{{Short description|Trojan asteroid}} {{Use dmy dates|date=July 2018}} {{Infobox planet | minorplanet = yes | name = 15977 Pyraechmes | background = #C2FFFF | image = | image_size = | caption = | discovery_ref = <ref name="MPC-object" /> | discoverer = LINEAR | discovery_site = Lincoln Lab's ETS | discovered = 19 June 1998 | mpc_name = 15977 Pyraechmes | alt_names = {{mp|1998 MA|11}}{{·}}{{mp|1999 NG|2}} | pronounced = | named_after = Pyraechmes | mp_category = Jupiter trojan<ref name="MPC-object" /><ref name="jpldata" /><br />{{nowrap|Trojan<ref name="MPC-Jupiter-Trojans" />{{·}}background<ref name="AstDys-object" />}} | orbit_ref = <ref name="jpldata" /> | epoch = 23 March 2018 (JD 2458200.5) | uncertainty = 0 | observation_arc = 64.37 yr (23,510 d) | aphelion = 5.4295 AU | perihelion = 4.9353 AU | semimajor = 5.1824 AU | eccentricity = 0.0477 | period = 11.80 yr (4,309 d) | mean_anomaly = 72.300° | mean_motion = {{Deg2DMS|0.0835|sup=ms}} / day | inclination = 17.344° | asc_node = 209.57° | arg_peri = 229.49° | jupiter_moid = 0.0328 AU | tisserand = 2.9070 | mean_diameter = {{val|43.53|0.86|ul=km}}<ref name="Grav-2012" /><br />{{val|51.53|3.86|u=km}}<ref name="AKARI" /> | rotation = {{val|250|5|ul=h}}<ref name="Stephens-2016j" />{{efn|name=lightcurve-plots-CS3}} | albedo = {{val|0.046}}<ref name="AKARI" /><br />{{val|0.071|0.008}}<ref name="Grav-2012" /> | spectral_type = C {{small|(assumed)}}<ref name="lcdb" /><br />B–V {{=}} {{val|0.748|0.033}}<ref name="Hainaut-2012" /><br />V–R {{=}} {{val|0.465|0.025}}<ref name="Hainaut-2012" /><br />V–I {{=}} {{val|0.906|0.026}}<ref name="Hainaut-2012" /> | abs_magnitude = 10.30<ref name="Grav-2012" /><br />10.40<ref name="MPC-object" /><ref name="jpldata" /><ref name="AKARI" /><ref name="lcdb" /> }}
'''15977 Pyraechmes''' (provisional designation '''{{mp|1998 MA|11}}''') is a Jupiter trojan from the Trojan camp, approximately {{convert|45|km|mi|abbr=off|sigfig=2|sp=us}} in diameter. It was discovered on 19 June 1998, by astronomers with the Lincoln Near-Earth Asteroid Research at the Lincoln Lab's ETS near Socorro, New Mexico, in the United States.<ref name="MPC-object" /> The suspected tumbler is also a slow rotator with a period of 250 hours.<ref name="lcdb" />
== Orbit and classification == Pyraechmes is a Jupiter trojan in a 1:1 orbital resonance with Jupiter. It is located in the trailering Trojan camp at the Gas Giant's {{L5}} Lagrangian point, 60° behind its orbit {{crossreference|(see Trojans in astronomy)}}.<ref name="MPC-Jupiter-Trojans" />
It orbits the Sun at a distance of 4.9–5.4 AU once every 11 years and 10 months (4,309 days; semi-major axis of 5.18 AU). Its orbit has an eccentricity of 0.05 and an inclination of 17° with respect to the ecliptic.<ref name="jpldata" /> The body's observation arc begins with a precovery published by the Digitized Sky Survey and taken at Palomar Observatory in December 1953, more than 44 years prior to its official discovery observation at Socorro.<ref name="MPC-object" />
== Numbering and naming == This minor planet was numbered by the Minor Planet Center on 26 July 2000 ({{small|M.P.C. 40994}}).<ref name="MPC-Circulars-Archive" /> It was named in April 2025 after Pyraechmes, a leader of the Paeonians who was killed by Patroclus.<ref name="WGSBN-V5-5"/>
== Physical characteristics == Pyraechmes is an assumed C-type asteroid.<ref name="lcdb" /> It has a typical V–I color index of 0.906 ''(see table below)''.<ref name="Hainaut-2012" />
