An orbit solution gives a single point representing 1950 DA’s highest probability position and velocity on 10 March 2001. It also describes a continuum of other solutions consistent with the measurements but of lower probability.
This “solution uncertainty region” was sampled to obtain sets of possible but less probable starting conditions on 10 March 2001. Each trace-point was then separately integrated 878 years to the A.D. 2880 encounter. The result represents the set of STATISTICALLY POSSIBLE trajectories.
For the depictions that follow, 500 possible starting conditions were used. Relativistic point-mass perturbations included in the numerical integration are those of the planets, Moon, and the major asteroids Ceres, Pallas and Vesta. Thermal re-reradiation, solar radiation pressure and other effects dependent on poorly known physical parameters such as composition, mass and thermal conductivity are not included here, but have the potential to cancel each other with the result being comparable to the original impact detection case shown here.
This “cloud” of particles does NOT represent lots of asteroids approaching together. It is instead the set of statistically possible positions of the single asteroid 1950 DA. Only one of the dots could be the actual trajectory of 1950 DA, but it is not known which one. Furthermore, systematic biases caused by unknown parameters could move the entire probability region away from the Earth. For example, if the asteroid’s spin pole points south, the cloud would pass far behind the Earth and there would be no hazard. If the asteroid’s polar axis points to the north, results could be similar to this reference (detection) case.
Distant view from north pole of solar system, looking down. Shows 1950 DA’s uncertainty region approaching Earth and being disrupted by the close encounter. The larger red dot is the highest probability position, surrounded by “virtual” 1950 DA positions of decreasing probability. Animation runs from 1 February through 18 Jun 2880. Animation from J. Giorgini (JPL).
View zooms in from north pole of solar system. It shows 1950 DA’s uncertainty region approaching Earth and being disrupted by the close encounter. The larger red dot is the highest probability position, surrounded by “virtual” 1950 DA positions of decreasing probability. The circle around the Earth depicts the orbit of the Moon. Animation runs from 3 March 2880 to 9 May 2880. Animation from J. Giorgini (JPL).
View rotates to an oblique perspective of the solar system as 1950 DA’s uncertainty region approaches Earth and is disrupted by the close encounter. The larger red dot is the highest probability position, surrounded by “virtual” 1950 DA positions of decreasing probability. Animation runs from 1 March 2880 to 3 May 2880. Animation from J. Giorgini (JPL).
Edge-on view of the Earth’s orbit as 1950 DA’s uncertainty region approaches Earth and is disrupted by the close encounter. The larger red dot is the highest probability case, surrounded by “virtual” 1950 DA positions of decreasing probability. Animation runs from 16 Feb 2880 to 1 Jul 2880. Animation from J. Giorgini (JPL).
This animation shows the resonance modulation of the 1950 DA uncertainty region between the years 2366 and 2631. Repetitive, periodic tugging on the asteroid by Earth’s gravity keeps the 1950 DA uncertainty cloud oscillating around the nominal position in the direction of motion, instead of simply spreading out over time. Animation from J. Giorgini (JPL).
