Image Credit: P. Marenfeld & NOAO/AURA/NSF
Astronomers using the Atacama Large Millimeter/submillimeter Array
(ALMA) have observed what may be the first-ever signs of windy weather
around a T Tauri star, an infant analog of our own Sun. This may help
explain why some T Tauri stars have disks that glow weirdly in infrared
light while others shine in a more expected fashion.
T Tauri stars are the infant versions of stars like our Sun. They are
relatively normal, medium-size stars that are surrounded by the raw
materials to build both rocky and gaseous planets. Though nearly
invisible in optical light, these disks shine in both infrared and
millimeter-wavelength light.
“The material in the disk of a T Tauri star
usually, but not always, emits infrared radiation with a predictable
energy distribution,” said Colette Salyk, an astronomer with the
National Optical Astronomical Observatory (NOAO) in Tucson, Ariz., and
lead author on a paper published in the Astrophysical Journal. “Some T
Tauri stars, however, like to act up by emitting infrared radiation in
unexpected ways.”
To account for the different infrared signature around such similar
stars, astronomers propose that winds may be emanating from within some T
Tauri stars’ protoplanetary disks. These winds could have important
implications for planet formation, potentially robbing the disk of some
of the gas required for the formation of giant Jupiter-like planets, or
stirring up the disk and causing the building blocks of planets to
change location entirely. These winds have been predicted by
astronomers, but have never been clearly detected.
Using ALMA, Salyk and her colleagues looked for evidence of a
possible wind in AS 205 N – a T Tauri star located 407 light-years away
at the edge of a star-forming region in the constellation Ophiuchus, the
Snake Bearer. This star seems to exhibit the strange infrared signature
that has intrigued astronomers.
With ALMA’s exceptional resolution and sensitivity, the researchers
were able to study the distribution of carbon monoxide around the star.
Carbon monoxide is an excellent tracer for the molecular gas that makes
up stars and their planet-forming disks. These studies confirmed that
there was indeed gas leaving the disk’s surface, as would be expected if
a wind were present. The properties of the wind, however, did not
exactly match expectations.
This difference between observations and expectations could be due to
the fact that AS 205 N is actually part of a multiple star system –
with a companion, dubbed AS 205 S, that is itself a binary star.
This multiple star arrangement may suggest that the gas is leaving
the disk’s surface because it’s being pulled away by the binary
companion star rather than ejected by a wind.
“We are hoping these new ALMA observations help us
better understand winds, but they have also left us with a new
mystery,” said Salyk. “Are we seeing winds, or interactions with the
companion star?”
The study’s authors are not pessimistic, however. They plan to
continue their research with more ALMA observations, targeting other
unusual T Tauri stars, with and without companions, to see whether they
show these same features.
T Tauri stars are named after their prototype star, discovered in
1852 – the third star in the constellation Taurus whose brightness was
found to vary erratically. At one point, some 4.5 billion years ago, our
Sun was a T Tauri star.
Other authors include Klaus Pontoppidan, Space Telescope Science
Institute; Stuartt Corder, Joint ALMA Observatory; Diego Muñoz, Center
for Space Research, Department of Astronomy, Cornell University; and Ke
Zhang and Geoffrey Blake, Division of Geological & Planetary
Sciences, California Institute of Technology,
The National Optical Astronomy Observatory is operated by Association
of Universities for Research in Astronomy Inc. under a cooperative
agreement with the National Science Foundation.
The National Radio Astronomy Observatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc. NRAO, together with its international
partners, operates ALMA – the world’s most powerful observatory
operating at millimeter and submillimeter wavelengths.
ALMA, an international astronomy facility, is a partnership of
Europe, North America and East Asia in cooperation with the Republic of
Chile. ALMA construction and operations are led on behalf of Europe by
ESO, on behalf of North America by the National Radio Astronomy
Observatory (NRAO), and on behalf of East Asia by the National
Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory
(JAO) provides the unified leadership and management of the
construction, commissioning and operation of ALMA.
Media Contact:
Dr. Katy Garmany
Deputy Press Officer
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8526
E-mail: kgarmany@noao.edu
Dr. Katy Garmany
Deputy Press Officer
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8526
E-mail: kgarmany@noao.edu
Science Contact
Dr. Colette Salyk
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
e-mail: csalyk@noao.edu
NRAO Media Contact
Charles Blue
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E-mail: cblue@nrao.edu
Charles Blue
Public Information Officer
National Radio Astronomy Observatory
520 Edgemont Road
Charlottesville, VA 22904
+1 434-296-0314
E-mail: cblue@nrao.edu
