{{Short description|Near-Earth asteroid}} {{Use dmy dates|date=March 2020}} {{Infobox planet | minorplanet = yes | name = 1685 Toro | background = #FFC2E0 | symbol = | image = 001685-asteroid shape model (1685) Toro.png | image_scale = | caption = Shape model of Toro from its lightcurve | discovery_ref = <ref name="jpldata" /> | discovered = 17 July 1948 | discoverer = C. A. Wirtanen | discovery_site = Lick Obs. | mpc_name = (1685) Toro | alt_names = 1948 OA | named_after = Betulia Toro Herrick<br />{{small|(wife Samuel Herrick)}}<ref name="springer" /> | mp_category = NEO{{·}}Apollo<ref name="jpldata" /><ref name="MPC-object" /><br />Mars-crosser | orbit_ref = <ref name="jpldata" /> | epoch = 5 May 2025 (JD 2460800.5) | uncertainty = 0 | observation_arc = 76.75 yr (28,032 days) | aphelion = 1.9643 AU | perihelion = 0.7714 AU | semimajor = 1.3679 AU | eccentricity = 0.4360 | period = 1.60 yr (584 days) | mean_anomaly = 319.462° | inclination = 9.382° | asc_node = 274.208° | arg_peri = 127.279° | moid = 0.0510 AU{{·}}19.9 LD | mean_diameter = {{val|3.810|0.049|ul=km}}<ref name="WISE" /><br />{{val|4.1|u=km}}<ref name="Harris-1998a" /><br />{{val|3.5|+0.3|-0.4|u=km}}<ref name=Durech/> | rotation = {{val|10.185|0.003|ul=h}}<ref name="Warner-2013a" /><br />{{val|10.1862|0.0006|u=h}}<ref name="Higgins-2008b" /><br />{{val|10.191|0.005|u=h}}<ref name="Warner-2016j" /><br />{{val|10.195|u=h}}<ref name="Torppa-2005" /><br />{{val|10.19540|u=h}}<ref name="De-Angelis-1995a" /><br />{{val|10.196|ul=h}}<ref name="Dunlap-1973" /><br />{{val|10.199|0.003}} h<ref name="Higgins-2011a" /><br />{{val|10.1995|0.0004}} h<ref name="Higgins-2008a" /><br />{{val|10.203|0.003}} h<ref name="Oey-2011d" /><br />{{val|10.197826|0.000002}} h<ref name=Durech/> | albedo = {{val|0.247|0.049}}<ref name="WISE" /><br />{{val|0.29|}}<ref name="Harris-1998a" /><br />{{val|0.38|0.33}}<ref name="Thomas-2011b" /> | spectral_type = {{plainlist| * S {{small|(Tholen)}}<ref name="jpldata" /> * S {{small|(SMASS)}}<ref name="jpldata" /> * S<ref name="Thomas-2014" /><ref name="lcdb" /> * B–V {{=}} 0.880<ref name="jpldata" /> * U–B {{=}} 0.470<ref name="jpldata" /> }} | abs_magnitude = 13.90<ref name="Harris-1998a" /><ref name="lcdb" />{{·}}{{val|14.02|1.11}}<ref name="Veres-2015" />{{·}}14.28<ref name="jpldata" />{{·}}14.23<ref name="WISE" /> }}
'''1685 Toro''' (''prov. designation'': {{mp|1948 OA}}) is an asteroid and near-Earth object of the Apollo group on an eccentric orbit. It was discovered on 17 July 1948, by American astronomer Carl Wirtanen at Lick Observatory on Mount Hamilton, California.<ref name="MPC-object" /><ref name="NYTimes" /> The stony S-type asteroid has a rotation period of 10.2 hours and measures approximately {{convert|4|km|mi|abbr=off|sigfig=2|sp=us}} in diameter. It is named for Betulia Toro Herrick, wife of astronomer Samuel Herrick.<ref name="springer" />
== Classification and orbit ==
Toro is an Apollo asteroid, a subgroup of near-Earth asteroids that cross the orbit of Earth. It orbits the Sun at a distance of 0.8–2.0 AU once every 584 days. Its orbit has an eccentricity of 0.44 and an inclination of 9° with respect to the ecliptic.<ref name="jpldata" />
This asteroid's orbit also shows a 5:8 resonance with Earth<ref name="Danielsson-1972" /> and a near 5:13 resonance with Venus. This near resonance results from Earth and Venus being in a near 8:13 resonance with each other. It was the third Apollo asteroid to be discovered. The current resonance with Earth will last for only a few thousand years. Calculations show that Toro will leave it in 2960 CE, and that it will enter the region of 5:13 resonance with Venus in 3470 CE. This is because the distance from Earth's orbit will become larger and that from Venus's orbit smaller. A study of long-term stability shows that the alternating resonances will possibly be broken roughly 3 million years from now because of close approaches between Toro and Mars.<ref name="Williams-1973" />{{better source needed|date=August 2025|reason=The source for this is an article from 1973, at which time Toro's orbit was not known with good precision, and the accuracy of orbit simulations was limited.}}
