Deepest Ever Look into Orion
Astronomers have unveiled the deepest view yet of the heart of the Orion Nebula. The scientists used the HAWK-I infrared instrument, deployed on the Very Large Telescope (VLT) in Chile, part of the European Southern Observatory (ESO), to create the spectacular image. It reveals about ten times as many brown dwarfs (objects intermediate between stars and planets) and planet-mass bodies than were previously known. The discovery, which challenges the widely accepted scenario for Orion's star formation history, appears in a paper in Monthly Notices of the Royal Astronomical Society.
The famous Orion Nebula spans about 24 light-years within the constellation of Orion, and is visible from Earth with the naked eye, as a fuzzy patch in Orion's sword, a line of stars below the more obvious belt. Some nebulae, like Orion, are strongly illuminated by ultraviolet radiation from the many hot stars born within them, so that gas atoms are stripped of their electrons, and the resulting plasma glows brightly.
At a distance of approximately 1350 light years from the Sun, the relative proximity of the Orion Nebula makes it an ideal test bed to better understand the process and history of star formation, and to determine how many stars of different masses form.
Amelia Bayo (Universidad de Valparaíso, Valparaíso, Chile; Max-Planck Institut für Astronomie, Königstuhl, Germany), a co-author of the new paper and member of the research team, explains why this is important: "Understanding how many low-mass objects are found in the Orion Nebula is very important to constrain current theories of star formation. We now realise that the way these very low-mass objects form depends on their environment."
This video gives a close-up view of a spectacular new image of the Orion Nebula star-formation region that was obtained from multiple exposures using the HAWK-I infrared camera on ESO’s Very Large Telescope in Chile. This is the deepest view ever of this region and reveals many more very faint planetary-mass objects than expected. Credit: ESO/H. Drass et al. Music: Johan B. Monell
This new image has caused excitement because it reveals an unexpected wealth of very-low-mass objects, which in turn suggests that the Orion Nebula may be forming proportionally far more low-mass objects than closer and less active star formation regions.
Astronomers count up how many objects of different masses form in regions like the Orion Nebula to try to understand the star formation process. Before this research the greatest number of objects were found to have masses of about one quarter that of our Sun. These observations give a tantalising hint that the number of planet-sized objects might be far greater than previously thought. Whilst the technology to readily observe these objects does not exist yet, ESO's future European Extremely Large Telescope (E-ELT), scheduled to begin operations in 2024, is designed to pursue this as one of its goals.
Lead scientist Holger Drass (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany; Pontificia Universidad Católica de Chile, Santiago, Chile) enthuses: "Our result feels to me like a glimpse into a new era of planet and star formation science. The huge number of free-floating planets at our current observational limit is giving me hope that we will discover a wealth of smaller Earth-sized planets with the E-ELT."
This research was presented in a paper entitled "The bimodal initial mass function in the Orion Nebula Cloud", by H. Drass et al., Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press.
A preprint of the paper is available on the arXiv.
The team is composed of H. Drass (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany; Pontificia Universidad Católica de Chile, Santiago, Chile), M. Haas (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany), R. Chini (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany; Universidad Católica del Norte, Antofagasta, Chile), A. Bayo (Universidad de Valparaíso, Valparaíso, Chile; Max-Planck Institut für Astronomie, Königstuhl, Germany), M. Hackstein (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany), V. Hoffmeister (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany), N. Godoy (Universidad de Valparaíso, Valparaíso, Chile) and N. Vogt (Universidad de Valparaíso, Valparaíso, Chile).
Notes for editors
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".
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