Astronomers discover galaxies spin like clockwork

Posted: March 14, 2018 by oldbrew in Astrophysics, Celestial Mechanics, research

Spiral galaxy [image credit: BBC]


Researchers refer here to ‘regularity in galaxies’.

Astronomers have discovered that all galaxies rotate once every billion years, no matter how big they are, reports Phys.org.

The Earth spinning around on its axis once gives us the length of a day, and a complete orbit of the Earth around the Sun gives us a year.

“It’s not Swiss watch precision,” said Professor Gerhardt Meurer from the UWA node of the International Centre for Radio Astronomy Research (ICRAR).

“But regardless of whether a galaxy is very big or very small, if you could sit on the extreme edge of its disk as it spins, it would take you about a billion years to go all the way round.”

Professor Meurer said that by using simple maths, you can show all galaxies of the same size have the same average interior density.

“Discovering such regularity in galaxies really helps us to better understand the mechanics that make them tick-you won’t find a dense galaxy rotating quickly, while another with the same size but lower density is rotating more slowly,” he said.

Professor Meurer and his team also found evidence of older stars existing out to the edge of galaxies.

“Based on existing models, we expected to find a thin population of young stars at the very edge of the galactic disks we studied,” he said.
“But instead of finding just gas and newly formed stars at the edges of their disks, we also found a significant population of older stars along with the thin smattering of young stars and interstellar gas.”

“This is an important result because knowing where a galaxy ends means we astronomers can limit our observations and not waste time, effort and computer processing power on studying data from beyond that point,” said Professor Meurer.

“So because of this work, we now know that galaxies rotate once every billion years, with a sharp edge that’s populated with a mixture of interstellar gas, with both old and young stars.”

Source: Astronomers discover galaxies spin like clockwork | Phys.org
– – –
Research paper: Cosmic clocks: A Tight Radius – Velocity Relationship for HI-Selected Galaxies

Comments
  1. TomO says:

    huh …

    stick that in your standard model pipe and smoke it.

  2. JB says:

    I invite them to go to the “very edge” of any galaxy and verify their thinking about the stars.

  3. p.g.sharrow says:

    This is very interesting. The only way this can be true is that there must be a connection between galaxies that would make them appear to function in lock step.

    I would propose that this would be the result of the field spin of the galactic prime or first proton at the center of it’s galaxy. Spinning gyroscopes tend to align and equalize themselves over time.

    All Protons are of the same average size, charge and spin and have a half life that exceeds the life of the Universe. Large things must follow the blue print of small things as the basic Laws of Physics are simple and true for large and small…pg

  4. oldbrew says:

    ‘galaxies spin like clockwork’

    Something must be setting the clock.

  5. clipe says:

    Hand wound or not?

  6. Curious George says:

    The assumption is that the whole galaxy rotates as a solid object. I find it difficult to reconcile with a shape of spiral galaxies.
    [video src="https://3c1703fe8d.site.internapcdn.net/newman/gfx/video/2018/1-astronomersd.mp4" /]

  7. Curious George says:

    [video src="https://3c1703fe8d.site.internapcdn.net/newman/gfx/video/2018/1-astronomersd.mp4" /]
    I hope wordpress would leave it as a link this time.

  8. p.g.sharrow says:

    Galaxies of all sizes spin at the same speed and spin as if their are solid. What does that do to Newtonian Physics? Free fall? and the concept of the nothingness of deep space?

    It appears that the Standard Model we all have been taught is a bit incorrect. 😉 Time to go back to the drawing board. Theories that don’t fit reality must be discarded, replaced…pg

  9. alanpoirier says:

    It’s an electric universe.

