How many stars in the universe?

[teamamerica]

You can round it off to the nearest trillion zillion if you like. I mean in the known universe ofcourse. I realise we can't see the ends of it.

 

[qso1]

I don't think its ever been estimated on a Universal scale. Our galaxy has been estimated to contain from 100 to 400 billion stars. If there are billions of galaxies in the Universe, the scale of the problem becomes readily apparent. Any estimate would have such a large error percentage that it could only be considered a guess.<br /><br />And as you pointed out, the known Universe.<br /><br />I should also mention we really don't have the capability to individually see stars in galaxies beyond ours. That is until one goes nova or supernova in relativelly close galaxies. And even those are the lens flares resulting from the telescope optical limitations. We couldnt count them even if we wanted to.<br /><br />BTW, cool link. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[doubletruncation]

A small point: we actually can resolve individual stars in other galaxies without requiring them to go supernova or whatnot (not resolve their disks of course, but resolve them from other stars, or in other words distinguish the light due to an individual star in a galaxy from the light due to all the other stars in that galaxy). Of course this is only true for the brightest stars (ones like the sun get lost in the general sea of light from the galaxy), but this is how, for example, you're able to measure the apparent brightnesses of Cepheids in other galaxies to get the distance to those galaxies. <div class="Discussion_UserSignature"> </div>

 

[teamamerica]

So we'd need to take averages then. Assuming that Physics works in the same way acroos all of Space and Galaxies vary in size, couldn't we just work out an average composition for galaxies in General and mutiply it out.<br /><br />

 

[derekmcd]

5x10^22<br /><br />Just a guess. 125 billion galaxies x 400 billion avg. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[enigma10]

give or take 125 billion. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <em>"<font color="#333399">An organism at war with itself is a doomed organism." - Carl Sagan</font></em> </div>

 

[qso1]

I see what your saying. But when I look at an image of a galaxy from say, the HST. I see what appear to be individual stars but I sometimes wondered if thats just the lens flare from one or several bright stars. The distances are so immense and angular separations of individual stars so small except where stars are relatively far from each other as in on the edge of the galaxy. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[doubletruncation]

Those are stars, often in the galaxy. Supergiant stars are bright enough to dominate over 10s to 100s of thousands of sun-like stars, and they're rare enough to be pretty well spread out over the galaxy. There can be groups of Supergiants in OB associations, those can be tough to resolve (though Hubble can do it for some OB associations in galaxies like M33). In nearby galaxies you can see individual stars that are even fainter than supergiants, Cepheids for example are not supergiants and you can see them out to about 30 megaparsecs (the distance to andromeda is about 0.77 megaparsecs). It's also true though that in the bulge of a galaxy it's a lot harder to make out individual stars. I think one reason it might seem like you can't make out individual stars is that most portraits of galaxies that you see are actually either very low resolution or zoomed-out. The actual data is usually much higher resolution (e.g. often many images must be mosaiced to make the final portrait) and not usually as photogenic. You can actually see a zoomed-in version of a hubble image of M51 at: http://hubblesite.org/gallery/album/tours/tour-m51/ (I don't believe that even this is at full resolution though).<br /><br />Another zoomed-in image of a galaxy (M33), this time showing a movie of variable stars, is at:<br />http://www.cfa.harvard.edu/~jhartman/M33_Movies_new.html<br />the bottom of the two movies is at full-resolution. To see the context look at:<br />http://www.cfa.harvard.edu/~jhartman/M33_Movie.html<br /><br />Some of the stars are fore-ground stars, often the very brightest stars in an image are fore-ground stars, so if you see a star with diffraction spikes it's probably a fore-ground star.<br /><br />Re. the original poster's questi <div class="Discussion_UserSignature"> </div>

 

[dannyd]

The ineffable number of stars in the universe - the mystery of existence - these phenomena by themselves should bond all mankind to one another in the great enterprise of exploration and explication rather than the mundane religious and political horse&%$#@! that seems to be our sad inheritance. -dannyd.

