HOW MANY HALOS? A simulation of halo formation by the accretion of large numbers of galaxies.
Image: Bullock & Johnston (2005)
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It's well known that the Milky Way is a spiral galaxy, a swirl of stars in an extended, many-armed disk. But the structure of the galaxy is far from two-dimensional. Above and below those familiar spiral arms is a lesser-known feature, a spherical swarm of stars that makes up a halo around the disk.
For decades the presence of the halo has prodded astronomers to ask big questions about its nature: How is it structured? How do stars in the halo compare with disk stars such as our sun, or to stars elsewhere in the halo? And just how did the halo get there? In recent years a group of astronomers has suggested an answer to some of those big questions by drawing on a large telescopic survey of the sky.
The halo, they have concluded, is composed of at least two distinct populations of stars, with different chemical makeups and different orbits. One group of stars, dubbed the inner halo, generally orbits closer to the galactic center, and its members tend to contain more heavy elements such as iron than do stars farther out. (Halo stars as a whole are depleted in these heavy elements, relative to stars in the galactic disk.) Stars of the outer halo occupy somewhat wider orbits around the galactic center, contain lower levels of heavy elements, and—unlike the inner halo—tend to follow retrograde orbits, circling the Milky Way in a direction counter to the rotation of the galactic disk.
"We don't think it's just one halo," says Timothy Beers, an astronomer at the National Optical Astronomy Observatory and Michigan State University, who was lead author on a recent study in The Astrophysical Journal. Beers, Daniela Carollo of Macquarie University in Australia and their colleagues based their analysis on data from the Sloan Digital Sky Survey, a long-running telescopic campaign based at Apache Point Observatory in New Mexico. "We advocate the position that we are looking at a minimum of a dual halo," he says.
As the Milky Way built up by accretion of smaller galaxies, the inner and outer halo would represent two different epochs of galactic assembly. "We actually think that the formation scenario was something you could describe as a multiphase assembly," Beers says. The inner halo would represent the remnants of relatively massive dwarf galaxies, which coalesced early on. Lighter-weight galaxies would have attached themselves later on in a very gradual agglomeration to form the outer halo.
The inner and outer halo are not cleanly divided, but the differences in how the two populations move could aid astronomers in finding extremely primitive stars, which contain primarily hydrogen and helium. Those were the raw materials for the first generation of stars, early in the history of the universe; subsequent generations contained heavier elements that were fused in stellar cores and supernovae and then released into interstellar space. "Knowing that you have this dichotomy helps direct us to finding these interesting low-metallicity stars," Beers says. Outer-halo stars could be identified for detailed study by their distinctive motions on the sky. "Those are the ones that tell the story of how the universe built its elements," Beers says.
But not everyone agrees that the facts support the dual-halo interpretation. "I have a very relaxed opinion about single halos, dual halos, multiple halos," says astrophysicist Ralph Schönrich, a NASA Hubble Fellow at The Ohio State University. "I don't mind any idea of a dual halo. It's just that I don't see any evidence for it."
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Add CommentTorroidial Curve. the possitioning of the halos are an occurance the magnetic polarities distribution. Thus we have space fabrik. so time yes is distributed as we see it more slowly. yet the occurance is at a normal rate. also if one would look the curves also match the male an female aspects of life.☺☻
Reply | Report Abuse | Link to thisWhat this debate completely overlooks is that the distant Milky Way halo objects DO each effectively independently orbit the galaxy's distant, central principal mass (the galactic disk and core), just as described by Kepler's 'laws' of planetary motion.
Reply | Report Abuse | Link to thisNo 'dark matter' is necessary to explain their rotational velocities, as they diminish as a function of their radii from the galactic center of mass just as Kepler described.
This result contradicts the flat rotation curves discovered for objects within spiral galaxies' disks that seemed to require the presence of enormous dark matter halos containing 6-10 times the mass of the galaxies' visible matter!
