Alkina: That wasn’t so bad.
Epo: The debris field was easy to navigate.
Granddaughter: Are those the planets?
Alkina: Yes. This system has seven planets; three rocky, four gaseous.
Alkina: Rocky planets are smaller than gaseous ones. They are made up of rocks and metals and have solid surfaces.
Alkina: Gaseous planets are larger and more massive. They are made mostly of hydrogen and helium and don’t have solid surfaces.
Epo: Gaseous, or Jovian, planets also have rings.
Granddaughter: But we’re going to a rocky one?
Alkina: Yes, a terrestrial planet is your new home.
Granddaughter: Ooooh, look at those rings!
What does it mean?
Jovian – or Jupiter-like planets do not have solid surfaces as they are composed primarily of helium and hydrogen. They typically have radii larger than 10,000 km (6,213.7 miles) with a mass over 1 x 1025 kg. Gaseous planets also have rings and many moons.
Terrestrial – or rocky planets are made of rock and minerals, have solid surfaces, and typically have radii smaller than 10,000 km (6,213.7 miles) with a mass less than 1 x 1024 kg. They typically have only one or two moons, if any.