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20461 Dioretsa
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<h2 id="classification-and-orbit">Classification and orbit</h2> <p>Dioretsa is a member of the <a href="/facts/Damocloid/HWYYcEhU">damocloids</a>,<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> with a <a href="/facts/Retrograde_orbit/1HCbwQqy">retrograde orbit</a> and a negative <a href="/facts/Tisserand%2527s_parameter/oBkehJM7">TJupiter</a> of −1.547. It is also a <a href="/facts/Centaur_(minor_planet)/jXpnm7dv">centaur</a>, as its orbit has a <a href="/facts/Semi-major_axis/l7JES2wo">semi-major axis</a> in between that of <a href="/facts/Jupiter/95m7XjMT">Jupiter</a> (5.5 <a href="/facts/Astronomical_unit/gjsbu5xU">AU</a>) <a href="/facts/Neptune/1eucwHIC">Neptune</a> (30.1 AU).<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> The <a href="/facts/Minor_Planet_Center/v8T7sdK4">Minor Planet Center</a> lists it as a critical object and (other) <a href="/facts/Unusual_minor_planet/ujRASlnu">unusual minor planet</a> due to an <a href="/facts/Orbital_eccentricity/WGlB4NBn">orbital eccentricity</a> of more than 0.5.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>It orbits the Sun at a distance of 2.4–45.4 AU once every 116 years and 10 months (42,686 days; semi-major axis of 23.9 AU). Its orbit has an eccentricity of 0.90 and an <a href="/facts/Orbital_inclination/TQCFWyfd">inclination</a> of 160<a href="/facts/Degree_(angle)/f48Ns8SX">°</a> with respect to the <a href="/facts/Ecliptic/cJxXDDDW">ecliptic</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Its <a href="/facts/Observation_arc/W7pFwuAk">observation arc</a> begins 12 months prior to its official discovery observation, with a <a href="/facts/Precovery/RbTUMt9F">precovery</a> image taken by <a href="/facts/Spacewatch/97cMRR0S">Spacewatch</a> at <a href="/facts/Steward_Observatory/zEh7Ixzx">Steward Observatory</a> in June 1998.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> As of 2021, it was last observed in 2000 and its orbit still has an <a href="/facts/Uncertainty_parameter/2nNqr9hG">uncertainty</a> of 2.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h3>Retrograde orbit</h3> <p>Dioretsa is the first <a href="/facts/Distant_minor_planet/WppkoW1G">distant object</a> with a retrograde orbit to be discovered, with <a href="/facts/1999_LE31/5o46dW07">1999 LE31</a>. An inclination of greater than 90° means that a body moves in a <a href="/facts/Prograde_and_retrograde_motion/1HCbwQqy">retrograde orbit</a>. Dioretsa's orbit is otherwise similar to that of a <a href="/facts/Comet/w34utQCd">comet</a>. This has led to speculation that Dioretsa was originally an object from the <a href="/facts/Oort_cloud/wdP3VNxd">Oort cloud</a>.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="naming">Naming</h2> <p>The minor planet's name "Dioretsa" is the word "<a href="/facts/Asteroid/g7Ulr1VB">asteroid</a>" spelled backwards (an <a href="/facts/Anadrome/de51UjE4">anadrome</a>), and is the first numbered of currently 136 known (see Data Base Search of the Minor Planet Center) <a href="/facts/List_of_exceptional_asteroids/sm8zjMNC">minor planets with a retrograde motion</a> in the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> The approved naming citation was published by the <a href="/facts/Minor_Planet_Center/v8T7sdK4">Minor Planet Center</a> on 1 May 2003 (<a href="/facts/Minor_Planet_Circulars/v8T7sdK4">M.P.C.</a> 48396).<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <h2 id="physical-characteristics">Physical characteristics</h2> <p>According to observations made with the 10-meter <a href="/facts/Keck_Telescope/4yhJmNde">Keck Telescope</a>, Dioretsa measures 14 kilometers in diameter and its surface has a low <a href="/facts/Astronomical_albedo/TJDRdKEB">albedo</a> of 0.03.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> It has an <a href="/facts/Absolute_magnitude/R8RVxkLx">absolute magnitude</a> of 13.8.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> As of 2018, Dioretsa's <a href="/facts/Asteroid_spectral_type/WoSTAYnh">spectral type</a> as well as its <a href="/facts/Rotation_period/vHcCt6cu">rotation period</a> and shape remain unknown.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p> <h2 id="external-links">External links</h2> <ul><li><a href="https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=20461+Dioretsa">20461 Dioretsa</a>, Small Bodies Data Ferret</li> <li><a href="http://www.minorplanet.info/PHP/lcdbsummaryquery.php">Asteroid Lightcurve Database (LCDB)</a>, query form (<a href="http://www.minorplanet.info/lightcurvedatabase.html">info</a> <a href="https://web.archive.org/web/20171216050541/http://www.minorplanet.info/lightcurvedatabase.html">Archived</a> 16 December 2017 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a>)</li> <li><a href="https://books.google.com/books?id=aeAg1X7afOoC&pg">Dictionary of Minor Planet Names</a>, Google books</li> <li><a href="https://www.minorplanetcenter.net/iau/lists/NumberedMPs020001.html">Discovery Circumstances: Numbered Minor Planets (20001)-(25000)</a> – Minor Planet Center</li> <li><a href="https://newton.spacedys.com/astdys/index.php?n=20461&pc=1.1.0">20461 Dioretsa</a> at <i>AstDyS-2, Asteroids—Dynamic Site</i> <ul><li><a href="https://newton.spacedys.com/astdys/index.php?n=20461&pc=1.1.3.0">Ephemeris</a> · <a href="https://newton.spacedys.com/astdys/index.php?n=20461&pc=1.1.4.0">Observation prediction</a> · <a href="https://newton.spacedys.com/astdys/index.php?n=20461&pc=1.1.1">Orbital info</a> · <a href="https://newton.spacedys.com/astdys/index.php?n=20461&pc=1.1.6">Proper elements</a> · <a href="https://newton.spacedys.com/astdys/index.php?n=20461&pc=1.1.7.0">Observational info</a></li></ul></li> <li><a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20020461">20461 Dioretsa</a> at