The
Hyades open star cluster in Taurus, one of the closest star clusters
Astronomers using K2, the refurbished Kepler Space Telescope, studied
solar-like oscillations in two stars in the cluster and used them to
obtain stellar properties.APOD; Jerry Lodriguss
Our
Sun vibrates due to pressure waves generated by turbulence in its upper
layers (the layers dominated by convective gas motions).
Helioseismology is the name given to the study of these oscillations,
which can shed light on the inner workings of the Sun. Astronomers
often detect brightness variations in other stars whose physical
processes make them variable, like the Cepheid variable stars used to
calibrate the cosmic distance scale, but it is much harder to detect
solar-like oscillations in stars that are driven by convection near the
star's surface ("astroseismology"). Open star clusters are well
understood and provide benchmarks for studying stellar evolution,
stellar rotation, stellar masses and ages, and many other properties,
and so astroseismology would be a valuable addition by providing
independent determinations of masses and ages for cluster members. But
astronomers have not been able to perform such measurements on main
sequence stars in an open cluster -- until now.
CfA astronomers Dave Latham, Allyson Bieryla, and Bob Stefanik were
part of a team using K2, the refurbished Kepler Space Telescope to
observe successfully these kinds of variations in main sequence stars.
Kepler was designed to look for exoplanet transits through continuous
and precise monitoring of a star's brightness. K2 stared at the stars
in the Hyades cluster, about 155 light-years away, and took a brightness
measurement roughly every minute for three months. The astronomers
found small brightness variations across many timescales, but in two
stars slightly larger than the Sun they found variations about every ten
minutes that were particularly intense, signaling solar-like
oscillations – the first ever such detections. Since the Hyades is an
important standard cluster, the team had already been monitoring its
stars for more than thirty-five years, and know that both of these two
stars are single. The scientists conclude among other things that stars
are very fast rotators (less than two days each; the Sun rotates in
26.2 days) which marks them as younger and quite different from the
older, slower rotating population in the cluster. The new results
illustrate the contribution that asteroseismology can make to the study
of open star clusters, and the team plans to continue this work with
future K2 observations.
Reference(s):
"Asteroseismology
of the Hyades with K2: First Detection of Main-Sequence Solar-Like
Oscillations in an Open Cluster," Mikkel N. Lund,Sarbani Basu,Vıctor
Silva Aguirre,William J. Chaplin, Aldo M. Serenelli, Rafael A.
Garcıa,David W. Latham,Luca Casagrande,Allyson Bieryla,Guy R. Davies,
Lucas S. Viani, Lars A. Buchhave, Andrea Miglio,David R. Soderblom, Jeff
A. Valenti, Robert P. Stefanik, and Rasmus Handberg, MNRAS 463, 2600, 2016.
