What Are the Planets in Our Solar System?

What Are the Planets in Our Solar System?

In Our Corner of Space

pp. 328-329

A solar system is made up of a star and the planets and other bodies that revolve around

it.

The sun is the star at the center of our solar system.

Distances in the solar system are measured using the astronomical unit, or AU. One AU is the distance between Earth and the sun—about 150 million km.​

Earth = 1 AU

(1 AU =150 million km.)

Neptune = 30 x 1 AU

(150 million km. x 30)

Neptune is 30 times as far from the sun as Earth.

PLANETS

Our Solar System

Our solar system has eight planets—Mercury,

Venus, Earth, Mars, Jupiter, Saturn, Uranus, and

Neptune.

A planet is a large round body that

revolves around a star in a clear orbit.

PLANET - a celestial body moving in an elliptical orbit around a star.

Definition from Oxford Languages

What makes a planet a planet?

• It must orbit a star (in our cosmic neighborhood, the Sun).

• It must be big enough to have enough gravity to force it into a spherical shape.

• It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.

Into what two groups are the planets of the solar system divided?

INNER AND OUTER PLANETS

Dwarf Planets

Our Solar System

Dwarf planets, such as Pluto, are

nearly round bodies whose orbits cross

those of other bodies.

Photo by: NASA

p.329

• Planets are large solar system bodies.

• Dwarf planets are smaller than planets and their orbits are not clear of other objects.

Comet / Asteroid / Meteoroid

Our Solar System

Why are comets sometimes visible with the unaided eye, even though they are smaller than many asteroid?

When comets get near the sun, they develop glowing tails that can sometimes be seen from Earth.

Which characteristics do astronomers use to classify these different bodies?

They use size, shape, composition of the object, its location in the solar system, and type of orbit it has.

PLANETS NEAR AND FAR

Inner & Outer Planets

The solar system's planets are divided into two groups.

HOW AND WHY ARE THE PLANETS IN EACH GROUP DIFFERENT?

Solve -------

• 142,984 - 4, 879 = ? km. ; 88,846 - 3,032 = ? miles

• Jupiter's diameter is 138,105 km. (85, 814 miles) bigger than Mercury's

MERCURY / VENUS / EARTH / MARS

INNER PLANETS

Open Ended

Survivor—Mars!

Suppose you have the chance to go to Mars. Think

about what Mars is like. Make a list of things you would

need to survive on Mars, and explain your choices.​

THE RIGHT SPOT

EARTH

The life zone is the region of space where the temperature range allows life to thrive.

Life Zone

• Scientists think it is because Earth is the only planet within the solar system’s life

  zone.

• Earth sits near the center of the life zone.

• Our solar system’s life zone

  begins just outside Venus’s orbit

  and ends before the orbit of Mars.

Our solar system’s life zone

begins just outside Venus’s orbit

and ends before the orbit of Mars.

Why Earth can support life?

Earth's Atmosphere

• Earth’s atmosphere traps solar energy to keep Earth’s temperature comfortable.

• It contains the gases that most living things

  need.

• It also protects living things from harmful solar radiation.

Earth's Oceans

• Earth’s oceans help

  maintain the temperature.

• The oceans store and distribute heat from the sun. Ocean currents carry heat away from the equator and toward

  the poles.

• 
  

Earth's Oceans

• Without the oceans to store and distribute heat from the sun,

  some places on Earth would be extremely cold or extremely hot.​

The temperature range of Earth

is ideal for many living things.​

Open Ended

Explain why life could not thrive on Mars and Venus.

Sum It Up Answers

• 1. moons

• 2. gas giants (Uranus & Neptune are particularly considered also as ice giants)

• 3. rings

• 4. temperatures

• 5. Outer Planets (Jovian Planets)

Sum It Up Answers

• 6. hard

• 7. moons

• 8. rings

• 9. diameters

• 10. Inner Planets (Terrestrial Planets)

Brain Check Answers

• Neptune - H.

• Mercury - C.

• Mars - E.

• Saturn - D.

• Earth - F.

Brain Check Answers

• Uranus - B.

• Jupiter - A.

• Venus - G.