  10. p.g.sharrow says:

    Mass/inertia and gravity are external to mater not internal. It is a matter of charge/energy resistance to change in motion. The existence of Mater in motion creates tension in the fabric of space/Aether that resists changes that creates effects of mass/inertia. The vectorsation of that stress is gravity. Charge in chaos of deep space verses organized and therefor reduced charge of Mater. Remember Protons are reduced charge or positive, Neutrons are plus/minus or neutral. Electrons represent charge that repels all other charge, and creates an electrostatic balance with it’s Protons.The charge balance of Mater is lower then the charge density of the fabric of space/Aether that charge gradient causes linear acceleration warpage in the dielectric of Mater, Gravity! acceleration…pg

  11. tallbloke says:

    PG: Galaxies of all sizes spin at the same speed and spin as if their are solid.

    George: The assumption is that the whole galaxy rotates as a solid object.

    That’s not what I read. “But regardless of whether a galaxy is very big or very small, if you could sit on the extreme edge of its disk as it spins, it would take you about a billion years to go all the way round.”

    That’s different to claiming galaxies rotate as solid discs.

  12. oldbrew says:

    ‘you won’t find a dense galaxy rotating quickly, while another with the same size but lower density is rotating more slowly’

    Do galaxies have identical internal dynamos? 😉

  13. tallbloke says:

    OB: No, but maybe the answer is more obvious. Instead of asking why galaxies of different sizes all have outer edges spinning at the same rate, we should ask what sort of energy field pervades the whole universe that compels them to do so.

  14. JKrob says:

    can the same observation be applied to the outer edge rain bands of tropical cyclones?

  15. Jim says:

    So, the gravitational model is out? Accreation model out, and electric model never considered. Interesting. So, their differing size must be a mistake. If they all rotate at the same speed. I would bet on observation time, for the next grant.

  16. p.g.sharrow says:

    The absolute speed at the galactic rim would be faster in larger galaxies to maintain the same rotational speed…pg

  17. oldbrew says:

    p.g. – they reported:

    “But regardless of whether a galaxy is very big or very small, if you could sit on the extreme edge of its disk as it spins, it would take you about a billion years to go all the way round.”

    So yes, like a position on a bicycle wheel, anywhere completes a revolution in the same time.

  18. p.g.sharrow says:

    interesting;
    so what sets this speed limit to the rim speed or better yet limits the core speed of rotation to maintain the rim speed? Resistance to acceleration of mass/Inertia at the rim reduces the Angular Momentum at the core? As the galaxy gets larger it’s core slows……….the mass/inertia is on the outside! of the bubble! Newtonian physics does work…pg

  19. p.g.sharrow says:

    Better if I had said that the resistance to acceleration is strongest at the outside of the bobble, therefor mass/inertia effects are greatest in the outside or rim of the Galactic Mater bobble where the stress of organized Mater against the Chaos of space is greatest…pg

  20. oldbrew says:

    Professor Meurer said that by using simple maths, you can show all galaxies of the same size have the same average interior density.

    Another common factor to bear in mind.

  21. p.g.sharrow says:

    The spiral nature of the outer disk of the large Galaxy would indicate some torque slippage between the core and rim. So the rim must encounter some braking against the fabric of space…pg

  22. oldbrew says:

    Wikipedia: The mass estimations for galaxies based on the light they emit are far too low to explain the velocity observations.

    The galaxy rotation problem is the discrepancy between observed galaxy rotation curves and the theoretical prediction, assuming a centrally dominated mass associated with the observed luminous material. When mass profiles of galaxies are calculated from the distribution of stars in spirals and mass-to-light ratios in the stellar disks, they do not match with the masses derived from the observed rotation curves and the law of gravity.

    http://en.wikipedia.org/wiki/Galaxy_rotation_curve#Description

  23. astroclimateconnection says:

    This is the reason that they are claiming this result:

    If galaxies share a common drop-off in the density of matter (i.e. gas, dust and stars) with distance from their centre, then to a rough approximation you only have to have the following happen to get the results that are claimed in this article.

    a. A galaxy’s absolute size (R_edge) is proportional to its total mass (M_tot)

    i.e. R_edge = k1 x M_tot

    b. A galaxy’s angular velocity (omega) is proportional to its total mass (M_tot)

    i.e omega = k2 x M_tot

    where k1 and k2 are constants of proportionality.

