Discovery triples number of stars in universe

Dec 01, 2010
Filtering out the light from brighter stars, astronomers detected the faint signature of small, dim red dwarf stars in nearby elliptical galaxies (right), and found these are much more numerous than in our own Milky Way (left). This finding suggests that the total number of stars in the universe could be up to three times higher than previously thought. Credit: Illustration by Yale University

Astronomers have discovered that small, dim stars known as red dwarfs are much more prolific than previously thought—so much so that the total number of stars in the universe is likely three times bigger than realized.

Because red dwarfs are relatively small and dim compared to stars like our Sun, astronomers hadn't been able to detect them in other than our own Milky Way and its nearest neighbors before now. As such, they did not know how much of the total stellar population of the universe is made up of red dwarfs.

Now astronomers have used powerful instruments on the Keck Observatory in Hawaii to detect the faint signature of red dwarfs in eight massive, relatively nearby galaxies called elliptical galaxies, which are located between about 50 million and 300 million light years away. They discovered that the red dwarfs, which are only between 10 and 20 percent as massive as the Sun, were much more bountiful than expected.

"No one knew how many of these stars there were," said Pieter van Dokkum, a Yale University astronomer who led the research, which is described in Nature's Dec.1 Advanced Online Publication. "Different theoretical models predicted a wide range of possibilities, so this answers a longstanding question about just how abundant these stars are."

The team discovered that there are about 20 times more red dwarfs in elliptical galaxies than in the Milky Way, said Charlie Conroy of the Harvard-Smithsonian Center for Astrophysics, who was also involved in the research.

"We usually assume other galaxies look like our own. But this suggests other conditions are possible in other galaxies," Conroy said. "So this discovery could have a major impact on our understanding of galaxy formation and evolution."

The biggest galaxies in the universe are elliptical galaxies like the one in this artist's conception. The largest of these hold over one trillion stars according to astronomical census takers, compared to 400 billion in our Milky Way. However, new research shows that elliptical galaxies actually hold five to ten times as many stars as previously believed. Credit: David A. Aguilar (CfA)

For instance, Conroy said, galaxies might contain less dark matter—a mysterious substance that has mass but cannot be directly observed—than previous measurements of their masses might have indicated. Instead, the abundant red dwarfs could contribute more mass than realized.

In addition to boosting the total number of stars in the universe, the discovery also increases the number of planets orbiting those stars, which in turn elevates the number of planets that might harbor life, van Dokkum said. In fact, a recently discovered exoplanet that astronomers believe could potentially support life orbits a star, called Gliese 581.

"There are possibly trillions of Earths orbiting these ," van Dokkum said, adding that the red dwarfs they discovered, which are typically more than 10 billion years old, have been around long enough for complex life to evolve. "It's one reason why people are interested in this type of star."

Explore further: Australian researchers pioneer a 'Google street view' of galaxies

More information: Citation: DOI: 10.1038/nature09578

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User comments : 30

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Simonsez
3.2 / 5 (10) Dec 01, 2010
Could this higher number of stars, previously unknown and unexpected, possibly account for some of the "missing" matter they are calling "dark"?
jscroft
4.3 / 5 (11) Dec 01, 2010
That's what the article says.

One wonders what ELSE may be unaccounted for. The possibility arises that exotic dark matter may no longer be required.
shavera
4.3 / 5 (3) Dec 01, 2010
I don't think it'd affect our galaxy's rotation rate (a signature of dark matter) as they found these stars to be more plentiful in other galaxies. However, maybe it's part of the weak gravitational lensing??
Skeptic_Heretic
4.8 / 5 (5) Dec 01, 2010
Could this higher number of stars, previously unknown and unexpected, possibly account for some of the "missing" matter they are calling "dark"?

