Astronomers peer inside stars, finding giant magnets

October 22, 2015
This artist's representation of a red giant star with a strong internal magnetic field shows sound waves propagating in the stellar outer layers, while gravity waves propagate in the inner layers where a magnetic field is present.

Astronomers have for the first time probed the magnetic fields in the mysterious inner regions of stars, finding they are strongly magnetized.

Using a technique called asteroseismology, the scientists were able to calculate the strengths in the fusion-powered hearts of dozens of , that are evolved versions of our sun.

"In the same way medical ultrasound uses to image the interior of the human body, asteroseismology uses sound waves generated by turbulence on the surface of stars to probe their inner properties," says Caltech postdoctoral researcher Jim Fuller, who co-led a new study detailing the research.

The findings, published in the October 23 issue of Science, will help astronomers better understand the life and death of stars. Magnetic fields likely determine the interior rotation rates of stars; such rates have dramatic effects on how the stars evolve.

Until now, astronomers have been able to study the magnetic fields of stars only on their surfaces, and have had to use supercomputer models to simulate the fields near the cores, where the nuclear-fusion process takes place. "We still don't know what the center of our own sun looks like," Fuller says.

Red giants have a different physical makeup from so-called main-sequence stars such as our sun—one that makes them ideal for asteroseismology (a field that was born at Caltech in 1962, when the late physicist and astronomer Robert Leighton discovered the solar oscillations using the solar telescopes at Mount Wilson). The cores of red-giant stars are much denser than those of younger stars. As a consequence, sound waves do not reflect off the cores, as they do in stars like our sun. Instead, the sound waves are transformed into another class of waves, called gravity waves.

"It turns out the gravity waves that we see in the red giants do propagate all the way to the center of these stars," says co-lead author Matteo Cantiello, a specialist in stellar astrophysics from UC Santa Barbara's Kavli Institute for Theoretical Physics (KITP).

This conversion from sound waves to gravity waves has major consequences for the tiny shape changes, or oscillations, that red giants undergo. "Depending on their size and internal structure, stars oscillate in different patterns," Fuller says. In one form of oscillation pattern, known as the dipole mode, one hemisphere of the star becomes brighter while the other becomes dimmer. Astronomers observe these oscillations in a star by measuring how its light varies over time.

When are present in a star's core, the fields can disrupt the propagation of gravity waves, causing some of the waves to lose energy and become trapped within the core. Fuller and his coauthors have coined the term "magnetic greenhouse effect" to describe this phenomenon because it works similarly to the greenhouse effect on Earth, in which greenhouse gases in the atmosphere help trap heat from the sun. The trapping of inside a red giant causes some of the energy of the star's oscillation to be lost, and the result is a smaller than expected dipole mode.

In 2013, NASA's Kepler space telescope, which can measure stellar brightness variations with incredibly high precision, detected dipole-mode damping in several red giants. Dennis Stello, an astronomer at the University of Sydney, brought the Kepler data to the attention of Fuller and Cantiello. Working in collaboration with KITP director Lars Bildsten and Rafael Garcia of France's Alternative Energies and Atomic Energy Commission, the scientists showed that the magnetic greenhouse effect was the most likely explanation for dipole-mode damping in the red giants. Their calculations revealed that the internal magnetic fields of the red giants were as much as 10 million times stronger than Earth's magnetic field.

"This is exciting, as internal magnetic fields play an important role for the evolution and ultimate fate of stars," says Professor of Theoretical Astrophysics Sterl Phinney, Caltech's executive officer for astronomy, who was not involved in the study.

A better understanding of the interior magnetic fields of stars could also help settle a debate about the origin of powerful magnetic fields on the surfaces of certain neutron stars and white dwarfs, two classes of stellar corpses that form when stars die.

"The magnetic fields that they find in the red-giant cores are comparable to those of the strongly magnetized white dwarfs," Phinney says. "The fact that only some of the red giants show the dipole suppression, which indicates strong core fields, may well be related to why only some stars leave behind remnants with strong magnetic fields after they die."

The asteroseismology technique the team used to probe red giants probably will not work with our sun. "However," Fuller says, "stellar oscillations are our best probe of the interiors of stars, so more surprises are likely."

The paper is entitled "Asteroseismology Can Reveal Strong Internal Magnetic Fields in Red Giant Stars."

