

All Disk Galaxies Rotate Once Every Billion Years (astronomy.com) 89
According to a new study published in The Monthly Notices of the Royal Astronomical Society, astronomers discovered that all disk galaxies rotate about once every billion years, no matter their size or mass. Astronomy Magazine reports: To carry out the study, the researchers measured the radial velocities of neutral hydrogen in the outer disks of a plethora of galaxies -- ranging from small dwarf irregulars to massive spirals. These galaxies differed in both size and rotational velocity by up to a factor of 30. With these radial velocity measurements, the researchers were able to calculate the rotational period of their sample galaxies, which led them to conclude that the outer rims of all disk galaxies take roughly a billion years to complete one rotation. However, the researchers note that further research is required to confirm the clock-like spin rate is a universal trait of disk galaxies and not just a result of selection bias. Based on theoretical models, the researchers also expected to find only sparse populations of young stars and interstellar gas on the outskirts of these galaxies. But instead, they discovered a significant population of much older stars mingling with the young stars and gas.
Odd. (Score:1)
That's interesting.
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Mice devs left the debug setting of galacticRotationPeriodInYears = 1000000000 on during the final build.
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But Wait! I just disproved that in 30 seconds of googling:
about 230 million years Yes, the Sun - in fact, our whole solar system - orbits around the center of the Milky Way Galaxy. We are moving at an average velocity of 828,000 km/hr. But even at that high rate, it still takes us about 230 million years to make one complete orbit around the Milky Way! The Milky Way is a spiral galaxy. [google.com]
WTF?
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If the galaxy is like a pizza, the rotation period is the same no matter how close to the middle your pepperoni is. If the galaxy is like a glass of chocolate milk, the inside spiral can complete multiple rotations before the exterior spiral as the chocolate syrup is added.
Given the spirals do not increase in density, it is likely to be like a pizza, therefore all parts have the same rotation period.
Why? (Score:2)
OK, but why? It seems counter-intuitive that dense galaxies and sparse galaxies, big galaxies and small galaxies, would all rotate at roughly the same speed. The astronomy.com article is light on details and the Royal Astronomical
Re:Why? (Score:5, Insightful)
No, we don't understand the mechanics of galactic rotation, it is not the rate expected from observed matter and gravity and so we postulate "dark matter".
Why indeed....big question
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OK, but why? It seems counter-intuitive that dense galaxies and sparse galaxies, big galaxies and small galaxies, would all rotate at roughly the same speed. The astronomy.com article is light on details and the Royal Astronomical Society's abstract is somewhat incomprehensible to a layman like myself.
Can someone explain?
Obviously, greater minds than mine were the ones to calculate this, but I can't help but wonder... could they have made a mistake? It's like when they found a particle that went faster than light- and it turned out they measured it wrong. When scientists announce something truly strange (no matter how smart they are), the knee jerk reaction is "are they right"?
If they are right, it's unlikely that this is all a coincidence.
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Most likely gravity behaves differently at very (very) long distances than the usual inverse square. Kinda like how things behave differently at very very high speeds (i.e. special relativity)
I haven't figured out exactly how this works or even any way to prove it happens, but when I do work it out I'll let you guys know.
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OK, but why? It seems counter-intuitive that dense galaxies and sparse galaxies, big galaxies and small galaxies, would all rotate at roughly the same speed. The astronomy.com article is light on details and the Royal Astronomical Society's abstract is somewhat incomprehensible to a layman like myself.
Can someone explain?
More than likely, it just means that these are large complicated systems and the results that come from observation don't match up with the theoretical model somebody created. It's just a sign to go back to the drawing board and see what they missed and come up with a new model. That the angular velocity of galaxies are somewhat close to each other is probably just the result of certain terms canceling out. The real world works that way a great deal and can appear "elegant" without too much deeper meaning.
H
Oversimplified (Score:5, Interesting)
TFS oversimplifies things a bit. The finding is that the outer edge of these galaxies rotates at about the same rate for all of them. That's not entirely surprising: the more massive the galaxy, the faster the rotation at any given distance, but also the more distant the outer rim. It also implies a similar ration of dark matter to familiar matter across these galaxies - which again isn't shocking, but is interesting if the ration has to be very similar. If it's confirmed they really do line up this closely that's probably big news for those modelling galaxy formation.
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Also, I apparently can't type "ratio".
