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EI2GYB > ASTRO 11.10.25 11:06l 89 Lines 5069 Bytes #15 (0) @ WW
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Subj: Young sunlike star reveals rapid two-year magnetic cycle
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Young sunlike star reveals rapid two-year magnetic cycle
Scientists at the Leibniz Institute for Astrophysics Potsdam (AIP) have
uncovered the intricate magnetic heartbeat of a distant star remarkably similar
to our own sun-but much younger and more active. This study, part of the "Far
Beyond the Sun" campaign, follows nearly three years of ultra-precise
observations and sheds new light on how stars like our sun generate their
magnetic fields-and how these fields evolve over time.
The results appear in the article "Far Beyond the Sun III: The Magnetic Cycle
of ? Horologii" on the arXiv preprint server.
The star at the heart of this research is Iota Horologii (nicknamed "? Hor," in
the constellation Horologium, the pendulum clock at the southern sky), located
roughly 56 light years from Earth. At about 600 million years old-far younger
than our 4.6 billion-year-old sun-? Hor spins faster and displays far more
vigorous magnetic activity than the sun.
By pointing the HARPS polarimeter on the European Southern Observatory's 3.6 m
telescope at La Silla Observatory in Chile toward this star, AIP researchers
collected 199 nights of spectropolarimetric data over six observing seasons.
Using an advanced technique known as Zeeman Doppler Imaging (ZDI), the team
transformed these measurements into 18 distinct "maps" of ? Hor's large scale
magnetic field, spread over roughly 140 full rotations of the star. These maps
chart how magnetic features appear, vanish, and even flip polarity-phenomena
that trace the deep-seated dynamo processes within the star's turbulent
interior.
One of the most remarkable findings is that ? Hor completes a full magnetic
cycle-equivalent to the sun's 22-year cycle-in just above two years (about 773
days). Over this period, the star's magnetic north and south poles reverse,
only to switch back again, creating a rhythmic magnetic heartbeat far faster
than our sun.
Perhaps even more exciting is the creation of the first "magnetic butterfly
diagrams" for a star beyond our own. On the sun, these diagrams track the
latitudinal migration of sunspots and magnetic field as the cycle progresses:
spots emerge at mid-latitudes and steadily drift toward the equator.
By averaging the mapped magnetic field strength at different latitudes for each
epoch, AIP scientists produced analogous diagrams for ? Hor-revealing how its
magnetic regions migrate poleward and equatorward over each cycle.
From these stellar butterfly diagrams, the team extracted direct estimates of
large scale flows on ? Hor's surface. They found that radial field regions
migrated toward the polar regions at speeds of 15-78 m/s (comparable to a
high-speed train), while the toroidal field drifts toward the equator proceeds
at 9-19 m/s (average car speed), both substantially faster than the
corresponding solar flows. This marks the first measurement of such meridional
(poleward) and equatorward flows on any star besides the sun.
"These results offer a critical benchmark for understanding magnetic
dynamos-the engines that drive stellar and solar activity," says Dr. Julian
Alvarado G¢mez, lead investigator at AIP.
"By comparing ? Hor's rapid magnetic cycle and strong activity to the sun's
more leisurely 22 year rhythm, we gain deeper insight into how factors like
rotation rate and age influence magnetic evolution."
Furthermore, magnetic activity governs stellar winds, flares, and high energy
radiation-all of which can shape the environments of orbiting planets. Insights
from ? Hor, which hosts at least one known exoplanet, help astronomers assess
how young sun-like stars might influence the habitability of worlds in their
system.
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