NASA: Planet-Forming Disks Might Put the Brakes on Stars

Posted: September 15, 2013 by tallbloke in Astrophysics, Celestial Mechanics, Electro-magnetism, solar system dynamics

This finding from NASA opens up the possibility that the rotation rate of stars is linked to the disposition of the mass surrounding them. It discusses proto-planetary discs, but since the mass in that disc ends up concentrated in planets with magnetosphere’s which the Star maintains ‘flux tube’ connections with, the effect never reduces to zero. We have discovered interesting numerical relations between solar rotation rates and planetary orbital periods which indicate such a relationship exists to this day in our own solar system. More on that soon.

spitzer-star-brakes

. Image credit: NASA/JPL-Caltech

NASA press release:
Astronomers using NASA’s Spitzer Space Telescope have found evidence that dusty disks of planet-forming material tug on and slow down the young, whirling stars they surround.

Young stars are full of energy, spinning around like tops in half a day or less. They would spin even faster, but something puts on the brakes. While scientists had theorized that planet-forming disks might be at least part of the answer, demonstrating this had been hard to do until now.

“We knew that something must be keeping the stars’ speed in check,” said Dr. Luisa Rebull of NASA’s Spitzer Science Center, Pasadena, Calif. “Disks were the most logical answer, but we had to wait for Spitzer to see the disks.”


Rebull, who has been working on the problem for nearly a decade, is lead author of a new paper in the July 20 issue of the Astrophysical Journal. The findings are part of a quest to understand the complex relationship between young stars and their burgeoning planetary systems.

Stars begin life as collapsing balls of gas that spin faster and faster as they shrink, like twirling ice skaters pulling in their arms. As the stars whip around, excess gas and dust flatten into surrounding pancake-like disks. The dust and gas in the disks are believed to eventually clump together to form planets.

Developing stars spin so fast that, left unchecked, they would never fully contract and become stars. Prior to the new study, astronomers had theorized that disks might be slowing the super speedy stars by yanking on their magnetic fields. When a star’s fields pass through a disk, they are thought to get bogged down like a spoon in molasses. This locks a star’s rotation to the slower-turning disk, so the shrinking star can’t spin faster.

To prove this principle, Rebull and her team turned to Spitzer for help. Launched in August of 2003, the infrared observatory is an expert at finding the swirling disks around stars, because dust in the disks is heated by starlight and glows at infrared wavelengths.

The team used Spitzer to observe nearly 500 young stars in the Orion nebula. They divided the stars into slow spinners and fast spinners, and determined that the slow spinners are five times more likely to have disks than the fast ones.

“We can now say that disks play some kind of role in slowing down stars in at least one region, but there could be a host of other factors operating in tandem. And stars might behave differently in different environments,” Rebull said.

Other factors that contribute to a star’s winding down over longer periods of time include stellar winds and possibly full-grown planets.

If planet-forming disks slow down stars, does that mean stars with planets spin more slowly than stars without planets? Not necessarily, according to Rebull, who said slowly spinning stars might simply take more time than other stars to clear their disks and develop planets. Such late-blooming stars would, in effect, give their disks more time to put on the brakes and slow them down. –

Read the rest here.

Comments
  1. oldbrew says:

    Disk brakes 🙂

  2. tallbloke says:

    With electromagnets squeezing the brake pads by the look of it.

  3. Hans Jelbring says:

    Spin orbital coupling just isn´t fully understood neither when stars form or in our own neighbourhood. Earth rotation speeds up when the lunar declination is high and is at a minimum when moon is at earth´s equator plane. See work by Li Guioqing “27.3 and 13.6-day atmospheric Tide and Lunar forcing on Atmospheric Circulation. (Chinese Academy of Sciences, 2004)

  4. tallbloke says:

    Hi Hans. Is that because the lunar gravitation pulls the atmosphere away from the equator, thus reducing the Earth’s moment of inertia?

  5. Sparks says:

    “NASA: Planet-Forming Disks Might Put the Brakes on Stars”

    Hey! that’s my idea!

