The Orion Nebula and cluster from the VLT Survey Telescope
The jewel in Orion’s sword
The Orion Nebula showing three populations of young stars
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Using new observations from ESO’s VLT
Survey Telescope, astronomers have discovered three different
populations of young stars within the Orion Nebula Cluster. This
unexpected discovery adds very valuable new insights for the
understanding of how such clusters form. It suggests that star formation
might proceed in bursts, where each burst occurs on a much faster
time-scale than previously thought.
OmegaCAM — the wide-field optical camera on ESO’s VLT Survey Telescope (VST) — has captured the spectacular Orion Nebula
and its associated cluster of young stars in great detail, producing a
beautiful new image. This object is one of the closest stellar nurseries
for both low and high-mass stars, at a distance of about 1350
light-years [1].
But this is more than just a pretty picture. A team led by
ESO astronomer Giacomo Beccari has used these data of unparallelled
quality to precisely measure the brightness and colours of all the stars
in the Orion Nebula Cluster. These measurements allowed the astronomers
to determine the mass and ages of the stars. To their surprise, the
data revealed three different sequences of potentially different ages.
“Looking at the data for the first time was one of
those ‘Wow!’ moments that happen only once or twice in an astronomer's
lifetime,” says Beccari, lead author of the paper presenting the results. “The
incredible quality of the OmegaCAM images revealed without any doubt
that we were seeing three distinct populations of stars in the central
parts of Orion.”
Monika Petr-Gotzens, co-author and also based at ESO Garching, continues, “This
is an important result. What we are witnessing is that the stars of a
cluster at the beginning of their lives didn’t form altogether
simultaneously. This may mean that our understanding of how stars form
in clusters needs to be modified.”
The astronomers looked carefully at the possibility that
instead of indicating different ages, the different brightnesses and
colours of some of the stars were due to hidden companion stars, which
would make the stars appear brighter and redder than they really were.
But this idea would imply quite unusual properties of the pairs, which
have never before been observed. Other measurements of the stars, such
as their rotation speeds and spectra, also indicated that they must have
different ages [2].
“Although we cannot yet formally disprove the
possibility that these stars are binaries, it seems much more natural to
accept that what we see are three generations of stars that formed in
succession, within less than three million years,” concludes Beccari.
The new results strongly suggest that star formation in the
Orion Nebula Cluster is proceeding in bursts, and more quickly than had
been previously thought.
Notes
[1] The Orion Nebula has been studied by many of ESO’s telescopes,
including images in visible light from the MPG/ESO 2.2-metre telescope (eso1103) and infrared images from VISTA (eso1701) and the HAWK-I instrument on the Very Large Telescope (eso1625).
[2] The group also found that each of the three different generations rotate at different speeds — the youngest stars rotate the fastest, and the oldest stars rotate the slowest. In this scenario, the stars would have formed in quick succession, within a time frame of three million years.
More Information
This research was presented in a paper entitled “A Tale of
Three Cities: OmegaCAM discovers multiple sequences in the color
magnitude diagram of the Orion Nebula Cluster,” by G. Beccari and
colleagues, to appear in the journal Astronomy & Astrophysics.
The team is composed of G. Beccari, M.G. Petr-Gotzens and
H.M.J. Boffin (ESO, Garching bei München, Germany), M. Romaniello (ESO;
Excellence Cluster Universe, Garching bei München, Germany), D. Fedele
(INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy), G. Carraro
(Dipartimento di Fisica e Astronomia Galileo Galilei, Padova, Italy), G.
De Marchi (Science Support Office, European Space Research and
Technology Centre (ESA/ESTEC), The Netherlands), W.J. de Wit (ESO,
Santiago, Chile), J.E. Drew (School of Physics, University of
Hertfordshire, UK), V.M. Kalari (Departamento de Astronomía, Universidad
de Chile, Santiago, Chile), C.F. Manara (ESA/ESTEC), E.L. Martin
(Centro de Astrobiologia (CSIC-INTA), Madrid, Spain), S. Mieske (ESO,
Chile), N. Panagia (Space Telescope Science Institute, USA); L. Testi
(ESO, Garching); J.S. Vink (Armagh Observatory, UK); J.R. Walsh (ESO,
Garching); and N.J. Wright (School of Physics, University of
Hertfordshire; Astrophysics Group, Keele University, UK).
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
Giacomo Beccari
ESO
Garching bei München, Germany
Tel: +49 89 3200 6195
Email: gbeccari@eso.org
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Souce: ESO/News
