From ESO: “A Tale of Three Stellar Cities”

ESO 50 Large

European Southern Observatory

27 July 2017
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

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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.

ESO Omegacam on VST at ESO’s Cerro Paranal observatory,with an elevation of 2,635 metres (8,645 ft) above sea level

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.

Orion Nebula M. Robberto NASA ESA Space Telescope Science Institute Hubble

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).

ESO HAWK-I the ESO Very Large Telescope at the Paranal Observatory in Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

[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).

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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 this beautiful new image. This famous object, the birthplace of many massive stars, is one of the closest stellar nurseries, at a distance of about 1350 light-years.

On this plot different populations of young stars are marked in different colours. The blue ones are oldest and the red youngest, with green ones an intermediate age. These stars seems to have formed in three bursts of star formation during the last three million years.

Credit:

ESO/G. Beccari


Stellar explosions are most often associated with supernovae, the spectacular deaths of stars. But new ALMA observations of the Orion Nebula complex provide insights into explosions at the other end of the stellar life cycle, star birth. This ESOcast Light takes a quick look at the important facts.

The video is available in 4K UHD.

The ESOcast Light is a series of short videos bringing you the wonders of the Universe in bite-sized pieces. The ESOcast Light episodes will not be replacing the standard, longer ESOcasts, but complement them with current astronomy news and images in ESO press releases.

Credit:
ESO.

Editing: Herbert Zodet.
Web and technical support: Mathias André and Raquel Yumi Shida.
Written by: Lauren Fuge, Hannah Dalgleish, Oana Sandu and Richard Hook.
Music: Thomas Edward Rice.
Footage and photos: ALMA (ESO/NAOJ/NRAO), J. Bally, ESA/Hubble, M. Kornmesser, L. Calçada and H. Drass et al.
Directed by: Herbert Zodet.
Executive producer: Lars Lindberg Christensen.

See the full article here .

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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, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

ESO LaSilla
ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO VLT
VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

ESO Vista Telescope
ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

ESO NTT
ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO VLT Survey telescope
VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

ALMA Array
ALMA on the Chajnantor plateau at 5,000 metres.

ESO E-ELT
ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

ESO APEX
APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

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