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That was considered decades ago. The problem with thinking of galaxies in the classic 1/r^2 gravitational sense is that it implies that the spiral structure we observe in so many galaxies should have destroyed itself within a few billion years (a few rotations). There's something else going on with how they rotate that we don't understand. This apparent cons
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Something to consider [sciencedaily.com]:
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Is that a subtle "electrical universe" plug? If so, well played.
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Also one needs to note that they are talking about the the visible edge of the disk which is defined by where the disk star population ends. This is not the edge of galactic system as their is a massive halo of dark matter extending far out from the visible disk.
In the conclusion section of the paper they make the following key observation Continuous cosmic accretion provides a natural explanation for the RV relation and is their preferred explanation, but the paper is not seeking to establish that.
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"The leading theory regarding the spokes' composition is that they consist of microscopic dust particles suspended away from the main ring by electrostatic repulsion, as they rotate almost synchronously with the magnetosphere of Saturn."
This is NOT like galactic rotation or any kind of like a solid disk. These formations are influenced by the rotation of Saturn's magnetosphere which you should expect to rotate as a coherent unit.
Re:The obvious problem with this (Score:4, Interesting)
Your speculation fails the sniff test.
The electromagnetic force affects a very, very short distance.
If galaxies are "communicating," with each other and are similar to synchronized swimmers, it's going to be via gravity (including the little-understood dark matter) or perhaps entanglement on a quantum level.
There's a lot we don't know, and the substance of this article is on that list.
This is a preliminary finding and serves as a clue, only.
This recent revelation, if verified, could lead us to a solution for the asymmetry between matter and anti-matter.
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You're applying the wrong toolbox - electrostatics. The macroscopic behavior of charged particles is defined by the domain of plasma physics, not electrostatics. You can observe this simple fact by observing any novelty plasma globe: Plasmas form into filaments within the laboratory, and these filaments conduct electric currents. The filaments tend to wrap around one another without combining, demonstrating both a long-range attraction and a short-range repulsion. What this means, in practice, is that t
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Plasma theory does not work here because of the density/temperature disconnect.
Plasma is hot, dense, and without solid clumps of matter (or anti-matter) because elemental particles are too active to coalesce.
In intergalactic space, the near vacuum allows for an atom per cubic meter, which meets the definition of very near absolute zero temperature.
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Re: "Plasma is hot, dense"
Somebody needs to alert all of the office building managers who have been using plasma-based lighting (aka "fluorescent lights") above everybody's heads that plasmas are always hot.
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What if I am the source?
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Here's [spaceweathergallery.com] a shot of the aurora that you may have missed. Long-range attraction, short-range repulsion. You can derive this from the math. Fluids equations will not be of much help. It's called a Birkeland current.
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Let me give you another example of a vindication which everybody missed for electricity in space doing things of importance:
In July of 2016, it was admitted that many galaxies exhibit two separate bulges [newscientist.com]:
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For now (science is fluid) the likelihood of a non-rotating black hole is very slim.
The in-fall of mass in an accretion disk has an angular momentum that will be rotating in unison with other particles in orbit around the event horizon.
Those particles will produce an electromagnetic field.
However, the the electrical charge of the black hole will be neutral.
That same accretion disk will make sure of that.
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More so, they believe galazies actually HAVE a rotation speed, but they are not rigid, so they don't. The arms are just standard waves of density not something that moves matter around, all the matter have different rotational speeds depending on how far away from the center they are, otherwise the outer parts would be moving faster than the speed of light.
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You're not the keeper of some incredible insight that none of us here has ever thought of.
It is typical, absolutely typical behaviour for people who think they are privy to such incredible revelations to assume that others have not also: thought about them, considered them, investigated them, and subsequently discarded them.
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your electric universe nonsense has been debunked many times. Black holes in this universe are electrically neutral, even the stars they came from are. The charged particles emitted from a star, including our sun, are both positive and negative.
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What I've observed over time are a lot of poorly-argued hit pieces which people who claim to believe in peer review immediately adopted as truth. In some cases -- as in the case of Professor Koberlein of RIT [briankoberlein.com] -- there have been some glaring errors in his analysis.
For example, this claim he made in that article (below) is completely false, and there is -- to this day -- no retraction observable in the article posted to his own personal blog:
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This is nonsense. There is no conceivable way for you to connect the premise with the conclusion. But it doesn't really matter, does it? Because any flimsy rationalisation of the so-called "electric universe" hypothesis doesn't need even a sliver of scientific rigour applied to it in order for its proponents to claim it as gospel. It just has to "make sense" in the same way a thousand dead religions used to for their own followers.
