The Planets

What does the solar system include?

The Sun, Eight planets, Five dwarf planets, Hundreds of moons, Thousands of asteroids and comets

Where is our solar system located?

In the Milky Way galaxy, specifically in the Orion Arm.

What is the speed of our solar system's orbit around the galactic center?

About 515,000 mph (or 828,000 kph).

How long does it take to complete one orbit around the galactic center?

About 230 million years.

What is a planet?

An extremely large, round mass of rock and metal or gas that moves in a circular path around the sun or another star.

What is a star?

A very large ball of burning gas in space, seen as a point of light in the night sky.

What is a moon?

The round object that moves around the Earth and can be seen at night.

What is a dwarf planet?

A round mass of metal, rock, or gas that is not large enough to be considered a planet.

Name three dwarf planets in the solar system.

Ceres, Pluto, Eris

What are the terrestrial planets?

Mercury, Venus, Earth, Mars

What are the giant planets?

Jupiter, Saturn, Uranus, Neptune

What is the distance from the Sun for Earth?

1.00 AU

What is the revolution period of Jupiter?

11.86 years

What is the diameter of Mercury?

4,878 km

What is the mass of Saturn?

5,686 x 10 kg

What is the density of Neptune?

1.6 g/cm³

Which planet has the highest density?

Earth (5.5 g/cm³)

Which planets rotate counterclockwise?

All except Venus and Uranus

What defines the plane of the ecliptic?

The plane passing through the sun's equator

What are the daytime temperatures on Mercury?

Up to 800°F (430°C)

What are the nighttime temperatures on Mercury?

Down to -180°C

Why is Mercury not the hottest planet?

Venus is hotter due to its dense atmosphere.

What is the radius of Mercury?

1,516 miles (2,440 km)

What is the average distance of Mercury from the Sun?

36 million miles (58 million km) or 0.4 AU

How long does sunlight take to reach Mercury?

3.2 minutes

Where is possible water ice found on Mercury?

In the poles inside deep, permanently shadowed craters.

What is the orbital period of Mercury?

88 Earth days

How long does it take for Mercury to rotate once?

59 Earth days

What is the axis tilt of Mercury?

2°, meaning no seasons.

When was Mercury formed?

4.5 billion years ago

What is the strength of Mercury's magnetic field?

About 1% of Earth's strength.

Does Mercury have any moons or rings?

No moons. No rings.

What is the core radius of Mercury?

1,289 miles (2,074 km)

What does the surface of Mercury resemble?

The Moon, heavily cratered from impacts.

What are the names of the large basins on Mercury?

Caloris Basin: 960 miles (1,550 km) wide. Rachmaninoff Basin: 190 miles (306 km) wide

What is unique about Mercury's atmosphere?

It has a thin exosphere instead of a traditional atmosphere.

What are the main components of Mercury's exosphere?

Mainly oxygen, sodium, hydrogen, helium, and potassium.

What is the average temperature on Venus?

900°F (475°C)

Why is Venus the hottest planet?

Due to runaway greenhouse effect

Who is Venus named after?

Roman goddess Venus (Greek: Aphrodite)

What is the potential for life on Venus?

Surface too hot and toxic; upper atmosphere may support microbes

What is the distance from the Sun to Venus?

67 million miles (108M km) / 0.72 AU

What is the diameter of Venus?

7,521 miles (12,104 km)

How does Venus's day length compare to its year length?

Day: 243 Earth days; Year: 225 Earth days

What direction does the Sun rise on Venus?

Spins backward → Sun rises west, sets east

When did Venus form?

4.6 billion years ago

Does Venus have a magnetosphere?

No internal field; has induced magnetic field

How many moons does Venus have?

No moons, but has quasi satellite Zoozve

What is the surface pressure on Venus?

~92× Earth’s

What is the main component of Venus's atmosphere?

Thick CO₂ atmosphere with sulfuric acid clouds

What are notable surface features on Venus?

Ishtar Terra, Aphrodite Terra, Maxwell Montes

What is the geological state of Venus's surface?

Geologically young surface (~150M years) with volcanoes

What are the surface temperatures of Earth like?

