A Seemingly Square Corona, Sun's Crown (APOD 08 Aug 2008)

[neufer]

http://apod.nasa.gov/apod/ap080808.html

http://apod.nasa.gov/apod/ap080727.html

[orin stepanek]

http://apod.nasa.gov/apod/ap080808.html

http://apod.nasa.gov/apod/ap080727.html

Makes one wonder if the corona is showing the way the sun will shed it shell when it is time to go?

Orin

[bystander]

Makes one wonder if the corona is showing the way the sun will shed it shell when it is time to go?

I had similar thoughts and I think there's something to that. The corona is influenced by the sun's magnetic fields and solar wind. IMHO any mass ejected by the sun will be affected in the same way. Art? Chris? Henk? Anybody

[emc]

I witnessed an electric motor explode once… I was curious if the 120 VAC from the house outlet would make the 12 VDC model racecar motor I was tinkering with run faster… I remember a blinding white flash as I was peering hopefully at the motor… but do not recall any detail as to whether the explosion followed the armature housing magnetic poles or not. At the time, I did not even know to look for such things. So as much as I would love to add something to the discussion, I reckon I am not much help with the Sun blowing up thing.

[orin stepanek]

I witnessed an electric motor explode once… I was curious if the 120 VAC from the house outlet would make the 12 VDC model racecar motor I was tinkering with run faster… I remember a blinding white flash as I was peering hopefully at the motor… but do not recall any detail as to whether the explosion followed the armature housing magnetic poles or not. At the time, I did not even know to look for such things. So as much as I would love to add something to the discussion, I reckon I am not much help with the Sun blowing up thing.

Ed; I don't think I'll be around to observe it.

Orin

[emc]

Makes one wonder if the corona is showing the way the sun will shed it shell when it is time to go?

Hi Orin,

After seeing neufer’s subtle comparison of the Sun’s corona and IC 4406, I was wondering the same thing as you and bystander.

Perhaps a best guess scenario of the Sun’s nebula evolution could be modeled with computers. I couldn’t find anything on the www about it but that doesn’t mean someone isn’t working on it. Would be cool to see!!! 8)

[henk21cm]

I had similar thoughts and I think there's something to that. The corona is influenced by the sun's magnetic fields and solar wind.

The corona lies between the photosphere and the solar wind. It is pretty hot: a few million K. It is basically a plasma, highly ionized, multiple electrons stripped off their atoms.

IMHO any mass ejected by the sun will be affected in the same way.

Well, that depends. The corona is a very thin medium. The magnetic forces of the solar field influence the path which thin matter will follow. The magnetic pressure is large compared to the thermodynamical pressure of the gasses. However, when larger and bulkier chunck of sun are ejected, the thermodynamic pressure of the gas will increase and eventually overcome the magnetic pressure.

In the image of todays APOD 4 coronal streamers can be seen. Suppose the sun is a civilian clock. The streamers are at 2, 4, 8 and 10 o'clock. Between 2 and 4 and between 8 and 10 two coronal holes are visible. At 1 o'clock an active loop area is visible, with a flare loop closer to the limb of the moon. Active loop area's are formed by the protuberances (this may not be a correct English word, i cannot find any good description in my dictionaries) These protuberances are arcs of matter between the North and South pole of a solar spot. It is like a prominence, however the latter extends further into the corona. At 6 and 12 o'clock polar plumes are visible. Matter is ejected and it follows the radial direction of the magnetic field. The similarity in shape with the seemingly square nebula of nearly two weeks ago is striking.

[ironic]Maybe any of you has seen the same as i did: the image resembles a white sheet, loaded with a heavy ball on it, and a bright light behind the sheet. The folds in the sheet, as caused by the ball, are the structure in the corona. [/ironic]

[Arramon]

http://apod.nasa.gov/apod/ap080808.html



Now that is an awesome image showing the Sun's brilliance without actually blinding someone. =)

Explanation: During a total solar eclipse, the Sun's extensive outer atmosphere, or corona, is an inspirational sight. The subtle shades and shimmering features of the corona that engage the eye span a brightness range of over 10,000 to 1, making them notoriously difficult to capture in a single picture. But this composite of 28 digital images ranging in exposure time from 1/1000 to 2 seconds comes close to revealing the crown of the Sun in all its glory. The telescopic views were recorded near Kochenevo, Russia during the August 1 total solar eclipse and also show solar prominences extending just beyond the edge of the eclipsed sun. Remarkably, features on the dark near side of the New Moon can also be made out, illuminated by sunlight reflected from a Full Earth.

