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gzhpcu
2009-Feb-10, 07:40 AM
Based on the following "guesstimates":

- average of 2 x 1011 stars per galaxy
- 5 x 1011 galaxies in universe

= 1023 stars in the universe

Any other guesses?


why don't the subscripts work??

antoniseb
2009-Feb-10, 08:06 AM
There was a serious article a couple years ago that estimated it at sixty-nine sextillion.

astromark
2009-Feb-10, 09:19 AM
I would advise you to direct an inquire to the ' SEARCH '... You should soon find all the information you are looking for.
Very recently a thread about the number of galaxies in the whole universe explored this subject and how the Hubble Ultra Deep Field helped form some of the answers.
The number of Stars in the universe is a question we can not answer with absolute certainty. We know of star forming regions where the birth of new stars is ongoing. We know of the high probability that some stars we see the light image of may not still be stars. The image we see is older than humanity. We can not count what we can not see. We can make a very good estimates, based on very good observations and information learned .. But to try to be so specific and say 23 billion to the 40th power.. is a nonsense. I have a recollection of some vague statment... ' There are more stars in the universe than sand grains on planet Earth.'
I would take the liberty to change that. There are more galaxies than sand grainuals... and then multiply be 300,000,000,000... Its pointless, meaningless, trivial. The number you seek is so very big. Very very big. Some might argue that with the expansion rate known. We can never know.

gzhpcu
2009-Feb-10, 11:48 AM
Antoniseb (or anyone else),
Do you have any idea why I can't get the exponets to work? Thanks

trinitree88
2009-Feb-10, 12:08 PM
Antoniseb (or anyone else),
Do you have any idea why I can't get the exponets to work? Thanks

gzhpcu. When you use the superscripts...sup...and subsrcipts, sub...the vB code must be on. For some reason, it is not always on days, though I find it on in the afternoon and evenings. You can rewrite using the edit function if you sign in later. pete

tusenfem
2009-Feb-10, 12:09 PM
gzhpcu I edited your message, now the subscripts are correct but there are no colours anymore. You did something weird with lots and lots of color command.

gzhpcu
2009-Feb-10, 12:27 PM
gzhpcu I edited your message, now the subscripts are correct but there are no colours anymore. You did something weird with lots and lots of color command.
Thanks, but I did not add any colors at all...:confused: When I wanted to edit the message, I saw really funny code...

WayneFrancis
2009-Feb-10, 01:11 PM
since I believe the universe could very well be infinite, flat and unbounded I'll put in the conservative estimation of

Argos
2009-Feb-10, 01:30 PM
I think gzhpcu is talking about the observable universe. Anything beyond the horizon has no meaning.

Swift
2009-Feb-10, 02:40 PM
Based on the following "guesstimates":

- average of 2 x 1011 stars per galaxy
- 5 x 1011 galaxies in universe

= 1023 stars in the universe

I hope we have 6.02 x 1023 stars in the Universe, because then we would have a mole of stars. :D

George
2009-Feb-10, 03:02 PM
We know of star forming regions where the birth of new stars is ongoing. We know of the high probability that some stars we see the light image of may not still be stars. Nice point. The more distance galaxies now have a net increase in the number of existing stars, which we can not yet observe.


I would take the liberty to change that. There are more galaxies than sand grainuals... Huh? Are you going for the whole enchilada and far beyond our observable universe?


I hope we have 6.02 x 1023 stars in the Universe, because then we would have a mole of stars. :D :) You only need very rougly a baker's dozen more than our observable number.

Jeff Root
2009-Feb-10, 03:09 PM
I suspect that there is no such thing as "the average number of stars
in a galaxy". Galaxies are all different sizes, with a size distribution that
may not be Gaussian. A large galaxy may be high mass or low. A galaxy
may have most of its mass in the form of stars, or most of it in the form
of gas and dust, or most of it in the form of dark matter.

A galaxy might have many of its stars eaten up by a supermassive
black hole, or it might not have a supermassive black hole at all. Some
galaxies may have many low-mass stars and few high-mass stars,
while others might have predominantly hi-mass stars.

These characteristics change over time.

How is "the visible Universe" defined? Is it a practical definition,
a theoretical definition, or an arbitrary definition?

-- Jeff, in Minneapolis

gzhpcu
2009-Feb-10, 03:19 PM
I suspect that there is no such thing as "the average number of stars
in a galaxy". Galaxies are all different sizes, with a size distribution that
may not be Gaussian. A large galaxy may be high mass or low. A galaxy
may have most of its mass in the form of stars, or most of it in the form
of gas and dust, or most of it in the form of dark matter.

A galaxy might have many of its stars eaten up by a supermassive
black hole, or it might not have a supermassive black hole at all. Some
galaxies may have many low-mass stars and few high-mass stars,
while others might have predominantly hi-mass stars.

These characteristics change over time.

How is "the visible Universe" defined? Is it a practical definition,
a theoretical definition, or an arbitrary definition?

-- Jeff, in Minneapolis
I know, that is why I termed it a "guesstime" hoping to get a ball park figure.
I would assume the visible Universe is everything within a range of 13.6 billion years...

