Unit 1.1

Science solar systems lesson 1

What does the word "planet" mean in Greek?

"Planetes," which means "wanderers."

Why did ancient people call planets "wanderers"?

Unlike other stars, planets appear to move in a pattern that is different from the rest of the stars.

What is the order of the planets in our solar system (starting from the Sun)?

Mercury, Venus, Earth, Mars, Ceres (dwarf planet), Jupiter, Saturn, Uranus, Neptune.

How long is a day on Earth?

24 hours.

How long is a day on Mercury?

175 days and 23 hours.

How long is a day on Venus?

116 days and 18 hours.

How long is a day on Mars?

24 hours and 39 minutes.

How long is a day on Jupiter?

9 hours and 56 minutes.

How long is a day on Saturn?

10 hours and 47 minutes.

How long is a day on Uranus?

17 hours and 14 minutes.

How long is a day on Neptune?

16 hours and 6 minutes.

What is the "Time period (T)" of a planet?

The time taken for a planet to complete one orbit around the Sun.

What happens to a planet's time period (T) as its distance from the Sun increases?

It increases. (The farther the planet, the longer its year).

How long is one year on Mercury?

88 days.

How long is one year on Venus?

225 days.

How long is one year on Earth?

365 days.

How long is one year on Mars?

2 years.

How long is one year on Jupiter?

12 years.

How long is one year on Saturn?

29 years.

How long is one year on Uranus?

84 years.

How long is one year on Neptune?

165 years.

What is the Solar Nebula Theory?

The theory that the solar system formed from a cloud of space particles (nebula).

What are the 5 main steps of the Solar Nebula Theory?

1. A cloud of space particles existed as a nebula.

2. The clouds collapsed, forming a disk of dust and gas.

3. Gravity gathered dust/gas, the center got hot, and nuclear fusion started (birth of a star).

4. Leftover materials gathered due to gravity to form gas giants.

5. Remaining dust formed planets, moons, dwarf planets, asteroids, and comets.

According to the Solar Nebula Theory, what happened to the material left over after the Sun was born?

The material left by the Sun clumped together into bigger and bigger pieces.

Why did only rocky things survive close to the Sun?

Only rocky things could survive the heat close to the Sun, so gaseous and icy material collected further away.

What are comets and asteroids?

The leftover remains of the solar system's formation.

How long ago did the solar system form?

About 4.6 billion years ago.

What might have caused the initial cloud of gas and dust to collapse?

Possibly the shockwave of a nearby supernova explosion.

What percentage of the material did the Sun gobble up during its formation?

99.8%

What is the Asteroid Belt?

A region between Mars and Jupiter containing remnants of the solar system's formation.

What is the Kuiper Belt?

A region beyond Neptune containing icy objects and dwarf planets (like Pluto).

What is the Oort Cloud?

A distant, spherical shell of icy objects at the outermost edge of the solar system.

Why is every textbook picture of the solar system technically "wrong"?

You cannot show both the planet sizes and their relative distances in the correct scale on one page.

What is the distance from the Sun to Earth in AU?

1 AU (Astronomical Unit).

What is 1 AU in kilometers?

150 million km.

What is the distance from the Sun to Mercury?

57 million km (0.387 AU).

What is the distance from the Sun to Venus?

108 million km (0.722 AU).

What is the distance from the Sun to Mars?

228 million km (1.52 AU).

What is the distance from the Sun to Jupiter?

779 million km (5.2 AU).

What is the distance from the Sun to Saturn?

1.43 billion km (9.58 AU).

What is the distance from the Sun to Uranus?

2.88 billion km (19.2 AU).

What is the distance from the Sun to Neptune?

4.5 billion km (30.1 AU).

What is the distance from the Sun to Pluto?

5.91 billion km (39.5 AU).

What are the names of the two spacecraft launched in 1977 to study the outer solar system?

Voyager 1 and Voyager 2.

When was Voyager 1 launched?

September 5, 1977.

When was Voyager 2 launched?

August 20, 1977.

What rare alignment allowed the Voyagers to visit all four giant outer planets?

A once-in-a-lifetime alignment that occurs once every 176 years.

How did the Voyagers travel from one planet to the next?

By using the gravity of each planet to swing the spacecraft on to the next (gravity assist).

Which planets did Voyager 2 visit?

Jupiter, Saturn, Uranus, and Neptune.

Which planets did Voyager 1 visit?

Jupiter and Saturn.

What is the Golden Record?

A message from humanity to the cosmos carried by Voyager 1, including greetings in 55 languages, pictures, and music.

What is the Heliosphere?

The bubble-like region of space dominated by the Sun's solar wind.

What is the Heliopause?

The boundary where the Sun's solar wind ends and interstellar space begins.

What is the Termination Shock?

The point where the solar wind slows down to subsonic speeds.

What is the Heliosheath?

The region between the termination shock and the heliopause.

Where are the Voyager spacecraft today?

In interstellar space, beyond the heliopause.

How far away is Voyager 1 from Earth (approx. as of the notes)?

~14.9 billion miles.

How far away is Voyager 2 from Earth (approx. as of the notes)?

~12.4 billion miles.

What does the Hubble Space Telescope image show along the Voyager paths?

Sightlines along the paths of Voyager 1 & 2, showing the termination shock, heliopause, and local interstellar cloud.

What is the difference between mass and weight?

Mass is the amount of matter in an object (same everywhere). Weight is the force of gravity on that mass (changes depending on the planet).

If your mass is 50 kg on Earth, what is your mass on Mars?

50 kg (Mass is the same everywhere).

If you weigh 110 lbs on Earth, what would you weigh on Mars?

42 lbs (Weight changes due to gravity).

Why is your weight different on other planets?

Because the force of gravity is different on other planets.