{{Short description|Main-belt asteroid}} {{Use dmy dates|date=October 2019}} {{Infobox planet | minorplanet = yes | name = 6498 Ko | background = #D6D6D6 | image = | image_size = | caption = | discovery_ref = <ref name="jpldata" /> | discovered = 26 October 1992 | discoverer = K. Endate<br />K. Watanabe | discovery_site = Kitami Obs. | mpc_name = (6498) Ko | alt_names = {{mp|1992 UJ|4}}{{·}}1964 PM<br />{{mp|1971 QK|3}}{{·}}{{mp|1994 CD|4}} | named_after = Ko Nagasawa<br />{{small|(Japanese scientist)}}<ref name="springer" /> | mp_category = main-belt{{·}}Flora<ref name="lcdb" /> | orbit_ref = <ref name="jpldata" /> | epoch = 4 September 2017 (JD 2458000.5) | uncertainty = 0 | observation_arc = 62.24 yr (22,734 days) | aphelion = 2.6660 AU | perihelion = 1.8955 AU | semimajor = 2.2807 AU | eccentricity = 0.1689 | period = 3.44 yr (1,258 days) | mean_anomaly = 149.16° | mean_motion = {{Deg2DMS|0.2861|sup=ms}} / day | inclination = 7.9910° | asc_node = 149.63° | arg_peri = 156.73° | dimensions = 3.99 km {{small|(calculated)}}<ref name="lcdb" /> | rotation = 500 h{{efn|name=lcdb-Pravec}}{{efn|name=Pravec-alt-lightcurve-plot}} | albedo = 0.24 {{small|(assumed)}}<ref name="lcdb" /> | spectral_type = S<ref name="lcdb" /> | abs_magnitude = 13.5<ref name="jpldata" />{{·}}13.71{{efn|name=lcdb-Pravec}}{{·}}{{val|13.92|0.47}}<ref name="Veres-2015" />{{·}}14.16<ref name="lcdb" /> }}
'''6498 Ko''', provisional designation {{mp|1992 UJ|4}}, is a stony Flora asteroid and exceptionally slow rotator from the inner regions of the asteroid belt, approximately 4 kilometers in diameter. The asteroid was discovered on 26 October 1992, by Japanese amateur astronomers Kin Endate and Kazuro Watanabe at Kitami Observatory on eastern Hokkaidō, Japan.<ref name="MPC-Ko" /> It was named for Japanese scientist Ko Nagasawa.<ref name="springer" />
== Orbit and classification ==
''Ko'' is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 1.9–2.7 AU once every 3 years and 5 months (1,258 days). Its orbit has an eccentricity of 0.17 and an inclination of 8° with respect to the ecliptic.<ref name="jpldata" />
A first precovery was taken at Palomar Observatory in 1954, extending the asteroid's observation arc by 38 years prior to its discovery.<ref name="MPC-Ko" />
=== Minor-planet close approaches ===
Although ''Ko'' does not cross the orbit of any planet, it does make close approaches to other large asteroids, such as 29 Amphitrite, which it approached within 0.038 AU in 1915. Further close approaches will take place in 2025 and 2135 at a distance of 0.012 and 0.009 AU, respectively. On 14 November 2009, the asteroid also made a close encounter with 3 Juno at a distance of about 0.047 AU.<ref name="jpldata" />
== Physical characteristics ==
=== Slow rotator ===
A rotational lightcurve of ''Ko'' was obtained from photometric observations by Czech astronomer Petr Pravec at the Ondřejov Observatory in June 2012. It rendered an exceptionally long rotation period of 500 hours with a brightness amplitude of 0.6 in magnitude ({{small|U=2}}).{{efn|name=lcdb-Pravec}}{{efn|name=Pravec-alt-lightcurve-plot}}
=== Diameter and albedo ===
The ''Collaborative Asteroid Lightcurve Link'' assumes an albedo of 0.24, derived from the Flora family's largest member and namesake, the asteroid 8 Flora, and calculates a diameter of 4.0 kilometers with an absolute magnitude of 14.16.<ref name="lcdb" />
== Naming ==
This minor planet was named in honor of Japanese scientist Ko Nagasawa (born 1932), who became a keen researcher of meteors and workes for the Public Information Office at the National Astronomical Observatory of Japan, after retiring from the Earthquake Research Institute, University of Tokyo in 1994.<ref name="springer" />
