4A2 The Solar System

Question 1

Define:

Solar system

Answer 1

A collection of the Sun, planets, moons, asteroids, comets, and other celestial bodies bound by gravity.

The Sun is the central star, with planets and smaller objects orbiting around it in elliptical paths.

Question 2

How long ago did the solar system form?

Answer 2

About 4.6 billion years ago.

This age is determined through radiometric dating of meteorites and lunar samples.

Question 3

How many planets are in the solar system?

Answer 3

Eight

The planets, in order from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Question 4

What is the solar nebula theory?

Answer 4

Theory that the solar system formed from a rotating gas and dust cloud.

This cloud, called the solar nebula, collapsed under gravity, leading to the formation of the Sun and the planets.

Question 5

True or False:

The planets formed before the Sun.

Answer 5

False

The Sun formed first as the central mass of the nebula, and planets formed later from the remaining material in the disk.

Question 6

What is a flat, rotating disk of gas and dust around a protostar?

Answer 6

Protoplanetary disk

This disk is where planets, moons, and other bodies form through accretion of material.

Question 7

Fill in the blank:

The Sun forms at the ______ of the protoplanetary disk.

Answer 7

center

The majority of the material in the collapsing nebula collects at the center, forming the Sun.

Question 8

What are planetesimals?

Answer 8

Small, solid objects formed from clumped dust and gas.

Planetesimals are the building blocks of planets, growing through collisions and accumulation of material.

Question 9

How do terrestrial planets form?

Answer 9

By the accumulation of rocky materials.

In the inner disk, metals and silicates condense due to higher temperatures, creating rocky planets.

Question 10

What causes gas giants to form in the outer solar system?

Answer 10

The accumulation of ices and gases around a solid core.

Lower temperatures in the outer disk allow volatile compounds to condense, leading to the formation of gas and ice giants.

Question 11

True or False:

Jupiter is thought to have formed first among the planets.

Answer 11

True

Its massive size and strong gravity likely allowed it to dominate and shape the outer solar system.

Question 12

What role does gravity play in the formation of the solar system?

Answer 12

It pulls material together to form stars, planets, and other bodies.

It is the fundamental force that drives the collapse of the nebula and the accretion of planetesimals.

Question 13

What are the two main types of planets in the solar system?

Answer 13

• Terrestrial
• Gas giants

Terrestrial planets are rocky and dense, while gas giants are large and composed mainly of hydrogen and helium.

Question 14

Fill in the blanks:

The asteroid belt lies between ______ and ________.

Answer 14

Mars ; Jupiter

It is thought to be made of leftover planetesimals that never formed into a planet due to Jupiter’s gravitational influence.

Question 15

What lies beyond Neptune and contains icy bodies and dwarf planets?

Answer 15

The Kuiper Belt

It is the source of many short-period comets and includes Pluto.

Question 16

What surrounds the solar system and is the source of long-period comets?

Answer 16

The Oort Cloud

It is the source of long-period comets and marks the outermost boundary of the Sun’s gravitational influence.

Question 17

Why are inner planets smaller than outer planets?

Answer 17

They formed in a region with less material and higher temperatures.

The inner disk lacked the ices and gases abundant in the cooler outer disk.

Question 18

Fill in the blank:

The process of smaller objects sticking together to form larger ones is called _________.

Answer 18

accretion

Accretion is the dominant mechanism by which planets and other bodies grow in size.

Question 19

What is the frost line in the solar system?

Answer 19

The boundary beyond which ices can condense.

Located between Mars and Jupiter, it divides the rocky inner planets from the gas and ice giants.

Question 20

True or False:

The Sun contains over 99% of the solar system’s mass.

Answer 20

True

The Sun’s massive size allows it to dominate the solar system gravitationally.

Question 21

What is the primary composition of the Sun?

Answer 21

Hydrogen and helium.

These light elements fuel nuclear fusion, producing the Sun’s energy.

Question 22

True or False:

Comets are made of rock and metal.

Answer 22

False

Comets are primarily composed of ice, dust, and organic compounds.

Question 23

How many layers does the Sun have?

Answer 23

Six

The Sun has six main layers: three internal layers (core, radiative zone, convective zone) and three atmospheric layers (photosphere, chromosphere, corona).

Question 24

What is the core of the Sun?

Answer 24

The innermost layer where nuclear fusion occurs.

The Sun’s core is where hydrogen atoms fuse into helium, releasing energy in the form of light and heat.

Question 25

# Define: Nuclear fusion

Answer 25

The **process** in which hydrogen nuclei combine to form helium through a series of reactions. ## Footnote This process *powers* the Sun and provides the energy it radiates into space.

Question 26

# True or False: The Sun’s surface is called the **photosphere**.

Answer 26

True ## Footnote The photosphere is the Sun’s *visible surface*, from which light is emitted.

Question 27

# Fill in the blank: The Sun's radiative zone is **located** between the core and \_\_\_\_\_\_ the convective zone.

Answer 27

below ## Footnote The *radiative zone* transfers energy outward through radiation.

