Transcript Veres
Peter Vereš, Juraj Tóth, Leonard Kornoš Search for very close approaching NEAs Comenius University, Bratislava, Slovakia Faculty of mathematics, physics and informatics Department of astronomy, physics of the Earth and meteorology Objectives • Create NEA model population • Simulation of geometrical conditions during close Earth encounters • Detection probability of synthetic population Known NEA population • Known NEO counts versus models 05/01/2006 Size NEA NEC PHO IEO 3769 77 774 5 Known population Bottke model 2001 Rabinowitz model 1994 Stuart model 2004 D>1000m 75050 20 95% 73% 71% D>100m 3026253 137 8,7% 3,2% 3,2% D>10m 3747 14 38 5.105 % 10 5 % 3.104 % depending on avg. A Known NEA population • Orbital elements & size distribution of NEA • Smaller NEAs – lesser count • Closest approaches to the Earth within Moon orbit distance & their size distribution Survey programs Limiting conditions: V 5log(r ) H 2.5log 1 G 1 G2 0.63 1 exp 3.33 tan 2 1.22 2 exp 1.87 tan 2 H C 5log10 D 2,5log10 A Our work: albedo vs. diameter G 0,15;0, 40 Apparent magnitude 120 Absolute magnitude – Albedo - Size 18m – 1km 23m – 100m 28m – 10m WFS • Idea to search in the close Earth vicinity, wide field vs. low limit. mag. WFS: LINEAR: f=0,15m f=2,2m WFS limitations 0,18m 1,00m 15°2 2°2 14m 20m 450°/h 210°/h 30s 5s Creating model population Models versus known population Creating model population Random number generation according to distributions a, e, i, H NEO space correction Angular elements – random seed N bodies – each contains 6 orbital elements, size (H) Generation accuracy 10 964 780 synthetic bodies Numerical integration Numerical integrator (Montebruck-Pfleger) JPL database DE406 (accuracy +3000years = ~25m in planets orbits) Multistep backward integration of Adams-Bashforth-Moulton type Perturbing elements vs. Keplerian motion, 12-grade of accuracy Reduction: only Sun & Earth perturbing Input (name, MJD, a, e, i,, , v, H) Output (name, MJD, , R, h, Ph, RA, DC ) Integration time 1 year Output conditions: V<14m a (mean Earth-Moon distance) Results Inside Moon orbit Results Annual size distribution inside Moon orbit Results reduction for WFS • Possible discoveries for H>19 bodies + visual mag. condition = 18 discoveries • For H>19, >0,46AU, 30 , angular velocity limiting magnitude correction for WFS, site of observation – declination restriction, obs. time restriction = 3,6 – 5,4 discoveries • Analyzing each encounter as real (real time and date, RA & DA, time spent inside search area ) = 3,35 discoveries • Synthetic asteroid No. 2 961 437 collides with the Earth H 25, 6 D ~ 26m Results reduction for WFS Apparent movement of 18 simulated bodies, their orbit type & sizes Final results • 80 NEA inside Moon orbit annually • 18 NEA are capable to find under ideal conditions annually with WFS • 3 NEA are easily to find with WFS Modra annually • Optimistic models expect up to 120 discoveries with WFS • Limiting magnitude +18m & preserving wide field expect rapid number of discoveries in the close Earth vicinity • High angular motion is expected 1 60'/ min Future • Actual & accurate models • Higher number of integrated orbits – bodies down to bolid size (1 meter) • Longer integration time – fluctuations and orbits perturbation due to close encounters • Build of WFS, discoveries & confirmation of our model and other models • Upgraded survey system with +18m limit magnitude