18493 Demoleon
{{Use dmy dates|date=July 2018}}
{{Infobox planet
| minorplanet = yes
| name = 18493 Demoleon
| background = #C2FFFF
| image =
| image_size =
| caption =
| discoverer = E. W. Elst
| discovery_site = La Silla Obs.
| discovered = 17 April 1996
| mpc_name = (18493) Demoleon
| alt_names = {{mp|1996 HV|9}}{{·}}{{mp|2000 RZ|31}}
| pronounced = {{IPAc-en|d|ᵻ|'|m|oʊ|l|i|ə|n}}Noah Webster (1884) A Practical Dictionary of the English Language
| named_after = Δημολέων Dēmoleōn
{{small|(Greek mythology)}}
| mp_category = Jupiter trojan
{{nowrap|Trojan{{·}}background}}
| epoch = 23 March 2018 (JD 2458200.5)
| uncertainty = 0
| observation_arc = 28.31 yr (10,339 d)
| aphelion = 5.7852 AU
| perihelion = 4.8105 AU
| semimajor = 5.2979 AU
| eccentricity = 0.0920
| period = 12.19 yr (4,454 d)
| mean_anomaly = 210.34°
| mean_motion = {{Deg2DMS|0.0808|sup=ms}} / day
| inclination = 17.198°
| asc_node = 215.55°
| arg_peri = 89.277°
| jupiter_moid = 0.2104 AU
| tisserand = 2.9020
| mean_diameter = {{val|33.47|0.45|ul=km}}
{{val|40.33|u=km}} {{small|(calculated)}}
| rotation = {{val|14.43|0.01|ul=h}}{{efn|name=lightcurve-plots-CS3}}
| albedo = {{val|0.057}} {{small|(assumed)}}
{{val|0.083|0.013}}
| spectral_type = C {{small|(assumed)}}
B–V {{=}} {{val|0.703|0.073}}
V–R {{=}} {{val|0.395|0.047}}
V–I {{=}} {{val|0.775|0.073}}
}}
18493 Demoleon ({{IPAc-en|d|ᵻ|'|m|oʊ|l|i|ə|n}}provisional designation {{mp|1996 HV|9}}) is a Jupiter trojan from the Trojan camp, approximately {{convert|33|km|mi|abbr=off|sigfig=2|sp=us}} in diameter. It was discovered by Belgian astronomer Eric Elst at ESO's La Silla Observatory in northern Chile on 17 April 1996. The dark Jovian asteroid has a rotation period of 14.4 hours. It was named after the Trojan warrior Demoleon from Greek mythology.
Orbit and classification
Demoleon is a dark Jovian asteroid 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 on its orbit {{crossreference|(see Trojans in astronomy)}}. It is also a non-family asteroid of the Jovian background population. It orbits the Sun at a distance of 4.8–5.8 AU once every 12 years and 2 months (4,454 days; semi-major axis of 5.3 AU). Its orbit has an eccentricity of 0.09 and an inclination of 17° with respect to the ecliptic. The body's observation arc begins with a precovery published by the Digitized Sky Survey and taken at Palomar Observatory in November 1989, more than 6 years prior to its official discovery observation at La Silla.
Naming
This minor planet was named from Greek mythology after the Trojan warrior Demoleon, son of Antenor, who was a counselor to King Priam. Demoleon, a valiant champion of war was killed by Achilles, whose spear struck Demoleon on the temple through his bronze-cheeked helmet, crushing the bone so that the brain inside was shed in all directions. The official naming citation was published by the Minor Planet Center on 27 May 2010 ({{small|M.P.C. 70409}}).
Physical characteristics
Demoleon is an assumed C-type asteroid, while most larger Jupiter trojans are D-types. It has a low V–I color index of 0.775 (see table below).
= Rotation period =
In November 2014, a rotational lightcurve of Demoleon was obtained over a total of seven nights of photometric observations by Robert Stephens at the Center for Solar System Studies in Landers, California. Lightcurve analysis gave a rotation period of {{val|14.43|0.01}} hours with a brightness amplitude of 0.18 magnitude ({{small|U=2}}).{{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, Demoleon measures 33.47 kilometers in diameter and its surface has an albedo of 0.083, while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 40.33 kilometers based on an absolute magnitude of 10.7.
{{Largest Jupiter trojans}}
Notes
{{notelist|refs=
{{efn|name=lightcurve-plots-CS3|1=Lightcurve plots of (18493) Demoleon from [http://www.planetarysciences.org/plots/RDS/18493_DEMOLEON_2014-11-12.PNG Nov 2014] by Robert Stephens at the Center for Solar System Studies {{Obscode|U81}}. Quality code is 2+ (lightcurve rating at CS3). Summary figures at the [https://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=18493%7CDemoleon LCDB] and [http://www.planetarysciences.org/PHP/CS3_Lightcurves.php CS3].}}
}}
References
{{reflist|30em|refs=
|type = 2018-02-24 last obs.
|title = JPL Small-Body Database Browser: 18493 Demoleon (1996 HV9)
|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2018493
|publisher = Jet Propulsion Laboratory
|accessdate = 4 July 2018}}
|title = 18493 Demoleon (1996 HV9)
|work = Minor Planet Center
|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=18493
|accessdate = 4 July 2018}}
|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 = 4 July 2018}}
|title = MPC/MPO/MPS Archive
|work = Minor Planet Center
|url = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
|accessdate = 4 July 2018}}
|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=18493 online catalog])
|title = Asteroid (18493) Demoleon – Proper Elements
|publisher = AstDyS-2, Asteroids – Dynamic Site
|url = https://newton.spacedys.com/astdys/index.php?n=18493&pc=1.1.6
|access-date= 4 July 2018}}
|title = LCDB Data for (18493) Demoleon
|publisher = Asteroid Lightcurve Database (LCDB)
|url = https://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=18493%7CDemoleon
|accessdate = 4 July 2018}}
|first1 = Robert D. |last1 = Stephens
|first2 = Daniel R. |last2 = Coley
|first3 = Linda M. |last3 = French
|date = July 2015
|title = Dispatches from the Trojan Camp - Jovian Trojan L5 Asteroids Observed from CS3: 2014 October - 2015 January
|journal = The Minor Planet Bulletin
|volume = 42
|issue = 3
|pages = 216–224
|issn = 1052-8091
|bibcode = 2015MPBu...42R.216S
}}
|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
}}
}}
External links
- [https://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://books.google.com/books?id=aeAg1X7afOoC&pg Dictionary of Minor Planet Names], Google books
- [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=18493+Demoleon Asteroid 18493 Demoleon] {{Webarchive|url=https://web.archive.org/web/20180704153611/https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=18493%20Demoleon |date=4 July 2018 }} at the Small Bodies Data Ferret
- {{AstDys|18493}}
- {{JPL small body}}
{{Minor planets navigator |(18492) 1996 GS2 |number=18493 | }}
{{Small Solar System bodies}}
{{Authority control}}
{{DEFAULTSORT:Demoleon}}