What dates are accepted for the age of the Sun?

[Robittybob1]

This review mentions some terms that could be studied:

 

http://astrobites.org/2011/03/11/review-article-protoplanetary-disks-and-their-evolution/

This dissipation could be explained by the “UV switch” model, where, once accretion onto the star stops, photoevaporation from UV photons clears the circumstellar gas quickly. Higher mass stars will clear their disks quicker, due to higher accretion rates and the increased radiation field. Hotter stars emit more energetic photons, while lower mass stars will retain their disks for longer. Once the inner disk is drained and a hole has developed, the inner edge of the disk is directly exposed to these UV photons and the disk begins to photoevaporate away beginning with the inner edge. This disk then becomes a transition disk, which, at most, comprise 20% of the observed disk population. Based upon observations, the time spent as a transition disk is relatively brief, which implies that the near-IR excess of the SED always disappears before the mid-IR and far-IR excesses do, which means that the disk is clearing from the inside out. Additionally, a lack of near-IR excess could imply an inner hole in the disk due to giant planet formation.

That is an interesting idea where the disk clears from the inside out as giant planets are forming within the disk.

The other idea that the leading edge of the protoplanetary disc is being dissolved away through photoevaporation.

 

In the paper above it also mentions the Yarkovsky Effect. Diagram of this effect on this site.http://earthsky.org/astronomy-essentials/the-yarkovsky-effect-pushing-asteroids-around-with-sunlight

It seems that the push is dependent on the object rotating in the right direction.

 

The differential Doppler effect that is from the energy levels from photons from the two hemispheres of the Sun (i.e. the side coming toward you and the half going away. The energy is higher on the approaching side.

Edited February 12, 2016 by Robittybob1

[Robittybob1]

Is there any actual experimental results which show that photons released from moving material has a higher frequency in the direction of travel? Was this the Ives Stilwell experiment?

[Mordred]

One of the numerous experiments, key note radar guns use the same principle.

 

Some of the other experiments are mentioned here.

 

https://en.m.wikipedia.org/wiki/Ives%E2%80%93Stilwell_experiment

[Robittybob1]

One of the numerous experiments, key note radar guns use the same principle.

 

Some of the other experiments are mentioned here.

 

https://en.m.wikipedia.org/wiki/Ives%E2%80%93Stilwell_experiment

That link to the Mossbauer rotor experiment made me think of this effect! https://en.wikipedia.org/wiki/Ives%E2%80%93Stilwell_experiment#M.C3.B6ssbauer_rotor_experiments

 

If the Earth moves around the Sun at = 2.978589 x 10^4 m/s.

Surface of the Sun moves at (kilometers per second)…………………………………….….. 1.9 km/sec

So how much faster would the young Sun be spinning?

http://spacemath.gsfc.nasa.gov/weekly/4Page1.pdf

 

That brings up a whole lot of questions that need to be answered:

Does that mean the direction photons emanating from the Sun is not radially but has a element of forward motion for they came out of a moving surface? So does every interaction of a photon on to a particle of dust would have a component of momentum in the forward direction?

Could a young sun could be spinning at a rate that far exceeds the current rotation rate? Could this spin rate be due to the infalling matter adding extra angular momentum to the Sun

How fast do young stars rotate? Is the Sun losing angular momentum as it radiates its energy and mass?

 

Could these effects nullify P-R drag in the early solar system, but would be effective under the current spin rates?

All I was wanting to know was did the Early Solar System have dust obscuring the PMS Sun, thereby allowing a habitable zone closer in? I think this dustiness is a taken and then I'm asking the experts whether the P-R drag would be less likely to clear the inner SS in a situation with a larger faster spinning young Sun? If that was so could it be argued the dust would remain for a longer period than is being predicted using the current Sun parameters?

Edited February 12, 2016 by Robittybob1

[Mordred]

It's been a few months since I looked directly at PR. I do recall having a good article on the subject. I'll dig it up as well as review the subject. The dust interactions If I recall only influences extremely minor size particles. It's influence is more upon the leftovers from other clearing processes. A later stage,

 

As far as rate of spin and PR I need to review.

