Magnetic field around young star captured

October 27, 2014, Netherlands Organisation for Scientific Research (NWO)

For the first time astronomers, including SRON astronomer Woojin Kwon, have been able to capture the magnetic field in the accretion disk around a young star. The shape of the field was a big surprise. The discovery suggests that magnetic fields play an important role in forming a planetary system like our own, but that the process is more complicated than our current understanding. The research results have been published in this week's issue of Nature.

Stars are formed in cold and dense cores of molecular clouds. During the collapse of a core into a new young star (called a protostar) a circumstellar disk is created. This disk will eventually form planets and become a system like our solar system. However, in the early stages, this circumstellar disk is responsible for allowing mass to accrete on the protostar. This accretion is thought to be regulated by magnetic fields. Different theoretical models suggest different morphologies. The magnetic fields in the disk may be toroidal (i.e., circular fields in the disk) or poloidal (i.e., fields emanating from the poles of the protostar). Unfortunately, numerous observations in search of the magnetic field morphology have found no detection.

CARMA

An international team of astronomers, with SRON astronomer Woojin Kwon, used the Combined Array for Research in Millimeter-wave Astronomy (CARMA) of radio telescopes located in California, U.S.A., in an attempt to determine the shape of magnetic fields in the disk of the T Tauri star HL Tau. T Tauri stars are class of very young , still in the process of gravitational contraction. HL Tau has been forming for approximately 1 million years and is located 450 light-years away. From Earth, HL Tau has the brightest T Tauri star disk at millimeter wavelengths.

CARMA did indeed capture a magnetic field, which is the first detection of the magnetic field morphology in a T Tauri star disk."The discovery suggests thatmagnetic fields are important in forming a planetary system like our own," Woojin Kwon says. " While the magnetic field appears significantly more toroidal than poloidal, neither morphology is a good fit. This is at odds with current theoretical expectations, which suggests that the role of magnetic fields is more complicated than our current understanding." Future observations with the Atacama Large Millimeter Array in Chile are forthcoming and will provide better insight on the role of magnetic fields in circumstellar disks.

Explore further: Infant solar system shows signs of windy weather

More information: "Spatially resolved magnetic field structure in the disk of a T Tauri star." Nature (2014) DOI: 10.1038/nature13850

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viko_mx
2.3 / 5 (3) Oct 28, 2014
I do not fully understand the process accretion or formation of star systems with a central star and planets orbiting around them from a gas cloud. I can not find the reason why the star contain mostly light chemical elements such as (H, He, Li), while solid planets like the Earth, Venus and Mercury, located close to the star, contain mostly heavy elements. The same problem I find with gas giants such as Jupiter and Saturn and their significantly differing from one another solid satellites. Center of gravity (local or global for the sistem) of this gas cloud should be pulling the first heavy elements and light elements must remain in its periphery.
antialias_physorg
3.7 / 5 (6) Oct 28, 2014
I can not find the reason why the star contain mostly light chemical elements such as (H, He, Li), while solid planets like the Earth, Venus and Mercury, located close to the star, contain mostly heavy elements.

Here's a simple explanation
http://www.spacea...e-dense/

The issue isn't so much that closer-in planets didn't have all those light materials around. It's just that they couldn't hold on to it due to radiation pressure from the star stripping it away. (similarly the moons of gas giants are too small to keep theirs. But the gas giants have enough gravitational pull to retain light elements)
antialias_physorg
4 / 5 (4) Oct 28, 2014
That's not the issue he had, he observed that all the heaviest elements are not at the center of a structure that was supposedly formed by "gravitational collapse".

Why would you expect them to? Not the entire proto-cloud goes into the star. And the star does contain a sizeable amount of the heavier elements (just also a lot more of the lighter ones...since it is rather massive). Star's aren't pure hydrogen helium and lithium.

Also...Titan has an atmosphere...just sayin.

