{{Short description|Hygiean asteroid}} {{Use dmy dates|date=October 2019}} {{Infobox planet | minorplanet = yes | name = 1200 Imperatrix | background = #D6D6D6 | image = | image_size = | caption = | discovery_ref = <ref name="jpldata" /> | discoverer = K. Reinmuth | discovery_site = Heidelberg Obs. | discovered = 14 September 1931 | mpc_name = (1200) Imperatrix | alt_names = 1931 RH{{·}}1929 CX<br />{{mp|1950 DC|1}}{{·}}1957 OY<br />A913 EC{{·}}A915 TL<br />A924 GC | pronounced = {{IPAc-en|ɪ|m|p|ə|ˈ|r|eɪ|t|r|ɪ|k|s}}<ref>{{OED|imperator}}</ref> | named_after = empress {{small|(in Latin)}}<ref name="springer" /> | mp_category = main-belt{{·}}{{small|(outer)}}<ref name="lcdb" /><br />Hygiea<ref name="Ferret" /> | orbit_ref = <ref name="jpldata" /> | epoch = 4 September 2017 (JD 2458000.5) | uncertainty = 0 | observation_arc = 101.75 yr (37,165 days) | aphelion = 3.3873 AU | perihelion = 2.7436 AU | semimajor = 3.0654 AU | eccentricity = 0.1050 | period = 5.37 yr (1,960 days) | mean_anomaly = 114.85° | mean_motion = {{Deg2DMS|0.1836|sup=ms}} / day | inclination = 4.5935° | asc_node = 204.77° | arg_peri = 51.583° | dimensions = {{val|36.00|0.42}} km<ref name="Masiero-2012" /><br />{{val|37.36|9.71}} km<ref name="Nugent-2016" /><br />39.39 km {{small|(derived)}}<ref name="lcdb" /><br />{{val|39.52|3.9}} km<ref name="SIMPS" /><br />{{val|42.006|0.390}} km<ref name="Masiero-2014" /><br />{{val|42.777|0.309}} km<ref name="WISE" /><br />{{val|43.64|0.61}} km<ref name="AKARI" /> | rotation = {{val|13.34|0.11}} h<ref name="Holliday-2001a" /><br />{{val|17.769|0.002}} h<ref name="geneva-obs" /> | albedo = {{val|0.04|0.04}}<ref name="Nugent-2016" /><br />0.0545 {{small|(derived)}}<ref name="lcdb" /><br />{{val|0.060|0.002}}<ref name="AKARI" /><br />{{val|0.0609|0.0118}}<ref name="WISE" /><br />{{val|0.065|0.009}}<ref name="Masiero-2012" /><br />{{val|0.0714|0.017}}<ref name="SIMPS" /> | spectral_type = C {{small|(assumed)}}<ref name="lcdb" /> | abs_magnitude = 10.50<ref name="SIMPS" /><ref name="WISE" /><ref name="AKARI" />{{·}}{{val|10.74|0.28}}<ref name="Veres-2015" />{{·}}10.80<ref name="lcdb" /><ref name="Masiero-2012" />{{·}}10.9<ref name="jpldata" />{{·}}10.91<ref name="Nugent-2016" /> }}
'''1200 Imperatrix''' (provisional designation '''{{mp|1931 RH}}''') is a carbonaceous Hygiean asteroid from the outer regions of the asteroid belt, approximately {{convert|40|km}} in diameter. It was discovered by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory on 14 September 1931.<ref name="MPC-object" /> The asteroid was named after the Latin word for empress.
== Orbit and classification == Imperatrix is a member of the Hygiea family ({{small|601}}),<ref name="Ferret" /> a very large asteroid family named after 10 Hygiea, the main belt's fourth-largest asteroid. 'mperatrix orbits the Sun in the outer main-belt at a distance of 2.7–3.4 AU once every 5 years and 4 months (1,960 days). Its orbit has an eccentricity of 0.11 and an inclination of 5° with respect to the ecliptic.<ref name="jpldata" />
The body's observation arc begins with its first identification as {{mp|A913 EC}} at Simeiz Observatory in March 1913, more than 18 years prior to its official discovery observation at Heidelberg.<ref name="MPC-object" />
== Physical characteristics == Imperatrix is an assumed C-type asteroid which is also the overall spectral type of the Hygiea family.<ref name="lcdb" /><ref name="Nesvorny-2014" />{{rp|23}}
=== Rotation period === In August 2000, a rotational lightcurve of Imperatrix was obtained from photometric observations at the River Oaks Observatory ({{small|915}}) in Texas. Lightcurve analysis gave a rotation period of 13.34 hours with a brightness variation of 0.23 magnitude ({{small|U=2}}).<ref name="Holliday-2001a" /> In September 2011, photometric observations by French amateur astronomers Pierre Antonini and René Roy gave a refined period of 17.769 hours with an amplitude of 0.21 magnitude ({{small|U=3}}).<ref name="geneva-obs" />
=== Diameter and albedo === According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Imperatrix measures between 36.00 and 43.64 kilometers in diameter and its surface has an albedo between 0.04 and 0.0714.<ref name="Masiero-2012" /><ref name="Nugent-2016" /><ref name="SIMPS" /><ref name="Masiero-2014" /><ref name="WISE" /><ref name="AKARI" />
The ''Collaborative Asteroid Lightcurve Link'' derives an albedo of 0.0545 and a diameter of 39.39 kilometers based on an absolute magnitude of 10.8.<ref name="lcdb" />
Four stellar occultation events by 1200 Imperatrix have been observed, all in 2021.
