Re: A Magnetic Surprise

Well teacher, they didn't mention the age of this star and didn't mention
the possibiliy
of the very early stages of instability either.



"Sam Wormley" <swormley1@xxxxxxxxx> wrote in message
news:RLNDh.2555$u93.2335@xxxxxxxxxxxx
A Magnetic Surprise
http://sciencenow.sciencemag.org/cgi/content/full/2007/223/1

By Phil Berardelli
ScienceNOW Daily News
23 February 2007

Astronomers have detected a strong magnetic field emanating from a star
that computer models say shouldn't be able to produce one. The field is
coming from a star called AB Aurigae--located about 460 light-years
away--and its existence lends further credence to one of the more
bizarre astronomical discoveries in recent years.

Powerful magnetic fields aren't easy for stars to generate. Until now,
astronomers assumed that they only arose inside the fierce internal
furnaces of hot, young stars much larger than the sun, or from the
violent interaction between two closely orbiting stars in a binary
system. Neither situation is true for AB Aurigae. The star is only
about 2.7 times the mass of our sun, which should make it too small and
cool to produce a strong magnetic field. But when a team led by Manuel
Guedel of the Paul Scherrer Institute in Villigen, Switzerland, used
the European Space Agency's orbiting XMM-Newton x-ray observatory to
scan the young star, they picked up an x-ray signal, evidence of strong
magnetism. What's more, AB Aurigae's x-ray, optical, and ultraviolet
radiation all vary in intensity during the same 42-hour cycle, meaning
the star itself is the only possible x-ray source.

Further observations and analysis revealed that AB Aurigae's x-rays are
emanating from high above its surface, says Guedel. That's a clear sign
that the solar winds flowing from both of the star's hemispheres are
being pulled back and slammed together by magnetic lines of force. The
resulting collisions are generating x-rays, but what is creating the
magnetism?

Guedel says his team might have found the answer in an unlikely source:
phenomena called fossil magnetic fields. As his group will report in an
upcoming issue of Astronomy and Astrophysics, other researchers have
predicted that, rather than being generated solely by stars themselves,
such fields can also develop within stellar-forming clouds. When new
stars are born nearby, they can grab onto parts of the preexisting
fields and continue to generate them. "We cannot prove that this is
what happened [with AB Aurigae]," Guedel says, but no other explanation
from stellar dynamic theory makes sense. He adds that now astronomers
can take a close look at other similar stars--called Herbig stars--to
see whether their x-rays are being generated by fossil magnetic fields
as well.

If confirmed, the findings would be an important illustration of how a
young star can interact with the surrounding material in a stellar
nursery, in terms of latching onto a fossil magnetic field, says
astrophysicist Rachel Osten of NASA's Goddard Space Flight Center in
Greenbelt, Maryland. No one knows whether the other Herbig stars are
generating x-rays from interactions with as-yet-hidden binary
companions, Osten says, but AB Aurigae does not appear to have a
companion. And whatever the source, she adds, "we know these stars
can't generate magnetic fields on their own."

© 2007 American Association for the Advancement of Science


.

Relevant Pages

  • Unique observations of newborn star provide information on solar systems origin (Forwarded)
    ... A new study has caught a newborn star similar to the sun in a fiery outburst. ... which was conducted by a team of astronomers headed by Joel Kastner ... "In FU-Orionis stars, these outbursts are very brief," says Weintraub, associate ... request for viewing time on the orbiting Chandra X-ray observatory. ...
    (sci.astro)
  • Re: Colonizing a Neutron Star
    ... electronics. ... Radiation shielding I figure can be taken care of by suitable ... amounts of water and/or deflecting magnetic fields, ... Type II civilization in this scenario by definition (granted the star ...
    (rec.arts.sf.science)
  • Re: Colonizing a Neutron Star
    ... affected by magnetic fields. ... After all, we're talking a Kardashev ... Well, if you're going to go down that road, why not posit a civilization advanced enough that it can find a more convenient way of extracting power than building a _manned_ station in close vicinity to a neutron star? ...
    (rec.arts.sf.science)
  • Astronomers Discover Dusty Remains of Two Terrestrial Planets
    ... Two terrestrial planets orbiting a mature sun-like star some 300 ... light-years from Earth recently suffered a violent collision, ... astronomers at UCLA, Tennessee State University and the California ...
    (sci.space.news)
  • Integral reveals new class of supergiant X-ray binary stars (Forwarded)
    ... ESA's Integral gamma-ray observatory has discovered a new, highly populated class of X-ray fast 'transient' binary stars, undetected in previous observations. ... The new class of double star systems is characterised by a very compact object that produces highly energetic, recurrent and fast-growing X-ray outbursts, and a very luminous 'supergiant' companion. ... Scientists have called such class of objects 'supergiant fast X-ray transients'. ...
    (sci.astro)