Now is that corona being shaped by the magnetic field lines of the Sun? Looks like it from the lines they are in. Most excellent composite.

[Doum]

Henk you said,

"the thermodynamic pressure of the gas will increase and eventually overcome the magnetic pressure. "


Now i'm wondering, aint the magnetic field also increase as the sun compact itself and about ready to blow ensuring then that the magnetic pressure will hold just long enough for the ionise gas to start moving toward the line of force before that strong magnetic pressure collapse?

Then it mean that after a few century or millenia we will be able to see at what time the magnetic force of a star collapse when it explode by lookin at the nebula shape. So, different sun exploding create diffrent nebula according to it's size and content and revolution and magnetic field it had at the moment of explosion. I have a headache now.

[starnut]

Henk you said,

"the thermodynamic pressure of the gas will increase and eventually overcome the magnetic pressure. "


Now i'm wondering, aint the magnetic field also increase as the sun compact itself and about ready to blow ensuring then that the magnetic pressure will hold just long enough for the ionise gas to start moving toward the line of force before that strong magnetic pressure collapse?

Then it mean that after a few century or millenia we will be able to see at what time the magnetic force of a star collapse when it explode by lookin at the nebula shape. So, different sun exploding create diffrent nebula according to it's size and content and revolution and magnetic field it had at the moment of explosion. I have a headache now.

Not sure what you meant by the sun "ready to blow". If you meant blowing up like a supernova, it aint gonna happen to the sun. Reason: the sun is not massive enough to go supernova at the end of its life. It happens only to stars having at least 8 solar masses.

Gary

[Cherie]

In another thread about this recent eclipse, Bystander posted a site that explains beautifully the "square" or rectangular corona.

http://www.exploratorium.edu/eclipse/2008/index.html

As I understand it, because the sun, in its 11-year cycle of "hot" to "cool," is currently in the cool phase, the corona appears bi-polar, whereas photos from eclipses during the "hot" phase show fully orbed excitement of the corona.

Thank you, Bystander, for this great link. Really enjoyed, and learned a lot from, the 1-hour replay of the recent full eclipse over China.

Cherie

[Doum]

Hello Starnut, you said:
"Not sure what you meant by the sun "ready to blow"."

Sorry for my bad english. To me all star are sun. I should of use the word "star".

And i was doing a wild guess on nova and supernova "star" that explode and the nebula shape it create.
So, does a star magnetic field increase as a star shrink before explosion?
Is it plausible?

[henk21cm]

Henk you said,

"the thermodynamic pressure of the gas will increase and eventually overcome the magnetic pressure. "

Now i'm wondering, aint the magnetic field also increase as the sun compact itself and about ready to blow ensuring then that the magnetic pressure will hold just long enough for the ionise gas to start moving toward the line of force before that strong magnetic pressure collapse?

That was exactly what i meant but failed to express properly in a short reply. I distinghuish three cases:

1. Little matter, much magnetism
2. Much matter, little magnetisme
3. Matter and magnetism are equally strong

Little and much are relative concepts. The basic idea is that magnetic fields can not move through a plasma. Seen from the other side: plasma can not move through (perpendicular to) a magnetic field. The origin of this is the Lorentz force, named after Hendrik Anton Lorentz, who lived in the last decades of the 19th century and the early decades of last century.

