Missing stars: Hubble observations cast further doubt on how globular clusters formed

November 20, 2014, ESA/Hubble Information Centre
This NASA/ESA Hubble Space Telescope image shows four globular clusters in the dwarf galaxy Fornax. Credit: NASA, ESA, S. Larsen (Radboud University, the Netherlands)

Thanks to the NASA/ESA Hubble Space Telescope, some of the most mysterious cosmic residents have just become even more puzzling. New observations of globular clusters in a small galaxy show they are very similar to those found in the Milky Way, and so must have formed in a similar way. One of the leading theories on how these clusters form predicts that globular clusters should only be found nestled in among large quantities of old stars. But these old stars, though rife in the Milky Way, are not present in this small galaxy, and so, the mystery deepens.

Globular clusters—large balls of stars that orbit the centres of galaxies, but can lie very far from them—remain one of the biggest cosmic mysteries. They were once thought to consist of a single population of stars that all formed together. However, research has since shown that many of the Milky Way's had far more complex formation histories and are made up of at least two distinct populations of stars.

Of these populations, around half the stars are a single generation of normal stars that were thought to form first, and the other half form a second generation of stars, which are polluted with different chemical elements. In particular, the polluted stars contain up to 50-100 times more nitrogen than the first generation of stars.

The proportion of polluted stars found in the Milky Way's globular clusters is much higher than astronomers expected, suggesting that a large chunk of the first generation star population is missing. A leading explanation for this is that the clusters once contained many more stars but a large fraction of the first generation stars were ejected from the cluster at some time in its past.

This explanation makes sense for globular clusters in the Milky Way, where the ejected stars could easily hide among the many similar, old stars in the vast halo, but the new observations, which look at this type of cluster in a much smaller galaxy, call this theory into question.

Astronomers used Hubble's Wide Field Camera 3 (WFC3) to observe four globular clusters in a small nearby galaxy known as the Fornax Dwarf Spheroidal galaxy.

"We knew that the Milky Way's clusters were more complex than was originally thought, and there are theories to explain why. But to really test our theories about how these clusters form we needed to know what happened in other environments," says Søren Larsen of Radboud University in Nijmegen, the Netherlands, lead author of the new paper. "Before now we didn't know whether globular clusters in smaller galaxies had multiple generations or not, but our observations show clearly that they do!"

The astronomers' detailed observations of the four Fornax clusters show that they also contain a second polluted population of stars [2] and indicate that not only did they form in a similar way to one another, their formation process is also similar to clusters in the Milky Way. Specifically, the astronomers used the Hubble observations to measure the amount of nitrogen in the cluster stars, and found that about half of the stars in each cluster are polluted at the same level that is seen in Milky Way's globular clusters.

This high proportion of polluted second generation stars means that the Fornax globular clusters' formation should be covered by the same theory as those in the Milky Way.

Based on the number of polluted stars in these clusters they would have to have been up to ten times more massive in the past, before kicking out huge numbers of their first generation stars and reducing to their current size. But, unlike the Milky Way, the galaxy that hosts these clusters doesn't have enough old stars to account for the huge number that were supposedly banished from the clusters.

"If these kicked-out stars were there, we would see them—but we don't!" explains Frank Grundahl of Aarhus University in Denmark, co-author on the paper. "Our leading formation theory just can't be right. There's nowhere that Fornax could have hidden these ejected , so it appears that the clusters couldn't have been so much larger in the past."

This finding means that a leading theory on how these mixed generation globular clusters formed cannot be correct and astronomers will have to think once more about how these mysterious objects, in the Milky Way and further afield, came to exist.

The new work is detailed in a paper published today, 20 November 2014, in The Astrophysical Journal.

Explore further: Hubble revisits a globular cluster's age

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movementiseternal
Nov 20, 2014
This comment has been removed by a moderator.
katesisco
1 / 5 (4) Nov 20, 2014
Exactly!
They did all form at the same time.
About this 'kicked out' theory: No
There is a black hole without a galaxy:http://finance.ya...dGlkAw--
I suspect that electromagnetism is so strongly intensified under certain circumcstances that the black hole reaches maximum containment and violates space/time. In other words it jumps thru space and time. That is not a wormhole.
Perhaps our galaxy was once the Magellenic galaxy whose black hole reached maximum overload and jumped, leaving scattered bits behind as the Greater and Lesser Magellenic Clouds.
It is worth considering that a pulse of energy washed over the the entire U or a local area and caused the bh jumps. If our planetary system is manupilated by alligmments, then is the U controlled by alignments also?
Tuxford
1 / 5 (4) Nov 20, 2014
Theories All Wrong. Merger maniacs still perplexed. Of coarse they are wrong, since globular clusters, like galaxies, grow from the inside out, with new matter generated largely from within the massive core star at their centers. Eventually, ejected from the galaxy, they grow large enough to spawn a new galaxy themselves, leading to further growth into galactic clusters in the very long term.

yyz
4.4 / 5 (7) Nov 20, 2014
"...globular clusters, like galaxies, grow from the inside out, with new matter generated largely from within the massive core star at their centers."