Toro{{'}}s Earth minimum orbit intersection distance of {{convert |0.051|AU |km |abbr=on |lk=off |sigfig=3}},<ref name="jpldata" /> is just above the 0.05 AU requirement to be listed as a potentially hazardous asteroid. With an orbital uncertainty ''U'' = 0, its orbit and future close approaches are well determined.<ref name="jpldata" />
Toro's orbit may be similar to that of the Sylacauga meteorite, the first meteorite authenticated to have struck a human.<ref name="Povenmire-1995" />
== Naming ==
This minor planet was named after the maiden name of Betulia (née Toro) Herrick, wife of American astronomer Samuel Herrick. Herrick had studied the asteroid's orbit, and requested the name, along with the other asteroid, 1580 Betulia.<ref name="springer-Betulia" /><ref name="Bio-calisphere" /> The official {{MoMP|1685|naming citation}} was published by the Minor Planet Center on 10 March 1966 ({{small|M.P.C. 2504}}).<ref name="DoMP-Circular-dates" />
== Physical characteristics ==
In the Tholen and SMASS taxonomic scheme, Toro is characterized as a stony S-type asteroid.<ref name="jpldata" /> It is reported to be composed of L chondrite<ref name="Hartmann" /> with a high albedo in the range of 0.24–0.34. It has an extremely well-measured rotation period of 10.2 hours.<ref name="Warner-2013a" /><ref name="Higgins-2008b" /><ref name="Torppa-2005" /><ref name="De-Angelis-1995a" /><ref name="Dunlap-1973" /><ref name="Higgins-2011a" /><ref name="Higgins-2008a" /><ref name=Durech/> Its rotation period is slowly increasing due to the YORP effect.<ref name=Durech/>
== References == <references>
<ref name="jpldata">{{cite web |type = 2025-04-16 last obs. |title = JPL Small-Body Database Browser: 1685 Toro (1948 OA) |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001685 |publisher = Jet Propulsion Laboratory |accessdate = 18 August 2025}}</ref>
<ref name="springer">{{cite book |title = Dictionary of Minor Planet Names |url = https://archive.org/details/dictionaryminorp00schm |url-access = limited |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |chapter = (1685) Toro |page = [https://archive.org/details/dictionaryminorp00schm/page/n147 134] |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_1686}}</ref>
<ref name="MPC-object">{{cite web |title = 1685 Toro (1948 OA) |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=1685 |accessdate = 22 December 2016}}</ref>
<ref name="DoMP-Circular-dates">{{cite book |title = Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008) |chapter = Appendix – Publication Dates of the MPCs |last = Schmadel |first=Lutz D. |publisher = Springer Berlin Heidelberg |page = 221 |isbn = 978-3-642-01964-7 |doi = 10.1007/978-3-642-01965-4 |year = 2009 |bibcode = 2009dmpn.book.....S |chapter-url= https://cds.cern.ch/record/1339661}}</ref>
<ref name="lcdb">{{cite LCDB|number = 1685 |accessdate = 22 December 2016}}</ref>
<ref name="Harris-1998a">{{Cite journal |author = Harris, Alan W. |date = February 1998 |title = A Thermal Model for Near-Earth Asteroids |journal = Icarus |volume = 131 |issue = 2 |pages = 291–301 |bibcode = 1998Icar..131..291H |doi = 10.1006/icar.1997.5865}}</ref>