Nope. There is a complex figuring process involved in determining the mass of a galaxy and the mass of the universe. Discovering that red dwarf stars are more common just puts a face to a quantity of matter we already knew of.
Raveon
2.3 / 5 (4) Dec 01, 2010
This won't account for all the missing matter by itself. It does point to the probable fact that we still aren't seeing all the red dwarf or brown dwarf stars. And who knows what else we aren't seeing yet, or what can't ever be seen. Maybe WIMPS and MACHOS will finally die as those theories should have right from the start, string theory will follow eventually too.
kshultz222_yahoo_com
1.7 / 5 (6) Dec 01, 2010
Raveon, I have always believed that dark matter wasn't real, and that we just need to admit that we just haven't "found" or accounted for all the ordinary matter yet. Some people are going to feel really foolish when the truth is known...A lot of senseless waste of careers, IMO.
eachus
5 / 5 (5) Dec 01, 2010
Even if this discovery increases the estimate of the amount of baryonic (regular) matter in the Universe it won't make a significant dent in the dark matter total. Besides, there is independent lensing data from dark matter that really is dark. ;-)

On the other hand, "dark" matter as large transparent (H2+He?) gas clouds surrounding galaxies might explain all of dark matter. How do you find out? Look for dimming of high-energy vs. low-energy UV from supernovas and quasars behind clouds of dark matter. Will this require a new generation of UV sensitive telescopes? Probably. Could be done from balloons, but satellites are better.
Tuxford
1.7 / 5 (9) Dec 01, 2010
Red dwarfs are just easier to detect. There will be even more brown dwarf stars. Both of which are now shown to fall along the stellar mass-luminosity relation, along with the gas giants of our solar system (best available data). Paul LaViolette has predicted this effect as well, and that these red and brown dwarfs are actually younger stars, slowly growing through nucleation, and generating their own heat through photon-blue shifting genic energy production within. There should be a large population of both types.

Although inconvenient for many preconceptions, his cosmogenic model fits more and more recent observations. Note: giant ellipticals are the final stage of galactic evolution in the LaViolette cosmology. Often daughter satellite galaxies born within the larger parent galaxy can be seen, such as in M31.
Bradfield
not rated yet Dec 01, 2010
So who's kidding who regarding the number of stars :

http://www.physor...ace.html

Obviously with the right astronomical tools to hand there is no enigma!

StarGazer2011
1 / 5 (2) Dec 01, 2010
Another source of missing matter in galaxies would be all the 'hot jupiters'. The original mass calculations were done in an era before the prevalence of planetary bodies were known. Back of envelope: (10^10 stars * 50% likelyhood of hot jupiter)/1000 (1 solar mass = 1000 jupiter mass) = 5* 10^7 (50,000,000) extra solar equivalent masses previously unaccounted for.
El_Nose
4.5 / 5 (4) Dec 01, 2010
@jscroft --

I read a different article on this that was linked through slashdot - you will have to find it for yourself -- but it basically stated that this find does a couple things

If ellipticals have three times the number of stars it might resolve the long standing issue that elliptical maodels demanded that those galaxies for some reason had more dark matter associated with them than spirals. By increasing the number of stars by a factor of 10 you create an enourmous amount of mass now in the galaxy and the models behave better ( we assumed 100 red dwarf per sun like star -- these finding push that to 1000:1 - elliptical were thought to hold 1 trillion stars - now its closer to 10 trilion ) - note no one has rereun the models yet for this new revalation but intuition moves in this direction

Also there is the issue that by increasing the red dwarfs you intristicly increa the number of planets/comet/dust/metoer/asteriod - that sort of thing
El_Nose
5 / 5 (2) Dec 01, 2010
also - this is an area where the Webb telescope will finally give a better indication of number of stars out there -- and may give is more info on if those are just really really cool hydrogen clouds out there inbetween galaxies -- the Webb will be an infrared telescope.