Edited February 12, 2016 by Mordred

[Robittybob1]

But imagine if all the dust has to move outward, and never inward and all the outward paths are blocked by more dust. The clearing of the inner SS could be a much slower process.

First study I located seemed to turn up some very surprising figures where the surface rotation speeds of the young stars like the Sun matched that of a planet/debris at the Earth's radius, and far exceeded this speed as the contraction continued to a MS star.

So would that even make P-R effect change signs? i.e The inner SS would be cleared outwardly and not inwardly anymore because the angle the photon takes hits the dust particle from behind and always speeds it up. Whereas the current Sun equatorial region moves slower than the dust so it strikes on the leading edge (in the diagrams on P-R at least).

 

[This seems to be supported by what we see in the NASA images of dust discs. I always think it looks like material is flowing outward rather than inward.]

 

http://articles.adsabs.harvard.edu/full/1993AJ....106..372E

Edited February 12, 2016 by Robittybob1

[Robittybob1]

@Mordred was it you you suggested looking into "density waves"? I see there are many studies on density waves do you have a particular favourite?

Post Script:

@Mordred

I found the post so no need to reply to this request thanks.

Edited February 12, 2016 by Robittybob1

[Mordred]

I don't have a particular favorite. Here is the two articles I was thinking of.

 

http://astro.berkele...y/kimura02a.pdf

 

This one has Poynting vector as well but it's mainly the solar wind influence.

 

http://www.ieap.uni-...ing/et2/et2.pdf.

 

you may have read them before as I posted them in one of your older threads.

 

http://www.scienceforums.net/topic/88734-can-anything-fall-into-the-sun/page-1

[Robittybob1]

I don't have a particular favorite. Here is the two articles I was thinking of.

 

http://astro.berkele...y/kimura02a.pdf

 

This one has Poynting vector as well but it's mainly the solar wind influence.

 

http://www.ieap.uni-...ing/et2/et2.pdf.

 

you may have read them before as I posted them in one of your older threads.

 

http://www.scienceforums.net/topic/88734-can-anything-fall-into-the-sun/page-1

Those first three links did not work. Please if you could give me the title I'll see if I can locate them. That was a good thread! "Can anything fall into the Sun?"

I see the P-R drag was discussed there too. http://www.scienceforums.net/topic/88734-can-anything-fall-into-the-sun/page-2#entry865556

 

This was a good link to the paper on "Planet-disk interaction and orbital evolution" http://arxiv.org/pdf/1203.1184v2.pdf

 

Thanks for the links Mordred.

Edited February 13, 2016 by Robittybob1

[Mordred]

If you goto the original thread the links works there. When I did the copy paste from that thread it copied the scienceforum address.

[Robittybob1]

If you goto the original thread the links works there. When I did the copy paste from that thread it copied the scienceforum address.

this was one of your helpful posts. ...break complex operations into managable portions.... very helpful thanks.

http://www.scienceforums.net/topic/93393-asteroids-of-the-asteroid-belt/page-2#entry904655

 

Forgot to stress the hydrodynamic aspect.

For example Google " nebula hydrodynamics". You will find a good collection of articles and related formulas.

Those should take you from an isothermal sphere to protoplanetary disk, to density wave.

In those articles look for key terminology. Write them down then study each separately (including formulas).

That's how you develop your research and tools to model build.

Just like programming break complex operations down into manageable portions.

Edited February 13, 2016 by Robittybob1

[Robittybob1]

It's been a few months since I looked directly at PR. I do recall having a good article on the subject. I'll dig it up as well as review the subject. The dust interactions If I recall only influences extremely minor size particles. It's influence is more upon the leftovers from other clearing processes. A later stage,

 

As far as rate of spin and PR I need to review.

@Mordred - Did you make any headway on this?