  6. Hans Jelbring says:

    Well, Consider the following facts, Rog.
    Gravity do influence the mass of ocean and solid Earth adding mass in line with the the centre of mass of Earth and the sun and the moon producing spring tide and neep tide when they do or don’t line up. Thes physical facts suprisingly do not influence the length of the day (LOD) as a first order effect which they ought to do. The period that should show up in LOD is as you know a synodic month (29.53059 Days). The first order effect causing LOD variations (<60 Days) is associated with lunar declination which has a period of a siderial month (27.32166) days or half it. This LOD effect is almost independant of the distance between Earth and moon but it does affect LOD as a minor second order effect. Li Guioqing has understood the importance of these facts. Very few western scientists have reacted on his article and understood the fundametal importance of it. The Newtonian gravity model is just not applicabel and has no explanation to offer. Make your own deductions. The basic raw data is avilable for anyone to study which I have done and Li is on target.

  7. Hans Jelbring says:

    Sorry, it should be “…when they line or or don´t line up.” in my comment above. I try to keep my erroneous statements down to less than 1 of 10 but that is hard (not counting spelling errors).

    [Reply] No problem, fixed.

  8. tallbloke says:

    Hans, that sounds very interesting. Thanks for alerting us to Li’s paper. I will put this one on my ‘to do’ list for now, because I’m in the middle of my phi investigation. It sounds like an interesting puzzle for people adept at the maths required to work on it.

  9. Brian H says:

    One problem with the skater-arms analogy is that skaters’ arms are solidly linked to their bodies at the shoulders. Disks and planets, not so much.

  10. Carla says:

    The opposite of this would be then..

    During times of higher solar activity planets slow down in rotation speed.

    During times of lower solar activity planets speed up rotation speed.

    So would it then be during times of low solar activity that there might be a connection to a planetary influence slowing down the rotation of the star?

    Not to mention the unmentionables that could be more processes at work as yet unknown..

  11. Larry Ledwick (hotrod) says:

    This is perfectly understandable, the debris disk around the star would contain lots of para-magnetic materials and electrical conductors. Both would transfer energy from the star to the disk as the magnetic field lines of the star swept through the disk.

    http://en.wikipedia.org/wiki/Magnetic_damping

  12. tallbloke says:

    Hi Larry. As I understand it, ‘magnetic field lines’ only exist on diagrams. However, there’s been plenty of interaction between the magnetism of our star and the proto-planetary disk and it’s still going on with the planets now they’re formed. Look at the strong auroras on Earth, and the other magnetospheric planets.

  13. Larry Ledwick (hotrod) says:

    Which is the point I was making. There is a well known and obvious explanation in this type of magnetic interaction that would explain the debris disk “tugging” on the star and slowing it down.

    If the slowing spin of the star is due to this magnetic interaction with the material in the cloud as I described, it would however probably be more correct to say that the star transfers momentum out into the debris disk through this magnetic coupling as it contracts and its magnetic influence gets stronger and the star tries to spin faster than the nearby debris cloud as it contracts.

    As shown by the video, any strong spinning magnet would experience a strong retardation if paramagnetic materials moving slower than the spinning magnetic field were inside the magnetic field.

    The net effect is that the spinning magnet would be slowed and the paramagnetic materials would be accelerated (spin rate increased) by the magnetic interaction, transferring momentum outward into the debris cloud as the system contracts preserving angular momentum for the entire system.

    This would also explain why the entire debris cloud does not coalesce into the star, but over time segregates into lumps that orbit fast enough to avoid falling into the star.

    This might also help explain the rotational velocity curves of galaxies and the why it is uniform with distance rather than the expected slowing as you move out from the center of the galaxy.

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

  14. suricat says:

    arry Ledwick (hotrod) says: September 22, 2013 at 2:22 am

    Nice post ‘hotrod’! Do you realise that ‘Stars’ throwing out dust and planets to stabilise their rotation rate was first proposed by Arthur C Clark? No surprise then that the theory was ‘side-stepped’ by the ‘main stream’ science of the day.

    From the moment that ‘fusion’ commences, the agglomeration of ‘a mass’ by gravitational influence undergoes a ‘change of state’. The mass becomes an ’emitter’ of ‘de-constructed mass’ (plasma [stellar wind and photon energy])’.