Fiery Phoenix
2009-Feb-10, 03:30 PM
I agree with Jeff on this one. Things such as the number of stars in the Universe aren't exactly as simple as they sound. We can't see the outermost limits of the Universe. In fact, we're not even sure if the Universe is infinite or not. What we can see and observe is the visible Universe. So, if we do manage to accurately calculate the number of stars somehow, we won't have calculated the number of stars in the Universe as a whole; just our Universe - the visible one.

That being said, we could probably calculate the number of stars in spiral galaxies only (since, I imagine, they're the easiest to calculate), after estimating the number of spiral galaxies that we can see. And from there, we could perhaps estimate how many stars there are in the visible Universe. Whether by multiplying that number by another or otherwise.

Gigabyte
2009-Feb-10, 03:48 PM
Doesn't current theory say the number of stars is decreasing?

George
2009-Feb-10, 03:52 PM
IHow is "the visible Universe" defined? Is it a practical definition, a theoretical definition, or an arbitrary definition? The Hubble Ultra Deep Field would be the best measure of the observable no. of galaxies. The ~ 10,000 galaxies seen there extrapolates to about 130 billion observable galaxies.

Gigabyte
2009-Feb-10, 05:30 PM
This is a very good question! There are too many stars for scientists to actually count one-by-one, so other methods of estimating the total number of stars are used. We believe that there are on the order of 1021 stars in our Universe. If you write that number out, it looks like this: 1,000,000,000,000,000,000,000. This is a lot of stars!
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970115.html



The figure -- 7 followed by 22 zeros or, more accurately, 70 sextillion -- was calculated by a team of stargazers based at the Australian National University.
http://www.cnn.com/2003/TECH/space/07/22/stars.survey

Lets go to wikianswers then.


There is no exact answer known to this question. Astronomers have ways of estimating the number of stars in the universe. It seems to be commonly accepted in the astronomical community that there are about 70,000,000,000,000,000,000,000 (22 zeroes) or 70 sextillion stars.

Hmmm .... that's a lot of stars.

gzhpcu
2009-Feb-10, 05:49 PM
Lets go to wikianswers then.
Quote:
There is no exact answer known to this question. Astronomers have ways of estimating the number of stars in the universe. It seems to be commonly accepted in the astronomical community that there are about 70,000,000,000,000,000,000,000 (22 zeroes) or 70 sextillion stars.

So that's pretty close to my "guesstimate"...:)

mugaliens
2009-Feb-10, 06:01 PM
Any other guesses?

Four?


why don't the subscripts work??

You mean, these subscripts? Try not using the WYSIWYG editor and hand-input the brackets and codes manually.


There was a serious article a couple years ago that estimated it at sixty-nine sextillion.

Well! That's a good deal more than four... Looks to be about this many: 69,000,000,000,000,000,000,000.

astromark
2009-Feb-10, 06:23 PM
With the deepest respect; back in post 3.Most of this has been said. So the number of stars in the observable universe is greater than 69,000,000,000,000,000,000,000.
Lets not let the facts spoil a good story... If it took the Hubble Telescope a hundred hours to attain that light image of a tiny fraction of the sky. We understand to do the whole sky would take decades. and that counting galaxies is not counting stars. The best we can do is guess. I can live with that. We have no choice.

George
2009-Feb-10, 08:38 PM
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970115.html

That was given long before the HUDF imaging, which revealed a much more robust number of galaxies. Those questions are so old that it was back when the Sun was yellow (http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/990108a.html). ;)
The 125 billion plus number of galaxies is a solid starting number of galaxies. Guessing an average number of stars is a must, but I can't imagine anything less than 200 billion we we consider all the likely number of red and brown dwarfs that must be out there, so the 69 sexy number (hey, I just noticed that :hand:), ok, 70 sextillion number of stars seems like a nice guess.

Gigabyte
2009-Feb-10, 09:14 PM
I included an old answer, (which is still up), to point out how the estimates have changed. I'm quite sure our current estimate is just as accurate as the old one.

kzb
2009-Feb-11, 01:03 PM
<<The 125 billion plus number of galaxies is a solid starting number of galaxies. Guessing an average number of stars is a must, but I can't imagine anything less than 200 billion we we consider all the likely number of red and brown dwarfs that must be out there>>

I think 200 billion stars per galaxy is too high an estimate. That's one of the usual figures quoted for the Milky Way, which is far bigger than the median galaxy size. After all, in our local group of 35 galaxies, there is only one galaxy that may be bigger than the Milky Way, M31. The rest are smaller, most considerably smaller.

I'd make a complete guess that the figure to use is an order of magnitude less, giving "only" 7 sextillion.

Amber Robot
2009-Feb-11, 05:15 PM
why don't the subscripts work??

By the way, you were using superscripts, not subscripts. :whistle:

Gigabyte
2009-Feb-11, 05:30 PM
Doh!

gzhpcu
2009-Feb-11, 05:39 PM
By the way, you were using superscripts, not subscripts. :whistle:
Guess that explains it...:doh::)