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S Ori J053810.1-023626
	; S Ori 70 in the near-infrared; Credit: ESO VLT HAWKI
Observation data; Epoch J2000 Equinox J2000
Constellation	Orion
Right ascension	05h 38m 10.10s
Declination	−02° 36′ 00.0″
Characteristics
Spectral type	T6
Apparent magnitude (H)	20.07
Astrometry
Proper motion (μ)	RA: 10 mas/yr ; Dec.: 5 mas/yr
Distance	1,150 ly ; (352 pc)
Details
Mass	3 MJup
Surface gravity (log g)	3.5 cgs
Age	3 Myr
Other designations
	Mayrit 520267; S Ori 70; S Ori J053810.1-023626
Database references
SIMBAD	data

S Ori 70 or S Ori J053810.1-023626 is a mid-T type astronomical object in the foreground of the σ Orionis cluster, which is approximately 1,150 light-years from Earth. It was discovered on November 24, 2002 by M. R. Zapatero-Osorio and E. L. Martin's team at the Roque de los Muchachos Observatory. It has yet to be determined if it is a field brown dwarf or a 3-million-year-old planet that is part of a cluster. Near-infrared spectroscopy images taken three years after its discovery led to the first motion measurements for the object. Its behavior is significantly different from what may be expected; it was further described as either a low-gravity atmosphere or an atmosphere with metallicity. The object's small proper motion suggests that it is further away than expected if it were a single field T dwarf.

Discovery

The σ Orionis open cluster has been the focus of Osorio's team observations due to the age of the cluster (approximately 3 to 8 million years). The cluster also has low extinction, its distance is convenient, and it is observed to be rich and dense. Using the 4.2-meter (170-inch) William Herschel Telescope in a pencil-beam deep mini-survey measuring 55 square minutes of arc at a sensitivity of 21 magnitudes in the J and H Bands^[6] allowed the team to find S Ori 70. The raw data collected was reduced to IRAF (an acronym for Image Reduction and Analysis Facility), a standard technique used with near-infrared images; after subtracting the sky background and dark current, an extracted object spectrum was derived. It was the faintest and coolest member found in the cluster and was named S Ori 70.

Argument of the initial study

Adam J. Burgasser^[9]^[10] examined the claims of Osorio's T-type brown dwarf discovery and its spectroscopically verified low-mass. A comparison of the J band spectrum between S Ori 70 and other field objects was done. The J band spectrum revealed a distinct triangular-shaped spectral morphology which was previously explained by Zapatero-Osorio and Martín was due to the surface's low gravity. In order to see if similar discrepancies occurred in the T dwarf's behavior, Burgasser's team compared data from the claims of Osorio to that of standard COND models. Identical wavelength scales interpolated through both empirical and model spectra were Gaussian smoothed; this showed that best-fit spectral models can yield skewed gravities for late-type field T dwarfs which resulted in the underestimation of age and mass. Burgasser concluded that S Ori 70 is not a member of the Sigma Ori cluster but is rather a foreground field brown dwarf. Further study of the object suggest that the low gravity was not from the field T dwarf but rather a nearby background star.^[9] As of 2009 no direct scientific data have dispelled nor confirmed either conclusion.

It could be the first "free floating" non-stellar planet discovered^[5] with a mass of 3 M_J, but needs confirmation.

References

^ ^a ^b ^c ^d Faherty, Jacqueline K.; Burgasser, Adam J.; Cruz, Kelle L.; Shara, Michael M.; Walter, Frederick M.; Gelino, Christopher R. (2009). "The Brown Dwarf Kinematics Project I. Proper Motions and Tangential Velocities for a Large Sample of Late-Type M, L, and T Dwarfs". The Astronomical Journal. 137 (1): 1. arXiv:0809.3008. Bibcode:2009AJ....137....1F. doi:10.1088/0004-6256/137/1/1.
^ Zapatero-Osorio, María Rosa; Béjar, V. J. S.; Bihain, G.; Martín, Eduardo L.; Rebolo, Rafael; Villó-Pérez, I.; Díaz-Sánchez, A.; Pérez Garrido, A.; Caballero, J. A.; Henning, T.; Mundt, R.; Barrado y Navascués, D.; Bailer-Jones, C. A. L. (2008). "New constraints on the membership of the T dwarf S Ori 70 in theσ Orionis cluster". Astronomy & Astrophysics. 477 (3): 895–900. arXiv:0710.2776. Bibcode:2008A&A...477..895Z. doi:10.1051/0004-6361:20078600. S2CID 15928749.
^ Martín, Eduardo L.; Zapatero-Osorio, María Rosa (2003). "Spectroscopic Estimate of Surface Gravity for a Planetary Member in the σ Orionis Cluster". The Astrophysical Journal. 593 (2): L113. arXiv:astro-ph/0307268. Bibcode:2003ApJ...593L.113M. doi:10.1086/378313.
^ ^a ^b Peña Ramírez, K.; Zapatero-Osorio, María Rosa; Béjar, V. J. S.; Martin, Eduardo L.; Rebolo, Rafael; Villo-Perez, I.; Diaz-Sanchez, A.; Perez-Garrido, A.; Caballero, J. A.; Henning, T.; Mundt, R.; Barrado y Navascues, D.; Bailer-Jones, C. A. L. (2015). "Characterization of the known T-type dwarfs towards the σ Orionis cluster". Astronomy and Astrophysics. 574: A118. arXiv:1411.3370. Bibcode:2015A&A...574A.118P. doi:10.1051/0004-6361/201424816. S2CID 118498007.
^ ^a ^b "Mysterious Object Might be First Extrasolar Planet Photographed". Silver Star Academy. Archived from the original on 2011-07-16. Retrieved 2010-02-08.
^ ^a ^b ^c ^d Martín, Eduardo L. (2004). "S Ori 70: Still a strong cluster planet candidate". arXiv:astro-ph/0410678.
^ Kenyon, M. J.; Jeffries, R. D.; Naylor, Tim; Oliveira, J. M.; Maxted, P. F. L. (2005). "Membership, binarity and accretion among very low-mass stars and brown dwarfs of the σ Orionis cluster". Monthly Notices of the Royal Astronomical Society. 356 (1): 89. arXiv:astro-ph/0409749. Bibcode:2005MNRAS.356...89K. doi:10.1111/j.1365-2966.2004.08455.x.
^ Burgasser, Adam J.; Geballe, T. R.; Leggett, S. K.; Kirkpatrick, J. Davy; Golimowski, David A. (2006). "A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs". The Astrophysical Journal. 637 (2): 1067–1093. arXiv:astro-ph/0510090. Bibcode:2006ApJ...637.1067B. doi:10.1086/498563.
^ ^a ^b Burgasser, Adam J.; Kirkpatrick, J. Davy; McGovern, Mark R.; McLean, Ian S.; Prato, L.; Reid, I. Neill (2004). "S Orionis 70: Just a Foreground Field Brown Dwarf?". The Astrophysical Journal. 604 (2): 827–831. arXiv:astro-ph/0312285. Bibcode:2004ApJ...604..827B. doi:10.1086/382129. S2CID 14102676.
^ "T dwarfs". MIT.edu. Retrieved 2010-02-08.