[Mordred]

Yeah it's pretty much as I recalled. The dust particles involved are roughly 1 micron in size. It would be like trying to planet build with the dust on your computer screen.

 

In the other posts you had I mentioned a few other processes though I can't recall the names atm.

 

Those would be your main contribution models. PR is too minor an influence

[Robittybob1]

Yeah it's pretty much as I recalled. The dust particles involved are roughly 1 micron in size. It would be like trying to planet build with the dust on your computer screen.

 

In the other posts you had I mentioned a few other processes though I can't recall the names atm.

 

Those would be your main contribution models. PR is too minor an influence

So are you saying that the rotational velocity of the Sun in the Pre main sequence stage (PMS) would have no effect on PR drag?

There are plenty who estimate the Sun being much larger and spinning faster during this period.

The P-R formula does not have an expression for the rotation rate of the Sun. It seems to make the assumption the rays are emitted from a point source, but in fact the radiation comes from the surface of the Sun and that surface is moving.

Edited February 18, 2016 by Robittybob1

[Mordred]

PR is calculated by radiation pressure. Essentially the radiation pressure heats up the smaller particles in an isotropic manner. (Due to small size). The particles themself release this gained heat this release causes loss of angular momentum (this is your drag in this instance) and subsequently orbit decay until the particle falls into the Sun. The closer the particle gets to the Sun the greater the angular momentum drag.

The rotation of the Sun itself wouldn't really matter look at the sheer volume of the Sun compared to a speck of dust. Now place that speck day for example the orbit of Mercury.

 

How could the suns rotation possibly matter.

 

Not that the direction the radiation comes from would change anything.

 

The key point is the dust speck is small enough 1 micron that no matter which direction it gets the radiation from, it's going to release the heat in every direction. This is the drag. (A good example is use a blowtorch to heat loose iron filings.

 

Can you measure a heat difference from one side of the filing compared to any other surface point? The answer will be no, and as such it makes no difference what direction the blow torch flame is coming from.)

 

Then it's orbit decay vs the Suns gravity and the dust particles angular momentum.

Edited February 18, 2016 by Mordred

[Robittybob1]

PR is calculated by radiation pressure. Essentially the radiation pressure heats up the smaller particles in an isotropic manner. (Due to small size). The particles themself release this gained heat this release causes loss of angular momentum (this is your drag in this instance) and subsequently orbit decay until the particle falls into the Sun. The closer the particle gets to the Sun the greater the angular momentum drag.

The rotation of the Sun itself wouldn't really matter look at the sheer volume of the Sun compared to a speck of dust. Now place that speck day for example the orbit of Mercury.

 

How could the suns rotation possibly matter.

 

Not that the direction the radiation comes from would change anything.

 

The key point is the dust speck is small enough 1 micron that no matter which direction it gets the radiation from, it's going to release the heat in every direction. This is the drag. (A good example is use a blowtorch to heat loose iron filings.

 

Can you measure a heat difference from one side of the filing compared to any other surface point? The answer will be no, and as such it makes no difference what direction the blow torch flame is coming from.)

 

Then it's orbit decay vs the Suns gravity and the dust particles angular momentum.

See if I can explain my logic to you again.

Open this link https://en.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect#/media/File:Poynting-Robertson_effect.png

 

There are two ways of looking at the cause of the effect diagram A or B.

In both cases there is an arrow named "v" which is the relative velocity difference between the Sun and the particle.

If that "v" was reduced or brought down to zero or even reversed would that make the P-R effect behave differently?

Did you say "yes"? or "no"?

I will go on once I know your opinion on the above. Basically I'm asking whether the magnitude of the "v" has a influence on the effect.

[Mordred]

v is the orbital velocity,

 

all you needed to is read the page I linked to you in PM. You won't reverse v. Its the relation between the force caused by the Poynting vector and force of gravity for changes in orbit...the link also explains the image you posted under how the two observers define the cause of motion change.