    Following the ‘ignition’ of fusion, the ‘stellar wind’ impinges upon the mass that is falling into the Barycentre of the system, however, the masses falling into the Barycentre consists of anything from dust particles to atoms. Thus, atoms may well be ‘blown away’, but dust particles (with their greater inertia) may well be imparted with ‘spin’ from this process (‘spin’ develops into an electromagnetic property).

    You may well ask ‘how can spin change the property of a mass?’. Well it doesn’t (negligible) for an ‘atom’, but ‘molecules’ and ‘larger massive constructions’ exhibit electrostatic polarisation. IOW, they display a +ive pole and -ive pole for the purpose of ‘electrical polarity’ (or ‘electrical potential’ [EMF]).

    This process is more than my post can elucidate here. Can I continue TB?

    Best regards, Ray.

  15. tallbloke says:

    Be my guest Ray. Send me a longer write up for a new post if you like.

  16. suricat says:

    tallbloke says: September 26, 2013 at 8:45 am

    Er, “a longer write up”? No. The reason I asked for a continuance is because I’m completely unqualified in this area. I base my conclusions upon deductive logic from my understanding of engineering science, thus I’ll not submit an OP, but anyone has my permission to use, or progress further, any ideas that I post on-line. Consider it open source because if it was worth anything, I’d have probably patented it. 😉

    To begin with we need to take into consideration a ‘stellar system’ that we’re all well acquainted with, so that a reasonable comparison can be made by your readers. Discussion on ‘other’ stellar systems will be confusing in that the ‘stellar wind’ varies in speed and the stars ‘brilliance’ also varies (not to mention the mass within the system). I choose Sol’s system and Earth as an introduction. Do you agree?

    Best regards, Ray.

  17. suricat says:

    suricat says: September 27, 2013 at 2:45 am

    I’ll wait a bit longer for a rebuttal, if none, I’ll continue where time constraints permit.

    Best regards, Ray.

  18. tallbloke says:

    Please go ahead Ray, I’m interested in your ideas. We have recently been finding some very curious relationships between spin and orbit that need an explanation. So how will the solar wind impart spin by bombarding the dayside of proto-planets with radiation?

  19. wayne says:

    I’ll add two cents though everyone might already be aware of all of said, maybe not.

    Speaking of planar galaxies, let’s say that there is always an ongoing transfer of angular momentum from the central galaxy collective of stars to those at the outer edges which would in fact make them rotate faster than expected in a static case.

    μ = 4π²a³/T² in m³/s²
    μ being the GM (gravity times mass)
    a being the semi-major axis (m)
    T being the period (s)

    Mercury: 4·π² ·   57900000000.0³ /    7600521.6² = 1.3265e+020
    Earth:   4·π² ·  149600000000.0³ /   31558118.4² = 1.3271e+020
    Neptune: 4·π² · 4495100000000.0³ / 5200329600.0² = 1.3259e+020

    For our solar system, all of the planets calculate by that equation give the same value to be close to the average of about 1.3275E+20 m³/s² which not surprisingly is the GM (gravity times mass) of the sun. That is how the sun is weighed when adjusted for the best estimate of the universal gravitational constant.

    But you have to ask, do stars near the center of a flat galaxy ‘feel’ the same gravity from mass as those on the perimeter. Does Pluto ‘feel’ the same gravity from the mass of the solar system as Mercury? No, they do not, not on the average. Does gravity appear concentrated at the center as most are aware and is therefore constant? Yes, then no. A star, lets say orbiting an assumed black hole at the center will ‘feel’ only the black holes gravity pull while stars at the perimeter are under the influence of all of the stars orbiting at less distance from the core and that by itself also makes stars on the edge to orbit faster relative to that calculated of those near the center (adjusted for a), the GM of the collective galaxy scale from low near the center to full mass at the edges. In Pluto’s case the combined mass of all inward planets plus the sun is very close to just the mass of the sun itself so that does not generally show up in orbital distance and periods data. NASA data on their web right now implies that Pluto feels even less of a central mass, not more as it should… there are always deviations from ‘correct’. Most of the other planets plot more or less linearly and do show a slight upward slope as expected.

    It seemed as if some statements above in the comments where not playing those factors in.

  20. suricat says:

    tallbloke says: October 2, 2013 at 12:50 am

    “So how will the solar wind impart spin by bombarding the dayside of proto-planets with radiation?”

