| 词条 | 984 Gretia |
| 释义 |
| minorplanet = yes | name = 984 Gretia | background = #D6D6D6 | image = 984Gretia (Lightcurve Inversion).png | image_size = 265 | caption = 3D-model of Gretia based on its lightcurve | discovery_ref = | discoverer = K. Reinmuth | discovery_site = Heidelberg Obs. | discovered = 27 August 1922 | mpc_name = (984) Gretia | alt_names = 1922 MH{{·}}1973 LC A910 BA{{·}}A915 DA | pronounced = | named_after = {{small|Greta, sister-in-law of astronomer Albrecht Kahrstedt}} [2] | mp_category = main-belt{{·}}{{small|(middle)}} background | orbit_ref = | epoch = 4 September 2017 (JD 2458000.5) | uncertainty = 0 | observation_arc = 94.45 yr (34,499 days) | aphelion = 3.3562 AU | perihelion = 2.2495 AU | semimajor = 2.8028 AU | eccentricity = 0.1974 | period = 4.69 yr (1,714 days) | mean_anomaly = 65.271° | mean_motion = {{Deg2DMS|0.2100|sup=ms}} / day | inclination = 9.0930° | asc_node = 314.21° | arg_peri = 55.494° | dimensions = {{val|31.91|3.1}} km[4][5] {{val|32.449|0.306}} km[6] {{val|34.91|0.47}} km[7] {{val|36.600|0.187}} km[8] | rotation = {{val|5.560|0.018}} h[9] {{val|5.76|}} h[10] {{val|5.778|0.001}} h[11] {{val|5.778026|0.000001}} h[12] {{val|5.77827|0.00005}} h[11] {{val|5.7789|0.0002}} h[14] {{val|5.780|0.001}} h[15] {{val|5.781|}} h[16][17] | albedo = {{val|0.3566|0.0863}}[8] {{val|0.360|0.012}}[7] {{val|0.421|0.038}}[6] {{val|0.4239|0.095}}[4] | spectral_type = SMASS {{=}} Sr {{·}}S [5] B–V = {{val|0.950|0.030}}[9] | abs_magnitude = 9.03[4][5][7][8]{{·}}{{val|9.52|0.16}}[30] }}984 Gretia, provisional designation {{mp|1922 MH}}, is a stony background asteroid from the central regions of the asteroid belt, approximately {{convert|32|km|mi|abbr=off|sp=us}} in diameter. It was discovered by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory on 27 August 1922.[31] The asteroid was named after Greta, sister-in-law of ARI-astronomer Albrecht Kahrstedt.[31] Orbit and classificationGretia is a background asteroid that has not been associated with any known asteroid family. It orbits the Sun in the central main belt at a distance of 2.2–3.4 AU once every 4 years and 8 months (1,714 days). Its orbit has an eccentricity of 0.20 and an inclination of 9° with respect to the ecliptic.It was first observed as {{mp|A910 BA}} at the discovering observatory in 1910, and five years later as {{mp|A915 DA}} at the United States Naval Observatory. The body's observation arc begins at Vienna Observatory in September 1922, two weeks after its official discovery observation.[31] NamingThis minor planet was named after Greta, sister-in-law of Albrecht Kahrstedt (1897–1971), a German astronomer at ARI and director of the institute's Potsdam division, who requested the naming of this asteroid and 1026 Ingrid (daughter of Greta) in a personal letter to the discoverer in February 1926.[2][36] Kahrstedt himself was honored with the naming of {{MoMP|1587|1587 Kahrstedt}}. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 ({{small|H 94}}).[2] Lutz Schmadel quoted an excerpt of Kahrstedt's letter in his Dictionary of Minor Planet Names (LDS).[36] Physical characteristicsIn the SMASS classification, Gretia is a Sr-subtype that transitions between the common S-type and rare R-type asteroids. LightcurvesSince 1997, a large number of rotational lightcurves of Gretia have been obtained from photometric observations. Analysis of the best-rated lightcurves gave a rotation period of 5.778 hours with a maximal brightness amplitude from 0.26 to 0.75 magnitude ({{small|U=2–3}}).[9][10][11][12][14][15][16][17] The asteroid's spin axis of (92.0°, 67.0°) and (247.0°, 48.0°) in ecliptic coordinates (λ, β) have also been derived from modeled lightcurves ({{small|Q=3}}).[12] Diameter and albedoAccording 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, Gretia measures between 31.91 and 36.60 kilometers in diameter and its surface has a high albedo between 0.3566 and 0.4239.[4][6][7][8] The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an exceptionally high albedo of 0.4239 and a diameter of 31.91 kilometers with an absolute magnitude of 9.03.[4][5] References1. ^1 2 3 {{cite book |title = Dictionary of Minor Planet Names – (984) Gretia |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |page = 85 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_985 |chapter = (984) Gretia }} [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]2. ^1 2 {{cite book |title = Dictionary of Minor Planet Names – (1026) Ingrid |last = Schmadel | first = Lutz D. |publisher = Springer Berlin Heidelberg |page = 88 |date = 2007 |isbn = 978-3-540-00238-3 |doi = 10.1007/978-3-540-29925-7_1027 |chapter = (1026) Ingrid }} 3. ^1 2 3 {{cite web |title = 984 Gretia (1922 MH) |work = Minor Planet Center |url = http://www.minorplanetcenter.net/db_search/show_object?object_id=984 |accessdate = 26 August 2017}} 4. ^1 2 3 {{cite web |title = Asteroids and comets rotation curves – (984) Gretia |last = Behrend |first = Raoul |publisher = Geneva Observatory |url = http://obswww.unige.ch/~behrend/page3cou.html#000984 |accessdate = 26 August 2017}} 5. ^1 2 3 {{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. 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6 : Background asteroids|Discoveries by Karl Wilhelm Reinmuth|Minor planets named for people|Named minor planets|Sr-type asteroids (SMASS)|Astronomical objects discovered in 1922 |
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