 

From the perspective of the grain of dust circling a star (panel (a) of the figure), the star's radiation appears to be coming from a slightly forward direction (aberration of light). Therefore the absorption of this radiation leads to a force with a component against the direction of movement. The angle of aberration is extremely small since the radiation is moving at the speed of light while the dust grain is moving many orders of magnitude slower than that.

 

From the perspective of the star (panel (b) of the figure), the dust grain absorbs sunlight entirely in a radial direction, thus the grain's angular momentum is not affected by it. But the re-emission of photons, which is isotropic in the frame of the grain (a), is no longer isotropic in the frame of the star (b). This anisotropic emission causes the photons to carry away angular momentum from the dust grain.

 

Impact of the effect on dust orbitsEdit

Particles with have radiation pressure at least half as strong as gravity, and will pass out of the Solar System on hyperbolic orbits.^[3] For rocky dust particles, this corresponds to a diameter of less than 1 µm.^[4]

Particles with may spiral inwards or outwards depending on their size and initial velocity vector; they tend to stay in eccentric orbits.

Particles with take around 10,000 years to spiral into the sun from a circular orbit at 1 AU. In this regime, inspiraling time and particle diameter are both roughly .^[5]

 

^{https://en.m.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect}

Edited February 18, 2016 by Mordred

[Robittybob1]

v is the orbital velocity,

 

all you needed to is read the page I linked to you in PM. You won't reverse v. Its the relation between the force caused by the Poynting vector and force of gravity for changes in orbit...

 

....

 

It is the orbital velocity if you consider the Sun to be stationary. Then "v" is just the orbital speed but if the Sun is not statioary but rotating by applying relative motion v is the instantaneous velocity difference. OK that is not what the article says but that is the claim of error I am making. It should be relative velocity difference for if the surface of the Sun matched the orbital velocity any photon would not have any aberration diagram (a) or in diagram (b) any photon carrying away more momentum at emission is balanced by the momentum gained by the dust at the time of absorption.

 

 

Maybe we can't resolve this here. I wonder if someone else would care to comment.

 

Is this the title of the page you linked?

Protoplanetary Disk Resonances and Type I Migration

or this one? "Poynting–Robertson effect"

https://en.m.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect

[Mordred]

Last link

 

Robbitty if you want to model something based upon the metrics involved in a model. It's a good idea to work the formulas out and try some examples.

 

The problem here is the metrics involved have nothing to do with the orbital speed of the sun. The metrics are specific to radiation pressure emitted by the Sun vs the orbital velocity of the particle. The most you can change with the Poynting vector metrics as designed is change orbits...

 

Due to the SIZE of particles involved, A SPINNING Sun makes no difference. The particle will still radiate the heat gain in the SAME manner.

 

This is the part you obviously keep missing. ITS the dust itself radiating the heat that causes DRAG.

 

NOT the direction of radiation.

 

This is the wrong theory to get the mechanism your seeking.

 

The mechanism that does involve sun rotation rate is density waves with Limbart resonance. The other link I sent on pm

 

On the other model all particle sizes are involved.

Edited February 19, 2016 by Mordred

[Robittybob1]

Last link

 

Robbitty if you want to model something based upon the metrics involved in a model. It's a good idea to work the formulas out and try some examples.

 

The problem here is the metrics involved have nothing to do with the orbital speed of the sun. The metrics are specific to radiation pressure emitted by the Sun vs the orbital velocity of the particle. The most you can change with the Poynting vector metrics as designed is change orbits...

 

Due to the SIZE of particles involved, A SPINNING Sun makes no difference. The particle will still radiate the heat gain in the SAME manner.

 

This is the part you obviously keep missing. ITS the dust itself radiating the heat that causes DRAG.

 

NOT the direction of radiation.

 

...

So you reckon the incoming radiation doesn't impart any momentum to the dust particle? What principle is that? Conservation of momentum would play a part surely.

 

 

 

This is the wrong theory to get the mechanism your seeking.

