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WASP-15b
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<h2 id="discovery">Discovery</h2> <p>WASP-15 was first observed by the WASP-South branch of the <a href="/facts/SuperWASP/fp58Y205">SuperWASP</a> project, which operates from the <a href="/facts/South_African_Astronomical_Observatory/F1cjYtGC">South African Astronomical Observatory</a>, between May 4, 2006, and July 17, 2006. It was later observed by WASP-South from January 31, 2007, to July 17, 2007, and from January 31, 2008, to May 29, 2008.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> Further analysis taken from 24,943 collected data points revealed eleven full or partial transits.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>Follow-up observations were conducted by a European and American science team at the 1.2 m <a href="/facts/Leonhard_Euler_Telescope/p8ezh3mG">Leonhard Euler Telescope</a> at <a href="/facts/La_Silla_Observatory/zFMd09aY">La Silla Observatory</a> in Chile, which further raised the possibility of the existence of a planet in WASP-15's orbit; use of the <a href="/facts/CORALIE_spectrograph/p8ezh3mG">CORALIE spectrograph</a> on the Euler Telescope between March 6, 2008, and July 17, 2008, revealed that the variations in <a href="/facts/Doppler_spectroscopy/0uTvj3pq">radial velocity measurements</a> were not because of an <a href="/facts/Eclipsing_binary/TYlDe1bD">eclipsing binary</a> star system.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>CORALIE and the <a href="/facts/High_Resolution_Echelle_Spectrometer/4yhJmNde">High Resolution Echelle Spectrometer</a> (HIRES) revealed the spectrum of WASP-15, which was used to derive the star's characteristics.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> The science team studying WASP-15 found that, after running best-fit models, WASP-15's radial velocity and transit shifts were most likely due to the existence of a planet.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>WASP-15's planet, WASP-15b, had one of the lowest densities known amongst extrasolar planets when it was discovered. Its discovery paper was published by the <a href="/facts/American_Astronomical_Society/f5ohaItD">American Astronomical Society</a> on April 29, 2009, in the <i><a href="/facts/Astronomical_Journal/vH6a7o0U">Astronomical Journal</a></i>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h2 id="host-star">Host star</h2> <p class="note">Main article: <a href="/facts/WASP-15/V3dqet2S">WASP-15</a></p> <p>WASP-15 is an <a href="/facts/Stellar_classification/dYrIuK9H">F-type</a> star located in the <a href="/facts/Centaurus_(constellation)/NQEDC6xA">Centaurus</a> constellation. It is located approximately 290 <a href="/facts/Parsec/SwSsk57J">parsecs</a> (900 <a href="/facts/Light_year/IGc5NdQb">light years</a>) from Earth and has an <a href="/facts/Apparent_magnitude/7pCTF1Me">apparent magnitude</a> of 10.9, making it invisible to the unaided eye. The star is 1.18 times <a href="/facts/Solar_mass/j6Auhku8">more massive</a> than the Sun, and has a <a href="/facts/Solar_radius/5t1Xavju">radius</a> that is 1.477 times larger than that of the Sun, making it more diffuse. WASP-15 has an <a href="/facts/Effective_temperature/RY30DaSY">effective temperature</a> of 6300 <a href="/facts/Kelvin_scale/E3trzC4C">K</a>, and is thus hotter than the Sun, although at 3.9 billion years, it is also younger. WASP-15 has a <a href="/facts/Metallicity/nhhPqbYF">metallicity</a> of [Fe/H] of -0.17, which means that it has 68% of the iron found in the Sun.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h2 id="characteristics">Characteristics</h2> <p>WASP-15b has a <a href="/facts/Jupiter_mass/EtLUmeEN">mass</a> of 0.542 times Jupiter's mass and a <a href="/facts/Jupiter_radius/sT995rQ5">radius</a> that is 1.428 times Jupiter's radius. Due in part to its proximity to its host star, a distance of 0.0499 <a href="/facts/Astronomical_units/gjsbu5xU">AU</a> (7,500,000 km), WASP-15b is greatly inflated, with a density of 0.247 g/cm3. Another factor, such as an internal heat source, is suspected to add to this extremely high radius and extremely low density.