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Discovery of Young, Isolated Planetary Mass Objects in the σ Orionis Star Cluster

Zapatero Osorio, M. R. and Béjar, V. J. S. and Martín, E. L. and Rebolo, R. and Barrado y Navascués, D. and Bailer-Jones, C. A. L. and Mundt, R. (2000) Discovery of Young, Isolated Planetary Mass Objects in the σ Orionis Star Cluster. Science, 290 (5489). pp. 103-107. ISSN 0036-8075.

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We present the discovery by optical and near-infrared imaging of an extremely red, low-luminosity population of isolated objects in the young, nearby stellar cluster around the multiple, massive star σ Orionis. The proximity (352 parsecs), youth (1 million to 5 million years), and low internal extinction make this cluster an ideal site to explore the substellar domain from the hydrogen mass limit down to a few Jupiter masses. Optical and near-infrared low-resolution spectroscopy of three of these objects confirms the very cool spectral energy distribution (atmospheric effective temperatures of 1700 to 2200 kelvin) expected for cluster members with masses in the range 5 to 15 times that of Jupiter. Like the planets of the solar system, these objects are unable to sustain stable nuclear burning in their interiors, but in contrast they are not bound to stars. This new kind of isolated giant planet, which apparently forms on time scales of less than a few million years, offers a challenge to our understanding of the formation processes of planetary mass objects.

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Rebolo, R.0000-0003-3767-7085
Additional Information:© 2000 American Association for the Advancement of Science. Received 6 July 2000; accepted 7 September 2000. We are indebted to I. Baraffe and the Lyon group for providing theoretical evolutionary tracks prior to publication. We also thank A. Burrows for facilitating an electronic version of his models. We are grateful to C. Gutie«rrez and J. Licandro for taking data necessary for calibrating some of the K images, and to C. Koresko for making available NIRC spectra of some of the reference objects. This paper is based on observations made with the 2.5-m Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, the Keck I and Keck II telescopes on the Mauna Kea Observatory, the 2.2- and 3.5-m telescopes on the German-Spanish Calar Alto Observatory, the 1.5-m Carlos Sánchez telescope on the Teide Observatory of the Instituto de Astrofísica de Canarias, and the 3.8-m UKIRT telescope on the Mauna Kea Observatory. Correction: “Floating through a cluster” (15 Feb., 1197). The mention of free-floaters in the M22 cluster was incorrect; it should instead have referred to the Orion cluster, as described by M. R. Zapatero Osorio et al., Science 290, 103 (2000).
Issue or Number:5489
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51781
Deposited By: Tony Diaz
Deposited On:14 Nov 2014 22:10
Last Modified:09 Mar 2020 13:19

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