| 词条 | (121514) 1999 UJ7 |
| 释义 |
|minorplanet = yes |name = {{mp|(121514) 1999 UJ|7}} |symbol = |background = #FA8072 |image = |caption = |discovery_ref = [1] |discoverer = 30 October 1999 by LINEAR |discovered = 30 October 1999 |discovery_site = Socorro |mpc_name = |mp_category = {{mpcat|Martian L4|125}} |alt_names = 2002 AC180[1] |orbit_ref = [1] |epoch = 13 January 2016 (JD 2457400.5) |aphelion = {{Convert|1.5843517|AU|Gm|abbr=on|lk=on}} |perihelion = {{Convert|1.4644704|AU|Gm|abbr=on}} |semimajor = {{Convert|1.5244110|AU|Gm|abbr=on}} |eccentricity = 0.0393206 |period = 1.88 yr (687.47 d) |avg_speed = |inclination = 16.75044° |asc_node = 347.37714° |mean_anomaly = 229.9277° |arg_peri = 48.35771° |satellites = |dimensions = ~1 km[4] |mass = |density = |surface_grav = |escape_velocity = |sidereal_day = |axial_tilt = |pole_ecliptic_lat = |pole_ecliptic_lon = |albedo = |temp_name1 = |mean_temp_1 = |max_temp_1 = |temp_name2 = |max_temp_2 = |spectral_type = X[5] |abs_magnitude = 16.9[1] |mean_motion = {{Deg2DMS|0.5236619|sup=ms}} / day |observation_arc = 21861 days (59.85 yr) |uncertainty = 0 |moid = {{Convert|0.47372|AU|Gm|abbr=on}} |jupiter_moid = {{Convert|3.49473|AU|Gm|abbr=on}} }}{{mp|(121514) 1999 UJ|7}} is a small asteroid orbiting near the {{L4|pt=yes}} of Mars (60 degrees ahead Mars on its orbit).[2] As of September 2011, {{mp|(121514) 1999 UJ|7}} is the only known asteroid to orbit the leading {{L4|pt=yes}} of Mars, although at least three other asteroids orbit Mars's trailing {{L5|pt=yes}}: 5261 Eureka, {{mpl|(101429) 1998 VF|31}}, and {{mpl|2007 NS|2}}.[2] Not only does {{mp|(121514) 1999 UJ|7}} orbit on the other side of Mars from other similar asteroids, its spectrum is different as well, which is puzzling because all of the Martian trojans seem to be in very stable orbits.[5] Orbit{{mp|(121514) 1999 UJ|7}} orbits around the {{L4|pt=yes}} of Mars in a very stable orbit and is large enough that the Yarkovsky effect will not affect its orbit.[2]Physical characteristicsDue to similarity in the measured brightness of {{mp|(121514) 1999 UJ|7}} with other Martian trojans, it is thought to be a small asteroid with an effective diameter on the order of {{Convert|1|km|sp=us}}.[2] Its spectrum suggests that it is an X-type asteroid, which is different from 5261 Eureka and {{mp|1998 VF|31}},[3] and is somewhat puzzling since different mineral compositions suggest different origins for the two groups of asteroids. The long lifetime of the orbits for these asteroids makes the possibility of one or more of them being interlopers unlikely, however. This suggests that either one or more of the Martian trojans was captured in such a way as to give it a long-term stable orbit (and it is therefore not a primordial Martian asteroid), or that some fusion or combination of previous asteroids resulted in the presently observed ones.[3] The Yarkovsky effect may provide a potential capture mechanism but not enough is known about the shapes of these objects to provide a useful Yarkovsky model.[3] See also
References1. ^1 2 3 {{cite web |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=121514;cad=1 |title=JPL Small-Body Database Browser: 121514 (1999 UJ7) |publisher=NASA/Jet Propulsion Laboratory |access-date=7 April 2016}} 2. ^1 2 3 4 {{Cite journal|title=Dynamics of Mars Trojans|first1=H.|last1=Scholl|last2=Marzari|first2=F.|last3=Tricarico|first3=P.|date=June 2005|journal=Icarus|volume=175|issue=2|pages=397–408|doi=10.1016/j.icarus.January+1,+20058|url=http://www.oca.eu/michel/PubliGroupe/Scholletal2005Icarus175.pdf|access-date=2009-04-22|archive-url=https://web.archive.org/web/20120216010052/http://www.oca.eu/michel/PubliGroupe/Scholletal2005Icarus175.pdf|archive-date=2012-02-16|dead-url=yes|df=}} 3. ^1 2 3 4 {{Cite journal|title=Spectroscopy and photometry of Mars Trojans|last1=Rivkin|first1=A. S.|last2=Binzel|first2= R. P.|last3= Howell|first3= E. S.|last4= Bus|first4= S. J.|last5= Grier|first5= J. A.|date=October 2003|journal=Icarus|volume=165|issue=2|pages=349–354|doi=10.1016/S0019-1035(03)00211-2|bibcode=2003Icar..165..349R}} External links
4 : Mars trojans|Discoveries by LINEAR|X-type asteroids|Astronomical objects discovered in 1999 |
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