After this a UV/x-ray telescope might be a good investment heck a radio wave telescope might be decent in space

that website i mentioned in the earlier post is
http://blogs.disc...tripled/
StarGazer2011
1.7 / 5 (6) Dec 01, 2010
alos there is a problem with the WIMP model, since WIMPs only interact with normal baryonic matter through gravity, and not electromagnetically. All stars would be accreting dark matter mass, altering their life cycles. The only way out of this is some rather heroic assumptions (and convenient) assumptions about angular momentum of DM vs NM (and no explaination of the cause of DM having more angular momentum).
DM is looking more and more like a solution in search of a problem, or ptolmic epicycles. Bring on the Copernican revolution!
StarGazer2011
1.1 / 5 (12) Dec 01, 2010
lol .. maybe all the 'Dark Matter' researchers can team up with Climate 'scientists', Economists, Catholic Priests and other people who draw a living convincing people of unlikely things only 'not necessarily' (in a modal logic sense) falsified by the data!
yyz
5 / 5 (1) Dec 01, 2010
Actually there are a few assumptions used by van Dokkum et al that may impact the conclusions they draw. One is the assumption that dwarf stars seen in these eight galaxies may have a different composition than similar stars in our galaxy (although metallicity should be near solar as these galaxies are 'nearby', in the Virgo and Coma clusters).

Second, as van Dokkum has noted elsewhere, extrapolating from these eight galaxies to the rest of the universe may be fraught with problems and needs further verification. Also, several assumptions are made as to the correct IMFs (Initial Mass Function) to fit the data and these could be faulty assumptions.

These observations are by no means Dark Matter killers, as we have independent estimates of DM mass distribution through strong lensing studies.

A preprint is available here: http://arxiv.org/...92v1.pdf
PureOcelot
1 / 5 (2) Dec 01, 2010
Why does dark matter have to be "mysterious" or "non-baryonic" in any way? Why can't dark matter just be burnt out stars and their dead planets? Why can't dark matter also be gas or "dust" clouds of completely normal particles? In other words, why can't dark matter simply be "anything that doesn't produce light?" Who says that this sort of matter can't possibly account for the "unexpected gravitational effects" we see throughout galaxies?

I agree whole-heartedly with El_Nose in that
by increasing the red dwarfs you intrinsically increase the number of planets/comets/dust/meteors/asteroids
- And Kuiper Belt/Oort Cloud equivalents and WHO KNOWS what else...if every star has all these constituent parts and space is littered with dust and debris, who says that we still need "mysterious dark matter" to account for this "missing mass?"
yyz
5 / 5 (3) Dec 01, 2010
Additionally, astrophysicist Richard Ellis was quoted by Yahoo! News:

"[The papers] biggest weakness might be its assumption that the chemical composition of dwarf stars is the same in elliptical galaxies as in the Milky Way. That might be wrong, Ellis said. Even if it is, it would mean there are only five times more red dwarf stars in elliptical galaxies than scientists previously thought, instead of 10 or 20, van Dokkum said.”

Science News has a piece on this paper, with some further caveats on the ramifications of these observations: http://www.scienc...of_stars
Tuxford
1 / 5 (5) Dec 01, 2010
Larger galaxies have a larger core 'mother star', which nucleates new matter at a much faster rate, ejecting more new material in ever more frequent explosive outbursts (note Fermi bubbles), creating more new young stars, streaming radially outward in all directions (ellipticals). Thus, we see larger population of younger red dwarfs than expected in these older massive ellipticals. This is consistent with LaViolette's “SubQuantum Kinectics” cosmogenic model.

Sometimes the simplest explanation is the best explanation. Or, come up with some other far flung assumptions to explain the observations. I know my choice.
resinoth
1 / 5 (3) Dec 02, 2010
all looks tasty...
don't screw this up, humans...
irjsiq
1 / 5 (3) Dec 02, 2010
Regarding 'a tripling of Stars in the (Known) Universe . . .
and: 'What If' . . .
"We Wake-up tomorrow,
"And,We actually Wake-UP?"

What Other Wonders await?

Roy J Stewart,
Phoenix AZ
El_Nose
not rated yet Dec 02, 2010
if we missed this many red dwarfs imagine how many brown dwarfs we cannot see -- then factor in hot jupiters orbiting these ....

