Mutual attraction. The binary Algol stars share a powerful, permanent magnetic field.
Credit: W. Peterson et al./NRAO/AUI/NSF
Posted on 01/18/2010 9:08:18 AM PST by neverdem
Mutual attraction. The binary Algol stars share a powerful, permanent magnetic field.
Credit: W. Peterson et al./NRAO/AUI/NSF
Taking advantage of an unusual pair of nearby stars, astronomers have for the first time captured images of a magnetic field generated by a star other than our sun. Studying that field should help researchers gain a much better understanding of the internal dynamics that produce stellar magnetic fields, which in our sun's case can influence everything from climate to satellite orbits to telecommunications.
Astronomers have indirectly detected magnetic activity associated with other stars. But because of the great distances and the limitations of telescopes, no one had been able to observe another star's magnetism directly. It's important to do so, however, because without other stars for comparison, astronomers can't determine whether the sun's magnetism is normal.
In today's issue of Nature, a team of astronomers reports a breakthrough. They collected images of the magnetic field generated by one of the stars in the Algol system, located about 93 light-years away. The two stars in the system--one about three times more massive than the sun and the other a little less massive--are so close to each other that one orbit takes only 3 days. The smaller star is the source of the magnetic field, and even though that field is about 1000 times stronger than the sun's, imaging it still required two arrays of radiotelescopes, plus two extra dishes, to detect the signals generated by magnetic fields. One array stretches from Hawaii to the Virgin Islands, whereas the other occupies an expanse of the New Mexico desert, and the individual dishes sit in West Virginia and Germany.
The resulting images show a giant magnetic loop extending from the north and south poles of the smaller star all the way to its larger partner, located about 9 million kilometers away. The loop persisted for all 6 months of observations, instead of flaring up and quieting down, like our sun's field. It's a mystery why the loop seems to be permanent, says astrophysicist and lead author William Peterson of the University of Iowa in Iowa City. He and colleagues plan to use the arrays to look for magnetic loops on other stars and investigate them with computer simulations.
The data on the Algol magnetic field are "quite beautiful," says astrophysicist Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. They're bound to "improve our ability to predict solar magnetic storms, which impact satellites orbiting the Earth." And extending the observations to other binary stars "is an important step toward understanding all magnetic structures in astrophysics, he says.
I know they are studying the magnetic fields of these stars but...technically, it is gravity that locks one star’s movements to another. Not magnetism.
At first glance I read that as,
“A large coronal loop in the Algore system”.
I wanted to scream, “NO PICTURES! “
If I remember my astronomy correctly, Agol is in the constellation Perseus, and stands for the head of Medusa. Your fear isn’t far misplaced. ;-)
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A star's magnetic field does have some mechanical effects on anything nearby that is either ionized (like interstellar gas) or conducts electricity (like the plasma in a nearby star). Mechanical magnetic effects on the rotation speed of a star are minute, but measurable.
For example, the rotating magnetic field of a spinning neutron star can thrash electrons in the interstellar medium so hard they are accelerated to relativistic speeds and give off visible synchrotron radiation (like the Crab Nebula). This transfer of mechanical energy causes the spinning star to slow down.
If a star is rotating within another star's magnetic field, it will encounter some resistance due to magnetic braking, though gravitational tidal forces are probably vastly more significant. On a smaller scale, convection currents in the Sun are impeded when they are forced to move across magnetic field lines; and this is why sunspots are cooler than the surrounding regions. (The rotating disk in a typical power meter, which passes through a pair of damping magnets, is another illustration of this principle.)
Well put.
Planetary rotation will also cause arcing and sparking in whatever atmosphere is present. Rotate metal through a magnetic field and you get electricity, after all.
Could be both. Or the magnetic effect might be trying to push them apart, but can't overcome the gravity force, although modifying its effect. Or the magnetic effect could be adding to the gravitational one, again modifying it's effect. Force is force, regardless of it's origin.
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