Explore further: Mysterious, massive, magnetic stars

More information: "Asteroseismology can reveal strong internal magnetic fields in red giant stars," by J. Fuller; L. Bildsten et al. DOI: 10.1126/science.aac6933

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30 comments

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bschott
2.3 / 5 (8) Oct 22, 2015
Progress....slowly but surely.
indio007
3.4 / 5 (10) Oct 22, 2015
Call the nobel committee! The are claiming they detected gravity waves!
redge_little
2.1 / 5 (7) Oct 22, 2015
In 2005, RBL first originally and correctly proposed that strong magnetic fields can determine the internal structures of the SUN and other stars. Moreover RBL in 2005 discovered, predicted and published that inside stars from the outer corona thermal energy and heat are transformed to gravity inward toward the surface of the sun (star) and the gravity transforms to magnetism inward toward the core. See pages 27 - 30 of "A Theory of the Relativistic Spinrevorbital" [http://www.academ...AB049585] click 'Full Text PDF' for a free download of the manuscript.
redge_little
1.6 / 5 (7) Oct 22, 2015
This manuscript was first archived in sci.print by RBL in 2005, but the archive crashed in 2008 by the moderator of the archive. RBL later published ( "A Theory of the Relativistic Spinrevorbital" ) this manuscript in a new archive in 2012 [http://vixra.org/abs/1212.0011 ]. The manuscript was modified and published in its latest version in Jan 2015 in Intl Journal of Physical Sciences!
redge_little
1.7 / 5 (6) Oct 22, 2015
Now later in Oct 2015 researchers UC Santa Barbara's Kavli Institute for Theoretical Physics have developed a techniques related for measuring magnetic fields deep inside stars based on the prior 2005 model of RBL. The techniques is based on what RBL previously proposed in 2005 that surface heat and sound transforms to gravity with inward distance and the gravity waves traveling inward toward the core of the star get trapped and transformed by the magnetic field in the core exactly as RBL proposed in 2005 [ http://www.academ...AB049585 ].
redge_little
1.7 / 5 (6) Oct 22, 2015
The surface oscillations of the star depends on the internal magnetic fields strength as it decreases with stronger internal magnetic field strength of the star. The technique measures the internal magnetic field of the stars on the basis of the magnitude surface oscillations of sound, heat and gravity. The measurement is totally based on the prior idea of RBL from 2005! I thank GOD for the vision!
Uncle Ira
4.1 / 5 (9) Oct 22, 2015
@ redge-Skippy. How you are?. I am good.

Calm down Cher. RBL stole that idea from Zephir-Skippy in 2003. That was what led him to the AWT in the first place.
carlo_piantini
1.8 / 5 (5) Oct 22, 2015
What is the possible justification for applying gravity waves to this model, when no such waves have been detected by any experiment to date? Seriously, what is with cosmology and the constant application of hypothesis that have no experimental support at all? In what other scientific domain to you get to apply widespread use of hypothesis that have absolutely no experimental support at all?
Gino
3.7 / 5 (3) Oct 23, 2015
Could we not have the strength of magnetic forces quoted in proper scientific units ie Telsa.s not times the Earths field strength , this is like quoting the mass of stars like a that of so many blue whales.
wduckss
2 / 5 (4) Oct 23, 2015
Another work that looks at the stars statically, without rotation about an axis.
All data are obtained for the Earth and its magnetic field is valid for all other bodies with a hot core. The difference make the rotation speed a certain body.
Red Star (except the stars with low mass, where red can mean the transitional phase) has a slow rotation about an axis ... white and blue very fast rotation, and the resulting data are in direktnov connection, with speeds of rotation.
On Earth, there is no radiation, no radiation to the stars, it means no nuclear processes only simple physics.
notsoeasytoforget
4.1 / 5 (15) Oct 23, 2015
Call the nobel committee! The are claiming they detected gravity waves!

Note that gravity waves are different than gravitational waves. Gravity waves are waves for which the restoring force is buoyancy. Ocean waves are an example of gravity waves. Gravity waves are routinely identified in oscillating stars. Gravitational waves on the other hand are ripples in the fabric of spacetime, predicted by general relativity and, as you correctly pointed out, worthy a Nobel prize.
notsoeasytoforget
4.2 / 5 (10) Oct 23, 2015
What is the possible justification for applying gravity waves to this model, when no such waves have been detected by any experiment to date? Seriously, what is with cosmology and the constant application of hypothesis that have no experimental support at all? In what other scientific domain to you get to apply widespread use of hypothesis that have absolutely no experimental support at all?


