star count

[mr. piper]

has anyone else heard the analogy that for every grain of sand on every beach on earth there are a million stars in the universe? seems pretty fantastic to me, but what do i know? i heard P.Moore say that most of the "stars" that we can see are actually galaxies with lots of stars, and there are plenty of those. incidentally are stars only found in galaxies or are there stand alone stars?

[jake-the-peg]

Not only is it fantastic but plain wrong. There are many more

http://chandra.harvard.edu/resources/faq/astrophysics/astrophysics-21.html

[landie]

My response to a similar recent question. I'm not saying it's right, but theories are always evolving.

According to recent theories, the universe as we know it is a mere fragment of a much larger 'multiverse'. The theory helps to explain the big bang, which was caused when two of an unlimited number of energy fields collided. Within the Multiverse there are an infinite number of so called universes. I believe the 'M' theory has something to do with it, but the eleventh dimension confuses me, i'm ok with four.

[jake-the-peg]

I notice that I didn't give an answer to the question about whether there are stars outside of galaxies.

Most stars seen to be in galaxies or in globular clusters associated with them. There are collisions between galaxies and in these cases starts can be flung out of galaxies.

There may be stars that have never been part of galaxies but I think it's unlikely as if there is enough matter for a single star to form then you would expect there to be enough matter for many.

You'd also be unlikely to find an individual star at the sort of distances that we're talking about.

Still the universe is a strange place, we may yet see a supernova from an unexpected quarter.

[Clanad]

Ummm... not so fast...The number of stars in the universe is 400 billion x 130 billion, or about 50,000 billion billion. A billion billion. That's 1,000,000,000,000,000,000. So, grasp the concept of a billion billion, then think of 50 thousand of those. Easy!

OK... so far...What are the dimensions of an average, sandy beach on Earth?  A U.S. Coastal Geomorphologist has provided some estimates. Take 360,000 kilometres of coast (the total coastline of the world is about 1 million kilometres, of which about 36 percent is sandy), mix with an average beach width of 50 metres (high to low tide lines), and add a dash of average beach depth of 4 metres.

The diameters of sand grains range from about 0.1 to 2 millimetres. Let's adopt an average diameter of 0.5 millimetres for arguments sake. Lets stack them simply, one on top of another (not very likely in a beach I admit), so that 8000 fit into 1 cubic centimetre.  The total number of sand grains on our Earth's beachs is then 600 billion billion. But what about sand dunes and sand below the low tide mark. Gotcha covered... Let's  increase the initial estimate by a factor of 3. That produces a grand total of about 2000 billion billion grains of sand on Earth.

The stars win! The excess factor (the number of stars divided by the number of grains) of 50,000/2000 or 25 is greater than an order of magnitude... And this doesn't take into account the new galaxies being discovered regularly.

BTW, jake, stars can only coalesce within gas clouds which also produce galxies...

Finally, the multi-universe theory is produced only by using "imaginary square root numbers".  Hawkings says he really doesn't have much confidence in it now...

[jake-the-peg]

Wow Clannad I'm impressed with your beach-work.

I'd be a bit careful with the astronomical logic though, because stars form from dust clouds and so do galaxies does not imply that all stars must be in galaxies.

Take Globular clusters for example - these are groups of less than a million stars that tend to orbit galaxies. These can loose stars due to the small number of members. And if globular clusters can form with less than a million stars it stands to reason that smaller groups of stars could have formed  that did not have enough gravitational mass to form a cluster.

I would however agree that there is little or  no chance of finding individual population I stars

As for multi-universes I'm afraid if there is no prospect of an idea ever being testable ( and I think it falls into this camp ) then for me it becomes a matter of faith and I'll leave it to the church of theoretical physics 

[Clanad]

That's an interesting point Jake... You are entirely correct in that the stars inhabiting Globular Clusters are not actually in it's galaxy neighbor(s) but orbit the galactic center.  The most intriguing aspect is that they appear to have formed at nearly the same time and appear to be some of the oldest structures in the observable universe.... Thanks for that...