| 词条 | (6491) 1991 OA |
| 释义 |
| minorplanet = yes | name = (6491) 1991 OA | background = #FFC2E0 | image = | image_size = | caption = | discovery_ref = | discovered = 16 July 1991 | discoverer = H. E. Holt | discovery_site = Palomar Obs. | mpc_name = (6491) 1991 OA | alt_names = | named_after = | mp_category = NEO{{·}}Amor{{·}}PHA | orbit_ref = | epoch = 4 September 2017 (JD 2458000.5) | uncertainty = 0 | observation_arc = 24.35 yr (8,895 days) | aphelion = 3.9772 AU | perihelion = 1.0227 AU | semimajor = 2.5000 AU | eccentricity = 0.5909 | period = 3.95 yr (1,444 days) | mean_anomaly = 215.03° | mean_motion = {{Deg2DMS|0.2493|sup=ms}} / day | inclination = 5.9464° | asc_node = 301.90° | arg_peri = 323.60° | moid = 0.0420 AU{{·}}16.4 LD | dimensions = 0.52 km {{small|(derived)}}[4] | rotation = {{val|2.69}} h[5] | albedo = 0.20 {{small|(assumed)}}[4] | spectral_type = S [4] | abs_magnitude = 18.77[4][5]{{·}}18.9 }}{{mp|(6491) 1991 OA}} is a highly eccentric, stony asteroid, classified as near-Earth object and potentially hazardous asteroid, approximately half a kilometer in diameter. It was discovered on 16 July 1991, by American astronomer Henry E. Holt at the U.S. Palomar Observatory in California.[11] Orbit and classificationThe S-type body is an Amor asteroid – a subgroup of near-Earth asteroids that approach the orbit of Earth from beyond, but do not cross it. It orbits the Sun at a distance of 1.0–4.0 AU once every 3 years and 11 months (1,444 days). Its orbit has an eccentricity of 0.59 and an inclination of 6° with respect to the ecliptic. Its minimum orbit intersection distance (MOID) with Earth is 0.0420 AU, and on 1 August 2086, it will make a close approach and pass by Earth at a distance of {{convert|0.09|AU|km|abbr=on|lk=off}}.[13] A first precovery was taken at the Australian Siding Spring Observatory in March 1991, extending the asteroid's observation arc by 4 months prior to its discovery.[11] Physical characteristicsIn 2000, a rotational lightcurve was published from photometric observations obtained by the Near-Earth Objects Follow-up Program during the early 1990s. The lightcurve rendered a rotation period of 2.69 hours with an brightness amplitude of 0.08 in magnitude ({{small|U=2}}).[5] The Collaborative Asteroid Lightcurve Link (CALL) assumes an albedo of 0.20 and derives a diameter of 0.53 kilometers, based on an absolute magnitude of 18.77.[4] NamingAs of 2017, {{mp|1991 OA}} remains unnamed.[11] References1. ^1 2 3 {{cite web |title = 6491 (1991 OA) |work = Minor Planet Center |url = http://www.minorplanetcenter.net/db_search/show_object?object_id=6491 |accessdate = 24 July 2016}} [1][2][3][4]2. ^1 2 3 4 5 {{cite web |title = LCDB Data for (6491) |publisher = Asteroid Lightcurve Database (LCDB) |url = http://www.minorplanet.info/PHP/GenerateALCDEFPage_Local.php?AstInfo=6491%7C |accessdate = 24 July 2016}} 3. ^1 {{cite web |quote = 2011-09-29 last obs |title = JPL Close-Approach Data: 6491 (1991 OA) |url = http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=6491;cad=1#cad |accessdate = 24 March 2012}} 4. ^1 2 3 {{cite journal |display-authors = 6 |first1 = A. |last1 = Erikson |first2 = S. |last2 = Mottola |first3 = J. S. V. |last3 = Lagerros |first4 = M. |last4 = Lindgren |first5 = J. |last5 = Piironen |first6 = T. |last6 = Oja |first7 = G. |last7 = Hahn |first8 = C.-I. |last8 = Lagerkvist |first9 = A. W. |last9 = Harris |first10 = A. |last10 = Nathues |first11 = G. |last11 = Neukum |date = October 2000 |title = The Near-Earth Objects Follow-up Program. III. 32 Lightcurves for 12 Objects from 1992 and 1995 |url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2000Icar..147..487E |journal = Icarus |volume = 147 |issue = 2 |pages = 487–497 |bibcode = 2000Icar..147..487E |doi = 10.1006/icar.2000.6457 |access-date= 1 January 2016}} }} External links
4 : Amor asteroids|Discoveries by Henry E. Holt|Potentially hazardous asteroids|Astronomical objects discovered in 1991 |
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