If the rotational characteristics of spiral galaxy disks seems to require enormous dark matter halos while the rotational characteristics of ordinary halo objects seem to preclude the existence of dark matter, there must be an error in at least one of the respective analysis!
Actually, Newton proved in his 'Principia' that Kepler's equations included an error component for non-zero mass orbitals. Kepler's empirically derived equations provided reasonably useful approximations, peculiarly well suited to the Solar system, whose mass is dominated by the Sun (containing 99.86% of total system mass).
The mass of spiral galaxies is largely distributed throughout their spiral disks. As a result, the motions of individual stars within the disks (especially at the disk periphery) are determined far more by their gravitational interactions with neighboring masses than any collective center of mass.
It has been demonstrated that the rotational characteristics of spiral galaxies can be described using Newtonian dynamics and universal law of gravitation, without dark matter or modified gravity. Please see: Feng & Gallo, (2011), "Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies", http://www.raa-journal.org/raa/index.php/raa/article/view/858
While the self-gravitating disks of spiral galaxies do not behave as planetary orbital systems, more distant objects at the galactic periphery do independently orbit the Milky Way 'just like planets in the Solar system'. This observation conflicts with the presence of an enormous dark matter halo containing most of the galaxy's mass. Please also see: Bratek et al, (2011), "Keplerian Ensemble Approximation. The issue of motions of Galactic halo compact objects", http://arxiv.org/abs/1108.1629
Please see a brief commentary with additional references: http://sciencewithoutfiction.com/uploads/JDwyer.PDF
You're so off-base it's pathetic. Newton is so over, anyway. Why bother quoting a has-been?
Reply | Report Abuse | Link to thisIt's obvious that these halos are being pushed out by excess heat generated by millions of planetary intelligences burning up their fossil fuels.
Tool-using intelligence is a galactic infection which needs to be stopped.
Right-wing Republican extremists must exist on many planets other than our own, and it's their use of tools which is causing the apparent warming of millions of planets - which in turn are the reason for galactic halo formation.
Reply | Report Abuse | Link to thisTo you, InquiryingIdiot, SaltnotPepper and Lunges I am sorry National Lampoon is no longer there for your wit. But I suggest this dog is in your hands, if you don't take two minutes and go to the real authority of all knonsense and pay homage to this page http://en.wikipedia.org/wiki/National_Lampoon_%28magazine%29 Remember The dogs life is in your hands.
Reply | Report Abuse | Link to thisOur you saying our galaxy has breast. No wonder it is called the milky way.. :)
Reply | Report Abuse | Link to thisCould we please stick to scientific comments and speculation? Political (and religious) commentary, except when some scientist asks innocently why GW deniers exist, is really out of place in these forums. The vast majority of you, when opening your mouth through your finger tips, only expose your ignorance and superstitution.
Reply | Report Abuse | Link to thisThe only reason my comment is not scientific is that I don't have enough facts to have an opinion; although the halo looks to me like something and would occur naturally in a spinning structure which contains a sufficient amount of star dust and other loose pieces.
Should read "...like something that would occur..."
Reply | Report Abuse | Link to thisFirst of all to Nagnostic, you saved the dog. Thank you. Grumpyoleman, thank you. I had been responding to several articles in a very serious tone using what science I do know and while I am not a PHD or anything but a self taught curious being that loves particle, quantum and some of where string theory is trying to go, I was shot down for missing what was being posted as gags by the voices above my comments.
Reply | Report Abuse | Link to thisI have been trying to get people to pay attention to some real science here on earth that would free us of our energy needs if funded but what I usually see is the crap/humor that preceeded my comments.
If you want to tickle your brain with some real science check out the following articles referenced in these links. http://www.scientificamerican.com/article.cfm?id=hydrogen-production-comes-natu&posted=1 It is something discovered in 1993 and deals with a Cyanobacterium that poops H2 and O2 prolifically. If you put the two together you get H2O and energy. It feeds on Chlorophyll (easily attainable) and has about a 3,000 to one return rate. It is sustainable which had been an early issue and will probably get reburied again until we are totally out of oil.
