Normally, the planets move west-to-east through the stars at night. This is referred to as prograde motion. However, peridiocally the motion changes and they move east-to-west through the stars. We call this retrograde motion. The retrograde motion continues for a short time and then the motion switches back to prograde.

Venus rotates slowly on its axis in a clockwise direction, which is referred to as a "retrograde" rotation because it is the opposite of the seven other planets. A rotation takes 243 Earth days, so a Venusian day is longer than a Venusian year.

Parallax. Astronomers derive distances to the nearest stars (closer than about 100 light-years) by a method called stellar parallax.

Due to Triton's retrograde orbit, its density, and its composition, astronomers theorize that Triton was not originally a satellite of Neptune. They theorize that Triton was captured by Neptune's gravitational pull, forcing it into an orbit around the planet.

Venus has a retrograde rotation which means it rotates on its axis in the opposite direction from the Earth's rotation. This causes the Sun to rise in the west and move eastward across the sky. Return to the StarChild Main Page

The spin axis of the Earth undergoes a motion called precession. If you have ever watched a spinning top, you know that its spin axis tends to stay pointed in the same direction. However, if you give it a slight nudge, the axis will start to change its direction, and its motion traces out a …

In July of 1999, the Space Shuttle Columbia was launched with its heaviest payload to that date. The payload was Chandra, NASA's new X-ray Observatory named after Subrahmanyan Chandrasekhar, one of the most prominent astrophysicists of the twentieth century.

A scale for measuring temperature where 0 Kelvin is equal to -273.16 degrees Celsius. Zero Kelvin is referred to as absolute zero, the point at which all motion within molecules comes to a stop. KILOGRAM 1000grams. A kilogram equals 2.2 pounds. KILOMETER 1000 meters. A kilometer equals 0.6214 miles. KILOPARSEC 1000 parsecs.

StarChild Question of the Month for February 1999 Question: What is an eclipse? Answer: An eclipse occurs when one object gets in between you and another object and blocks your view.

That means it is shaped like an egg. The Sun is in the center of the solar system. Our solar system is always in motion. Eight known planets and their moons, along with comets, asteroids, and other space objects orbit the Sun. The Sun is the biggest object in our solar system. It contains more than 99% of the solar system's mass.