ASTROMETRIC PROGRAM FOR NEAR-EARTH OBJECT SOURCES
by Sergio FOGLIA
UAI Minor Planets Section Recorder
F. Bisleri 11, I-20148 Milano, Italy
Abstract A new astroometric program is proposed for asteroids located in likely source regions supplying the near-Earth object population.
According to Morbidelli et al. (2003), near-Earth objects (NEOs) come mainly from 5 sources with the following contributions to the population: - the nu6 resonance region at the inner border of the asteroid main belt (37 ± 8 %), - the 3:1 resonance region in the middle of the asteroid main belt (23 ± 8 %), - the Intermediate Mars-Crossing (IMC) population (25 ± 3 %), - the Outer Belt (OB) population (8 ± 1 %), - and the population of dormant Jupiter Family Comets (JFC) (6 ± 4 %). Astrometric measurements of objects in these source regions would be very useful to increase knowledge about the NEO source population and solar system dynamics. Thus a new astrometric program for NEO source bodies involving amateur astronomers is suggested. For this program, most objects are usually brigther than 18.0 V magnitude and thus are within the range of equipment for many observers to obtain good measurements. Our goal is to suggest an observing program named Near Earth Objects Source Astrometric Program (NEOSAP) involving the following objects: Mars Crossers having q < 1.52 and Q > 1.52, where q and Q are perihelion and aphelion distances in AU; asteroids in the nu6 secular resonance; asteroids nearby to the 3:1 mean motion resonance with Jupiter. Interested observers will find ephemeris and other information at the following URL: http://www.uai.it/sez_ast/neosap.htm Astrometric measurements must be sent to the Minor Planet Center in the usual way; no other action is required by observers and the listed URL serves only to provide information and ephemerides for recommended targets. Figure 1 (next section) shows the distribution of these objects in the plane of the orbital elements semi-major axis (a) and inclination (i). Table I gives numbers of NEOSAP asteroids in the different categories: JR refers to asteroids nearby to the 3:1 mean motion resonance with Jupiter, MC are the Mars Crossers, NU are objects in the nu6 secular resonance. ----------------- JR 717 MC 726 MC + JR 5 MC + NU 10 NU 116 ----------------- Total 1574 ----------------- Table 1: numerosity of NEOSAP asteroids References Morbidelli et. al. (2003). Understanding the distribution on Near Earth Objects. http://www.obs-nice.fr/morby/ESA/ esa.html MPC Orbit Database. ftp://ftp-cfa.harvard.edu/pub/MPCORB/ 2003 Sep. 17, Minor Planet Center Proper Elements of Minor Planets. http://hamilton.dm .unipi.it/astdys/ 2003 Sep. 17, Asteroid Dynamic Site
Figure 1: NEOSAP (a,i) plane Figure 2 shows the numerosity of these objects in the plane of the orbital elements semi-major axis (a) and eccentricity (e): all asteroids with semi-major axis greather than 0.0 AU and less than 6.0 UA and eccentricity between 0 and 1 are shown as dots.
Figure 2: NEOSAP (a,e) plane Figure 3 shows the numerosity of these objects in the plane of the orbital elements eccentricity (e) and inclination (i): all asteroids with eccentricity greather than 0 and less than 1 and inclination between 0° and 90° are shown as dots.
Figure 3: NEOSAP (e,i) plane Figure 4 shows the numerosity of these objects in the plane of the orbital elements longitude of perielion (wo) and semi-major axis (a): all asteroids with longitude of perielion greather than 0° and less than 360° and semi-major axis between 0.0 AU and 6.0 AU are shown as dots.
Figure 4: NEOSAP (wo,a) plane
EPHEMERIS FOR 2004Opposition Date (TXT file, 17 kByte Ephemeris (TXT file, 142 kByte
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