Testing general relativity with high-precision measurements of asteroid trajectories

Program description

The trajectories of some asteroids are affected by sunlight, by the fact that the Sun is not perfectly spherical, and because of effects described in Albert Einstein's theory of General Relativity. Since 2001, we have been tracking the motion of asteroids that make very close approaches to the Sun with Arecibo radar measurements. Our goal is to detect anomalies in asteroid trajectories. We will test Einstein's theory, learn more about the precise shape of the Sun, and measure the influence of sunlight on asteroid trajectories.

Objects observed so far

Six suitable asteroids have been observed on at least two occasions, making these targets prime candidates for the realization of program goals (click on the links to learn more about individual asteroids):

Object First detection Second detection Third detection
1999 KW4 2001 May 25-28 2002 Jun 01-02 2017 May 27-30
2000 BD19 2006 Feb 26-27 2007 Dec 22-23 2020 Feb 8
1999 MN 2004 Jul 22-23 2005 May 30-31
1566 Icarus 2015 Jun 17-20
2000 EE14 2007 Mar 04-06 2008 Feb 28-29
2001 YE4 2002 Jan 10-11 2012 Jan 04-05 2016 Dec 28-29
2006 CJ 2012 Feb 06-07 2017 Feb 05-06
2004 KH17 2013 Jun 03
1998 TU3 2012 Aug 02 2019 Aug 09

Top priority targets

Our full list of top priority targets is maintained in an online database which is updated nightly. Table columns (which can be sorted and ordered) include the orbital parameters, years of apparitions, and years of detections. In the future, this table will be fully cross-linked with the asteroid radar database at radarastronomy.org


We received two 5-year grants from the Division of Astronomical Sciences of the National Science Foundation (AST-0606953 and AST-1109772) to fund a long-term investigation of the trajectories of asteroids. UCLA leads the investigation.


J.L. Margot, Candidate Asteroids for Discerning General Relativity and Solar Oblateness, American Astronomical Society, DDA meeting #34, #06.13, 2003.

J.L. Margot and J.D. Giorgini, Probing general relativity with radar astrometry in the inner solar system, Proceedings of IAU symposium 261: Relativity in Fundamental Astronomy - Dynamics, Reference Frames and Data Analysis, 261, p. 183-188, 2010.

A. H. Greenberg, J. L. Margot, A. K. Verma, P. A. Taylor, S. P. Naidu, M. Brozovic, L. A. M. Benner. Asteroid 1566 Icarus's size, shape, orbit, and Yarkovsky drift from radar observations. Astronomical Journal 153, 108, 2017.

A. K. Verma, J. L. Margot, A. H. Greenberg. Prospects of Dynamical Determination of General Relativity Parameter β and Solar Quadrupole Moment J2☉ with Asteroid Radar Astronomy. Astrophysical Journal 845, 166, 2017.