As asteroids travels through space, its illuminated surface is warmed by heat from the sun. As the surface cools, the emitted heat exerts a small thrust that can modify the asteroid’s trajectory over time.

Unfortunately, a phenomenon called the Yarkovsky effect can make these predictions difficult over long time periods.

This force can cause rotating asteroids to drift widely over time, making it hard for scientists to predict their long-term risk to Earth.

How does this effect work?

When sunlight strikes a rotating asteroid, the dayside heats up; as the asteroid turns, the night side cools and releases the heat, exerting a small thrust that can change the asteroid’s direction over time.

In order to learn more about this process on asteroid Bennu, NASA is sending a spacecraft called OSIRIS-REx to make detailed observations of Bennu’s shape, brightness, and surface features. These factors are thought to influence the Yarkovsky effect, and understanding how will enable scientists to better predict the orbit of Bennu and other near-Earth asteroids.


OSIRIS-REx Sample Return Mission launch and the visit to asteroid Bennu

Thursday, September 8, 2016 from Kennedy Space Center

OSIRIS-REx size comparison

Learn more about the mission objectives »

Uncovering the Secrets of Asteroids on NASATV

During this panel, NASA scientists (including myself) will discuss asteroids, how they relate to the origins of our solar system, and the search for life beyond Earth. Panelists for this conversation are:

  • Ellen Stofan, NASA chief scientist
  • Michelle Thaller, Deputy Director of Science Communications for NASA’s Science Mission Directorate
  • Lindley Johnson, Director of the Planetary Defense Coordination Office in NASA’s Science Mission Directorate
  • Alex Young, Associate Director for Science in the Heliophysics Science Division at Goddard