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> WASP-15b orbits its host star every 3.7520656 days. It also has an <a href="/facts/Orbital_inclination/TQCFWyfd">orbital inclination</a> of 85.5º, making it almost edge-on as seen from the Earth's perspective.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>The study in 2012, utilizing a <a href="/facts/Rossiter%E2%80%93McLaughlin_effect/QEMgxao5">Rossiter–McLaughlin effect</a>, have determined the planetary orbit is strongly misaligned with the equatorial plane of the star, misalignment equal to -139.6+4.3−5.2°. This spin-orbit angle is making orbit of WASP-15b <a href="/facts/Retrograde_and_prograde_motion/1HCbwQqy">retrograde</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="naming">Naming</h2> <p>In 2019 the <a href="/facts/International_Astronomical_Union/GMFPImXo">IAU</a> announced as part of <a href="/facts/NameExoWorlds/NpRMt4m0">NameExoWorlds</a> that WASP-15 and its planet WASP-15b would be given official names chosen by school children from <a href="/facts/Ivory_Coast/mSSED5Yl">The Ivory Coast</a>.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/SuperWASP/fp58Y205">SuperWASP</a></li></ul> <h2 id="external-links">External links</h2> <p> Media related to WASP-15b at Wikimedia Commons </p> <ul><li><a href="http://wasp-planets.net/wasp-planets/">http://wasp-planets.net/wasp-planets/</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"NameExoWorlds". 2019. Retrieved 6 September 2019. <a href="http://www.nameexoworlds.iau.org/" target="_blank">http://www.nameexoworlds.iau.org/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Jean Schneider (2010). "Notes for star WASP-15". Extrasolar Planets Encyclopaedia. Archived from the original on 2 December 2010. Retrieved 13 May 2011. <a href="https://web.archive.org/web/20101202051747/http://exoplanet.eu/star.php?st=WASP-15" target="_blank">https://web.archive.org/web/20101202051747/http://exoplanet.eu/star.php?st=WASP-15</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>West, R. G.; et al. (2009). "The Low Density Transiting Exoplanet WASP-15b". The Astronomical Journal. 137 (6): 4834–4836. arXiv:0902.2651. Bibcode:2009AJ....137.4834W. doi:10.1088/0004-6256/137/6/4834. S2CID 119291616. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Jean Schneider (2010). "Notes for star WASP-15". Extrasolar Planets Encyclopaedia. Archived from the original on 2 December 2010. Retrieved 13 May 2011. <a href="https://web.archive.org/web/20101202051747/http://exoplanet.eu/star.php?st=WASP-15" target="_blank">https://web.archive.org/web/20101202051747/http://exoplanet.eu/star.php?st=WASP-15</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Albrecht, Simon; Winn, Joshua N.; Johnson, John A.; Howard, Andrew W.; Marcy, Geoffrey W.; Butler, R. Paul; Arriagada, Pamela; Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian B.; Hirano, Teruyuki; Bakos, Gaspar; Hartman, Joel D. (2012), "Obliquities of Hot Jupiter Host Stars: Evidence for Tidal Interactions and Primordial Misalignments", The Astrophysical Journal, 757 (1): 18, arXiv:1206.6105, Bibcode:2012ApJ...757...18A, doi:10.1088/0004-637X/757/1/18, S2CID 17174530 <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>"NameExoWorlds". 2019. Retrieved 6 September 2019. <a href="http://www.nameexoworlds.iau.org/" target="_blank">http://www.nameexoworlds.iau.org/</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>"Naming". 2019. Retrieved 6 September 2019. <a href="https://wasp-planets.net/naming/" target="_blank">https://wasp-planets.net/naming/</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> </ol>