15 Sagittae

G-type main sequence star in the constellation Sagitta 250px 15 Sagittae and its companion Keck Observatory J2000.0 Sagitta 20 04 06.22077 +17 04 12.6766 5.80 main sequence G0V + L4 0.600 0.005 4.57 0.1 −387.472 −419.497 56.2724 0.0094 4.55 63.77 0.63 0.61 16.88 0.10 AU 0.4683 0.0032 0.0031 97.73 0.31 330.88 0.21 commas 2457070 11 JD 266.23 0.45 15 Sge A 1.114 0.013 1.051 0.010 5932 81 commas 1.224 0.043 +0.051 0.057 14.8 1.3 days 4.42 0.06 4.442 0.010 2.26 0.40 15 Sge B 75.39 0.67 0.81 0.09 0.08 6.46 0.62 0.57 -5 5.46 0.09 1544 26 31 commas 45.0 0.5 15 Sge +16°4121 779 190406 98819 7672 105635 3515 15872 1517 866 15+sge 15 Sagittae (15 Sge) is a star in the northern constellation Sagitta, located around 58 light years away from the Sun. It is visible to the naked eye as a faint, yellow-hued star with an apparent visual magnitude of 5.80. John Flamsteed labelled this star as z Sagittae, but the designation was dropped by later authors and is now largely unknown. Characteristics The spectrum of 15 Sagittae matches a spectral class of G0V, with the luminosity class V indicating it is a main sequence star fusing atoms of hydrogen into helium at its core. 15 Sagittae is a solar analog, having 1.11 times the mass of the Sun, 1.05 times the Sun's radius, and 1.22 times the Sun's luminosity, and an effective temperature of 5,932 K. This temperature also gives it the yellow hue typical of a G-type star. The abundance of metals in the stellar atmosphere (metallicity) is also close to solar, with an iron-to-hydrogen abundance ratio equivalent to 12% of that found in the Sun. The star's age is estimated at 2.26 billion years. Companion 15 Sagittae was the target of the first radial velocity survey from Lick Observatory, which found a drift due to a companion. In 2002, the cause of this was found to be a brown dwarf companion, 15 Sagittae B, detected via direct imaging at the Keck telescope. 15 Sagittae B is a high-mass brown dwarf of spectral class L4, making it a L dwarf. It has a radius equivalent to 81% that of Jupiter, an effective temperature of 1544 K C F in, and a luminosity of 0.000065 (6.5 -5) times that of the Sun. The brown dwarf has a cloudy atmosphere and an elemental abundance similar to that of the host star. Its projected rotational velocity is 45 km/s, relatively fast for a brown dwarf, making it highly suitable for Doppler imaging. The brown dwarf orbits with a period of 63.8 years around the primary star, having a semi-major axis of 16.88 astronomical units, a moderate eccentricity of 0.468, and an inclination of 97.7° relative to Earth. Along with its orbit, its mass has been determined dynamically with direct imaging, radial velocity variations caused by its gravitational pull around the star, and by the astrometric shift it exerts in the star's proper motion measurements taken by the Hipparcos and Gaia spacecraft over a 20-year timespan, yielding a value of 75 Jupiter masses. 15 Sagittae B therefore is part of a select group of brown dwarfs with masses, ages, and luminosities determined without relying on substellar evolution models, making it a useful object to test the accuracy of such models. At the discovery, it was thought to have a semi-major axis of 14 AU and a circular orbit viewed from pole-on, but these properties were later massively revised with more observations. It is now approaching the primary as viewed from Earth. References 98819 1 Crepp Justin R. Johnson John Asher Fischer Debra A. Howard Andrew W. Marcy Geoffrey W. Wright Jason T. Isaacson Howard Boyajian Tabetha von Braun Kaspar Hillenbrand Lynne A. Hinkley