At the ''Dodaira Station'', after which the minor planet 14313 Dodaira is named, Ko has obtained numerous photographic spectra of the 1965-Leonid meteor shower. The minor planet's name was proposed by the second discoverer, Kazuro Watanabe, following a suggestion by Japanese astronomer Kōichirō Tomita.<ref name="springer" /> The approved naming citation was published by the Minor Planet Center on 20 June 1997 ({{small|M.P.C. 30099}}).<ref name="MPC-Circulars-Archive" />
== Notes == {{notelist|refs=
{{efn|name=lcdb-Pravec|1=Pravec (2012): rotation period of {{val|500}} hours with a brightness amplitude of {{val|0.6}} magnitude. CALL assigned a quality-code Q of 2 to the measurement, which means, that the result is based on less than full coverage, and that the period may be wrong by 30 percent or so. Summary figures for (6498) Ko at [http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=6498%7CKo Collaborative Asteroid Lightcurve Link (CALL)] and [http://www.asu.cas.cz/~ppravec/neo.htm Pravec, P.; Wolf, M.; Sarounova, L. (2012)]}}
{{efn|name=Pravec-alt-lightcurve-plot|1= Pravec (2012): alternative [http://www.asu.cas.cz/~asteroid/06498.png lightcurve plot] with a period of 250 hours at [http://www.asu.cas.cz/~ppravec/neo.htm Pravec, P.; Wolf, M.; Sarounova, L. (2012)]}}
}} <!-- end of notelist -->
== References == {{reflist|30em|refs=
<ref name="jpldata">{{cite web |type = 2017-02-16 last obs. |title = JPL Small-Body Database Browser: 6498 Ko (1992 UJ4) |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2006498 |publisher = Jet Propulsion Laboratory |access-date = 21 June 2017}}</ref>
<ref name="springer">{{cite book |title = Dictionary of Minor Planet Names – (6498) Ko |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |page = 537 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_5909 |chapter = (6498) Ko }}</ref>
<ref name="MPC-Ko">{{cite web |title = 6498 Ko (1992 UJ4) |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=6498 |access-date = 4 July 2016}}</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 |access-date = 4 July 2016}}</ref>
<ref name="lcdb">{{cite LCDB|number = 6498 |access-date = 4 July 2016}}</ref>
<ref name="Veres-2015">{{cite journal |display-authors = 6 |first1 = Peter |last1 = Veres |first2 = Robert |last2 = Jedicke |first3 = Alan |last3 = Fitzsimmons |first4 = Larry |last4 = Denneau |first5 = Mikael |last5 = Granvik |first6 = Bryce |last6 = Bolin |first7 = Serge |last7 = Chastel |first8 = Richard J. |last8 = Wainscoat |first9 = William S. |last9 = Burgett |first10 = Kenneth C. |last10 = Chambers |first11 = Heather |last11 = Flewelling |first12 = Nick |last12 = Kaiser |first13 = Eugen A. |last13 = Magnier |first14 = Jeff S. |last14 = Morgan |first15 = Paul A. |last15 = Price |first16 = John L. |last16 = Tonry |first17 = Christopher |last17 = Waters |date = November 2015 |title = Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2015Icar..261...34V |journal = Icarus |volume = 261 |pages = 34–47 |bibcode = 2015Icar..261...34V |doi = 10.1016/j.icarus.2015.08.007 |arxiv = 1506.00762 |access-date= 4 July 2016}}</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://books.google.com/books?id=aeAg1X7afOoC&pg Dictionary of Minor Planet Names], Google books * [http://obswww.unige.ch/~behrend/page_cou.html Asteroids and comets rotation curves, CdR] – Observatoire de Genève, Raoul Behrend * [https://www.minorplanetcenter.net/iau/lists/NumberedMPs005001.html Discovery Circumstances: Numbered Minor Planets (5001)-(10000)] – Minor Planet Center * {{AstDys|6498}} * {{JPL small body}}
{{Minor planets navigator |6497 Yamasaki |number=6498 |6499 Michiko}} {{Small Solar System bodies}} {{Authority control}}
{{DEFAULTSORT:Ko}} 006498 Category:Discoveries by Kin Endate Category:Discoveries by Kazuro Watanabe Category:Named minor planets 006498 19921026