Question 28

What **happens** in the Sun’s convective zone?

Answer 28

Energy is **transferred** outward. ## Footnote Hot plasma rises toward the surface, cools, and sinks again, creating convection currents.

Question 29

What is the **chromosphere**?

Answer 29

The layer **above** the photosphere that emits a reddish glow. ## Footnote The chromosphere is visible *during* a solar eclipse and plays a role in emitting ultraviolet radiation.

Question 30

What is the Sun’s **corona**?

Answer 30

The **outermost** layer of the Sun’s atmosphere. ## Footnote The corona extends millions of kilometers into space and is visible during a total solar eclipse.

Question 31

# True or False: The Sun’s corona is **cooler** than its photosphere.

Answer 31

False ## Footnote The corona is much hotter, with temperatures reaching *1-3 million* degrees Celsius, compared to 5,500°C at the photosphere.

Question 32

# Fill in the blank: Sunspots are generally **found** in regions of \_\_\_\_\_ magnetic activity.

Answer 32

high ## Footnote Strong magnetic fields inhibit convection, making sunspots cooler and darker than their surroundings.

Question 33

# True or False: The Sun’s corona can be **observed** without a solar eclipse.

Answer 33

False ## Footnote The corona is usually obscured by the Sun’s brightness, but it is visible during a solar eclipse.

Question 34

What is the **temperature** of the Sun’s core?

Answer 34

Approximately **15 million** degrees Celsius. ## Footnote This extreme heat is necessary for nuclear fusion to occur.

Question 35

What is the primary **element** fueling the Sun’s fusion process?

Answer 35

Hydrogen ## Footnote Hydrogen fuses to form helium, releasing energy that powers the Sun.

Question 36

What type of **radiation** is primarily emitted from the Sun’s surface?

Answer 36

Visible light ## Footnote The Sun emits a spectrum of radiation, but visible light is the most prominent form we observe on Earth.

Question 37

# Fill in the blanks: The Sun is made up of **approximately** \_\_\_\_\_ hydrogen and \_\_\_\_\_ helium.

Answer 37

75%; 24% ## Footnote Hydrogen and helium make up the **majority** of the Sun’s composition, with trace amounts of heavier elements.

Question 38

# True or False: The Sun’s luminosity remains **constant** over time.

Answer 38

False ## Footnote The Sun’s luminosity can change due to **variations** in solar activity and its life cycle.

Question 39

How are **sunspots** formed?

Answer 39

Through the Sun’s magnetic field **disrupting** convection. ## Footnote Sunspots are *cooler* areas caused by magnetic fields that suppress the flow of hot gas from the interior.

Question 40

What can sunspots tell scientists about the Sun’s activity?

Answer 40

They indicate areas of **intense magnetic activity**. ## Footnote Sunspot numbers correlate with solar cycles, affecting space weather and solar radiation.

Question 41

What is the **shape** of the planets' orbits?

Answer 41

Elliptical ## Footnote According to Kepler’s first law, planets move in **elliptical** orbits with the Sun at one of the foci.

Question 42

What is Kepler’s **second** law of planetary motion?

Answer 42

A planet **sweeps** out equal areas in equal times. ## Footnote This means that a planet moves faster when it is closer to the Sun and slower when farther away.

Question 43

# True or False: Mercury is the planet **closest** to the Sun.

Answer 43

True ## Footnote Mercury orbits closest to the Sun, completing its revolution in just **88** Earth days.

Question 44

# Fill in the blank: A planet moves **fastest** in its orbit at \_\_\_\_\_\_\_\_.

Answer 44

perihelion ## Footnote **Perihelion** is the point in a planet’s orbit where it is closest to the Sun and moves fastest.

Question 45

What is the **point** in a planet’s orbit where it is farthest from the Sun?

Answer 45

Aphelion ## Footnote **Aphelion** is the point in a planet’s orbit where it is farthest from the Sun and moves slowest.

Question 46

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

Answer 46

About 27.3 days. ## Footnote This is the *sidereal month*, the time it takes for the Moon to complete one full orbit around Earth relative to the stars.

Question 47

# True or False: The Moon’s orbit is **tilted** by about 5 degrees relative to Earth’s orbit.

Answer 47

True ## Footnote The Moon’s orbital tilt causes eclipses to occur only when the paths of the Sun, Earth, and Moon align.

Question 48

# Fill in the blank: The **distance** from Earth to the Sun is approximately \_\_\_\_\_ million miles.

Answer 48

93 ## Footnote This is also known as 1 Astronomical Unit (AU), a unit of measurement for distances within the solar system.

Question 49

Which planet has the **longest** orbital period?

Answer 49

Neptune ## Footnote **Neptune** takes about 165 Earth years to complete one orbit around the Sun.

Question 50

How does the Sun’s gravity **affect** the planets?