== Naming == This minor planet was named "Imperatrix", which is Latin for empress. The naming was proposed by German ARI-astronomer Gustav Stracke, after whom 1019 Strackea was named. Any specific reference to an occurrence or person is unknown, according to the author of the ''Dictionary of Minor Planets'', Lutz Schmadel and his communications with Ingrid van Houten-Groeneveld, who also worked at Heidelberg).<ref name="springer" />
== References == {{reflist|30em|refs=
<ref name="jpldata">{{cite web |type = 2017-07-03 last obs. |title = JPL Small-Body Database Browser: 1200 Imperatrix (1931 RH) |url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001200 |publisher = Jet Propulsion Laboratory |accessdate = 26 September 2017}}</ref>
<ref name="springer">{{cite book |last = Schmadel | first = Lutz D. |title = Dictionary of Minor Planet Names |publisher = Springer Berlin Heidelberg |page = 100 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_1201 |chapter = (1200) Imperatrix }}</ref>
<ref name="MPC-object">{{cite web |title = 1200 Imperatrix (1931 RH) |work = Minor Planet Center |url = https://www.minorplanetcenter.net/db_search/show_object?object_id=1200 |accessdate = 26 September 2017}}</ref>
<ref name="geneva-obs">{{cite web |title = Asteroids and comets rotation curves – (1200) Imperatrix |last = Behrend |first = Raoul |publisher = Geneva Observatory |url = http://obswww.unige.ch/~behrend/page3cou.html#001200 |accessdate = 26 September 2017}}</ref>
<ref name="Masiero-2014">{{cite journal |display-authors = 6 |first1 = Joseph R. |last1 = Masiero |first2 = T. |last2 = Grav |first3 = A. K. |last3 = Mainzer |first4 = C. R. |last4 = Nugent |first5 = J. M. |last5 = Bauer |first6 = R. |last6 = Stevenson |first7 = S. |last7 = Sonnett |date = August 2014 |title = Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2014ApJ...791..121M |journal = The Astrophysical Journal |volume = 791 |issue = 2 |page = 11 |bibcode = 2014ApJ...791..121M |doi = 10.1088/0004-637X/791/2/121 |arxiv = 1406.6645 |access-date= 26 September 2017}}</ref>
<ref name="Ferret">{{cite web |title = Asteroid 1200 Imperatrix – Nesvorny HCM Asteroid Families V3.0 |work = Small Bodies Data Ferret |url = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=1200+Imperatrix#Asteroid%201200%20ImperatrixEAR-A-VARGBDET-5-NESVORNYFAM-V3.0 |accessdate = 26 October 2019}}</ref>
<ref name="Nesvorny-2014">{{Cite book |first1 = D. |last1 = Nesvorný |first2 = M. |last2 = Broz |first3 = V. |last3 = Carruba |date = December 2014 |chapter = Identification and Dynamical Properties of Asteroid Families |title = Asteroids IV |pages = 297–321 |bibcode = 2015aste.book..297N |doi = 10.2458/azu_uapress_9780816532131-ch016 |arxiv = 1502.01628 |isbn = 9780816532131}}</ref>
<ref name="lcdb">{{cite LCDB|number = 1200 |accessdate = 26 September 2017}}</ref>
<ref name="Masiero-2012">{{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 = C. |last6 = Nugent |first7 = M. S. |last7 = Cabrera |date = November 2012 |title = Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2012ApJ...759L...8M |journal = The Astrophysical Journal Letters |volume = 759 |issue = 1 |page = 5 |bibcode = 2012ApJ...759L...8M |doi = 10.1088/2041-8205/759/1/L8 |arxiv = 1209.5794 |access-date= 26 September 2017}}</ref>
<ref name="Nugent-2016">{{cite journal |display-authors = 6 |first1 = C. R. |last1 = Nugent |first2 = A. |last2 = Mainzer |first3 = J. |last3 = Bauer |first4 = R. M. |last4 = Cutri |first5 = E. A. |last5 = Kramer |first6 = T. |last6 = Grav |first7 = J. |last7 = Masiero |first8 = S. |last8 = Sonnett |first9 = E. L. |last9 = Wright |date = September 2016 |title = NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos |journal = The Astronomical Journal |volume = 152 |issue = 3 |page = 12 |bibcode = 2016AJ....152...63N |doi = 10.3847/0004-6256/152/3/63 |arxiv = 1606.08923 |doi-access = free }}</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=1200 online], [https://core.ac.uk/download/pdf/43545172.pdf AcuA catalog p. 153])</ref>
<ref name="SIMPS">{{cite journal |first1 = E. F. |last1 = Tedesco |first2 = P. V. |last2 = Noah |first3 = M. |last3 = Noah |first4 = S. D. |last4 = Price |date = October 2004 |title = IRAS Minor Planet Survey V6.0 |url = https://sbnarchive.psi.edu/pds3/iras/IRAS_A_FPA_3_RDR_IMPS_V6_0/data/diamalb.tab |journal = NASA Planetary Data System |volume = 12 |pages = IRAS-A-FPA-3-RDR-IMPS-V6.0 |bibcode = 2004PDSS...12.....T |accessdate = 22 October 2019}}</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}}</ref>
<ref name="Holliday-2001a">{{Cite journal |author = Holliday, B. |date = March 2001 |title = Photometry of Asteroid 191 Kolga and 1200 Imperatrix |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2001MPBu...28...13H |journal = The Minor Planet Bulletin |volume = 28 |page = 13 |bibcode = 2001MPBu...28...13H |access-date= 26 September 2017}}</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= 26 September 2017}}</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/NumberedMPs000001.html Discovery Circumstances: Numbered Minor Planets (1)-(5000)] – Minor Planet Center * {{AstDys|1200}} * {{JPL small body}}
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{{DEFAULTSORT:Imperatrix}} 001200 Category:Discoveries by Karl Wilhelm Reinmuth Category:Named minor planets 19310914