=== Rotation period === In August 2013, Robert Stephens at the Center for Solar System Studies observed Pyraechmes over three nights. However no meaningful rotational lightcurve could be determined, as the lightcurve's amplitude never varied more than 0.02 magnitude. A period of 11.17 hours was only derived for demonstration purpose ({{small|U=2-}}).<ref name="Stephens-2014c" /> In December 2015, Stephens obtained an improved lightcurve with a rotation period of {{val|250|5}} hours and a brightness variation of 0.30 magnitude ({{small|U=2-}}). This time the asteroid was observed on 16 nights over a period of one month. The photometric observations also revealed that this object possibly has a non-principal axis rotation, which is commonly known as tumbling.<ref name="Stephens-2016j" /><ref name="lcdb" />{{efn|name=lightcurve-plots-CS3}}
=== Diameter and albedo === According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer and the Japanese Akari satellite, Pyraechmes measures 43.53 and 51.53 kilometers in diameter and its surface has an albedo of 0.071 and 0.046, respectively.<ref name="Grav-2012" /><ref name="AKARI" /> The ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 46.30 kilometers based on an absolute magnitude of 10.4.<ref name="lcdb" />
{{Largest Jupiter trojans}}
== Notes == {{notelist|refs=
{{efn|name=lightcurve-plots-CS3|1=Lightcurve plots of (15977) 1998 MA11 from [http://www.planetarysciences.org/plots/RDS/15977_1998MA11_2013-08-28.PNG Aug 2013] and [http://www.planetarysciences.org/plots/RDS/15977_1998MA11_2015-12-01.PNG Dec 2015] by Robert Stephens at the Center for Solar System Studies {{Obscode|U81}}. Quality code is 1/2- (lightcurve rating at CS3). Summary figures at the [http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=15977%7C1998+MA11 LCDB] and [http://www.planetarysciences.org/PHP/CS3_Lightcurves.php CS3].}}
}} <!-- end of notelist -->
== References == {{reflist|30em|refs=
<ref name="jpldata">{{cite web |type = 2018-04-20 last obs. |title = JPL Small-Body Database Browser: 15977 (1998 MA11) |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2015977 |publisher = Jet Propulsion Laboratory |accessdate = 1 July 2018}}</ref>
<ref name="MPC-object">{{cite web |title = 15977 (1998 MA11) |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=15977 |accessdate = 1 July 2018}}</ref>
<ref name="MPC-Jupiter-Trojans">{{cite web |title = List of Jupiter Trojans |work = Minor Planet Center |first3 = V. |last3 = Carruba |date = 1 July 2018 |url = https://www.minorplanetcenter.net/iau/lists/JupiterTrojans.html |accessdate = 1 July 2018}}</ref>
<ref name="MPC-Circulars-Archive">{{cite web |title = MPC/MPO/MPS Archive |work = Minor Planet Center |url = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html |accessdate = 1 July 2018}}</ref>
<ref name="Grav-2012">{{cite journal |first1 = T. |last1 = Grav |first2 = A. K. |last2 = Mainzer |first3 = J. M. |last3 = Bauer |first4 = J. R. |last4 = Masiero |first5 = C. R. |last5 = Nugent |date = November 2012 |title = WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy |journal = The Astrophysical Journal |volume = 759 |issue = 1 |page = 10 |bibcode = 2012ApJ...759...49G |doi = 10.1088/0004-637X/759/1/49 |arxiv = 1209.1549 |s2cid = 119101711 }} ([http://vizier.cfa.harvard.edu/viz-bin/VizieR-6?-source=J/ApJ/759/49/table1&MPC=15977 online catalog])</ref>