The mechanism that does involve sun rotation rate is density waves with Limbart resonance. The other link I sent on pm

On the other model all particle sizes are involved.

I'll have a look at it.

[Mordred]

The formulas for how to compare the imparted momentum change in 'velocity" are in the link. Try them for a change. Don't blame me if a metric developed by someone else doesn't work for you.

 

Google the term the dust radiates the heat "isotropically". This means from the first image it radiates the heat in all directions.

 

The advanced metrics under SR involve relativistic beaming. Here is a worked example.

 

http://physics.stackexchange.com/questions/200968/why-is-radiation-under-poynting-robertson-drag-anisotropic

 

Now ask yourself the question " What does a spinning Sun have to do with the direction of radiation, when the radiation is moving at c? And in what direction? Away from the Sun in a straight line.....so how can this change with a fast spinning Sun?

 

What path does light follow...

Did you ever look at the distance radiation pressure works with the Poynting Robertson vector??

 

"The PoyntingRobertson effect applies to grain-size particles. From the perspective of a grain of dust circling the Sun, the Sun's radiation appears to be coming from a slightly forward direction (aberration of light). Therefore, the absorption of this radiation leads to a force with a component against the direction of movement. (The angle of aberration is extremely small since the radiation is moving at the speed of light while the dust grain is moving many orders of magnitude slower than that.) The result is a slow spiral of dust grains into the Sun. Over long periods of time this effect cleans out much of the dust in the Solar System.

 

While rather small in comparison to other forces, the radiation pressure force is inexorable. Over long periods of time, the net effect of the force is substantial. Such feeble pressures are able to produce marked effects upon minute particles like gas ions and electrons, and are important in the theory of electron emission from the Sun, of cometary material, and so on.

 

Because the ratio of surface area to volume (and thus mass) increases with decreasing particle size, dusty (micrometre-size) particles are susceptible to radiation pressure even in the outer solar system. For example, the evolution of the outer rings of Saturn is significantly influenced by radiation pressure"

 

https://en.m.wikipedia.org/wiki/Radiation_pressure

 

So what difference does a spinning Sun entail when the effect is the Entire solar system. ?????

Edited February 19, 2016 by Mordred

[Robittybob1]

The formulas for how to compare the imparted momentum change in 'velocity" are in the link. Try them for a change. Don't blame me if a metric developed by someone else doesn't work for you.

 

....

Now ask yourself the question " What does a spinning Sun have to do with the direction of radiation, when the radiation is moving at c? And in what direction? Away from the Sun in a straight line.....so how can this change with a fast spinning Sun?

 

What path does light follow...

Did you ever look at the distance radiation pressure works with the Poynting Robertson vector??

 

"The PoyntingRobertson effect applies to grain-size particles. From the perspective of a grain of dust circling the Sun, the Sun's radiation appears to be coming from a slightly forward direction (aberration of light). Therefore, the absorption of this radiation leads to a force with a component against the direction of movement. (The angle of aberration is extremely small since the radiation is moving at the speed of light while the dust grain is moving many orders of magnitude slower than that.) .....

 

So what difference does a spinning Sun entail when the effect is the Entire solar system. ?????

OK try this thought experiment you have a single dust particle at the distance of the Earth radius and you have the surface of the Sun moving such that one particular dust particle is always directly over the same dead centerpoint (that is a very slow rotating sun 1 year to make 1 revolution. (like a geocentric satellite but over the Sun instead)

A photon from a point dead center of the whole set up heads toward the dust particle that is over the dead center point of the Sun. 8 minutes later the photon arrives, is the dust particle still in line with the photon? Will they connect?

Personally I couldn't answer that question but you might or someone else might. If it misses the dust what do we have to do to make it strike the dust particle? Does the sideways motion of the Sun remain with the photon during the time it is in space?

 

Above you have "Sun's radiation appears to be coming from a slightly forward direction (aberration of light)" How did that happen? Are saying the photon has no or such a small sideways component that the dust sort of runs into it?

