Unit 4

Question 1

What is a star?

Answer 1

A massive collection of gases held together by its own gravity that emits huge amounts of energy.

Stars are luminous because they give off their own light. Our star is the Sun, which is a medium-sized star.

Question 2

Define a planet.

Answer 2

A large, round celestial object that travels around a star and is non-luminous.

Planets reflect light from the Sun.

Question 3

What are moons?

Answer 3

Natural satellites that travel around planets or dwarf planets and are much smaller than planets.

Moons are also non-luminous.

Question 4

What is an orbit?

Answer 4

A closed path that a celestial object or satellite stays in as it travels around another celestial object.

Question 5

What is a galaxy?

Answer 5

A large collection of dust, gas, billions of stars, planets, and other celestial objects.

Earth is part of the Milky Way Galaxy.

Question 6

How long does it take for Earth to complete one rotation?

Answer 6

24 hours.

Question 7

What is the direction of Earth’s rotation when viewed from above the North Pole?

Answer 7

Counter-clockwise.

Question 8

What determines the length of days and nights on Earth?

Answer 8

The Earth’s revolution around the Sun.

Question 9

What is the tilt of the Earth’s axis?

Answer 9

23½º.

Question 10

What are the three factors that allow life on Earth to be possible?

Answer 10

• Earth’s position in space
• Earth’s magnetic field
• Earth’s atmosphere

Question 11

List the inner planets.

Answer 11

• Mercury
• Venus
• Earth
• Mars

Question 12

What is unique about Venus?

Answer 12

It is the hottest planet, covered in thick sulphuric acid clouds, and has incredibly high atmospheric pressure.

Question 13

What is significant about Earth?

Answer 13

It’s the only planet known to have liquid water and life.

Question 14

What are the two moons of Mars?

Answer 14

• Phobos
• Deimos

Question 15

What is the Asteroid Belt?

Answer 15

It lies between Mars and Jupiter and consists of small chunks of rock.

Question 16

List the outer planets.

Answer 16

• Jupiter
• Saturn
• Uranus
• Neptune
• Pluto (disputed)

Question 17

What is Jupiter known for?

Answer 17

Being the largest planet in the solar system and having a massive storm system known as the Great Red Spot.

Question 18

What is unique about Saturn?

Answer 18

It is famous for its rings, which are composed of bits of rock.

Question 19

How does Uranus rotate?

Answer 19

It spins on its side with its north pole sometimes pointing directly to the sun.

Question 20

What is the composition of comets?

Answer 20

Composed of rock and ice, often described as dirty snowballs.

Question 21

What is the Big Bang?

Answer 21

The scientific theory that the universe started from a singularity and has been expanding since.

Question 22

What is the Milky Way?

Answer 22

The galaxy that contains our solar system, approximately 90,000 light years across.

Question 23

What is the closest star to the Sun?

Answer 23

Alpha Centauri, approximately 4.33 light years away.

Question 24

What is the average size of the Sun?

Answer 24

About 1,391,980 km across.

Question 25

What are solar flares?

Answer 25

Eruptions that send streams of high-energy subatomic particles out into space.

Question 26

What is an eclipse?

Answer 26

An event where one celestial body moves into the shadow of another celestial body.

Question 27

What is a lunar eclipse?

Answer 27

When the moon moves into the Earth’s shadow.

Question 28

What is a solar eclipse?

Answer 28

When the Earth moves into the moon’s shadow.

Question 29

What is the Earth's only natural satellite?

Answer 29

The Moon.

Question 30

What is retrograde motion?

Answer 30

The apparent backward motion of planets in the sky.

Question 31

What is the purpose of the Earth's magnetosphere?

Answer 31

It protects Earth from solar wind and charged particles.

Question 32

True or False: The Sun is the largest object in the solar system.

Answer 32

True.

Question 33

Fill in the blank: The Moon's orbit around Earth takes about ______.

Answer 33

one month.

Question 34

What is the distance from the Sun to Earth in astronomical units?

Answer 34

1 AU (150,000,000 km) ## Footnote Astronomical Unit (AU) is a standard unit of measurement in astronomy.

Question 35

What are the four main layers of the Sun?

Answer 35

* Core * Radiative zone * Convective zone * Corona ## Footnote Each layer has distinct characteristics and functions.

Question 36

What is the temperature of the Sun's core?

Answer 36

15,000,000°C ## Footnote The core is where nuclear fusion occurs.

Question 37

What is a solar prominence?

Answer 37

Streams of glowing gas that arch into space and return to the Sun ## Footnote Solar prominences are often associated with solar flares.

Question 38

What is a solar flare?

Answer 38

Eruptions that send streams of high-energy subatomic particles out into space ## Footnote Solar flares can impact space weather and communications on Earth.

Question 39

What are sunspots?

Answer 39

Cooler areas (4000 °C) on the Sun’s surface that come and go every 11 years ## Footnote Sunspots are indicators of solar activity cycles.

Question 40

What is the composition of the Sun?

Answer 40

* 73% Hydrogen * 25% Helium * 2% Other gases ## Footnote This composition is crucial for the Sun's energy generation through nuclear fusion.

Question 41

What process generates energy in the Sun?

Answer 41

Nuclear fusion of hydrogen atoms to form helium ## Footnote This process releases a large amount of energy, which powers the Sun.

Question 42

How long has the Sun existed and how much longer will it last?

Answer 42

5 billion years old and will last for 5 billion more ## Footnote The Sun is currently in the middle of its life cycle.

Question 43

What is the distance from the Earth to the Moon?

Answer 43

384,400 km ## Footnote This distance varies slightly due to the Moon's elliptical orbit.

Question 44

How long does it take the Moon to orbit the Earth?

Answer 44

27.3 days ## Footnote This period is also how long it takes the Moon to rotate on its axis.

Question 45

What is the 'dark side of the Moon'?

Answer 45

The side of the Moon that always faces away from the Earth ## Footnote The Moon is tidally locked with Earth, showing only one face.

Question 46

What are the phases of the Moon?

Answer 46

There are 8 phases, including waxing crescent, full Moon, and waning crescent ## Footnote These phases result from the Moon's position relative to Earth and the Sun.

Question 47

What is a solar eclipse?

Answer 47

Occurs when the Moon is directly between the Sun and Earth, casting a shadow on Earth ## Footnote Solar eclipses can be total or partial depending on the observer's location.

Question 48

What is a lunar eclipse?

Answer 48

Occurs when Earth is directly between the Sun and the Moon, casting a shadow on the Moon ## Footnote Lunar eclipses can also be partial or total.

Question 49

What is the definition of rotation?

Answer 49

Spinning of a body around an internal axis (e.g., Earth = 24 hrs) ## Footnote This is different from revolution, which refers to orbiting another object.

Question 50

What is a comet?

Answer 50

An ice and dust ball with a tail near the Sun ## Footnote Comets are often visible from Earth when they come close to the Sun.

Question 51

What is a meteorite?

Answer 51

A meteor that hits Earth ## Footnote Meteorites can vary in size and composition.

Question 52

What defines a dwarf planet?

Answer 52

Orbits the Sun, is round, but does not 'clear its neighborhood' ## Footnote Pluto is a well-known example of a dwarf planet.