 

[SpeedFreek]

The thread about abstract thought leads me to ask for the question to be qualified. <img src="/images/icons/wink.gif" /><br /><br />How many stars in the universe... when?<br /><br />In our observable universe since the beginning of time, but with their light reaching us right now (for as we observe further we see further back in time)?<br /><br />Stars that exist within our universe at this moment in time (but the light from them hasn't reached us yet)?<br /><br />Probably 2 very different answers. (And the second question gets even more complicated, the more you think about it!)<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[qso1]

Thanks, and thanks for those links. I sure would like to have seen the movies but I'm always operating stonehenge computers.<br /><br />But I saw enough from the M-51 image to see a lot more individual stars are imaged. The foreground stars I've been aware of and can usually tell one of those from stars actually in the galaxy being observed. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[nexium]

I think 5 times 10 22 is a reasonable estimate for the universe as we observe it now. That does not include compact stars, so the main sequence stars of the most distant galaxies are likely down by about 2% so 4.9 times 10 22 if you want to subtract the ones whose light is still arriving even though they are off main sequence. Likely there have been few new galaxies, the last 12 billion years, but some galaxies have resent new born stars so that brings us back to about 5 times 10 22 Perhaps 10 23 as the estimates have increased over the past century, so estimates are more likely to increase than decrease in the coming decade.<br />Nearly all the class m stars are still main sequence and more than 1/2 of the class k stars are still main sequence. As little as 1% of all stars are likely class O, B, A, F, and G. Neil

 

[qso1]

speedfreek:<br />How many stars in the universe... when?<br /><br />Me:<br />Nobody has anything even approaching an accurate count for stars in the Universe now, or in the past. There are simply too many. With billions of galaxies, each containing at least 200 billion stars, you get the picture.<br /><br />And as you pointed out, the further they are, the longer their light takes to reach us. Numerous stars we see today may already be long gone so they couldn't be accurately counted, nor could stars that exist but we are unable to see yet due to their light not yet reaching us.<br /><br />Don't forget numerous red dwarfs we cannot see. We can't see the vast majority of them in our own galaxy, much less in other galaxies. Although I assume they are included in stellar estimates. As "TeamAmerica" mentioned in the first post, "You can round it off to the nearest trillion zillion if you like". And that pretty well sums it up.<br /><br />speedfreek:<br />Probably 2 very different answers. (And the second question gets even more complicated, the more you think about it!)<br /><br />Me:<br />You betcha. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[flash_gordon]

Has anybody here ever heard of a search engine? No offence.<br /><br />References.<br /><br />Astrobio Q <i>Apr 25, 2004</i><br />The number of stars in the visible universe is estimated to be 70 sextillion, or 70,000,000,000,000,000,000,000 (seven followed by twenty-two zeros). <br /><br />ESA Space Science <i>23 February 2004</i><br />Something like 10 to the power of 22 to 10 to the power of 24 stars in the Universe.<br /><br />These estimates were made only two months apart but I liked the astrobio paragraphs describing what these sorts of numbers mean.<br /><br /><b>Such a vast population can be compared in a list of the very biggest numbers imaginable, with some terrestrial references borrowed from a combination of science and poetry: <br /><br /><br />*ten times more than the number of grains of sand on Earth <br />*eleven times the number of cups of water in all the Earth's oceans <br />*ten thousand times the number of wheat kernels that have ever been produced on Earth <br />*one hundred million times more than the number of ants in all the world <br />*one hundred million times the dollar value of all the market-priced assets in the world <br />*ten billion times the number of cells in a human being <br />*one hundred billion times the number of letters in the 14 million books in the Library of Congress</b><br /><br />I'm feeling very small.

 

[qso1]

Flash_Gordon:<br />Has anybody here ever heard of a search engine? No offence.<br /><br />Me:<br />Non taken. I use them when necessary. In this case, all your getting from a search engine is another educated guess. Nobody knows the actual number of stars in the Universe and probably never will.<br /><br />Look at two of your references and how different they are, one says 7 followed by 22 zeros, another says 10 followed by 22 zeros...sizeable difference. I can do that but chose not to. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[finaldeathh]

