Orbits

The motion of a massive body around another body, governed by the force of gravity. Planets in our solar system follow an orbit around the Sun, as first noted by Johannes Kepler, in the shape of an ellipse. An orbit is actually composed of two motions: one directly toward the other body (planet or star...) and the another that points away. In the case of a circular orbit, these two component motions are orthogonal (90 degrees apart, or at right angles). Einstein would say that an orbit is actually a geodisc in space -- time, formed by the interaction between space and the mass of the two bodies.

Radio Programs

 Sirius B A close companion for a bright star Tuesday, January 31, 2012
Earth at Perihelion Snuggling close to the Sun Wednesday, January 4, 2012
Mars and Regulus Two old friends in the morning sky Thursday, November 10, 2011
Doomed Moons Recycling on a giant scale Saturday, September 24, 2011
ARTEMIS Teaching old spacecraft new tricks Monday, September 19, 2011
Earliest Sunrise Getting ready for some early sunshine Sunday, June 12, 2011
Urbain Leverrier A "calculated" planetary discovery Friday, March 11, 2011
More Moon and Jupiter Disappearing in the sunlight Monday, March 7, 2011
Upsilon Andromedae An out-of-whack solar system Wednesday, February 9, 2011
Mars in Conjunction Hiding in the bright sunshine Thursday, February 3, 2011
Earth at Perihelion Soaking up some extra sunlight Monday, January 3, 2011
Close Targets Grabbing a lingering visitor Friday, November 19, 2010
Asteroid Thruster Getting a push from day and night Thursday, September 2, 2010
Moon and Companions Drying out some lunar folklore Tuesday, July 13, 2010
Earth at Aphelion Our "eccentric" orbit around the Sun Monday, July 5, 2010
Mars and Regulus A planet speeds across the sky Sunday, June 6, 2010
Moon and Planets Speeding along with a quick planet Thursday, April 15, 2010
Moon and Spica Following the rhythms of the night Tuesday, March 30, 2010
Moon and Venus Harmonizing with a neighbor world Tuesday, March 16, 2010
Simon Newcomb Stepping across the solar system Friday, March 12, 2010
Mercury in the Morning A planet with double-dip sunrises Saturday, January 23, 2010
Dodging a Bullet Earth dodges a cosmic bullet Friday, January 22, 2010
Backwards Mars Mars heads the wrong direction Sunday, December 27, 2009
More Moon, Mars, and Gemini Catching up to a neighbor Sunday, October 11, 2009

Featured Images

The Sun as seen from space
 Close to the Sun Monday, January 3, 2011

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