Titan's rather big. ..Note that it doesn't have a hydrogen atmosphere (but nitrogen)...just sayin.
ccryder1947
1 / 5 (1) Oct 28, 2014
The primary source phenomena for a star or for a planet or for a moon or even right down to a comet is an ElectroMagnetoToroid or EMT. An EMT is an electric flux loop (or a magnetic flux loop) and the reason I say 'or' is because the phenomenon oscillates between these two states. As an electric flux loop its poloidal vectors are magnetic so the structure shows the characteristic signature of a magnetic dipole. However, by the simple pi/2 radian rotation of the flux density vector around the axis of the Poynting Vector (which is the cross product of E and H and is everywhere on the flux toroid a normal [perpendicular to the flux toroid's surface]) an EMT that was in the magnetic dipole state becomes an H (magnetic) flux loop and now its poloidal vectors are E so then it shows the characteristics of an electric dipole. Thus an EMT oscillates between the two states at a characteristic frequency that is dependent upon the flux density and the size.
ccryder1947
1 / 5 (2) Oct 28, 2014
The sun, itself is an EMT or rather the underlying phenomena of a star is a large scale EMT that oscillates between the two states of being either an electric dipole (during solar maximum) or a magnetic dipole (during solar minimum). During the compact H-loop mode of an EMT it creates (via an ex nihilo process) quantum scale copies of itself and those quantum scale copies are nothing more or less than neutrons. So, large scale EMTs generate the mass that will later compose the bulk matter of a comet or a planet or of a star if the EMT is sufficiently large.
ccryder1947
1 / 5 (2) Oct 28, 2014
More about EMTs. Since the Poynting Vector is everywhere a normal or perpendicular to a flux toroid's surface (which is really an equipotential surface of the toroid). When the Poynting Vector is integrated over the entire surface it gives the total power crossing the surface in watts per square meter. When there is a pi/2 radian rotation of the flux density vector around the axis of the Poynting Vector everywhere on the flux toroid not only does the flux toroid change from being an E-flux toroid to an H-flux toroid or vice-versa, the Poynting Vector's direction flips directions from pointing outward to pointing inward (or vice-versa) so over time the structure is completely conservative. EMTs are what furnishes the universe with matter from planets to stars to comets down to Ball Lightning events. Stellar Jet systems (like HH-30, for example) are creating vast amounts of matter right in front of the whole scientific world's eyes and telescopes and they still don't seem to get it.
ccryder1947
1 / 5 (2) Oct 28, 2014
The idea of an EMT and its dynamic oscillations and ability to create new matter was first conceived of by Charles Cagle in the late 1990's based largely on evidence of a ball lightning event that was written up in Scientific American in 1886. see: 'Curious Phenomenon In Venezuela'; Cowgill, Warner; ScientificAmerican, 55:389, December 18, 1886.

Any competent professor of E.E. when presented with the dynamics of an E-flux loop will agree with the analysis that an E-loop will convert to an H-loop by the pi/2 radian rotation of the flux density vector around the axis of the Poynting Vector everywhere on the flux toroid and than an H-loop can change back to an E-loop via the same flux density rotation. Further they'll agree that the E-loop mode with be a magnetic dipole and the H-loop mode will be an electric dipole. Our sun displays this oscillation going from solar max to solar minimum and vice-versa. They've yet to understand that solar max is electric dipole mode.
viko_mx
1 / 5 (2) Oct 29, 2014
I read the explanation on the site, but I see several problems in it. It attempts to explain the processes of formation of the planets after the sun has already formed. But the processes of formation of stars and planets can be run simultaneously while the star shape, then can complete the formation of the planets. The question is why during the formation of the central star, where we do not have high temperature heavy elements do not come first in it? Center of gravity should be pulling these elements in its vicinity, and their concentration close to the star must fall, not rise as is. When the sun is already formed and light elements are heated by the star, they create presure on heavy elements necessary for the formation of solid planets, until they reach sufficient distance and cool. But chilled heavy elements can not stick progressively in larger units because collisions between them are fragile.
viko_mx
1 / 5 (2) Oct 29, 2014

This is a problem for the formation of the Earth and Mars because their sufficient distance from the sun. Assuming that the rings of Saturn are billions of years old, why they exist now if such unifying processes are possible? Finally why the moons of Jupiter or Saturn are solid and so different from each other, unlike planets that orbit around? There was no high temperatures from the beginig. The gas cloud is relatively homogeneous in the whole volume, and especially in such a narrow zone in which the planet formed.
antialias_physorg
5 / 5 (4) Oct 29, 2014
The question is why during the formation of the central star, where we do not have high temperature heavy elements do not come first in it?