Carlo, gravity waves are different than gravitational waves. Gravity waves are waves for which the restoring force is buoyancy. Ocean waves are an example of gravity waves. Gravity waves are routinely identified in oscillating stars and this work is based on solid observational evidence.
Gigel
4.5 / 5 (8) Oct 23, 2015

"Using a technique called asteroseismology, the scientists were able to calculate the magnetic field strengths in the fusion-powered hearts of dozens of red giants, stars that are evolved versions of our sun."

The use of scientific sounding terms does not change the essence of a nonsense. There is no way to determine what is happening in the cores of stars through remote observation. But in today's pseudo science philosophers speculators are in vogue.

Read the original article and if you have any significant observations to make to the procedures used by its authors, then write a reply article with your observations to the Science journal. "There is no way" is a very general and ambiguous statement and it doesn't make much sense.
NIPSZX
2.3 / 5 (3) Oct 23, 2015
I am curious, how come we can't see the center of our own Sun, but can view the centers of other stars??
antialias_physorg
4.6 / 5 (11) Oct 23, 2015
Call the nobel committee! The are claiming they detected gravity waves!

What is the possible justification for applying gravity waves to this model, when no such waves have been detected

We're talking about seismology here - not Relativity.
Gravity waves in seismology are different critter than gravity waves in Relativity. To give them their proper names:
Seismology/fluid dynamics: g-mode waves or gravity waves (buoyancy-gravity driven waves in a fluid/gaseous medium)
Relativity: gravitational waves (ripples in spacetime curvature)

There is no way to determine what is happening in the cores of stars through remote observation

Ever seen an ultrasound image? Do you doubt that ultrasound images give a good representation of what happens inside your body? Seismology is the same thing (just applied to larger bodies)
carlo_piantini
4.6 / 5 (9) Oct 23, 2015
@notsoeasytoforget and antialias: thank you! For a good minute there I was seriously confused as to how this was acceptable. I appreciate the clarification!
carlo_piantini
3 / 5 (3) Oct 23, 2015
Likewise, can anyone explain a bit more about what they mean in terms of sound waves? It isn't actually sound as it is on Earth, i.e. pressure waves in the oxygen around us. So, what is actually waving in the star when they call it "sound"? Is the plasma on the surface of the star undergoing some kind of longitudinal pressure? And how? Electrostatically, or via magnetohydrodynamics?
antialias_physorg
4.6 / 5 (10) Oct 23, 2015
It isn't actually sound as it is on Earth, i.e. pressure waves in the oxygen around us.

Well..on Earth it's mostly in the nitrogen, of which there is a lot more than the oxygen ;-)

Stars are mainly balls of plasma - and actually not all that dense at the surface. E.g. the photosphere is only about 1/1000th as dense as air at sea level on earth. A sound wave (in science) is just a pressure wave moving through a medium (which may be a solid, a liquid, a gas or plasma) it's not something that is limited to human-ear-audible atmsopheric waves.

Is the plasma on the surface of the star undergoing some kind of longitudinal pressure?

Not an expert on this - but there are places on the sun which are cooler and hotter (sunspots are cooler) which lead to dyxnamic flow phenomena. There's magnetic field fluxes going on. And of course there are planets in orbit tugging at it every which way (The sun experiences tides just like Earth oceans do)...
antialias_physorg
4.6 / 5 (9) Oct 23, 2015
...but I can imagine that one could well use observed coronal mass ejections as sources of sound waves. Much like we use seismic charges on Earth for geologic surveys, or how natural earthquakes can give a pretty good picture of the Earth's interior by when and how they show up on seismographs located around the globe.
carlo_piantini
4 / 5 (4) Oct 23, 2015
@antialias: Go figure, I hadn't known that about nitrogen. Thanks for the heads up :) Also, thank you for the further clarification about the sound wave issue - I know that the photosphere is significantly less dense than the rest of the sun, but I had no idea that it was by so much.
my2cts
4 / 5 (12) Oct 23, 2015

"Using a technique called asteroseismology, the scientists were able to calculate the magnetic field strengths in the fusion-powered hearts of dozens of red giants, stars that are evolved versions of our sun."