The Webb telescope will be awesome when it arrives

the more i think about it the more i think we should do a extremely low infrared and radio telescope and see what we can see -- what are the arguments against

--- (funny thought) they get the Webb up there, the shields unfold properly and they take the first pictures in the lowest infrared and the picture comes back totally red -- they assume its calibrated wrong -- work on it silently for a month -- then they figure out, there are actually so many stars out there that when you try to image the sky its totally red light fulfilling Olbers' paradox. --- that sir would be funny
El_Nose
not rated yet Dec 02, 2010
After thinking about the radio telescope in space - i am not sure it would be helpful -- the cosmic background radiation would probably saturate it and make the endeavour not much better than what we have on earth.

when thinking about the Webb -- well it would be cool to get a better idea about red dwarfs and possibly brown dwarfs -- but the better questions it could solve is if it can "see" any heat from inter galaxtic gases and get a handle on how much cooler matter is out there
Waterdog
1 / 5 (1) Dec 02, 2010
If looking far away is like looking back in time as they say, then why can't we track the development of a given galaxy from the past until the present by just looking at different distances? They have been giving off light continuously so theoretically if you look at a distance of say 2 billion light years you should be able to see the Milky Way's light that it emitted 2 billion years ago, right? I know we can't do this but the reason escapes me.
Shootist
1 / 5 (1) Dec 04, 2010
Why does dark matter have to be "mysterious" or "non-baryonic" in any way? Why can't dark matter just be burnt out stars and their dead planets? Why can't dark matter also be gas or "dust" clouds of completely normal particles? In other words, why can't dark matter simply be "anything that doesn't produce light?" Who says that this sort of matter can't possibly account for the "unexpected gravitational effects" we see throughout galaxies?


Do you want an answer?

http://www.centau...comments
lexington
not rated yet Dec 04, 2010
@ Waterdog we can't look at different distances unless we can travel those distances. All our telescopes are stuck near Earth. Even if they weren't we'd have to be able to outpace light.
SteveL
5 / 5 (2) Dec 05, 2010
Late in the game, but love the title of this article. As if those stars weren't already there.

I agree with eachus; This new data, once it goes mainstream is likely to change the ratios for baryonic matter, dark matter and dark energy, but not significantly.

On another note.. Someone who knows how - please update Wikipedia on their Dark Matter article. They are confusing us by calling it "Baryonic Dark Matter". My layman's understanding is that there are two forms of matter, baryonic (normal) and non-baryonic (dark). These two articles conflict:

http://en.wikiped...k_matter
http://map.gsfc.n...ter.html
SteveL
5 / 5 (1) Dec 06, 2010
Another source of missing matter in galaxies would be all the 'hot jupiters'. The original mass calculations were done in an era before the prevalence of planetary bodies were known. Back of envelope: (10^10 stars * 50% likelyhood of hot jupiter)/1000 (1 solar mass = 1000 jupiter mass) = 5* 10^7 (50,000,000) extra solar equivalent masses previously unaccounted for.


I really don't think adding 0.1% (using your ratio of 1000:1) to the mass of the universe by adding in new Jupiter-sized masses is going to provide any significant difference. Also, we really don't have much statistical certainty concerning a universal average mass for planets that are orbiting stars.
enter_name_here
not rated yet Dec 07, 2010
Pfffttt....
All this nonsense about dark matter - don't you guys realise the supposed 'missing' matter is accounted for in the crystal spheres?

But seriously it's hugely refreshing to see an intelligent, coherent thread for a change - as hard to find as Mr. Higgs' boson on most sites.
Modernmystic
1 / 5 (2) Dec 07, 2010
Interesting, but not that exciting to me anyway.

Red Dwarfs are not good places for smart aliens to grow up.
Decimatus
2 / 5 (1) Dec 13, 2010
What about stellar mass blackholes? In 13 billion years, who knows how many of these could be piling up in the dark spaces in between? Or dormant neutron stars. Combined with red dwarfs, brown dwarfs, hot jupiters, gas, random rocks, etc.

There could be a stellar mass blackhole within a lightyear or two and we probably wouldn't find it for decades.

There could be supermassive blackholes in intergalactic space for all we know, out there coasting along in the darkness.

Anyway, like many others, I believe that there is good reason to question the likelyhood of darkmatter. Maybe it exists, maybe not.

We just have to apply the facts as we find them.