Here's an unoriginal thought you might like to plant in your own head: Coming
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Re: "The further we progress in our understanding, the harder and harder it gets have such huge breakthroughs."
Cellular and Molecular Biology 51, 815-820 (2005)
Revitalizing Science In A Risk-averse Culture: Reflections On The Syndrome And Prescriptions For Its Cure
G.H. Pollack
Dark Matter? (Score:2)
Okay, so the larger the galaxy, the faster it must spin to complete a rotation in the same time as a smaller galaxy. The more mass a galaxy has means more for dark matter to gravitationally interact with it.. could it be repelling it somehow in order to accelerate it? Or attracting it?
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You are correct, that was badly worded. I was thinking in terms of the extended outer rim of a larger galaxy, having a larger circumference than a smaller galaxy; if you were to overlay one over the other, that extended outer rim would be spinning faster (tangential velocity?) than the outer circumference of the smaller galaxy. If I'm not mistaken, dark matter was theorized because the outer rim's tangential velocity of any given elliptical galaxy is a greater than it is closer to the core, such that the
cough crappy simulation cough (Score:2)
i mean really,
#define kGALAXY_ROT_SPD 1000000000
?
No, they don't (Score:2)
Well, I am sure you can find a spot or a metric where the numbers fit, like the researchers here did, but galaxies are not rigid and thus does not have a constant rotations per billion year for every part of it.
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Or is that just the rotation rate out where we are (an unfashionable district of the western spiral arm), and the rim takes longer?
I think that's the case. Just like our own sun doesn't rotate uniformly, the interior of a spiral galaxy rotates faster than the outer rim.
Galaxies are not rigid discs, they're made up of particulate matter. Each particle is free to move according to the particular forces acting upon it. Think water swirling the drain rather than a record spinning on a player.
Phonograph records (Score:3)
Galaxies are indeed not rigid disks, but the remarkable thing is that your garden-variety spiral galaxy behaves much more like a rigid disk than your angular-momentum-conserving bathtub drain. These rotation rates, by the way, are measured using the Doppler shift observed in spectrographic observations of those galaxies.
It is hypothesized that the "halo" of a spiral galaxy must either contain considerable unobserved "dark matter" or Newton's laws of acceleration and gravitation need a correction term.
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It is hypothesized that the "halo" of a spiral galaxy must either contain considerable unobserved "dark matter" ...
It is not quite correct to say that the halo of a spiral galaxy must either contain considerable unobserved dark matter.
We can tell that the mass is there by the motion of the visible stars in the halo, which provides mass distribution maps. The gravity produced by dark matter is every bit as valid a means of detection as photons, or by mass inferred by the orbital rate of inner parts of globular clusters, or any other astrophysical context where gravitation is the means of observation.
Observations of the s
Margin of error (Score:2)
In addition to selection bias, as the summary noted, there is also the matter of sample size, compared to the entire universe. The margin of error would have to be very large.
Also, can one really estimate motion in terms of billion-year cycles from studies conducted over, at most, a few years?
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Well, the variation in rotational speed of the sample is pretty high, but it *is* interesting that it isn't higher. The summary didn't say if there was a correlation between galaxy size and measured rotational speed, so they may not have noticed one. Either having one or not having one would be interesting, and limit the explanations.
OTOH, I do agree that "all" is a bit of an overstatement. Even "all observable" wouldn't justify "all", and the method of observation requires that the galaxy be nearly edg
Intergalactic Police (Score:1)
Obviously the Intergalactic Police are making sure they do not travel faster than the posted galactic speed limit.
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299,792 km/sec. Its not just a good idea, its the law.
Gravity (Score:1)
It all has to do with Gravity, once we figure that out then the rest will fall into place.
Does the universe rotate around the point where the Big Bang happened?
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The point where the Big Bang happened is everywhere.
God's Wristwatch (Score:2)
That existence is pretty much what I am expecting some scientist to figure out a long time from now, get supremely depressed, and end it all taking his secrets with him.
So we tell time?
Well no, the Universe tells time, you do practically nothing.
What does he use it for? Wouldn't he always know what time it is?
Mostly just as an accessory, he likes how it looks. I mean you have an iPhone don't you?
Oh my God.
Exactly.
Party on, old dudes. (Score:2)
"But instead, they discovered a significant population of much older stars mingling with the young stars and gas."
Sounds like an Oscars after-party.