With the Sun moving so slowly the surface speed will be nowhere enough to keep up with the dust particle, so I get a feeling the photon has to be angled slightly ahead of the dead center line. But then does that mean the photon will strike the dust with an angle slightly behind? - No because the dust is on a circular path around the Sun the dust will have curved slightly down by the time the photon arrives to strike it midpoint underneath.

Edited February 19, 2016 by Robittybob1

[pavelcherepan]

 

 

Does the sideways motion of the Sun remain with the photon during the time it is in space?

 

I'm pretty sure that that's nothing to do with "sideways motion of the Sun", whatever that is. It only has to do with the actual orbital velocity of the particle. No matter if it's in solar-stationary orbit, the particle is still moving in its orbit.

 

And also the Sun-stationary orbit would have a semi-major axis of (with modern day Sun):

 

[latex]a=\sqrt[3]{\frac{T^2*\mu}{4*\pi^2}} = \sqrt[3]{\frac{(25*24*60*60)^2*1.327*10^{20}}{4*\pi^2}}=2.16*10^9 m[/latex], which is within Sun's corona and the particle would evaporate sort of instantly.

 

 

 

Above you have "Sun's radiation appears to be coming from a slightly forward direction (aberration of light)" How did that happen? Are saying the photon has no or such a small sideways component that the dust sort of runs into it?

 

As far as I understand it, a photon wouldn't have any "sideways component" simply for the reason that from the instance the photon is created it's travelling at c. Adding a sideways component to its velocity would result in final velocity that can be above c, which is obviously impossible.

[Robittybob1]

 

I'm pretty sure that that's nothing to do with "sideways motion of the Sun", whatever that is. It only has to do with the actual orbital velocity of the particle. No matter if it's in solar-stationary orbit, the particle is still moving in its orbit.

 

And also the Sun-stationary orbit would have a semi-major axis of (with modern day Sun):

 

[latex]a=\sqrt[3]{\frac{T^2*\mu}{4*\pi^2}} = \sqrt[3]{\frac{(25*24*60*60)^2*1.327*10^{20}}{4*\pi^2}}=2.16*10^9 m[/latex], which is within Sun's corona and the particle would evaporate sort of instantly.

 

 

As far as I understand it, a photon wouldn't have any "sideways component" simply for the reason that from the instance the photon is created it's travelling at c. Adding a sideways component to its velocity would result in final velocity that can be above c, which is obviously impossible.

Thanks for attempting the thought experiment.

It is a thought experiment where the particle is orbiting the Sun where the Earth used to be, so at that distance it will take year to orbit the Sun.

We also engineer the Sun to slow its rotation to match the dust, that is why it can out that far for the Sun has been slowed.

(You certainly showed real skill with the LaTex Cheers)

So instead of a photon imagine a laser gun on the surface of the Sun. How do you hit the heliocentric particle? Which way do you point the laser?

When do you fire the laser, does it help to fire it earlier? No that can't work for it is always directly above.

Any angled trajectory would still have a speed of light of c. (The angle the laser is moved away from the vertical is so slight but light speed stays at c.)

 

 

Edited February 19, 2016 by Robittybob1

[pavelcherepan]

 

 

How do you hit the heliocentric particle? Which way do you point the laser?

 

It's not too hard to calculate if you know the direction the particle is moving. The angular velocity of the body at the same orbit as the Earth will be:

 

[latex]\omega=\frac{2*\pi}{365*24*60} = 1.19*10^{-5} radians/min[/latex]

 

We observe the particle an then aim the laser to 16 minutes ahead of it's observed position, because it was there 8 minutes ago and it will take another 8 minutes for the laser beam to reach it. Then we should aim at 1.19*10^-5*16 = 1.9*10^-4 radians ahead of it's observed location. And if the aim is good enough, we should hit it.

 

Anyway, how is this relevant to the topic of discussion? What does this have to do with the age of Sun?

Edited February 19, 2016 by pavelcherepan