    Thanks for the positive response TB, but there’s an ambiguity in the word ‘radiation’ that needs to be cleared up before we start.

    There are two energy transfer agents that are covered by the term ‘radiation’. These are the ‘particle bombardment’ (‘PB’ for the want of keystrokes) type, and the ‘electro-magnetic propagation’ (‘EM’) type.

    PB transfers energy by way of its mass momentum energy on impact with another mass entity. However, if the ‘bombarding particle’ possesses a ‘charge’ (electrical potential) quality, its mass momentum energy may well be dissipated by its interaction with/within the magnetic field surrounding the bombarded entity.

    EM propagation transfers energy by way of ‘magnetic flux teleconnection’ between the ‘source mass’ of the magnetic flux that ’emits’ the perturbation to the magnetic field and the ‘sink mass’ of the magnetic flux that ‘absorbs’ the perturbation from the magnetic field. This form of energy transfer is, unlike PB, an energy transfer over a, sometimes great (light years), distance.

    Now, before you say that “cosmic rays are particles that travelled light years to reach us” I’ll say that “we don’t know where they came from, their speed was slower, and they’re a ‘mass impact event’ in any case”. EM propagation travels at ‘c’ in a perfect vacuum, so we can see the ‘vis’ spectra from neighbouring stars with minimal distortion from the influence of gravity (but with greater distortion from intervening dispersed mass [gas cloud etc.]), but ‘particle’ cosmic rays have had their original trajectory distorted by gravity to the extent that we don’t know where they came from because ‘they’re massive entities’ that adhere to gravitational potentials as they make their way to an ultimate destination.

    So you can see that the two types of energy transfer that are ‘inferred’ by the term ‘radiation’ are really ‘poles apart’ (although quantum mechanics would imply otherwise [QM seems only concerned with the energy within a parametrised ‘parcel’]).

    Enough on disambiguation. Think about a ping-pong ball floating upon a fountain of water at a rifle range in a local fair/fête. 😉

    That’s the best analogy that I can think of just now. I’ll elucidate later and respond to wayne’s post as well.

    Best regards, Ray.

  21. suricat says:

    wayne says: October 2, 2013 at 8:50 am

    “Speaking of planar galaxies, let’s say that there is always an ongoing transfer of angular momentum from the central galaxy collective of stars to those at the outer edges which would in fact make them rotate faster than expected in a static case.”

    What mechanism for the “ongoing transfer of angular momentum” do you suggest wayne?

    Also, what do you imply by “rotate faster than expected”? Is this ‘rotational speed’, ‘orbital speed’, or both?

    Best regards, Ray.

  22. suricat says:

    The ping-pong ball analogy explained (I hope)!

    ‘Solar wind’ is a ‘mass emission’ from Sol which is made up from ‘broken’ atoms that were ‘shaken apart’ by the extreme ‘SW’ (short wavelength) EM activity, gamma and x-ray bands, within Sol’s body of substance. The ‘Solar wind’ consists of protons and electrons, but not neutrons. This is either odd, or I am wrong.

    Although a ‘star’ (Sol in particular) ’emits’ massive particles, neutrons are not included in this emission. Perhaps a subject for ‘another post’, but pertinent here because Sol’s ‘mass emission’ plays a crucial role in ‘planetary rotation’ (not so much ‘orbital rotation’) within the ‘Solar’ system, but there are ‘other influences’ (attractors) that may well confuse this issue.

    Whatever! The ‘mass emission’ issue provides the ‘driver’ for planetary ‘rotation’. This is provided by the weight of mass from the Solar wind hitting the planet. If the planet was stationary, and not orbiting the star, the weight of mass hitting the planet would be equal about the centre of the planet facing the star, but the planet is ‘orbiting’ the star and this is not the case. Due to the planet’s ‘orbital flight’ it collects more mass in the direction of its flight, as the orbit is at ~’a right angle’ to the outflow of Solar wind mass, than it collects in its ‘trailing’ hemisphere. This sets up a torque between the ‘leading’ and ‘trailing’ hemispheres of the planet’s orbital flight and generates rotation perpendicular to the orbital plane.

