Overview of Planets (Audrey Alestra)

Overview of Planets

By: Audrey Alestra

INDEX

Types of Planets

Inner Planets

What is a Planet?

Outer Planets

Dwarf Planets

What is a Planet?

A planet is defined as a celestial body which meets the requirements of... 1. Orbiting around a star (in our case the Sun) 2. Has a roundish shape (spherical shape, or the proper term is a hydrostatic equilibrium shape) due to its gravity 3. has cleared its orbit of surrounding debris. Types of Planets: classified into categories such as terrestrial and gas giants based on their physical characteristics and what they are made of. (NASA, What is a Planet?)

Types of Planets

Terrestrial

Gas Giants

• Do not have hard surfaces because they are made mostly of gas
• "Mostly composed of helium and/or hydrogen" and has a solid core (NASA)
• Planets of the Solar System: Jupiter, Saturn, Uranus, and Neptune

(NASA, What is a Gas Giant?)

• Made of "rock, silicate, water and/or carbon"
• "Also has a composition that is " mostly rock or iron, and a solid or liquid surface" (NASA)
• Planets in the Solar System: Mercury, Venus, Earth, and Mars

(NASA, Terrestrial)

Check Your Understanding #1

Inner Planets

• Mercury

- "Innermost planet"- Hot surface - May have ice on its poles

• Venus

-Has cloudy atmosphere due to dense and hot carbon dioxide (CO2) atmosphere

• Earth

- Only liveable planet in the Solar System - Has a "oxygen-rich atmosphere" - Has 1 moon

• Mars

- Atmosphere has CO2 - Has polar caps made of CO2 and water; evidence shows there may have been larger bodies of water long ago (Doody, Chapter 1: The Solar System)

Outer Planets

• Jupiter

- Largest planet in our Solar System- Has "stong magnetic feild"

• Saturn

- Has several rings

• Uranus

- "rotates on its side" - Made of rock and ice - Has "extensive atmosphere" made of hydrogen and helium - Cold planet

• Neptune

- Made of rock and ice - Has "extensive atmosphere" made of hydrogen and helium - Cold planet (Doody, Chapter 1: The Solar System)

check Your UnderstandinG #2

Dwarf Planets

• NASA states that a dwarf planet must have 3 things. To be a dwarf planet they need to...

" 1) Orbit its host star (In our solar system that’s the Sun) 2) Be mostly round. 3) Be big enough that its gravity cleared away any other objects of similar size near its orbit around the Sun"

• Pluto

- Was "considered" to be the 9th planet in our Solar System, but is now labeled as a dwarf planet

References

Doody, D. (2022, March). Basics of Spaceflight: Chapter 1: The Solar System. NASA Science. https://science.nasa.gov/learn/basics-of-space-flight/chapter1-2/ National Aeronautics and Space Administration. (n.d.). Dwarf Planets. NASA Science. Retrieved September 21, 2025, from https://science.nasa.gov/dwarf-planets/ National Aeronautics and Space Administration. (n.d.). Terrestrial. NASA Science. Retrieved September 21, 2025, from https://science.nasa.gov/exoplanets/terrestrial/ National Aeronautics and Space Administration. (n.d.). What is a Gas Giant?. NASA Science. Retrieved September 21, 2025, from https://science.nasa.gov/exoplanets/gas-giant/ National Aeronautics and Space Administration. (2025). What is a Planet?. NASA Science. https://science.nasa.gov/solar-system/planets/what-is-a-planet/

THANKS!