<ref name="WISE">{{cite journal |display-authors = 6 |first1 = A. |last1 = Mainzer |first2 = T. |last2 = Grav |first3 = J. |last3 = Masiero |first4 = E. |last4 = Hand |first5 = J. |last5 = Bauer |first6 = D. |last6 = Tholen |first7 = R. S. |last7 = McMillan |first8 = T. |last8 = Spahr |first9 = R. M. |last9 = Cutri |first10 = E. |last10 = Wright |first11 = J. |last11 = Watkins |first12 = W. |last12 = Mo |first13 = C. |last13 = Maleszewski |date = November 2011 |title = NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results |journal = The Astrophysical Journal |volume = 741 |issue = 2 |page = 25 |bibcode = 2011ApJ...741...90M |doi = 10.1088/0004-637X/741/2/90 |arxiv = 1109.6407|s2cid = 118700974 }}</ref>
<ref name="Dunlap-1973">{{Cite journal |first1 = J. L. |last1 = Dunlap |first2 = T. |last2 = Gehrels |first3 = M. L. |last3 = Howes |date = August 1973 |title = Minor planets and related objects. IX. Photometry and polarimetry of (1685) Toro |journal = Astronomical Journal |volume = 78 |page = 491 |bibcode = 1973AJ.....78..491D |doi = 10.1086/111447|doi-access= free }}</ref>
<ref name="De-Angelis-1995a">{{Cite journal |author = De Angelis, G. |date = May 1995 |title = Asteroid spin, pole and shape determinations |journal = Planetary and Space Science |volume = 43 |issue = 5 |pages = 649–682 |bibcode = 1995P&SS...43..649D |doi = 10.1016/0032-0633(94)00151-G}}</ref>
<ref name="Torppa-2005">{{Cite journal |display-authors = 6 |first1 = J. |last1 = Torppa |first2 = K. |last2 = Aksnes |first3 = Z. |last3 = Dai |first4 = T. |last4 = Grav |first5 = G. |last5 = Hahn |first6 = T. |last6 = Laakso |first7 = C.-I. |last7 = Lagerkvist |first8 = K. |last8 = Muinonen |first9 = J. |last9 = Niemelaa |first10 = J. |last10 = Naaraanen |first11 = H. |last11 = Rickman |first12 = J. |last12 = Virtanen |date = August 2005 |title = Spins and Shapes of Potentially Hazardous Asteroids |journal = American Astronomical Society |volume = 37 |page = 643 |bibcode = 2005DPS....37.1526T}}</ref>
<ref name="Higgins-2008a">{{Cite journal |last1 = Higgins |first1 = David |date = March 2008 |title = Asteroid Lightcurve Analysis at Hunters Hill Observatory and Collaborating Stations: April 2007 - June 2007 |journal = Minor Planet Bulletin |url = http://www.minorplanet.info/MPB/issues/MPB_35-1.pdf |volume = 35 |issue = 1 |pages = 30–32 |bibcode = 2008MPBu...35...30H |issn = 1052-8091 |accessdate = 17 March 2020}}</ref>
<ref name="Higgins-2008b">{{Cite journal |display-authors = 6 |last1 = Higgins |first1 = David |last2 = Pravec |first2 = Petr |last3 = Kusnirak |first3 = Peter |last4 = Hornoch |first4 = Kamil |last5 = Brinsfield |first5 = James W. |last6 = Allen |first6 = Bill |last7 = Warner |first7 = Brian D. |date = September 2008 |title = Asteroid Lightcurve Analysis at Hunters Hill Observatory and Collaborating Stations: November 2007 - March 2008 |journal = Minor Planet Bulletin |url = http://www.minorplanet.info/MPB/issues/MPB_35-3.pdf |volume = 35 |issue = 3 |pages = 123–126 |bibcode = 2008MPBu...35..123H |issn = 1052-8091 |accessdate = 17 March 2020}}</ref>
<ref name="Higgins-2011a">{{Cite journal |last1 = Higgins |first1 = David |date = January 2011 |title = Period Determination of Asteroid Targets Observed at Hunters Hill Observatory: May 2009 - September 2010 |journal = Minor Planet Bulletin |url = http://www.minorplanet.info/MPB/issues/MPB_38-1.pdf |volume = 38 |issue = 1 |pages = 41–46 |bibcode = 2011MPBu...38...41H |issn = 1052-8091 |accessdate = 17 March 2020}}</ref>
<ref name="Oey-2011d">{{Cite journal |last1 = Oey |first1 = Julian |date = October 2011 |title = Lightcurve Analysis of Asteroids from Leura and Kingsgrove Observatory for the Second Half of 2009 and 2010 |journal = Minor Planet Bulletin |url = http://www.minorplanet.info/MPB/issues/MPB_38-4.pdf |volume = 38 |issue = 4 |pages = 221–223 |bibcode = 2011MPBu...38..221O |issn = 1052-8091 |accessdate = 17 March 2020}}</ref>
