An international team
of astronomers from Chile and Germany has managed to capture an image of
unprecedented detail of another star — that isn’t the Sun — the red supergiant
star Antares. The team has also made the first map of the velocities of
material in the atmosphere of a star other than the Sun, revealing unexpected
turbulence in the extended atmosphere of Antares.
Image description: This
artist’s impression shows the red supergiant star Antares. Image credit: M.
Kornmesser / ESO.
Antares, also
designated Alpha Scorpii, is a well-studied, close red supergiant star at a
distance of 554 light years. It is the fifteenth-brightest star in the night
sky and the brightest star in the constellation of Scorpius. With a diameter
about 700 times that of the Sun and a mass about 12 times solar, Antares is one
of largest stars.
This is the most
detailed image ever of the red supergiant star Antares, or any other star apart
from the Sun. Image credit: K. Ohnaka / ESO.
It is thought that
Antares started life with a mass more like 15 times that of the Sun, and has
shed three solar-masses of material during its life. To directly see the gas
motions in its atmosphere, Dr. Keiichi Ohnaka of the Universidad Católica del
Norte in Chile and co-authors observed Antares with ESO’s Very Large
TelescopeInterferometer (VLTI) located on Cerro Paranal in Chile.
“How stars like Antares
lose mass so quickly in the final phase of their evolution has been a problem
for over half a century,” Dr. Ohnaka said.
“VLTI is the only
facility that can directly measure the gas motions in the extended atmosphere
of Antares — a crucial step towards clarifying this problem. The next challenge
is to identify what’s driving the turbulent motions.”
The astronomers created
the first two-dimensional velocity map of the atmosphere of a star other than
the Sun. They did this using the VLTI with three of the Auxiliary Telescopes
and an instrument called AMBER to make separate images of the surface of
Antares over a small range of infrared wavelengths.
They then used these
data to calculate the difference between the speed of the atmospheric gas at
different positions on the star and the average speed over the entire star.
This resulted in a map of the relative speed of the atmospheric gas across the
entire disc of Antares — the first ever created for a star other than the Sun.
“We found turbulent,
low-density gas much further from the star than predicted,” the authors said.
“The movement could not
result from convection, that is, from large-scale movement of matter which
transfers energy from the core to the outer atmosphere of many stars.”
“A new, currently
unknown, process may be needed to explain these movements in the extended atmospheres
of red supergiants like Antares.”
The research is published
in the journal Nature.
Reference: sci-news
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