White dwarf
stars locked in binary systems can
spawn solar flares, spots and
other activity in their otherwise calm stellar neighbors, astronomers said this
week.
Strong
magnetic fields from the white
dwarf stars, which are burned out old stars, can provide a sort of
electrical kick start for solar activity by reaching inside their fast-spinning
partners, researchers said.
“Like Dr.
Frankenstein zapping an inert corpse, the white dwarfs in these systems produce
very strong electrical currents inside the bodies of their partner star, which
can create violent eruptions where there otherwise would be little if any,”
said astronomer Stella Kafka, of the National Optical Astronomy Observatory
(NOAO), who led one of two studies into the phenomenon.
Kafka and
her colleagues analyzed four sets of highly energetic binary star systems,
known as polars, to pin down the effects of white dwarfs on their stellar
neighbors.
The
research was presented at a meeting of the American Astronomical Society in
Seattle.
A white
dwarf is the final stage for stars lacking enough mass to end their lives in
massive stellar explosions known as supernovas.
Our Sun and stars up to eight times its mass are destined to become white
dwarfs.
White
dwarfs tend to have masses about half that of the Sun, but it's all compressed into ball
with a diameter of planet Earth.
In polar
binary systems, white dwarfs are paired with a low-mass, cool star about the diameter
of Jupiter and a mass of one-fifth
or less that of the Sun. The arrangement makes for close quarters,
astronomically speaking, with the two stars orbiting each other in three hours
or less.
The stars
are so close that the intense magnetic field of the white dwarf actually passes
through part of its stellar neighbor, which astronomers believe is not massive
enough to generate flares or so-called “starspots”
on its own.
“This
discovery points to a new mechanism for the generation of stellar activity by
forces outside the star itself, a phenomenon that we have dubbed 'hyperactivity,'”
said study co-author Steve Howell, an astronomer with the NOAO and WIYN
Observatory at Arizona’s Kitt Peak National Observatory in Arizona.
The
research not only allows astronomers to better understand the interactions
between binary systems, but also between a close-orbiting planet and its parent
star, astronomers said.
Kafka and
her colleagues studied their target binary star systems using ground-based
telescopes at Kitt Peak and the European Southern Observatory’s Very Large
Telescope in Chile.
Editor's
Note: All
week, SPACE.com is providing complete
coverage of the 209th meeting of the American Astronomical Society.
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