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Planet Creates a Stellar Storm (Forwarded)



 
 
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Old January 9th 04, 06:13 AM
Andrew Yee
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Default Planet Creates a Stellar Storm (Forwarded)

National Research Council
Ottawa, Canada

CONTACTS:

Evgenya Shkolnik
University of British Columbia
Tel: 250.595.3801
email:
http://www.astro.ubc.ca
http://www.physics.ubc.ca

Gordon Walker
University of British Columbia
Tel: 250.592.6205
email:

David Bohlender
National Research Council of Canada / Herzberg Institute for Astrophysics
Tel: 250.363.0025
email:

http://www.hia.nrc.ca

FOR RELEASE: 9:00 AM EST, January 7, 2004

PLANET CREATES A STELLAR STORM

FIRST EVIDENCE OF AN EXTRA-SOLAR PLANET WITH A MAGNETIC FIELD

Canadian astronomers announced today the first evidence of a
magnetic field on a planet outside of our solar system which is
also the first observation of a planet heating its star. The
report was presented this morning by Ph.D. candidate Evgenya Shkolnik,
Dr. Gordon Walker, both of the University of British Columbia, Vancouver,
BC and Dr. David Bohlender of the National Research Council of Canada /
Herzberg Institute for Astrophysics, Victoria, BC at the meeting of the
American Astronomical Society in Atlanta, Georgia. The result may offer
clues about the structure and formation of the giant planet.

The trio observed the sun-like star HD179949 with the 3.6-meter (142-in)
Canada-France-Hawaii Telescope atop Mauna Kea, Hawaii (a 14,000-ft.
dormant volcano) using its high-resolution spectrograph called Gecko.
HD179949 is 90 light years away in the direction of the southern
constellation of Sagittarius (the Archer) but it is too faint to be seen
without a telescope. It was first reported to have a close-in planet by
Tinney, Butler, Marcy and others in the first results of the
Anglo-Australian planet search in 2000. The planet is at least 270 times
more massive than the Earth, almost as big as Jupiter, and orbits the
star every 3.093 days at 350,000 mph. Such tightly orbiting "roasters" or
"hot jupiters" make up 20% of all known extrasolar planets.

The star's chromosphere, a thin, hot layer just above the visible
photosphere, was observed in the ultraviolet light emitted by
singly-ionized Calcium atoms. Giant magnetic storms produce hot spots
which are visible as bright patches in this light. Such a persistent
hotspot is observed on HD 179949 keeping pace with the planet in its
3-day orbit for more than a year (or 100 orbits)! The hotspot appears to
be moving across the surface of the star slightly ahead of, but keeping
pace with the planet. Most evidence suggests the star is rotating too
slowly to carry the spot around so quickly.

The best explanation for this traveling hot spot is an interaction
between the planet's magnetic field and the star's chromosphere,
something predicted by Steve Saar of the Center for Astrophysics and
Manfred ****z of the University of Texas at Arlington in 2000. If so,
this is the first ever glimpse of a magnetic field on a planet outside of
our solar system, and may provide clues about the planet's structure and
formation.

"If we are indeed witnessing the entanglement of the magnetic field of a
star with that of its planet it gives us an entirely new insight into the
nature of closely bound planets." -- Dr. Gordon Walker

Obviously, more observations are needed to test if the magnetic
interaction is a transient event or something longer lasting. Also,
observations from the 8-meter Gemini-South Telescope in Chile of this
stellar system are underway in the infrared light emitted by Helium which
would map hotspots at higher levels of the chromosphere.

This work was supported by the Canadian Natural Science and Engineering
Research Council and the National Research Council of Canada.

IMAGE CAPTION:
[http://www.astro.ubc.ca/images/flare_400x296.jpg (16 KB)]
Shane Erno's conception of the flare.

 




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