## Radar observations of 2000 BD19

### Background

2000 BD19 is interesting because among all the numbered near-Earth asteroids (NEAs), it comes closest to the Sun. This extreme trajectory puts 2000 BD19 in an unusual dynamical class where various perturbations strongly affect the orientation of the orbit. With a change in orbit orientation ('perihelion shift rate') of 27 arcseconds per century, this near-Earth object (NEO) is one of our best candidates for measuring the perihelion shift due to general relativity (GR) and the oblate Sun (Margot and Giorgini, 2010).

These observations represent one component of a larger program in which the orbits of a dozen NEOs are monitored over several years to reduce uncertainties on GR parameters and to provide a dynamical measurement or upper bound on the gravitational quadrupole moment of the Sun (J2). Considerable improvements over previous studies involving Mercury and Icarus are expected because 1) several newly-discovered asteroids have orbits offering a better sensitivity to the solar J2, 2) our sample incorporates a range of heliocentric distances and inclinations that can unambiguously separate GR and J2 effects, 3) the center of mass locations of small bodies is more accurately determined than that of Mercury.

By obtaining precise radar astrometry for a number of objects at several apparitions, we can disentangle Yarkovsky, GR, and solar J2 perturbations on the orbit.

2000 BD19 (a = 0.876, e = 0.895, i = 25.7 deg) has an orbital period of 0.82 years, perihelion at 0.092 AU (only 20 solar radii) and aphelion at 1.66 AU. The object was detected during the 2006 and 2007 approaches. The 2011 approaches provides another good opportunity for astrometry (SNR/run in excess of 5) while the 2020 approach represents the best opportunity for physical characterization (SNR/run in excess of 100).

Figure 1: Predicted rates of perihelion shift due to GR alone for a number of newly discovered NEOs, compared to that of 1566 Icarus.

Figure 2: Trajectories of 2000 BD19 (solid) and Earth (dashed) looking down on the ecliptic plane. The Sun is at the origin and the vernal equinox is in the positive X-direction.

Return to the Dynamics of asteroids in Icarus-like orbits page.