For 1 the magnetic field puts constraints on the location of matter. The magnetic bottles as used in a tokamakis an earthbound demonstration of confinement of matter. The "Theta pinch" http://en.wikipedia.org/wiki/Pinch_(plasma_physics) in an electrical discharge is just another one. (The latter URL contains parentheses, which phpbb can not cope with)

For 2 the matter drags the magnetic field with it. That situation was what i meant with the line you quoted: the thermodynamical pressure of the plasma overcomes the magnetic pressure. The pressure of the ionized gas is so strong it will drag the magnetic field lines with it. Some astronomers see a neutron star as an example: the star collapsed from an odd million km to 10-100 km. The ionized outer rim of the neutron star compresses the field lines inward, reaching magnetic fields of the order of 0.1 MT.

For 3 it is both magnetic and thermodynamical influence. The bowshock of the solar wind at the front of the earth is an example. The field lines are copmpressed, however the solar wind follows the field lines of the earth's magnetic field and can enter the earth's atmosphere in the polar region of the earth only: Aurora Australis and Aurora Borealis.

Then it mean that after a few century or millenia we will be able to see at what time the magnetic force of a star collapse when it explode by lookin at the nebula shape.

It's more the size of the nebula and its radial velocity which gives an estimate of the age of a planetary nebula than its shape. If a pulsar is present within the nebula, the exponential decay in pulse frequency is just another good estimator for the age of the pulsar.

[emc]

Maybe any of you has seen the same as i did: the image resembles a white sheet, loaded with a heavy ball on it, and a bright light behind the sheet. The folds in the sheet, as caused by the ball, are the structure in the corona.

Hi Henk,

I had the same impression! (pun intended) It made me think of the ball rolling along a two-dimensional grid in the sheet analogy for Space curvature.

Gravity, light, sound, magnetic, electronic, oceanic, hand ( ) So many waves, so little time...

Regarding the planetary nebula phase of our Sun, I found this link from the Cat's Eye APOD caption to be very helpful... http://www.astro.washington.edu/balick/WFPC2/ The author expressed an opinion that the "planetary nebulae" would be better named "ejection nebulae" and you mentioned "ejection" in your post when describing the event. Why can't names be changed when new information comes to light??? Would be helpful for layman learners such as myself.

[orin stepanek]

Makes one wonder if the corona is showing the way the sun will shed it shell when it is time to go?

Hi Orin,

After seeing neufer’s subtle comparison of the Sun’s corona and IC 4406, I was wondering the same thing as you and bystander.

Perhaps a best guess scenario of the Sun’s nebula evolution could be modeled with computers. I couldn’t find anything on the www about it but that doesn’t mean someone isn’t working on it. Would be cool to see!!! 8)

What gets me to wonder is that most planetaries are hourglass; unless viewed from the end like the Ring Nebula. Maybe the star's poles has something to do with it?

Orin

[apodman]

Another link for the SEEMINGLY SQUARE (SS) collection:

http://antwrp.gsfc.nasa.gov/apod/ap010220.html

As long as we have SS dying stars and SS middle aged stars, why not an SS baby star?

[emc]

What gets me to wonder is that most planetaries are hourglass; unless viewed from the end like the Ring Nebula. Maybe the star's poles has something to do with it?

Makes sense to me... the rotation speed is greater at the equator and less at the poles so I believe ejected matter would tend to travel further from the equator.

Henk explained how the magnetic field will influence the ejected matter as long as the ejected matter's mass is less than the magnetic force.

Also I wondered if planets in the field of the ejected matter would have any effect on the nebula cloud formation?

[Doum]

Oh boy, was it easy to be wrong that easily?(I mean me being wrong.) Yea i was. I was seeing superconductivity in a star strarting to collapse before explosion thus creating higher magnetic field. Thanks henk21cm. Now i will try to revise my understanding of the law of physics. Being in chemistry analysis make me forget about the laws of physics very easily. And yet i use the ICP.AES in doing chemical analysis.

So it is not possible that the magnetic field of a star about to explode, will be estimate of what it was looking just before the explosion by looking at the gas expansion it create. (Meaning a few millenia later.) O.K.

[henk21cm]

Makes sense to me... the rotation speed is greater at the equator and less at the poles so I believe ejected matter would tend to travel further from the equator.