Answer 50

It **keeps** them in orbit. ## Footnote The Sun’s gravitational pull prevents the planets from flying off into space and maintains their orbital paths.

Question 51

What is the Moon's **cycle** from new moon to new moon called?

Answer 51

Synodic month. ## Footnote The *synodic month* lasts about 29.5 days and describes the Moon’s complete cycle of phases.

Question 52

# True or False: All planets in the solar system orbit in the **same** plane.

Answer 52

False ## Footnote While most planets’ orbits lie close to a region known as the *ecliptic plane*, they are not perfectly aligned due to slight inclinations

Question 53

What is the average orbital **speed** of Earth around the Sun?

Answer 53

About 29.78 km/s. ## Footnote Earth moves at this speed to **maintain** its orbit around the Sun, balancing gravitational pull with inertia.

Question 54

# Fill in the blank: The distance between Earth and the Sun is **referred** to as one \_\_\_\_\_\_\_\_.

Answer 54

Astronomical Unit | (AU) ## Footnote One AU is approximately 93 million miles, the average distance from Earth to the Sun.

Question 55

Which **planet** has the longest day?

Answer 55

Venus ## Footnote Venus takes about *243 Earth days* to complete one rotation on its axis, making its day longer than its year.

Question 56

# True or False The Sun's gravitational pull on the Moon is **stronger** than Earth's.

Answer 56

True ## Footnote The Sun’s gravity is much stronger because it is more **massive**, and it dominates the gravitational forces acting on the planets and moons.

Question 57

What is the **largest** planet in the solar system?

Answer 57

Jupiter ## Footnote **Jupiter** is the largest planet with a diameter of about 142,984 km, and it is primarily composed of hydrogen and helium.

Question 58

# True or False: The Moon is **classified** as a planet.

Answer 58

False ## Footnote The Moon is Earth's *natural satellite* and is not classified as a planet, as it orbits Earth and not the Sun.

Question 59

# Fill in the blank: A \_\_\_\_\_\_\_ is a small **icy** body that orbits the Sun, typically beyond Neptune.

Answer 59

comet ## Footnote **Comets** are made of ice, dust, and rocky material and often have a visible tail when they approach the Sun due to solar radiation.

Question 60

What is the main **difference** between asteroids and comets?

Answer 60

**Asteroids** are made of metal and rock, **comets** of ice, dust, and rock. ## Footnote Asteroids typically reside in the asteroid belt between Mars and Jupiter, whereas comets are found in the outer solar system.

Question 61

What is the name of the **largest** known asteroid?

Answer 61

Ceres ## Footnote **Ceres** is also classified as a dwarf planet and is the largest object in the asteroid belt between Mars and Jupiter.

Question 62

Which planet is known as the **red planet**?

Answer 62

Mars ## Footnote **Mars** is known as the red planet due to its reddish appearance, caused by iron oxide (rust) on its surface.

Question 63

# True or False: The gas giants in our solar system are all made **primarily** of rock and metal.

Answer 63

False ## Footnote The gas giants (Jupiter, Saturn, Uranus, and Neptune) are composed mostly of **hydrogen**, helium, and ice, rather than rock and metal.

Question 64

What is the **largest** moon in the solar system?

Answer 64

Ganymede ## Footnote **Ganymede** is a moon of Jupiter and is larger than the planet Mercury.

Question 65

# Fill in the blank: A/an \_\_\_\_\_\_ planet is a planet that orbits **outside** the asteroid belt.

Answer 65

outer ## Footnote The outer planets include Jupiter, Saturn, Uranus, and Neptune.

Question 66

What is the main **composition** of Saturn's rings?

Answer 66

Ice and rock particles. ## Footnote Saturn's **rings** are made of billions of small particles of ice and rock that vary in size from tiny grains to large chunks.

Question 67

Which planet has the **most** moons in the solar system?

Answer 67

Saturn ## Footnote **Saturn** has the most moons in the solar system with 146 confirmed moons as of late 2024; *Jupiter* follows with 95 moons.

Question 68

# Define: Dwarf planet

Answer 68

An **object** that orbits the Sun, is nearly spherical, but hasn't cleared its orbital path of debris. ## Footnote Examples of dwarf planets include Pluto, Eris, and Haumea.

Question 69

# True or False: Comets are usually **located** within the asteroid belt.

Answer 69

False ## Footnote Comets are typically located in the **outer** solar system, far beyond the asteroid belt, in regions like the Kuiper Belt and Oort Cloud.

Question 70

# Fill in the blank: The planet \_\_\_\_\_\_\_ is known for its **extreme** tilt, causing its seasons to be very different from other planets.

Answer 70

Uranus ## Footnote **Uranus** has an axial tilt of about 98 degrees, causing its poles to be in direct sunlight for many years at a time.

Question 71

What is another **term** for a moon that orbits a planet?

Answer 71

Satellite ## Footnote Moons are natural satellites that orbit planets, and some planets, like Jupiter, have many moons.