{{Short description|Carbonaceous asteroid}} {{Use dmy dates|date=October 2019}} {{Infobox planet | minorplanet = yes | name = 8991 Solidarity | background = #D6D6D6 | image = | image_size = | caption = | discovery_ref = <ref name="jpldata" /> | discovered = 6 August 1980 | discoverer = ESO | discovery_site = La Silla Obs. | mpc_name = (8991) Solidarity | alt_names = {{mp|1980 PV|1}}{{·}}1975 QB<br />{{mp|1979 HC|1}}{{·}}{{mp|1985 SD|3}}<br />{{mp|1988 FR|3}}{{·}}{{mp|1988 GW|2}} | named_after = Solidarity<br />{{small|(in memory of 9/11)}}<ref name="springer" /> | mp_category = main-belt{{·}}{{small|(middle)}}<ref name="lcdb" /> | orbit_ref = <ref name="jpldata" /> | epoch = 4 September 2017 (JD 2458000.5) | uncertainty = 0 | observation_arc = 41.57 yr (15,183 days) | aphelion = 3.2956 AU | perihelion = 2.2799 AU | semimajor = 2.7877 AU | eccentricity = 0.1822 | period = 4.65 yr (1,700 days) | mean_anomaly = 70.461° | mean_motion = {{Deg2DMS|0.2118|sup=ms}} / day | inclination = 6.7882° | asc_node = 286.51° | arg_peri = 312.52° | dimensions = {{val|8.385|0.342}} km<ref name="WISE" /><ref name="Masiero-2011" /><br />12.88 km {{small|(calculated)}}<ref name="lcdb" /> | rotation = {{val|5.2388|0.0034}} h<ref name="Waszczak-2016" /> | albedo = 0.057 {{small|(assumed)}}<ref name="lcdb" /><br />{{val|0.174|0.022}}<ref name="WISE" /><ref name="Masiero-2011" /> | spectral_type = C<ref name="lcdb" /> | abs_magnitude = {{val|12.37|1.03}}<ref name="Veres-2015" />{{·}}{{val|12.729|0.003}} {{small|(R)}}<ref name="Waszczak-2016" />{{·}}12.8<ref name="jpldata" />{{·}}12.9<ref name="WISE" />{{·}}13.18<ref name="lcdb" /> }}

'''8991 Solidarity''', provisional designation {{mp|1980 PV|1}}, is a carbonaceous asteroid from the middle region of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 6 August 1980, by observers at ESO's La Silla Observatory site in northern Chile.<ref name="MPC-Solidarity" /> The asteroid was named in response to the September 11 attacks.<ref name="springer" />

== Orbit and classification ==

''Solidarity'' orbits the Sun in the central main-belt at a distance of 2.3–3.3&nbsp;AU once every 4 years and 8 months (1,700 days). Its orbit has an eccentricity of 0.18 and an inclination of 7° with respect to the ecliptic.<ref name="jpldata" /> The first used observation was made at Cerro El Roble Observatory in 1979, extending the body's observation arc by 1 year prior to its official discovery observation at La Silla.<ref name="MPC-Solidarity" />

== Physical characteristics ==

=== Rotation period ===

In January 2011, a rotational lightcurve of ''Solidarity'' was obtained from photometric observations at the Palomar Transient Factory in California. It gave a rotation period of {{val|5.2388}} hours with a brightness variation of 0.19 magnitude ({{small|U=2}}).<ref name="Waszczak-2016" />

=== Diameter and albedo ===

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, ''Solidarity'' measures 8.4 kilometers in diameter and its surface has an albedo of 0.17,<ref name="WISE" /><ref name="Masiero-2011" /> while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 12.9 kilometers with an absolute magnitude of 13.18.<ref name="lcdb" />

== Naming ==

This minor planet was named "Solidarity" in response to the September 11 attacks. As a commemorative gesture, the IAU's Committee for the Nomenclature of Small Bodies chose three objects discovered in observatories on different continents and christened them with names representing some of the most basic and universal human values. The other two selections were 8990&nbsp;Compassion (discovered from Europe) and 8992&nbsp;Magnanimity (discovered from Asia).<ref name="springer" /> The official naming citation was published by the Minor Planet Center on 2 October 2001 ({{small|M.P.C. 43684}}).<ref name="MPC-Circulars-Archive" />

== References == {{reflist|30em|refs=

<ref name="jpldata">{{cite web |type = 2017-03-11 last obs. |title = JPL Small-Body Database Browser: 8991 Solidarity (1980 PV1) |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2008991 |publisher = Jet Propulsion Laboratory |access-date = 22 June 2017}}</ref>

<ref name="springer">{{cite book |title = Dictionary of Minor Planet Names – (8991) Solidarity |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |page = 674 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_7318 |chapter = (8991) Solidarity }}</ref>

<ref name="MPC-Solidarity">{{cite web |title = 8991 Solidarity (1980 PV1) |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=8991 |access-date = 10 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 = 10 July 2016}}</ref>

<ref name="lcdb">{{cite LCDB|number = 8991 |access-date = 10 July 2016}}</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 |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2011ApJ...741...90M |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 |access-date= 10 July 2016}}</ref>

<ref name="Waszczak-2016">{{cite journal |display-authors = 6 |first1 = Adam |last1 = Waszczak |first2 = Chan-Kao |last2 = Chang |first3 = Eran O. |last3 = Ofek |first4 = Russ |last4 = Laher |first5 = Frank |last5 = Masci |first6 = David |last6 = Levitan |first7 = Jason |last7 = Surace |first8 = Yu-Chi |last8 = Cheng |first9 = Wing-Huen |last9 = Ip |first10 = Daisuke |last10 = Kinoshita |first11 = George |last11 = Helou |first12 = Thomas A. |last12 = Prince |first13 = Shrinivas |last13 = Kulkarni |date = September 2015 |title = Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2015AJ....150...75W |journal = The Astronomical Journal |volume = 150 |issue = 3 |page = 35 |bibcode = 2015AJ....150...75W |doi = 10.1088/0004-6256/150/3/75 |arxiv = 1504.04041 |access-date= 10 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= 10 July 2016}}</ref>

<ref name="Masiero-2011">{{cite journal |display-authors = 6 |first1 = Joseph R. |last1 = Masiero |first2 = A. K. |last2 = Mainzer |first3 = T. |last3 = Grav |first4 = J. M. |last4 = Bauer |first5 = R. M. |last5 = Cutri |first6 = J. |last6 = Dailey |first7 = P. R. M. |last7 = Eisenhardt |first8 = R. S. |last8 = McMillan |first9 = T. B. |last9 = Spahr |first10 = M. F. |last10 = Skrutskie |first11 = D. |last11 = Tholen |first12 = R. G. |last12 = Walker |first13 = E. L. |last13 = Wright |first14 = E. |last14 = DeBaun |first15 = D. |last15 = Elsbury |first16 = T. IV |last16 = Gautier |first17 = S. |last17 = Gomillion |first18 = A. |last18 = Wilkins |date = November 2011 |title = Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2011ApJ...741...68M |journal = The Astrophysical Journal |volume = 741 |issue = 2 |page = 20 |bibcode = 2011ApJ...741...68M |doi = 10.1088/0004-637X/741/2/68 |arxiv = 1109.4096 |access-date= 4 December 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|8991}} * {{JPL small body}}

{{Minor planets navigator |8990 Compassion |number=8991 |8992 Magnanimity}} {{Small Solar System bodies}} {{Authority control}}

{{DEFAULTSORT:Solidarity}} 008991 008991 Category:Named minor planets 19800806