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The Question
(Submitted November 07, 1996)
How does the Sun just stay in one spot and how do all of the
other planets stay on course/track ?
The Answer
The planets in our solar system stay on track because of the force of gravity.
This is identical the same force that holds us on the Earth. Imagine shooting
a rocket--the faster you fire the rocket, the farther it goes. If you fire it
fast enough, it will escape the Earth's gravity and go into outer space. You
could also fire the rocket into an orbit around the Earth by propelling it
fast enough that it doesn't hit the ground, but not fast enough to escape the
Earth's gravity. This is what NASA does when it launches the space shuttle
into an orbit. In the same way, all of the planets, along with other things
like comets, are in an orbit around the Sun. Just like the Sun's gravity
keeps the planets into a stable orbit, the planets exert an equal force on the
Sun (gravity is a two-way street), but the Sun is so massive that it hardly
budges.
Andy Ptak and the Ask a High-Energy Astronomer team
Questions on this topic are no longer responded to by the "Ask a
High-Energy Astronomer" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html
for help on other astronomy Q&A services.
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