The Solar System

Question 1

How many planets orbit around the Sun?

Answer 1

8

Question 2

List planets in order from the Sun

Answer 2

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Question 3

Mnemonic to remember order of planets

Answer 3

My Very Easy Method Just Sums Up Nothing

Question 4

All planets orbit the Sun in what kind of path?

Answer 4

Elliptical paths

Question 5

What is the Solar System?

Answer 5

The sun and all the objects that orbit it (planets, moons, asteroids and comets).

Question 6

What is Pluto?

Answer 6

Not a planet. Pluto is a dwarf planet.

Question 7

What are moons?

Answer 7

Natural satellites of planets. They orbit planets.

Question 8

What are asteroids?

Answer 8

Lumps of rock that range in diameter from 1 to 1000km.

Question 9

Where do most asteroids orbit the Sun?

Answer 9

In a belt between Mars and Jupiter

Question 10

What can sometimes happen to asteroids?

Answer 10

They can be thrown out of their orbit and pass near Earth.

Question 11

What are comets?

Answer 11

Extraterrestrial bodies made of ice and dust that travel around the Sun in eccentric orbits.

Question 12

What is an eccentric orbit?

Answer 12

One that is very elongated.

Question 13

Why are comets sometimes close to the Sun and visible from Earth, and sometimes very far away (beyond Pluto)?

Answer 13

Comets have eccentric (very elongated) orbits.

Question 14

What is the tail of a comet made from?

Answer 14

Small particles and ice.

Question 15

What is the heliocentric theory?

Answer 15

Where the Sun is at the centre of the Solar System.
It stated that the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn and all the stars moved around the Sun in circular paths.

Question 16

What was the geocentric theory?

Answer 16

Where the Earth was at the centre of the Universe.

Question 17

Why were only six planets originally known?

Answer 17

Uranus and Neptune cannot be seen without a telescope.

Question 18

What three major problems could the geocentric theory not explain?

Answer 18

1. The strange retrograde (looping) motion of Jupiter and Saturn
2. The phases of Mercury and Venus
3. The changes in brightness of Mars and Venus

Question 19

What are phases of planets?

Answer 19

Changing, crescent-shaped appearances.

Question 20

Who proposed the theory of epicycles to explain Jupiter’s retrograde motion?

Answer 20

A Greek astronomer named Ptolemy

Question 21

What did the theory of epicycles propose?

Answer 21

Jupiter moved in a circular path around a point as it orbited around the Earth.

Question 22

What was the purpose of the theory of epicycles?

Answer 22

To explain why Jupiter appeared to loop back on itself as it orbited the Earth.

Question 23

Who proposed the heliocentric theory and when?

Answer 23

Nicolas Copernicus in 1515.

Question 24

Why was the heliocentric theory not accepted?

Answer 24

It challenged the teaching of the Church that God put the Earth at the centre of the Universe.
The Church was very powerful at this time.

Question 25

What theory for the Solar System is universally accepted today?

Answer 25

The heliocentric theory.

Question 26

How did Newton explain why planets orbited the Sun?

Answer 26

Any two masses in the Universe attract each other.

Question 27

What does gravitational force increase with?

Answer 27

Masses of the objects

Question 28

What makes the gravitational force between two objects decrease?

Answer 28

Increasing distance between the objects

Question 29

Where does the gravitational force between two objects act?

Answer 29

Along a line connecting their centres of mass.

Question 30

What provides the centripetal force for orbital motion?

Answer 30

Gravity

Question 31

What is the Moon?

Answer 31

The natural satellite of Earth

Question 32

What are artificial satellites around the Earth used for? [3]

Answer 32

1. Communications 2. Weather forecasting 3. Monitoring agricultural land use

Question 33

Why do satellites not need energy to maintain motion?

Answer 33

They are well above the atmosphere so there is no frictional force opposing their motion.

Question 34

How do satellites get electrical energy?

Answer 34

Photocells convert light energy from the Sun to electrical energy.

Question 35

What are geostationary (geosynchronous) satellites?

Answer 35

Satellites placed about 36,000 km above the equator. | They take 24 hours to orbit the Earth.

Question 36

Why do geostationary satellites appear to remain over the same spot?

Answer 36

They orbit the Earth in 24 hours, but the Earth takes 24 hours to spin on its axis.

Question 37

How must geostationary satellites orbit?

Answer 37

1. In the equatorial plane | 2. In the same direction as the Earth spins on its axis.

Question 38

What are geostationary satellites used for?

Answer 38

1. Communications | 2. Global Positioning Systems

Question 39

What are low polar orbit satellites?

Answer 39

Satellites that sweep over both poles while the Earth rotates beneath them. Their full orbits last a few hours.

Question 40

How do low polar orbit satellites work?

Answer 40

Each time they come around, they scan a different part of the Earth. The whole surface can be monitored each day.

Question 41

What are low polar orbit satellites used for?

Answer 41

1. Weather forecasting | 2. Monitoring movements in the ice sheets at the poles.

Question 42

What can astronomical telescopes on satellites do which makes them very useful?

Answer 42

1. Take photos without the blurring caused by Earth's atmosphere 2. View planets, stars and galaxies in more detail 3. Take photos in the X-ray, ultraviolet, infrared and radio wave areas of the electromagnetic spectrum.