Date: 5 Dec 2003
NASA scientists used radar images to detect a tiny but theoretically important force acting on asteroids by measuring an extremely subtle change in a near-Earth asteroid's orbital path. This force, called the Yarkovsky Effect, is produced by the way an asteroid absorbs energy from the sun and re-radiates it into space as heat. The research will impact how scientists understand and track asteroids in the future.
Asteroid 6489 Golevka is only one half-kilometer (.33 mile) across, although it weighs in at about 210 billion kg (460 billion pounds). Golevka is also relatively well characterized, having been observed via radar in 1991, 1995, 1999 and 2003. An international team of astronomers used this comprehensive data set to make a detailed analysis of the asteroid's orbital path. The data prove asteroids can propel themselves through space, although very slowly.
The idea behind the Yarkovsky Effect is the simple notion that an asteroid's surface is heated by the sun during the day and then cools off during the night. Because of this, the asteroid tends to emit more heat from its afternoon side, just as the evening twilight on Earth is warmer than the morning twilight. This unbalanced thermal radiation produces a tiny acceleration that had previously been unmeasured.
Last Update: 11 Apr 2011 (AMB)