I have my doubts, so lets do a "back of an envelope" calculation. According to the solar wiki the equatorial rotation is 14.18º/day. From º to radians multiply by π and divide by 180, from days to seconds multiply by 86400. The conversion factor is about 2E-8, so the circle frequency ω=3E-6 radians/second. The centrifugal acceleration is ω²R, with R=7E8 m. That leads to an equatorial centrifugal acceleration of about 6E-3 m/s²

Now assume the sun is nearly spherical, not as irregularly shaped as the Kuiperbelt object named Santa. In a reasonable approximation the acceleration of gravity at the solar equator is GM/R² where G is the gravitational constant (6.67E-11 Nm²/kg²), M is the solar mass (2E30 kg) and R = 7E8 m. The equatorial acceleration of gravity is then approximately 260 m/s². Approximately and about mean 1 digit, so 260 might be 300 or 200 as well.

Compare the equatorial centrifugal force 6E-3 with the acceleration of gravity 260 m/s² Their quotient is of the order of 2E-5 or 20 ppm. In my opinion that is minute. Effects of turbulence in the ejected mass are larger than the difference as caused by centrifugal acceleration.

I was seeing superconductivity in a star strarting to collapse before explosion thus creating higher magnetic field.

Superconductivity is explained by the formation of Cooper pairs. Bardeen, Cooper and Schrieffer received a Nobel prize for their explication of superconductivity in 1972, which Heike Kamerlingh Onnes has discovered in 1911. A Cooper pair consists of two electrons with opposite spin. They are attracted by each other, in spite of the repulsive forces due to their equal signed charge. It is a kind of Bose-Einstein condensate, the latter two predicted in the nineteen twenties. The bond is kept togehther as long as the thermal exitations (phonons) are sufficiently low. That is the reason why superconductivity takes place at low temperatures. At least you will need liquid nitrogen (77K) to cool the matter down, so that Cooper pairs may form. Temperatures in the photosphere of a red giant, of about 2000 K, are a bit too high, thermal exitations are 1.5 to 2 orders of magnitude too high to allow for the formation of Cooper pairs.

Another argument why superconductivity is an unlikely phenomenon to play a significant role in a stellar explosion: the Meisner effect. This effect prevents magnetic fields to penetrate into a superconducting material. So superconducting stellar material moving in the stellar magnetic field is rather unlikely.

So it is not possible that the magnetic field of a star about to explode, will be estimate of what it was looking just before the explosion by looking at the gas expansion it create.

IMHO that is rather unlikely. Vincent Icke et al. have developed a mathematical model that describes the interaction between the originally ejected material and the stellar wind. The popular version of the article i would like to quote now, is at the desk of the editor of the magazine of our local astronomy club. The less popular (easy to read) version can be found on the website of Vincent Icke. The images and the Flash movies on his site bare similarity with the shape of the "Red rectangle" nebula. It might be possible that i did not fully understood your final remark. So, alternatively, if by any means it would be possible to estimate the current magnetic field of the imploded star, an estimation (of a few orders of magnitude) can be given of the strength of the magnetic field of the star before it exploded. The shape of a stellar field, well, i fully agree with Art Neuendorffer, that is dipolar, just like a bar magnet.

[Doum]

Thanks henk,

Now i have new fascinating reading to do on that subject to better understand it.

[iamlucky13]

Now is that corona being shaped by the magnetic field lines of the Sun? Looks like it from the lines they are in. Most excellent composite.

Yep.

Anybody know what this is? Venus? Mercury?

[henk21cm]

Anybody know what this is? Venus? Mercury?

Neither of them. The object is about 1º from the center of the sun. Mercury is over 3º, Venus even further.

[emc]

Makes sense to me... the rotation speed is greater at the equator and less at the poles so I believe ejected matter would tend to travel further from the equator.