Not sure what you are asking here. The heavier elements are seeded in the proto disk from other supernovae . You will not find rocky planets around first generation stars (unless they were captured from other, second generation stars).

Center of gravity should be pulling these elements in its vicinity

Acceleration of heavy elements to a mass is the same as light elements (drop a feather and a hammer in vacuum and they fall at the same rate)

The planets (and the central mass) accrete all kinds of stuff until the star lights up. It's only after that the inner planets lose their lighter elements. (Also note that planets aren't fixed to certain orbits forever. There's a fair chance that they move around during their lifetime due to gravitational disturbance from other planets or largish impacts.)
viko_mx
1 / 5 (1) Oct 29, 2014
The gravitational force between objects depends on their mass.
antialias_physorg
5 / 5 (2) Oct 29, 2014
The gravitational force between objects depends on their mass.

The force between two massive objects is proportional to the masses involved. But the acceleration generated by a force is inversely proportional to the mass. The masses cancel out and the acceleration for any object (massive or less massive) comes out the same.
viko_mx
1 / 5 (1) Oct 29, 2014
You are right about acceleration - a = F / m;
However, in the volume of protostar there is gradient of heavy to light elements allocated from the core to the surface. When fusion reactions begin light elements of protostar located farther away from the core will be blown away from the star by radiation pressure.
antialias_physorg
5 / 5 (3) Oct 29, 2014
When fusion reactions begin light elements of protostar located farther away from the core will be blown away from the star by radiation pressure.

I guess you answered your own question then: Once the star has started fusion the radiation pressure also blows away any lighter elements further out (e.g. those accreted around the inner plants).

Because, this time there is a constant force (radiation pressure...or more accurately: number photons impacting a given area) which means lighter elements get accelerated faster than not so light elements. I.e. it is more likely that lighter elements subject to such radiation pressure escape their respective gravity well while the heavier ones remain. The further out you go (and the heavier the planet) the less likely that becomes as radiation pressure decreases with the distance squared.

The star can hold on to most of its stuff as it is a quite deep gravity well.
http://xkcd.com/681/
viko_mx
1 / 5 (1) Oct 29, 2014
Light elements in the periphery of the protostar will be blown away due to radiation, but the problem is that there are no heavy elements where there are solid planets in this situation. If there remained a small percentage of heavy elements, they will be carried away by the light elemets and will be located where they are gas giants, because heavy elements have less acceleration, but greater moment of inertia than the light elements. As always, the question comes down to math and possibly computer simulations.
antialias_physorg
5 / 5 (3) Oct 29, 2014
is that there are no heavy elements where there are solid planets in this situation

Why not? The heavy elements, like the light elements are evenly distributed throughout the protodisk prior to start of fusion.
And light accelerated light elements don't 'carry away' heavy elements any more than they do other light elements (by what mechanism do you suppose that happens?) - especially if the planet's already formed before the star burst into life. Because then you r stuff is already down a gravity well. and to escape a gravity well you need escape VELOCITY. Since light elements are accelerated more by a given pressure/force they will more easily attain escape velocity than heavy elements - hence you get a speration effect.

