, and get an estimated size from there. It should be an easy exercise to get a piece of paper and draw lines of that length, to scale. Wiki may not be the most trustworthy reference for star data, but I think it will do to get a quick verification. Also, there are several videos on youtube that make similar comparisons. Unfortunately I don't have youtube access right now, but perhaps another member has one bookmarked.

Video Version (http://www.youtube.com/watch?v=Tfs1t-2rrOM)

astromark
2009-Aug-18, 07:27 AM
... A Hhemm... excuse me, When I said " Hundreds of times that distance." I was right. I did not say how many hundreds did I... So what fraction of 100,000 is 4.2 Ummm...?:) if you look at it again you will note that I was already concerned that I was derailing the thread... 'Ullsokk'.,In the OP did ask a question about our small sun. We have fixed that. That link to the U-tube film is good for this demonstration. Thanks WyneFrancis., I hope we have not frightened him away...:(

Amber Robot
2009-Aug-18, 12:48 PM
Something is wrong with the comparison of Betelgeuse and the Eta Carina nebula. If that comparison were true, we'd have some awesome HST images of the surface of Betelgeuse.

Caelus
2009-Aug-18, 08:43 PM
I think VV Cephei is wrong too... Wikipedia says A is 1600-1900 times the suns diameter and B is 10 times the suns diameter... and they look a lot closer in size than that in the picture...

mugaliens
2009-Aug-19, 05:36 AM
I suppose there are a few stars that orbit our galaxy 210,000 light years from the center. but a considerably smaller radius is typically suggested for the radius of our galaxy. Can someone tell us the current main stream radius or diameter? Neil

Are you looking for a radius wherein half the mass of our galaxy is inside the radius and half outside of it?

Frog march
2009-Aug-19, 08:42 AM
perhaps if r is the radius where there is equal mass inside and outside this circle, then the radius of that galaxy would be r*sqr(2), as that would be true for a uniform disk, I think.

astromark
2009-Aug-19, 10:11 AM
The question is not that complicated... Half the mater...NO. Neil just wants to know the size of the Galaxy. r = 100,000 ly or give or take a few.
Can you understand how hard that is to measure ?
Mark rolls out nine metres of metal tape..., and rolls it up again.:)

mugaliens
2009-Aug-19, 07:34 PM
The question is not that complicated... Half the mater...NO. Neil just wants to know the size of the Galaxy. r = 100,000 ly or give or take a few.
Can you understand how hard that is to measure ?

The reason I asked has to do with the fact that our galaxy has lurkers many times beyond the distance of the furthest Milky Way star.

Choosing a mean mass radius is a good way to ascertain the relative sizes of galaxies.

Cougar
2009-Aug-19, 08:03 PM
r = 100,000 ly or give or take a few.

2r = 100,000 ly

Wouldn't want you taking a trip and wondering why it took you twice as long to get there... :o

astromark
2009-Aug-19, 08:24 PM
Mark pulls out tape and recalibrates scale ; r = 50,000 ly...Oops. and thank you.
Hmm, so I'm going to need more fuel...

robross
2009-Aug-20, 09:20 AM
The reason I asked has to do with the fact that our galaxy has lurkers many times beyond the distance of the furthest Milky Way star.

Choosing a mean mass radius is a good way to ascertain the relative sizes of galaxies.

I suppose we could also determine the distance of the closest satellite galaxy to us, and then by definition, any straggling stars orbiting closer than this distance would then be considered part of our galaxy.

Rob

Jeff Root
2009-Aug-20, 08:49 PM
Hey! Cool!

The person who made that graphic took the image of the Earth and Moon
side-by-side from my web page: Earth and Moon to Scale (http://www.freemars.org/jeff/planets/Luna/Luna.htm)
They were moved very slightly farther apart, resized, and lightened, but
that's basically the image I put together. From photos that I swiped from
NASA, of course. Apollo 17 image of Earth and (IIRC) Apollo 16 image of
the Moon. I'm not satisfied with the Moon image. I want to do it over
with a different one, or modify the Apollo 16 photo more than I already
did to try to make it look full.

-- Jeff, in Minneapolis

Argos
2009-Aug-20, 09:18 PM
I suppose we could also determine the distance of the closest satellite galaxy to us, and then by definition, any straggling stars orbiting closer than this distance would then be considered part of our galaxy.


The Canis Major DG Federation (http://en.wikipedia.org/wiki/Canis_Major_Dwarf_Galaxy) might not like that. ;)