the <i><a href="/facts/JPL_Small-Body_Database/YQQLDXng">JPL Small-Body Database</a></i> <ul><li><a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20020461&view=C">Close approach</a> · <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20020461&view=D">Discovery</a> · <a href="https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=20020461">Ephemeris</a> · <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20020461&view=V">Orbit viewer</a> · <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20020461&view=O">Orbit parameters</a> · <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20020461&view=P">Physical parameters</a></li></ul></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"20461 Dioretsa (1999 LD31)". Minor Planet Center. Retrieved 20 November 2018. <a href="https://www.minorplanetcenter.net/db_search/show_object?object_id=20461" target="_blank">https://www.minorplanetcenter.net/db_search/show_object?object_id=20461</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Johnston, Wm. Robert (7 October 2018). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 20 January 2018. <a href="http://www.johnstonsarchive.net/astro/tnoslist.html" target="_blank">http://www.johnstonsarchive.net/astro/tnoslist.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Harris, Alan W.; Delbó, Marco; Binzel, Richard P.; Davies, John K.; Roberts, Julie; Tholen, David J.; et al. (October 2001). "Visible to Thermal-Infrared Spectrophotometry of a Possible Inactive Cometary Nucleus". Icarus. 153 (2): 332–337. Bibcode:2001Icar..153..332H. doi:10.1006/icar.2001.6687. Retrieved 4 April 2016. <a href="http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2001Icar..153..332H" target="_blank">http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2001Icar..153..332H</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"20461 Dioretsa (1999 LD31)". Minor Planet Center. Retrieved 20 November 2018. <a href="https://www.minorplanetcenter.net/db_search/show_object?object_id=20461" target="_blank">https://www.minorplanetcenter.net/db_search/show_object?object_id=20461</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Johnston, Wm. Robert (7 October 2018). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 20 January 2018. <a href="http://www.johnstonsarchive.net/astro/tnoslist.html" target="_blank">http://www.johnstonsarchive.net/astro/tnoslist.html</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 20 November 2018. <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461" target="_blank">https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"List Of Other Unusual Objects". Minor Planet Center. 14 November 2018. Retrieved 20 November 2018. <a href="https://www.minorplanetcenter.net/iau/lists/t_others.html" target="_blank">https://www.minorplanetcenter.net/iau/lists/t_others.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 20 November 2018. <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461" target="_blank">https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"20461 Dioretsa (1999 LD31)". Minor Planet Center. Retrieved 20 November 2018. <a href="https://www.minorplanetcenter.net/db_search/show_object?object_id=20461" target="_blank">https://www.minorplanetcenter.net/db_search/show_object?object_id=20461</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 20 November 2018. <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461" target="_blank">https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Kankiewicz, Paweł; Włodarczyk, Ireneusz (11 July 2017). "Dynamical lifetimes of asteroids in retrograde orbits". Monthly Notices of the Royal Astronomical Society. 468 (4): 4143–4150. arXiv:1703.01824. doi:10.1093/mnras/stx558. ISSN 0035-8711. <a href="https://academic.oup.com/mnras/article/468/4/4143/3778505" target="_blank">https://academic.oup.com/mnras/article/468/4/4143/3778505</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Schmadel, Lutz D. (2006). "(20461) Dioretsa [24.4, 0.90, 160.2]". Dictionary of Minor Planet Names – (20461) Dioretsa, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 152. doi:10.1007/978-3-540-34361-5_1728. ISBN 978-3-540-34360-8. <a href="978-3-540-34360-8" target="_blank">978-3-540-34360-8</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>"MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 20 November 2018. <a href="https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html" target="_blank">https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Harris, Alan W.; Delbó, Marco; Binzel, Richard P.; Davies, John K.; Roberts, Julie; Tholen, David J.; et al. (October 2001). "Visible to Thermal-Infrared Spectrophotometry of a Possible Inactive Cometary Nucleus". Icarus. 153 (2): 332–337. Bibcode:2001Icar..153..332H. doi:10.1006/icar.2001.6687. Retrieved 4 April 2016. <a href="http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2001Icar..153..332H" target="_blank">http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2001Icar..153..332H</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>"JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 20 November 2018. <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461" target="_blank">https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>"JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 20 November 2018. <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461" target="_blank">https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020461</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>"LCDB Data for (20461) Dioretsa". Asteroid Lightcurve Database (LCDB). Retrieved 27 June 2017. <a href="http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=20461%7CDioretsa" target="_blank">http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=20461%7CDioretsa</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> </ol>