Another interesting discover was several years ago when a student/scientist at MIT discovered she could custom tip viruses to create anything that you can imagine,such as a computer the size and depth of a piece of paper maybe. DARPA is currently experimenting with flexible batteries for the service but that is the least of the possibilities and again this story got even harder to relocate. But you can start with http://web.mit.edu/newsoffice/2006/sciam-belcher.html and http://www.scientificamerican.com/article.cfm?id=angela-belcher-building-t .
Additionally two Nobel Prizes were awarded for work in Graphine which besides being an easy building block for nanotubes also has some interesting quantum effects that include tunneling 100% of the time. I have been preaching Carbon use instead of abuse for years to empty ears yet the science keeps proving me right. Recently diamonds (which by the way are now able to be grown from a seed in a heavy carbon gas environment) were shown to have entanglement features (HUGE) http://www.nature.com/news/entangled-diamonds-vibrate-together-1.9532 . Not to mention carbon composites etc.. but we continue to burn the stuff at our own danger.
If you want to read my take on Carbon here is my piece I wrote several years ago. http://peace-happy-n-alive.blogspot.com/2010/04/carbon-wearing-white-hat.html .
Reply | Report Abuse | Link to thisTo answer one last thing. Regarding our universe my take is that the whole universe may be alive and I am in good company with this (Freeman Dyson and to some degree Lee Smolin) and based on the large maps I have seen it appears to look like the inside of a cell with the galaxies acting something like atoms but much slower (only because of our perspective (we are tiny)). I loved Benoit Manderbolt and his view of Fractals and after studying the folly of infinity came up with a picture of a multiverse that I think is fractal shaped and Escher space bound. But that is my humble opinion.
To ALL - The MOST IDIOTIC comments EVER!!! Get lives!
Reply | Report Abuse | Link to thisPeterT
PeterT Whatever the T stands for. I am an old man with little time left and kind of enjoy some of the rift raft. But since you entered the conversation what more than a lecture that is the LAMEST LECTURE ever given what do you have to add to the story. Or are you in lack of said life also. As I breathe on my leash of O2 I will await your input, surely it will astound the idiots you so classify as ALL. And maybe the dog is in trouble again.
Reply | Report Abuse | Link to thisIf you have nothing positive to say, did not your mother tell you to keep your fingers off the keyboard. So in support of all of us IDIOTS put up or shut up. I look forward to your response and your deep knowledge of the universe. I would hope that it is something I can take to the grave or at least gravy.
To the rest of you fellow IDIOTS keep having fun life is short. Sometimes even in your fun there is wisdom, which is better than shouting from a soap box while adding nothing to the conversation.
PeterT good day Sir, good Day....
Clues to the formation of galaxies and of stars would be easier to perceive with the knowledge of some fundamentals, as given in: http://www.sittampalam.net/StarFormation.htm.
Reply | Report Abuse | Link to thisIn our universe of fractals, galaxies and stars form by fragmentation and nuclear fissure(increasing entropy) and NOT by agglomeration and nuclear fusion (decreasing entropy); and entropy is conserved in our universe. Get the whole picture with: http://www.sittampalam.net/TheCosmos.htm and http://www.sittampalam.net/TheGalaxy.htm.
"For decades the presence of the halo has prodded astronomers to ask big questions about its nature: How is it structured? How do stars in the halo compare with disk stars such as our sun, or to stars elsewhere in the halo? And just how did the halo get there?"
In what will become the standard model for cosmology. all such questions will also become readily answerable, simply and classical mechanically. For instance (in our fractal universe), the answers as to how the galactic halo is structured and how it got there are similar to those for the the solar halo, or heliosphere: The final decay of neutrons (from the central fission reactor) dominate the outermost fringes as also a buffer in intergalactic/interstellar space. There will thus be an enormous outward wind from the halo (see: http://www.sittampalam.net/TheSuperwind.htm ), the backpressure from which will keep even high-speed halo stars/orbital matter penned in (without the need for recourse to any mystical 'dark matter' for the corral).