Hey Tux, tell where this mythological "massive core star" is located in these globular clusters:

Segue 1: http://www.fromqu...ue-1.jpg

Palomar 5: http://jumk.de/as...ar-5.jpg

Terzan 7: http://www.nasa.g...zan7.jpg

And can you locate the " massive core star" in the ring galaxy II Zw 28?: http://scitechdai...I-28.jpg

Remember, you claim it's at the center of these objects (while you provide ZERO evidence BTW).

When you're done guessing, I have thousands of other similar examples of globular clusters and galaxies for you to explain.
hemitite
not rated yet Nov 20, 2014
When one of these clusters first formed, they most likely contained a population of massive stars that would have exploded into supernovas in a few million years. What would be the effect of such massive explosions in the very crowded central regions of a globular cluster? Perhaps the gas and dust of these supernova remnants might interact with nearby stars (no, I don't know how) to form new "metalized" stars seen in the newer population.
theon
1 / 5 (2) Nov 21, 2014
It is known that globular clusters came from the Jeans mechanism. Next, let a viscous instability immediately have fragmented that gas in earth mass clumps. Pollute its gas, make stars by gluing the part of the clumps. Let pollution go on and make further stars, there you are.
The day will come when people take GHD (Gravitational Hydrodynamics, the name of this theory) seriously. It can't go on with these enormous (but long predicted) surprises raining in every day. Which ever is our pet theory, it has a duty: it can not only disfunction, it has to work. Forget this LCDM, go for GHD.
cantdrive85
2 / 5 (4) Nov 23, 2014
"Our leading formation theory just can't be right."

Occasionally astrophysicists do get something right, sadly it usually is the realization that they have miserably wrong hypotheses.

"Before now we didn't know whether globular clusters in smaller galaxies had multiple generations or not, but our observations show clearly that they do!"

This may very well be part of the problem. Rather than trying to fit more ad hoc, a posteriori explanations, maybe a trip back to the fundamentals of star formation and evolution would be justified. Sadly, astrophysics doesn't like science anymore, they prefer their pseudoscientific metaphysics to reality.
Captain Stumpy
3 / 5 (6) Nov 23, 2014
Sadly, astrophysics doesn't like science anymore, they prefer their pseudoscientific metaphysics to reality.
@cd
sorry, you have your electric universe confused with actual science again

plus, you've not given any reputable evidence for your claims
and links to your idiot eu sites is not reputable, nor science
it is PSEUDOSCIENCE

you continually denigrate modern astrophysicists but you forget that you are the one constantly being caught promoting pseudoscience and lies!

take your insistence on astrophysicists not knowing plasma physics
then you get SCHOOLED with a single link: http://arxiv.org/...92v1.pdf
(from here: http://phys.org/n...een.html )

that single paper proved you wrong on that as well as blatantly ignoring empirical evidence in front of you because you have Dunning-Kruger and assume that your engineers know all about astrophysics!

rather than trying to promote PSEUDOSCIENCE
try using real science
DeliriousNeuron
1 / 5 (4) Nov 24, 2014
Go jump off a bridge Stumpydick! Before you go, delete your profile.
Have a nice day!
DeliriousNeuron
1 / 5 (4) Nov 24, 2014
We don't take a likein to your mainstream kind Stumpydick!
And no its not peer reviewed...such a waste of time nowadays.
Long live the Electric Universe! Why? Because it pisses of so many people here and because its simply correct.
We don't need elegant/romantic theories to explain anything like the mainstream fanboys push down the publics throat.
Captain Stumpy
5 / 5 (3) Nov 25, 2014
We don't take a likein to your mainstream kind Stumpydick!
And no its not peer reviewed...such a waste of time nowadays.
Long live the Electric Universe! Why? Because it pisses of so many people here and because its simply correct.
We don't need elegant/romantic theories to explain anything like the mainstream fanboys push down the publics throat.
Hey GROUPIE
1- i dont care if you "likein"[sic] me
2- of course it is not peer reviewed... pseudoscience never is
3- it can't be "simply correct" of all you have is conjecture and no peer reviewed empirical evidence from reputable sources
that doesn't make it "simply correct", it makes it PSEUDOSCIENCE
4- and apparently you don't need empirical evidence, the ability to make predictions, constraints within the known laws of physics or anything else either...

why?
because it is a faith, not a science
eu has been publicly debunked over and over
thanks for admitting your sole purpose is TROLLING
as if it weren't obvious
imido
Nov 25, 2014
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