I have my doubts, so lets do a "back of an envelope" calculation. According to the solar wiki the equatorial rotation is 14.18º/day. From º to radians multiply by π and divide by 180, from days to seconds multiply by 86400. The conversion factor is about 2E-8, so the circle frequency ω=3E-6 radians/second. The centrifugal acceleration is ω²R, with R=7E8 m. That leads to an equatorial centrifugal acceleration of about 6E-3 m/s²

Now assume the sun is nearly spherical, not as irregularly shaped as the Kuiperbelt object named Santa. In a reasonable approximation the acceleration of gravity at the solar equator is GM/R² where G is the gravitational constant (6.67E-11 Nm²/kg²), M is the solar mass (2E30 kg) and R = 7E8 m. The equatorial acceleration of gravity is then approximately 260 m/s². Approximately and about mean 1 digit, so 260 might be 300 or 200 as well.

Compare the equatorial centrifugal force 6E-3 with the acceleration of gravity 260 m/s² Their quotient is of the order of 2E-5 or 20 ppm. In my opinion that is minute. Effects of turbulence in the ejected mass are larger than the difference as caused by centrifugal acceleration.

Hi Henk,

You are in the playing field and I am just a spectator. Thanks for sharing your courteous thoughts. We are fortunate to have folks like you, Art Neuendorffer, Chris Peterson and several others sharing in Asterisk. I don’t hope to ever catch up to you guys technically but it’s certainly an enjoyable ride for me to be allowed to communicate.

[kovil]

Thanks Henk for your great posts.

" So, alternatively, if by any means it would be possible to estimate the current magnetic field of the imploded star, an estimation (of a few orders of magnitude) can be given of the strength of the magnetic field of the star before it exploded. The shape of a stellar field, well, i fully agree with Art Neuendorffer, that is dipolar, just like a bar magnet."

I was understanding that when a star goes nova or other type of explosion less intense than a supernova, it was because something interrupted the current flowing thru the star, and as a result the bottling magnetic fields collapsed and allowed the explosion. Another way of describing it might be to say the double layer collapsed.

Do you see things in this way?

kovil

[henk21cm]

I was understanding that when a star goes nova or other type of explosion less intense than a supernova, it was because something interrupted the current flowing thru the star, and as a result the bottling magnetic fields collapsed and allowed the explosion. Another way of describing it might be to say the double layer collapsed.

Do you see things in this way?

What i wrote is based on the interviews with an astro-physicist during the late eighties. She told me over the years a lot about magnetism in the universe, while i wrote down her knowledge and idea's for the quarterly magazine of our local astronomy club. My notes are gone, what is left are the odd 100 pages of the series of articles. These allow me to reconstruct the -based on commonly excepted idea's in the eighties- result of the collapse. Note: it is not a scientific publication, just a popular description.

(translated)
In 1933 the theory of neutron stars was developed. It was not possible to find a neutron star, due to its low luminosity. In 1968 Jocelyn Bell discovered to her surprise some scruff in her readings. This scruff had an origin in a magnetic field. What she found, turned out to be a pulsar. Its magnetic field is extremely strong. This is a consequence of the collapse of a star while the matter freezes the magnetic field. (Note 2008: Matter dominates the field). The number of field lines (B) within a collapsing cross section (e.g. the equatorial plane) must be constant during the collapse:

B = constant / R²          (R is the radius of the star)

When assuming an average field of e.g. our sun (B= 10 mT), the resulting field will increase, when the sun (R = 1E6 km) colllapses to a neutron star (R = 10 km), by a factor fo 1E10 to 0.1 GT. The -on average dipolar- structure of the field would have been conserved. As a consequence of the law of conservation of angular momentum, the rotational period will decrease:

M R² / T = constant       ( M is mass, R is radius, T is rotational period)

As an illustration: our sun. Lets assume that the core of our sun has a radius of 1E5 km (one tenth of the outer radius). The current rotational period is 28 days, that is about 2E6 s. When the core mass remains constant, the rotational period must decrease by a factor 1E8 to 2E-2 s. That is spinning 50 times per second around its axis. For the Crab pulsar the period found is 3E-2 s.

From what she told, it was evident that matter dominated the field. The field is frozen or anchored in the matter and when the matter collapses, it drags the magnetic field and compacts it. From what i read in your post, you assume that the magnetic field collapses and drags the matter with it. Your idea must be based on later (>2000) theories.