The use of scientific sounding terms does not change the essence of a nonsense. There is no way to determine what is happening in the cores of stars through remote observation. But in today's pseudo science philosophers speculators are in vogue.

Your religious delusions have caused a collapse of your cognitive brain functions.
Get shock treatment at the nearest psychiatric hospital, perhaps the damage is reversible.
my2cts
3 / 5 (6) Oct 24, 2015
Your definitions of what is rational and irrational are exactly complementary to mine!
Returners
1.8 / 5 (5) Oct 24, 2015
Gravitational waves on the other hand are ripples in the fabric of spacetime, predicted by general relativity and, as you correctly pointed out, worthy a Nobel prize.

GR is wrong.

Einstein and everyone looking for Gravitational Waves deserves IG-nobel prizes.
JustAnotherGuy
4.8 / 5 (5) Oct 24, 2015
@Ren82 vs @Ren82:
I believe that intelligent Creator who is eternal and uncreated, created the universe and everything in it with certain purpose.
"You are not witness of these events and have no historical documents for it, so you accepted this by faith." "This is irrational fate unsupported by scientific facts." "They the religion of the vain philosophers."
You actually believe that chaos was created the universe and the highly organized order in it.
"This is rational fate supported by scientific facts."
The theories and hypotheses that can not be verified are not true knowledge.
"Yes." "You did not know you so far?"

---------------------------
Sidenote: fate? wtf?
vidyunmaya
1 / 5 (4) Oct 24, 2015
Sub: magnetic fields- links space cosmology studies
This is the most welcome TREND-SET - Astronomy to catch-up with Cosmology studies.
The Science of Cosmology vedas interlinks -provide distinct inputs to science Advancement.
Cosmology is a border land between Science and philosophy. Plasma Regulated Electromagnetic phenomena in magnetic Field Environment sets the trend beyond Milky-way. Welcome East-west interaction. more projections in my books-1993-2015. See NANDI-new concept- and Super-impostion of Visible-invisible Matrix-Universe my papers COSPAR2015.About 12 books available through Lulu
Vidyardhi Nanduri {Independent Reseach]
my2cts
3.9 / 5 (7) Oct 25, 2015
It does not bother me much.

Clearly you are not interested in communication.
my2cts
3.7 / 5 (6) Oct 25, 2015
@Returners
You're just jealous of his Nobel prize.
Captain Stumpy
5 / 5 (4) Oct 25, 2015
@Returners
You're just jealous of his Nobel prize.
Obviously...

and it is apparent that she is also unaware of the meaning behind the Ig Nobel as well
The stated aim of the prizes is to "honor achievements that first make people laugh, and then make them think". The awards are sometimes veiled criticism (or gentle satire), but are also used to point out that even the most absurd-sounding avenues of research can yield useful knowledge.
https://en.wikipe...el_Prize

The Ig Nobel Prizes honor achievements that make people LAUGH, and then THINK. The prizes are intended to celebrate the unusual, honor the imaginative — and spur people's interest in science, medicine, and technology.
http://www.improbable.com/ig/

just because something gets an Ig Nobel, doesn't mean it isn't good science...
strange, yes...
but most often, we build upon things like this in ways we don't understand at first glance
SuperThunder
2.3 / 5 (3) Oct 25, 2015
I have devised an experiment which disproves this article. Behold my work, ye body of scientists, and larf.

First, I did exhaustive research in opening a beer and trying to remember some of the pithy comments made on this site, then I remembered the one about stars being made of water. This, I decided, is hilarious enough to proceed with.

Second, I devised a hypothesis based on my research : "If stars are magnetic, the water in my beer will also be magnetic."

Third, I devised an experiment by which I open another beer and leave it alone as a control beer while I try and drunkenly stick a magnet to the other beer bottle in order to test this. I noticed that the beers behaved similarly whether a magnet was being rubbed on it or not.

I conclude that the sun cannot have magnets in it because my beer does not and phys.org commenters wouldn't lie about stars being made of water.

For future experimenters, I would suggest using more beer and stronger magnets.

I love science.
SuperThunder
2.3 / 5 (3) Oct 25, 2015
Hey, could some of you guys could sponsor me, or put in a good word, for some LHC research time? I have an idea that beer atoms* accelerated to over 60% the speed of light will create high gravity lager waves when they collide.

*not my fault if your periodic table doesn't have beer atoms.

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