    EFFECT 1:

    This means that if you double the total mass of a galaxy (M_tot), you will double the absolute size of a galaxy (R_edge). Hence, if you could keep the galaxy’s angular-velocity of rotation (omega) constant, you will double the period of rotation at the edge of the galaxy (T_edge).

    EFFECT 2:

    However, if you double the total mass of a galaxy (M_tot), you will also double the galaxy’s angular velocity of rotation (omega). This will halve the the period of rotation at the edge of the galaxy (T_edge).

    Hence, the two effects 1 and 2 cancel each other out and so T_edge stays roughly the same.

    Background maths for those who are interested:

    1. The tangential speed-of-rotation (Vt) of matter at a given distance (R) from the centre of a galaxy

    is: Vt = R x omega (1)

    where omega is the angular-velocity.

    2. A disk that is rotating like a solid body will have a constant angular velocity (omega):

    3. Since omega = constant = (Vt / R) (2)

    this means that the Vt will increase in proportion to R.

    i.e. if you double your distance from the centre of any given galaxy, you will double the tangential rotation speed.

    4. The rotation period of matter at a distance R from the centre of a galaxy (T) is its circumference (C) divided by the tangential speed-of-rotation at that distance.

    i.e. T = (2 x pi x R) / Vt (3)

    5. From equations (2) and (3)

    T = (2 x pi x R) / (R x omega) (4)

    or T = (2 x pi) / omega = constant

    since omega is a constant for a solid body.

    6. Hence, T is inversely proportional to omega

    i.e. if you double omega for a galaxy it will halve its rotation period at a given distance R from the galaxy’s center (i.e T).

  24. p.g.sharrow says:

    A galaxy is not a solid body but behaves as if it were a solid body. The question is WHY !
    A galaxy is made up of millions of stars in “free fall” netted together by gravity and What that makes it behave as if were solid AND they all seem to rotate at the same speed regardless of size.
    All of the mathematics above does not explain this quirk…pg

  25. oldbrew says:

    IW wrote: ‘if you double your distance from the centre of any given galaxy, you will double the tangential rotation speed’

    Imagine a circle that fits exactly inside a square.
    Draw a line from their shared centre to the midpoint of one side of the square i.e. a radius.
    Now the distance from the midpoint to either of the two adjacent corners of the square = radius length.
    It’s also the tangent to the circle.
    Double the radius = double the tangent.

  26. astroclimateconnection says:

    oldbrew,

    If you have a stick that is rotating uniformly about one of its ends, the longer the stick, the faster the other end will move. The tangential velocity that I am referring to is the velocity at the free end of the stick that is at right angles to the length of the stick.

  27. astroclimateconnection says:

    p.g.sharrow,

    Good point. However, I was not trying to explain why galaxies appear to rotate like a solid body. All I was doing is explaining why these astronomers came to the conclusions that they published. The mathematics that I posted is basically correct, however it does a few conceptual flaws.
    It is a whole different kettle of fish to try to explain why stars, dust and nebula appear to collectively rotate as though they are solid body. I think that it may have something to do with the following:

    A. If galaxies share a common drop-off in the density of matter (i.e. gas, dust and stars) with distance from their centres then a galaxy’s absolute size (R_edge) should be proportional to its total mass (M_tot)

    i.e. R_edge = k1 x M_tot (1)

    Now to a rough approximation the mean density of a galaxy (Rho(R)) within a radius R is:

    Rho (R) = mass within radius R / volume out to radius R
    = M / ((4/3) x Pi x (R)^3))

    So for radius R = R_edge

    M_tot = Rho(R_edge) x 4 x Pi x ((R_edge)^3))

    Hence, for (1) to be true it would require that:

    Rho (R) to be inversely proportional (R)^2.

    i.e. the density of galaxies with radius (R) falls off as 1/ (R)^2).

    This is roughly what is observed in most galaxies, given that for a system of gas,
    dust and stars to be in virial equilibrium:

    2KE + 2U + W + M = 0

    where:

    KE = the kinetic energy
    U = the thermal energy
    W = the gravitational energy = – G x M^2 / R
    M = the magnetic energy

    i.e. the gravitational energy must be balanced by the other energies.