Sasha Carpenter John M. Brewer John M. The Dynamical Mass and Three-Dimensional Orbit of HR7672B: A Benchmark Brown Dwarf with High Eccentricity The Astrophysical Journal 751 2 97 14 June 2012 1112.1725 2012ApJ...751...97C 10.1088/0004-637X/751/2/97 16113054 1821708351374312064 Brown dwarf found around nearby sun-like star January 1, 2002 W. M. Keck Observatory Kamuela, Hawaii http://www.keckobservatory.org/brown_dwarf_found_around_nearby_sun-like_star/ August 13, 2019 1 Cumming Andrew Marcy Geoffrey W. Butler R. Paul The Lick Planet Search: Detectability and Mass Thresholds The Astrophysical Journal 526 2 890–915 December 1999 astro-ph/9906466 1999ApJ...526..890C 10.1086/308020 12560512 Liu Michael C. Fischer Debra A. Graham James R. Lloyd James P. Marcy Geoff W. Butler R. Paul Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672 1 The Astrophysical Journal 571 1 519–527 May 2002 astro-ph/0112407 2002ApJ...571..519L 10.1086/339845 11405638 Wang Ji Kolecki Jared R. Ruffio Jean-Baptiste Wang Jason J. Mawet Dimitri Baker Ashley Bartos Randall Blake Geoffrey A. Bond Charlotte Z. Calvin Benjamin Cetre Sylvain Delorme Jacques-Robert Doppmann Greg Echeverri Daniel Finnerty Luke 2022-03-25 Retrieving the C and O Abundances of HR 7672 AB: A Solar-type Primary Star with a Benchmark Brown Dwarf The Astronomical Journal 163 4 189 10.3847/1538-3881/ac56e2 free 2202.02477 2022AJ....163..189W 0004-6256 Brandt Timothy D. Dupuy Trent J. Bowler Brendan P. 2019-09-11 Precise Dynamical Masses of Directly Imaged Companions from Relative Astrometry, Radial Velocities, and Hipparcos–Gaia DR2 Accelerations The Astronomical Journal 158 4 140 10.3847/1538-3881/ab04a8 free 1811.07285 2019AJ....158..140B 1538-3881 Kasagi Yui Kawashima Yui Kawahara Hajime Kotani Takayuki Masuda Kento Ahn Kyohoon Guyon Olivier Hirano Teruyuki Jovanovic Nemanja Unveiling the Atmosphere of HR 7672 B from the Near-Infrared High-Resolution Spectrum Using REACH/Subaru The Astronomical Journal 2025-08-02 170 4 211 10.3847/1538-3881/adf730 free 2508.01281 2025AJ....170..211K Li Yaguang Liu Michael C. Dupuy Trent J. Huber Daniel Zhang Jingwen Hey Daniel Costa R. R. Larsen Jens Reersted Ong 王 J. M. Joel. Basu Sarbani Metcalfe Travis S. Zhou Yixiao van Saders Jennifer Bedding Timothy R. Hon Marc 2026-04-21 A Test of Substellar Evolutionary Models with High-precision Ages from Asteroseismology and Gyrochronology for the Benchmark System HR 7672AB The Astrophysical Journal 1002 1 13 10.3847/1538-4357/ae4bdb free 2512.06083 2026ApJ..1002...13L 0004-637X Nidever David L. Marcy Geoffrey W. Butler R. Paul Fischer Debra A. Vogt Steven S. Radial Velocities for 889 Late-Type Stars 1 The Astrophysical Journal Supplement Series 141 2 503–522 August 2002 10.1086/340570 astro-ph/0112477 2002ApJS..141..503N 51814894 15 Sge 2019-03-24 Wagman Morton Lost Stars: Lost, Missing, and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas-Louis de Lacaille, John Flamsteed, and Sundry Others McDonald & Woodward Publishing Company 2003 978-0-939923-78-6 https://books.google.com/books?id=TYLvAAAAMAAJ&q=7664 2025-11-16 The Colour of Stars December 21, 2004 Australia Telescope, Outreach and Education Commonwealth Scientific and Industrial Research Organisation http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html 2012-01-16 2013-12-03 https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html dead External links 15 Sagittae (SolStation) Category:G0V stars Category:L-type brown dwarfs Category:Brown dwarfs Category:Binary stars Category:Sagitta Category:Durchmusterung objects Sagittae, 15 0779 190406 098819 7672 0866