<ref name="AstDys-object">{{cite web |title = Asteroid (15977) 1998 MA11 – Proper Elements |publisher = AstDyS-2, Asteroids – Dynamic Site |url = https://newton.spacedys.com/astdys/index.php?n=15977&pc=1.1.6 |access-date= 1 July 2018}}</ref>
<ref name="lcdb">{{cite LCDB|number = 15977 |accessdate = 1 July 2018}}</ref>
<ref name="Stephens-2014c">{{Cite journal |first1 = Robert D. |last1 = Stephens |first2 = Linda M. |last2 = French |first3 = Chelsea |last3 = Davitt |first4 = Daniel R. |last4 = Coley |date = April 2014 |title = At the Scaean Gates: Observations Jovian Trojan Asteroids, July- December 2013 |journal = The Minor Planet Bulletin |volume = 41 |issue = 2 |pages = 95–100 |issn = 1052-8091 |bibcode = 2014MPBu...41...95S}}</ref>
<ref name="Stephens-2016j">{{Cite journal |first1 = Robert D. |last1 = Stephens |first2 = Daniel R. |last2 = Coley |first3 = Linda M. |last3 = French |date = July 2016 |title = A Report from the L5 Trojan Camp - Lightcurves of Jovian Trojan Asteroids from the Center for Solar System Studies |journal = The Minor Planet Bulletin |volume = 43 |issue = 3 |pages = 265–270 |issn = 1052-8091 |bibcode = 2016MPBu...43..265S}}</ref>
<ref name="AKARI">{{cite journal |display-authors = 6 |first1 = Fumihiko |last1 = Usui |first2 = Daisuke |last2 = Kuroda |first3 = Thomas G. |last3 = Müller |first4 = Sunao |last4 = Hasegawa |first5 = Masateru |last5 = Ishiguro |first6 = Takafumi |last6 = Ootsubo |first7 = Daisuke |last7 = Ishihara |first8 = Hirokazu |last8 = Kataza |first9 = Satoshi |last9 = Takita |first10 = Shinki |last10 = Oyabu |first11 = Munetaka |last11 = Ueno |first12 = Hideo |last12 = Matsuhara |first13 = Takashi |last13 = Onaka |date = October 2011 |title = Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey |journal = Publications of the Astronomical Society of Japan |volume = 63 |issue = 5 |pages = 1117–1138 |bibcode = 2011PASJ...63.1117U |doi = 10.1093/pasj/63.5.1117 |doi-access = }} ([http://vizier.cfa.harvard.edu/viz-bin/VizieR-5?-source=J/PASJ/63/1117/acua_v1&Num=15977 online], [https://core.ac.uk/download/pdf/43545172.pdf AcuA catalog p. 153])</ref>
<ref name="Hainaut-2012">{{Cite journal |first1 = O. R. |last1 = Hainaut |first2 = H. |last2 = Boehnhardt |first3 = S. |last3 = Protopapa |date = October 2012 |title = Colours of minor bodies in the outer solar system. II. A statistical analysis revisited |journal = Astronomy and Astrophysics |volume = 546 |page = 20 |bibcode = 2012A&A...546A.115H |doi = 10.1051/0004-6361/201219566 |arxiv = 1209.1896 |s2cid = 54776793}}</ref>
<ref name="WGSBN-V5-5">{{cite journal |title = ''WGSBN Bulletin'' 5, #5 |url = https://wgsbn-iau.org/files/Bulletins/V005/WGSBNBull_V005_005.pdf |journal = WGSBN Bulletin |publisher = International Astronomical Union |volume = 5 |issue = 5 |date = 7 April 2025 |accessdate = 7 April 2025}}</ref>
}} <!-- end of reflist -->
== External links == * [http://www.minorplanet.info/PHP/lcdbsummaryquery.php Asteroid Lightcurve Database (LCDB)], query form ([http://www.minorplanet.info/lightcurvedatabase.html info] {{Webarchive|url=https://web.archive.org/web/20171216050541/http://www.minorplanet.info/lightcurvedatabase.html |date=16 December 2017 }}) * [https://www.minorplanetcenter.net/iau/lists/NumberedMPs015001.html Discovery Circumstances: Numbered Minor Planets (15001)-(20000)] – Minor Planet Center * [https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=15977 Asteroid (15977) 1998 MA11] at the Small Bodies Data Ferret * {{AstDys|15977}} * {{JPL small body|id=2015977}}
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