Lyceum B - Astronomy - Week 15 - The Sun
- Mar 21, 2022
- 3 min read
Planets Orbiting the Sun
The word “planet” comes from the Greek word meaning “wanderer”.
How long does it takes a planet to orbit around the sun depends upon their distance from the Sun. Planets close to the Sun must travel faster in their orbit to keep from being pulled into the Sun by the Sun’s gravity. Outer planets travel at a slower speed.
Time it takes each planet for one orbit around the Sun:
Mercury - 3 months
Venus - 7 months
Earth - 12 months
Mars - 23 months
Jupiter - 142 months
Saturn - 354 months
Uranus - 1,008 months
Neptune - 1,978 months
Pluto - 2,976 months
Need: foam board / a drawing compass (or string and pencil in which you anchor the string to the center with the pencil anchored on the other end and draw a circle with the string pulled taunt) / colored markers / 9 toothpicks, 9 different colored pieces of construction paper for flags for the toothpicks
On the foam board, use a compass (or string and pencil) to draw a sun and 9 circles around the sun in the center. Use a different colored pencil for each circle.
On each circle, you will mark in black marker, dots for the months that each planet takes to orbit the sun. Align the first dot of each circle, so each planet will start from the same position. For the planets beyond Mars, just make 12 marks close together in one section of their circle, to symbolize their multitude of months that it takes those planets to orbit the sun. Align those 12 dots on each outer circle up together rather than scattering each planet’s orbit months in different sections of their circles.
So Mercury will have 3 dots spaced at equal distance around its circle.
Venus will have 7 dots spaced at an equal distance around its circle.
Earth will have 12 dots spaced at equal distance around its circle.
Mars will have 23 dots spaced at equal distance around its circle.
And the 5 outer planets will have 12 dots spaced close together, all aligned so that the starting dots are one behind the other.
Cut out a different color triangular flag for the nine toothpicks and tape a colored flag to a toothpick.
Place each flag on its starting dot “month”.
Now as each month goes by, move each planet to its next position dot “month” until 12 months goes by.
Which planet(s) made more than one orbit around the sun in that time period? Which went around just once?
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How the Outer Planets Move:
You will need a pole (the sun) and someone who is taller for the outer planet and someone who is shorter for Earth.
Tie two equal lengths of rope to a pole, placing them so that the out rope will not interfere with the Earth rope as they travel in their orbits. (Tie the ropes fairly loosely so they will not wrap around the pole. We are using them to keep a constant distance from the pole.) The Earth person should hold onto the middle of their rope while the Outer person should hold onto the end of their rope, so that they will not run into each other in their orbits.
Now both move around the pole in the same direction. Earth person should run while the Outer Planet person should move more slowly.
Notice as you, the Earth, overtake the Outer Planet person in your orbit. Do they seem to be moving forward or backward?
Viewed from Earth, sometimes the outer planets appear to be moving backwards in their orbits. Astronomers call this effect retrograde motion. Astrologers would say the planet was in “retrograde”. But it really wasn’t moving backwards, it just appeared that way, just as what happened in our experiment.
All of the planets in the Solar System revolve around the Sun, like a tetherball swinging slowly in a circle around the center pole.
The Sun is at the center and all of the planets go around the Sun.
The planets also rotate, or spin, as they revolve, like a basketball player twirling the basketball on the tip of their finger or how a top spins on the floor.
The planets turn around an imaginary line, or axis, that runs through the center of the planet.
Each planet takes a different amount of time to revolve around the Sun. Earth takes 365 1/4 days to orbit the Sun. Uranus takes 84 years to orbit the Sun. It takes Pluto 248 years to orbit the Sun.
Each planet rotates on its axis at a different speed. Earth rotates once every 24 hours. Jupiter rotates 30 times faster than Earth.
Videos:
Professor Dave Explains - The Life and Death of Stars: White Dwarfs, Supernovae, Neutron Stars, and Black Holes - 16:35 min
Eclipses: Crash Course Astronomy #5 - 10:31 min
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