    This means that for a rotating self-gravitating iso-thermal cloud of stars
    you find that the density with radius falls off as 1/ (R)^2.

    B. Now the question is why is a galaxy’s total angular velocity (omega)
    proportional to its total mass (M_tot)

    i.e omega = constant x M_tot

    This is complicated by the fact that many galaxies have had substantial accretion
    of matter over their life times because of mergers with surrounding galaxies.

    I do not have the expertise to answer this question.

  28. p.g.sharrow says:

    astroclimateconnection says:
    March 17, 2018 at 2:48 am

    Good effort above. While not a mathematician, I could follow your logic.
    As an electrician I lean toward electrical cause and effect. The geometry is kind of obvious.

    The forces that enforces this semi-rigid behavior that causes apparent greater acceleration of the rim as the galaxy gets larger is curious as is the observation that rotational progression is the same in all galaxies regardless of size. Most interesting indeed. A solid clue to universal physics…pg

  29. oldbrew says:

    Re: ‘The tangential velocity that I am referring to is the velocity at the free end of the stick that is at right angles to the length of the stick’

    Yes, like this…the tangent line is on an imaginary rotating square whose sides touch the circle at the midpoints.
    The radius in the diagram is meeting the tangent line at one of those midpoints.
    The distance from the meeting point (where the angle symbol is) to an adjacent corner of the square = 1 radius.
    Equivalently, one side of the square = 1 diameter.

  30. p.g.sharrow says:

    @oldbrew; old galaxy traveling at high speed :
    http://hubblesite.org/news_release/news/2018-17
    Very dense, old galaxy, that travels at retaliative speed of 2 million miles per hour.
    That is packing a huge amount of momentum!…pg

  31. oldbrew says:

    pg – The speed of a galaxy increases by 70 km/s for every 1 Mega parsec increase in its distance from the Earth.

    So if a galaxy is 60 million light years (18.4 Mega parsecs) from the Earth it will be moving away from us at 70×18.4 = 1288 km/s.

    http://www.schoolphysics.co.uk/age14-16/Astronomy/text/Galactic_speeds/index.html

    So galaxies are quite speedy, but obviously this one is a bit more so than its mates 😉

  32. Joe basel says:

    Old brew
    While space is expanding the galaxy is riding a wave.
    Its motion hasnt changed, either slowed or increased.
    The change in speed is you reading the lenght of time light reaches you.
    The rotation of all galactic mass is likewise given a starting motion.
    Other than a object getting a gravitainal slingshot, there hasnt been any added speed to any object from the time of creation.
    That other object would loss a equal amount.
    On a macro level.
    So it shouldnt be all that odd that galaxies are spining at about the same speed.
    You could even go faster than light, by riding a wave of space time, but not really moving.

    After E = mc², the fact that nothing can move faster than light is probably the most common fact known … insight was to realise a bubble could move at any speed as a rolling wave in spacetime.

    Just a laymans take.
    Joe

  33. oldbrew says:

    Synchronised Galactic Orbit Challenges Our Best Theory Of How The Universe Works
    Ryan F. Mandelbaum
    Feb 3, 2018

    Basically, scientists expected that Centaurus A would have randomly assorted dwarf galaxies, but instead, it appeared to have a ring of co-moving galaxies like our own, against the assumptions of the popular standard theory of the universe. The odds are around one in a thousand that a single galaxy would have a disk of coordinated dwarf galaxies like this. The odds that three galaxies would are a whole lot lower — unless our theory of galaxy formation is wrong. [bold added]

    http://www.gizmodo.com.au/2018/02/synchronized-galactic-orbit-challenges-our-best-theory-of-how-the-universe-works/

    Who exactly is ‘the popular standard theory of the universe’ popular with? 😎

    Apparently it’s marvellous apart from all the things it can’t explain – like where is 95%(?) of the universe 😐
    http://phys.org/news/2018-03-physicists-crossroads-universe.html

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