    This process is entirely mechanical and doesn’t take into account electromagnetic influences generated by the EM field which are probably more pertinent to this thread. However, once ‘rotation’ begins on a planet which possesses an ‘atmosphere’, extreme short-wave EM radiation from the star (gamma, x-ray and UV spectra) produces an ‘ionosphere’ region to the planet’s atmosphere. We ‘know’ that an ‘electric charge in motion’ produces a ‘current’, thus, the planet now hosts a ‘magnetic field’ (simply because it’s ‘rotating’). It’s quite possible that these ‘electrical properties’ produce a ‘braking effect’ to the planet’s rotation by way of ‘back EMF’ against the Solar wind, but I’ll leave this supposition for another post.

    I hope this makes sense. I sit at this box with a brandy and lemonade (because I like it), with ‘top-ups’ as needed. I think I’ll need to dry-out soon, hic. 😉

    Best regards, Ray.

  23. Brian H says:

    suricat;
    If you’re sober enough, could you clarify if you mean diurnal rotation or annual orbit?

  24. suricat says:

    Brian H says: October 5, 2013 at 5:43 am

    “If you’re sober enough, could you clarify if you mean diurnal rotation or annual orbit?”

    Hah! Yes Brian. I mean ‘diurnal rotation’. The orbital mechanics are much less affected. 🙂

    Best regards, Ray.

  25. tallbloke says:

    Ray: Due to the planet’s ‘orbital flight’ it collects more mass in the direction of its flight, as the orbit is at ~’a right angle’ to the outflow of Solar wind mass, than it collects in its ‘trailing’ hemisphere. This sets up a torque between the ‘leading’ and ‘trailing’ hemispheres of the planet’s orbital flight and generates rotation perpendicular to the orbital plane.

    There will also be more drag on the day-side due to radiation pressure and particle interaction than on the night-side. Small forces constantly applied. That will induce spin. Doesn’t work on Venus though, which means the forces making it spin the other way are stronger. Something acts to bring the spin rates of the planets into simple ratios with each others orbital periods. That must be harmonic resonance of some kind.

  26. suricat says:

    tallbloke says: October 5, 2013 at 8:38 am

    “There will also be more drag on the day-side due to radiation pressure and particle interaction than on the night-side. Small forces constantly applied. That will induce spin.”

    No, I’m sure you’ve ‘summed the vector forces’ for particle interaction to come to this conclusion (it also, wrongly, implies counter rotation torque). This only indicates a slight alteration to the ‘orbital mechanics’ for the planet. Your suggestion only, almost imperceptibly, slows the orbital speed and pushes the planet away from the star (changes the orbital vector), again, almost imperceptibly.

    If you’ve taken the trouble to calculate the average ‘angle of incidence’ between the planet’s ‘orbital vector’ and ‘Solar wind vector’ you’ll realise that the angle of the Solar wind pressure on the planet’s ‘disc’ sums to the total pressure applied by the Solar wind to the planet. Every engineer understands that the ‘Centre of Gravity’ for a ‘laminar’ is its ‘Centre of Area’ (which in this case is the centre of the disc).

    From here, if you project the 2D ‘angle of incidence’ to the distance from the centre of the planet to where the ‘effect’ is applied, you’ll find that the distance between this and the ‘gravitational effect at the same distance from the planet’s core’ reveals the distance at which the total Solar wind pressure provides the ‘torquing moment’.

    EM radiation from Sol only heats the day-side of the planet, is ~constant and can’t affect angular momentum. As one hemisphere is expanding and slowing angular momentum, the other hemisphere is contracting and speeding angular momentum.

    “Doesn’t work on Venus though, which means the forces making it spin the other way are stronger.”

    Venus (and Uranus) are exceptions to the rule, but Venus offers insight. Why is its rotation slowing? We don’t have observations that pre-date its theoretical ‘collision’, so we must assume that the planet is in a ‘state of distress’ WRT spin. This would also explain why its rotation is ‘slowing’ at such a rate.

    “Something acts to bring the spin rates of the planets into simple ratios with each others orbital periods. That must be harmonic resonance of some kind.”

    I tend to agree, but I’m not sure that we understand all the parameters yet. Do you think this could be to do with gravity at diminishing value as distance increases against mass collision hap stance (and I include ‘Stellar wind’)?

    Best regards, Ray.