<ref name="Warner-2013a">{{Cite journal |last1 = Warner |first1 = Brian D. |date = January 2013 |title = Asteroid Lightcurve Analysis at the Palmer Divide Observatory: 2012 June - September |journal = Minor Planet Bulletin |url = http://www.minorplanet.info/MPB/issues/MPB_40-1.pdf |volume = 40 |issue = 1 |pages = 26–29 |bibcode = 2013MPBu...40...26W |issn = 1052-8091 |accessdate = 17 March 2020}}</ref>
<ref name="Warner-2016j">{{Cite journal |last1 = Warner |first1 = Brian D. |date = July 2016 |title = Near-Earth Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2016 January–April |journal = Minor Planet Bulletin |url = http://www.minorplanet.info/MPB/issues/MPB_43-3.pdf |volume = 43 |issue = 3 |pages = 240–250 |bibcode = 2016MPBu...43..240W |issn = 1052-8091 |accessdate = 17 March 2020 |archive-date = 27 July 2021 |archive-url = https://web.archive.org/web/20210727032747/http://www.minorplanet.info/MPB/issues/MPB_43-3.pdf |url-status = dead }}</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 |journal = Icarus |volume = 261 |pages = 34–47 |bibcode = 2015Icar..261...34V |doi = 10.1016/j.icarus.2015.08.007 |arxiv = 1506.00762|s2cid = 53493339 }}</ref>
<ref name="Thomas-2011b">{{Cite journal |display-authors = 6 |first1 = C. A. |last1 = Thomas |first2 = D. E. |last2 = Trilling |first3 = J. P. |last3 = Emery |first4 = M. |last4 = Mueller |first5 = J. L. |last5 = Hora |first6 = L. A. M. |last6 = Benner |first7 = B. |last7 = Bhattacharya |first8 = W. F. |last8 = Bottke |first9 = S. |last9 = Chesley |first10 = M. |last10 = Delbó |first11 = G. |last11 = Fazio |first12 = A. W. |last12 = Harris |first13 = A. |last13 = Mainzer |first14 = M. |last14 = Mommert |first15 = A. |last15 = Morbidelli |first16 = B. |last16 = Penprase |first17 = H. A. |last17 = Smith |first18 = T. B. |last18 = Spahr |first19 = J. A. |last19 = Stansberry |date = September 2011 |title = ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population |journal = The Astronomical Journal |volume = 142 |issue = 3 |page = 12 |bibcode = 2011AJ....142...85T |doi = 10.1088/0004-6256/142/3/85|doi-access= free }}</ref>
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<ref name="Bio-calisphere">{{cite web |title = Samuel Herrick, Engineering; Astronomy: Los Angeles |work = Calisphere – University of California |url = http://content.cdlib.org/view?docId=hb9k4009c7;NAAN=13030&doc.view=frames&chunk.id=div00024&toc.depth=1&toc.id=&brand=calisphere |accessdate = 22 December 2016}}</ref>
<ref name="NYTimes">{{cite news |title = Science in Review: Research Work in Astronomy and Cancer Lead Year's List of Scientific Developments |author = Waldemar Kaempffert |newspaper = The New York Times |date = 26 December 1948 |page = 87 |issn = 0362-4331 |url = http://select.nytimes.com/gst/abstract.html?res=F00F1EFE3F5E167B93C4AB1789D95F4C8485F9 |accessdate = 4 August 2011}}</ref>
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<ref name="Hartmann">Hartmann, W. K. (2005). Moons & Planets (5th ed.). Belmont, Calif.: Brooks/Cole. {{asin|0534493939}}</ref>
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</references> <!-- end of reflist -->
== External links == * {{usurped|1=[https://web.archive.org/web/20170321170433/http://www.minorplanetobserver.com/pdolc/A1685_2012.HTM Lightcurve plot of 1685 Toro]}}, Palmer Divide Observatory, ''B. D. Warner'' (2012) * [http://www.minorplanet.info/PHP/OneAsteroidInfo.php Lightcurve Database Query] (LCDB), at ''www.minorplanet.info'' * [https://books.google.com/books?id=aeAg1X7afOoC&pg Dictionary of Minor Planet Names], Google books * {{NeoDys|1685}} * {{ESA-SSA|1685|Toro}} * {{JPL small body}}
{{Minor planets navigator |1684 Iguassú |number=1685 |1686 De Sitter}} {{Small Solar System bodies}} {{Authority control}}
{{DEFAULTSORT:Toro}} 001685 Category:Discoveries by Carl A. Wirtanen Category:Named minor planets 001685 001685 19480717