As always, the question comes down to math

Well, do the math. It's fairly simple. Gravity and radiation pressure.
viko_mx
1 / 5 (1) Oct 30, 2014
We accept by intuition that all elements in the gas cloud before starting the process of accretion are evenly distributed, although we can not be sure of that. With the beginig of process of accretion, the center of gravity began to attract mass to itself in which light elements emerge in the periphery and heavy sink to the center. Upon reaching a critical density and heat in the core, fusion reactions begin and part of the light elements in the outer layers of the young star are blown out at a certain speed and that creates pressure or shock wave that pushed relatively far away the remnants of the proto cloud on certain distance. The calculations are not so simple because we can not know the power of radiation presure in the beginning. The young star has not found a balance yet and is very unstable.
viko_mx
1 / 5 (1) Oct 30, 2014
During this period she throws at high speed a large amount of gas, so the initial mass of the star is elusive. Therefore, a computer simulation can give a rough answer, but exact reconstruction of the past is fundamentally impossible.Therefore I think that where there are solid planets in our solar system, the process of accretion can not explain it. There must have been other forces that were involved in this process.
viko_mx
1 / 5 (1) Oct 30, 2014
During this period she throws at high speed a large amount of gas, so the initial mass of the star is elusive. Therefore, a computer simulation can give a rough answer, but exact reconstruction of the past is fundamentally impossible.Therefore I think that where there are solid planets in our solar system, the process of accretion can not explain it. There must have been other forces that were involved in this process.
viko_mx
1 / 5 (1) Oct 30, 2014
cnt
antialias_physorg
5 / 5 (1) Oct 30, 2014
We accept by intuition that all elements in the gas cloud before starting the process of accretion are evenly distributed,

While it certainly needs not be absolutely evenly distributed - unless you can show a mechanism why it shouldn't be it's a good assumption.

The calculations are not so simple because we can not know the power of radiation presure in the beginning.
If you know the size of the star currently you can take a pretty good stab at what the initial radiation pressure was. Since fusion/not fusion is only a function of pressure the point can be established when it starts (roughly at 0.08 times the mass of the sun) and equilibrium between gravity and radiation pressure is quickly reached (there's really nothing much to upset it).
antialias_physorg
3.7 / 5 (3) Oct 30, 2014
Therefore I think that where there are solid planets in our solar system, the process of accretion can not explain it.

The argument that: You don't believe the simulations (for no given reason) that therefore accretion doesn't work is...not entirely a convincing argument to put it mildly.

If you have a problem with the theory and simulations then propose mechanisms (with math) that are observable in nature. Just invoking other (unspecified) forces doesn't cut it. What do you have in mind? Where are these forces observed?

viko_mx
1 / 5 (1) Oct 31, 2014
In fact acretion also is hipotetical but not observable in nature process. For this reason, scientists do computer simulations with many various input parameters, which when properly adjusted can provide approximately reliable picture by the methods of adjusting. But if a physical problem has more thаn one solution, sifting the true solution is not always an easy task.
antialias_physorg
4 / 5 (4) Oct 31, 2014
In fact acretion also is hipotetical but not observable in nature process.

Well, we observe loosely held together asteroids (basically piles of rubble held together by their gravity). So the statement that accretion isn't observable in nature is not correct.

This guy made an experimet on the ISS that looks like accretion in a bag
http://www.skyand...ic-bags/

And the CATE experiment just arrived at the ISS.
viko_mx
1 / 5 (1) Oct 31, 2014
I reviewed the link. It is known that some substances form crystal structures even under normal Earth gravity. Such a substance is salt. Moisture in the air also crystallized in the form of falling snowflakes and in this process are involved electrostatic forces.Relatively small difference in gravity is not so important as the environment in which these processes occur. Electrostatic forces have an effect on the small particles, but their effect on the particles with larger size and weight can be neglected. But this can not explain the content of the molten interior of the Earth and its nickel-iron core. The rings of Saturn and the other gas planets are examples that the process of accretion is not very reliable. The big difference in the chemical composition of the moons orbiting gas giants also raise a lot of questions.
antialias_physorg
4 / 5 (4) Oct 31, 2014
The big difference in the chemical composition of the moons orbiting gas giants also raise a lot of questions.

As noted: what question?

Small: cannot hold on to their atmosphere
Large: can hold on to atmosphere
Large and small from same initial cloud will turn out very dissimilar in composition after a time. What part of that is hard to grasp?

And not all these moons need to be native to their planets. Some could be captured objects.

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