"Stars of the outer halo occupy somewhat wider orbits around the galactic center, contain lower levels of heavy elements, and—unlike the inner halo—tend to follow retrograde orbits, circling the Milky Way in a direction counter to the rotation of the galactic disk"
In the highly rarefied regions of the outer halo, fission is enhanced, making stars to appear older (and depleted in heavy elements)than any of their siblings closer to the high-pressure central regions. All ejections from the galactic core are in retrograde orbit (to conserve angular momentum of the entire galaxy; eventually, the outermost ejecta (evolved now into stars) tend to lose kinetic energy and fall back, retracing their trajectories in the spiral arm, and back into the galactic hub, where the very old and the very new stars would seem to coexist).
Good exercise to answer all such questions (and many more) yourselves with the correct model now in hand. Good luck, and Cheers!
Eugene, you have some interesting ideals and I am happy to read your papers and go through your material. But we are still learning and I am not ready to throw nuclear fusion out the window. It may disrupt how the Thermal Nuclear Reactions occur. Granted they are initiated by a fissionable source but it is the bonding of Hydrogen into Helium and the release of energy that makes the boom bigger. Also to the best of all the science I have read the sun is taking Hydrogen and creating Helium which eventually turns to Oxygen or Carbon and when it gets to Iron the process breaks down and then size matters.
Reply | Report Abuse | Link to thisBut I will be happy to read your papers. You are recognized as someone who has submitted and you remind me of Hoyle with the steady state theory. More after I read your stuff. Thanks for the contribution, but you should make sure to credit that it is your point not an outside source making the claims.
I try explain issues with the research that originally established the perceived requirement for dark matter to explain observed rotation curves of spiral galaxies in their own context.
Reply | Report Abuse | Link to thisMore 'modern' readers might prefer a discussion of these same issues in the context of general relativity. Please see: J. D. Carrick and F. I. Cooperstock, (2010), "General relativistic dynamics applied to the rotation curves of galaxies", http://arxiv.org/abs/1108.1629
David, thanks for your kind response and for the advice, too. Glad also to take note of your interest in my work.
Reply | Report Abuse | Link to thisI reckon you nave already visited my 'Cosmos' and 'Galaxy' web pages give above (links therein open best with Internet Explorer).
Re the fusion of H nuclei to produce He, and then go onto C and O, Sir Fred Hoyle’s down-to-earth argument in this vibrational world is well worth for anyone to consider deeply, in this short clip: http://www.youtube.com/watch?v=nDBw-0bqzB4&feature=related.
Finally, my paper to Nature Physics (submitted, though unsuccessfully; no surprise at all!)may help you further toward that real world which should be empirical physics, the bedrock of science: http://www.sittampalam.net/NaturePreprint.pdf
Best regards, and Cheers!
I am a Freeman Dyson fan which default makes me a Feynman fan which indirectly makes me a Lee Smolin fan. I have especially enjoyed Dyson and Smolin books I have read and love the concepts put forth on quantum loop gravity. I also loved Benoit Manderbolt's work on Fractals and I think in the end he will be the most underestimated of the group.
Reply | Report Abuse | Link to thisOne part of entropy I have issue with is the self organization of life and evolution. It tends to use chaos and attractors to create order which is what made me a lover of fractals. Hoyle was a very smart man but when Hubble discovered the expansion of the universe and the COBE pictures came back it was hard to say that big bang was not a good solution.
I am intrigue by the implications of dark energy and perhaps that may become Hoyle's last laugh on steady state. I think we may be inside an event horizon and the illusion of dark energy is really the effect of where we are viewing. But that is just conjecture based on the description of the future evolution of the universe from the effects of dark energy.
Correction: the link provided to "General relativistic dynamics applied to the rotation curves of galaxies" was incorrect. The correct link is:
Reply | Report Abuse | Link to thishttp://arxiv.org/abs/1101.3224