Well, thank god someone actually had the balls to put up some numbers even if it's estimated. I was a little bit tired of you people just saying that it's nothing more than an educated guess.<br /><br />Let me tell you, every decision you make is an educated guess. Who knows EXACTLY and 100% sure whether your decision would be right or wrong? No one. Does that mean you shouldn't make a decision? No.<br /><br />And guess what? All the facts, theories, etc are all educated guesses. We just think that they are true because we believe that they make sense but who really knows, right?<br /><br />So instead of lowly critizing Flash_Gordon for what he contributed to this thread and mainly the QUESTION asked, maybe you, qso1, should googling. It's fun. <img src="/images/icons/smile.gif" /><br /><br /><br /><br /><br />

 

[qso1]

Scuse me, but where did I actually criticize Flash_Gordon. I stated pretty much what you stated. Its all educated guessing when it comes to counting stars anyway. Seems to me when people rely 100% on googling, they are failing to make their own educated guesses. After all, the people who put up the sources we google are people too. If all I have to do is google, what do I have to contribute? And why should I if I'm going to get slammed for not googling?<br /><br />But since you only seem to give googled links credibility, well, least now you got them. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[MeteorWayne]

One point is that this is a slightly educated guess. Many other guesses are much closer.<br />This one is really a crapshoot since there's so many unknowns.<br />It could be 1 X 10^42, rather than 10^24.<br />We don't know for sure what we can't see yet <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vogon13]

Actually, there is just the one, but it gets around.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[codominium]

<blockquote><font class="small">In reply to:</font><hr /><p>In this case, all your getting from a search engine is another educated guess. Nobody knows the actual number of stars in the Universe and probably never will. <p><hr /></p></p></blockquote><br /><br />I believe an estimated guess was all the original post asked for. Rounded off to the nearest trillion zillion sounds like a very loose guesstimate. <br /><br />Thanks everyone for a highly entertaining discussion. I've often wondered about the numbers of stars in the visible universe but I've never seen it discussed before.<br /><br />By the way, how many zero's in a trillion zillion? I confess I have no idea how big either of those figures are but multiplying them would come up with something similarly astronomical mightn't it? Perhaps too wide a margin of error?

 

[codominium]

Never mind.<br /><br />Just looked up Zillion in Wiki. <br /><br />"The word zillion does not refer to any specific mathematical quantity. Like the words bazillion, jillion, and so on, the term zillion is sometimes used as a fictitious name for an indefinite large number."<br /><br />A Trillion is 1,000,000,000,000 <br /><br />Googling really is fun!<br /><br />Doesn't answer my question but it does... sort of.<br /><br />

 

[alokmohan]

Yes as big a number.

 

[qso1]

CoDOMINIUM:<br />I believe an estimated guess was all the original post asked for.<br /><br />Me:<br />Thats correct. The search engine remark was mine rather than vogon13s. I got slammed for not googling what I already knew the answer to. I'm not one of the smartest people here and thats just a handicap I gotta live with which causes me to sometimes make mistakes. More mistakes than most posters here.<br /><br />My mistake here was being perhaps too literal in my interpretation of what I thought was being asked.<br /><br />The poster who criticized me for not googling assumed I was criticizing Flash_Gordon. For Flash_Gordon, if I came across that way, I'm sorry for doing so, that was not my intent.<br /><br />As for googling. I do research into topics that have specific, known answers. Anyone who has seen some of my posts knows this. But if we have to google for every concievable question...whats the point of discussion? If I suddenly became successful at writing and something of mine were published and people googled and got my work as a reference, am I somehow smarter?<br /><br />finaldeathh:<br />Who knows EXACTLY and 100% sure whether your decision would be right or wrong?<br /><br />Me:<br />What finaldeathh says is true of course. But to a point. We may not know 100% what something might be. But there are cases where we are certain enough to make the decision making easier. An example, if the question were asked as to what the diameter of the moon was. We don't know 100%...but we do know say, 90%. Had that been the question, I'd have done my usual 3 source check and if the answers were close enough . I could easily state the answer if I know it. But in the question posed here, the answer is one we are unable to get or know last I checked (Pre google days). Therefore I didn't see a need to google it. Someone else did and thats fine, and thats just me. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[alokmohan]

Then lets reply like this in each galaxy there are hundreds of biiolons of star.There are same number of galaxies in the universe.

 

[qso1]

You got it. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>