how many star in galaxy?

[yama]

how many star in galaxy?

[helghast]

it depends which galaxy. but i would say that there is at least a trillion ( thats 1,000,000,000) in the universe.

[fantastical]

I once read a parable in an astronomy class I had in college. It went like this: Why is the night sky not bright? If time in the universe has fully surpassed, every single point in the heavens would radiate light from a star. Why? Because, according to astronomy ie astronomers, there are an indefinite number of stars in our universe. If enough time had passed, it would allow the light from every star to reach us (earth).

What does this mean? It means our universe is still expanding, still growing, because not all the light from all the stars has had enough time to reach us. Indeed, the night sky, theoretically, should be fully bright, brighter than the day.

[fantastical]

sorry yama, I have strayed from the original question, I'll do that at times, but don't you don't you just love tangents.

As for the Milky Way, the number of stars is like in the trillions. But the number is also indefinite. Stars are continuosly dying, ones being generated. How a new star is born, I'm not quite sure. The formation of gases must begin the process. Don't black holes suck in a lot of light, maybe gas too? Maybe they're a refinery for star production?

[trilobite]

Current estimates (from various sources) put the figure at around 100 billion in our galaxy, the 'Milky Way' .

Apparently, visible stars only make up 10% of the mass of our galaxy

 

I've heard the 'Night sky is not bright because the Universe is not old enough'  scenario too, chaotic1, I remeber trying to get my head round it the first time I heard it, but it seems quite logical now.

 

And lastly, where are bernardo's and my initial answers to this thread? Have they been removed? If so, why? - they were actually the correct (accepted) answer !! (plus or minus 42 or 43)

[jimmer]

i'm feeling a bit pedantic today so i''d firstly like to say that 1000 000 000 is a billion not a trillion (which i think is 1000 000 000 000 or one million million) acorrding to this site:

http://curious.astro.cornell.edu/question.php?number=31

there are an estimated 100 billion stars (100 000 000 000) in the milky way.

 

jim 

[fantastical]

Right - Milky Way stars in the billions, not trillions. Six zeros after a digit for millions, Nine zeros for billions, Twelve for trillions, Fifteen for quadrillions, and so on in increments of three.

[bernardo]

Ditto to trilobite's question.

 

The correct answer (which was the very first answer in this thread, i.e.the answer which I gave, and which was correct in the first place) is that the number of stars in an average-sized galaxy is approximately 100,000,000,000 (i.e. a hundred thousand million), and that there are approximately 100,000,000,000 galaxies in the universe.  Goodness knows why anybody thought that it was worthy of being banned.

 

Incidentally:

deamo is incorrect in saying that 1,000,000,000 is a trillion.  1,000,000,000 is a thousand million;

 

jimmer and chaotic1 are incorrect in saying that 1,000,000,000 is a billion.  A billion is 1,000,000,000,000.

 

As is suggested by the etymology,

a million is a million to the power of 1

a billion is a million to the power of 2

a trillion is a million to the power of 3

a quadrillion is a million to the power of 4

and so on.

 

[SpecialAgent]

A lot

[QmunkE]

One Billion is 1,000 million,

not 1 million squared (million to the power 2)

[QmunkE]

At least, that is now the currently accepted level. The old british value for billion was indeed one million squared.

[bernardo]

No, Qmunk, a billion is not 1,000 million (10^9).  A billion is a million million (10^12).  It is true that the Americans (and increasingly also large elements of the British media) refer to 1000 million as a "billion", but the whole point is that they do so incorrectly.

[QmunkE]

"Billion" is just a word. The meaning of the word can change. I'm fairly certain that if you use "billion" the vast majority of people will believe this to mean 1,000,000,000