Moderate and habitable due to a balanced atmosphere and liquid water.

What is unique about Earth's name?

Only planet not named after a Greek or Roman deity; 'Earth' means 'ground' in Old English/Germanic.

When did life begin on Earth?

Around 3.8 billion years ago in Earth's oceans.

What is the diameter of Earth?

7,926 miles (12,760 km).

What is the distance from the Sun to Earth?

93 million miles (150 million km) or 1 AU.

How long is a day on Earth?

23.9 hours.

What is the tilt of Earth's axis?

23.4°, causing seasons.

When was Earth formed?

4.5 billion years ago from gas and dust around the young Sun.

What generates Earth's magnetosphere?

Molten iron core and fast rotation.

How many moons does Earth have?

One Moon, the 5th largest in the solar system.

What is the average distance from Earth to its Moon?

238,855 miles (384,400 km).

What is the inner core of Earth made of?

Solid iron and nickel, ~759 miles (1,221 km) radius, ~5,400°C.

What percentage of Earth's atmosphere is nitrogen?

78% nitrogen.

What protects Earth from harmful radiation?

The atmosphere.

What covers 70% of Earth's surface?

Water (oceans).

What causes earthquakes on Earth?

Plate tectonics.

What are the surface temperatures on Mars?

Temperatures range from 70°F (20°C) to negative 153°C

Why is Mars known as the 'Red Planet'?

Due to iron oxide (rust) in its soil.

What is the size of Mars compared to Earth?

Mars has a radius of 2,106 miles (3,390 km), about ½ Earth's size.

What is the distance from the Sun to Mars?

142 million miles (228 million km) or 1.5 AU.

What is the average day length on Mars?

A day on Mars is 24.6 hours, known as a 'sol'.

What are Mars' moons called?

Mars has two moons: Phobos and Deimos.

What is the composition of Mars' core?

Mars' core is made of iron, nickel, and sulfur.

What evidence suggests water on Mars?

Evidence includes dried riverbeds, minerals, polar ice, and underground ice.

What is the atmosphere of Mars like?

Mars has a thin, CO₂ rich atmosphere with nitrogen and argon.

What are the surface features of Mars?

Features include Olympus Mons (largest volcano) and Valles Marineris (massive canyon).

What is the tilt of Mars' axis?

Mars has a tilt of 25°, leading to distinct seasons.

When was Mars formed?

Mars formed 4.5 billion years ago from gas and dust.

What is the radius of Jupiter?

43,441 miles (69,911 km)

What is the distance from the Sun to Jupiter?

484 million miles (778 million km) = 5.2 AU

What is the day length on Jupiter?

9.9 hours

How long is a year on Jupiter?

12 Earth years (4,333 days)

What is the tilt of Jupiter's axis?

~3°

What is the largest moon of Jupiter?

Ganymede

What is unique about Europa, one of Jupiter's moons?

It may host a subsurface ocean.

What is the Great Red Spot on Jupiter?

A giant storm twice Earth's size, raging for 300+ years.

What are the main components of Jupiter's atmosphere?

Ammonia ice, ammonium hydrosulfide, water ice and vapor.

What is the composition of Jupiter?

Mainly hydrogen and helium.

What type of planet is Jupiter?

Gas giant

What is the pressure condition deep inside Jupiter?

Pressure and temperature soar to extreme levels.

What is the magnetosphere of Jupiter like?

Largest and strongest in the solar system, extends up to 2 million miles toward the Sun.

How many moons does Jupiter have?

95 known moons

What are Jupiter's rings made of?

Dust from meteoroid impacts on small moons.

What is the temperature condition in Jupiter's upper atmosphere?

Extremely cold due to distance from the Sun.

What is the composition of Saturn?

Mostly hydrogen and helium; no solid surface.

What is the diameter of Saturn?

74,897 miles (120,500 km) about 9× wider than Earth.

What is the distance of Saturn from the Sun?

886 million miles (1.4 billion km) = 9.5 AU.

How long is a day on Saturn?

10.7 hours second shortest in the solar system.