Delicate bubble of expelled material around the cool red star U Antliae
The star U Ant in the constellation of Antlia (The Air Pump)
Wide-field image of the sky around U Antliae
ALMA view of the motions of material in the shell around U Antliae
Videos
Flying from the Earth to the star U Antliae
Tomography of a cosmic bubble
Astronomers have used ALMA to capture a
strikingly beautiful view of a delicate bubble of expelled material
around the exotic red star U Antliae. These observations will help
astronomers to better understand how stars evolve during the later
stages of their life-cycles.
In the faint southern constellation of Antlia (The Air Pump)
the careful observer with binoculars will spot a very red star, which
varies slightly in brightness from week to week. This very unusual star
is called U Antliae and new observations with the Atacama Large Millimeter/submillimeter Array (ALMA) are revealing a remarkably thin spherical shell around it.
U Antliae [1] is a carbon star, an evolved, cool and luminous star of the asymptotic giant branch
type. Around 2700 years ago, U Antliae went through a short period of
rapid mass loss. During this period of only a few hundred years, the
material making up the shell seen in the new ALMA data was ejected at
high speed. Examination of this shell in further detail also shows some
evidence of thin, wispy gas clouds known as filamentary substructures.
This spectacular view was only made possible by the unique
ability to create sharp images at multiple wavelengths that is provided
by the ALMA radio telescope, located on the Chajnantor Plateau in
Chile’s Atacama Desert. ALMA can see much finer structure in the U
Antliae shell than has previously been possible.
The new ALMA data are not just a single image; ALMA
produces a three-dimensional dataset (a data cube) with each slice
being observed at a slightly different wavelength. Because of the Doppler Effect,
this means that different slices of the data cube show images of gas
moving at different speeds towards or away from the observer. This shell
is also remarkable as it is very symmetrically round and also
remarkably thin. By displaying the different velocities we can cut this
cosmic bubble into virtual slices just as we do in computer tomography
of a human body.
Understanding the chemical composition of the shells and
atmospheres of these stars, and how these shells form by mass loss, is
important to properly understand how stars evolve in the early Universe
and also how galaxies evolved. Shells such as the one around U Antliae
show a rich variety of chemical compounds based on carbon and other
elements. They also help to recycle matter, and contribute up to 70% of
the dust between stars.
Notes
[1] The name U Antliae reflects the fact that it is the fourth star that changes its brightness to be found in the constellation of Antlia (The Air Pump). The naming of such variable stars followed a complicated sequence as more and more were found and is explained here .
Notes
[1] The name U Antliae reflects the fact that it is the fourth star that changes its brightness to be found in the constellation of Antlia (The Air Pump). The naming of such variable stars followed a complicated sequence as more and more were found and is explained here .
More Information
This research was presented in a paper entitled “Rings and filaments. The remarkable detached CO shell of U Antliae”, by F. Kerschbaum et al., to appear in the journal Astronomy & Astrophysics.
This research was presented in a paper entitled “Rings and filaments. The remarkable detached CO shell of U Antliae”, by F. Kerschbaum et al., to appear in the journal Astronomy & Astrophysics.
The team is composed of F. Kerschbaum (University of
Vienna, Austria), M. Maercker (Chalmers University of Technology, Onsala
Space Observatory, Sweden), M. Brunner (University of Vienna, Austria),
M. Lindqvist (Chalmers University of Technology, Onsala Space
Observatory, Sweden), H. Olofsson (Chalmers University of Technology,
Onsala Space Observatory, Sweden), M. Mecina (University of Vienna,
Austria), E. De Beck (Chalmers University of Technology, Onsala Space
Observatory, Sweden), M. A. T. Groenewegen (Koninklijke Sterrenwacht van
België, Belgium), E. Lagadec (Observatoire de la Côte d’Azur, CNRS,
France), S. Mohamed (University of Cape Town, South Africa), C. Paladini
(Université Libre de Bruxelles, Belgium), S. Ramstedt (Uppsala
University, Sweden), W. H. T. Vlemmings (Chalmers University of
Technology, Onsala Space Observatory, Sweden), and M. Wittkowski (ESO)
The Atacama Large Millimeter/submillimeter Array (ALMA), an
international astronomy facility, is a partnership of ESO, the U.S.
National Science Foundation (NSF) and the National Institutes of Natural
Sciences (NINS) of Japan in cooperation with the Republic of Chile.
ALMA is funded by ESO on behalf of its Member States, by NSF in
cooperation with the National Research Council of Canada (NRC) and the
National Science Council of Taiwan (NSC) and by NINS in cooperation with
the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space
Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf
of its Member States; by the National Radio Astronomy Observatory
(NRAO), managed by Associated Universities, Inc. (AUI), on behalf of
North America; and by the National Astronomical Observatory of Japan
(NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides
the unified leadership and management of the construction,
commissioning and operation of ALMA.
ESO is the foremost intergovernmental astronomy
organisation in Europe and the world’s most productive ground-based
astronomical observatory by far. It is supported by 16 countries:
Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland,
Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden,
Switzerland and the United Kingdom, along with the host state of Chile.
ESO carries out an ambitious programme focused on the design,
construction and operation of powerful ground-based observing facilities
enabling astronomers to make important scientific discoveries. ESO also
plays a leading role in promoting and organising cooperation in
astronomical research. ESO operates three unique world-class observing
sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO
operates the Very Large Telescope and its world-leading Very Large
Telescope Interferometer as well as two survey telescopes, VISTA working
in the infrared and the visible-light VLT Survey Telescope. ESO is also
a major partner in two facilities on Chajnantor, APEX and ALMA, the
largest astronomical project in existence. And on Cerro Armazones, close
to Paranal, ESO is building the 39-metre Extremely Large Telescope, the
ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts
Franz Kerschbaum
University of Vienna
Vienna, Austria
Tel: +43 1 4277-51856
Email: franz.kerschbaum@univie.ac.at
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Links
Contacts
Franz Kerschbaum
University of Vienna
Vienna, Austria
Tel: +43 1 4277-51856
Email: franz.kerschbaum@univie.ac.at
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO/News
