Inner and Outer Planets

Front

Terrestrial Planets Noun

---

[tuh-res-tree-uhl plan-its]

Back

Terrestrial Planets

---

The four inner planets characterized by their solid, rocky surfaces, which are smaller and denser than the outer planets.

---

Example: This image shows the four terrestrial (or inner) planets of our solar system: Mercury, Venus, Earth, and Mars, which are the planets closest to the Sun.

Front

Gaseous Planets Noun

---

[gas-ee-uhs plan-its]

Back

Gaseous Planets

---

The four outer planets composed primarily of gases and lacking solid surfaces; they are also known as Jovian planets.

---

Example: This diagram shows the four gaseous planets with cutaway views of their interiors, revealing they are made mostly of gas and ice around a small core.

Front

Jovian Planets Noun

---

[joh-vee-uhn plan-its]

Back

Jovian Planets

---

A term for the large, gaseous outer planets, named after Jupiter, the largest planet in our solar system.

---

Example: The image groups the four outer gas giants—Jupiter, Saturn, Uranus, and Neptune—with a bracket, identifying them as the Jovian planets in our solar system.

Front

Atmosphere Noun

---

[at-muh-sfeer]

Back

Atmosphere

---

The layer of gases surrounding a planet or other celestial body, which is held in place by its gravity.

---

Example: This diagram shows Earth's atmosphere is a layer of gases divided into five distinct levels, each with unique characteristics like temperature and altitude.

Front

Natural Satellite Noun

---

[nach-er-uhl sat-uh-lite]

Back

Natural Satellite

---

An astronomical body, also known as a moon, that orbits a planet or another smaller body in space.

---

Example: The Moon is a natural satellite because it orbits a larger body, the Earth, held in its path by the force of gravity.

Front

Planetary Rings Noun

---

[plan-i-ter-ee rings]

Back

Planetary Rings

---

Thin discs composed of small particles of rock and ice that orbit a planet, such as those around gas giants.

---

Example: This image shows Neptune, an outer planet, and labels its faint planetary rings, including specific features like arcs, which are clumps of dust and ice.

Front

Great Red Spot Noun

---

[greyt red spot]

Back

Great Red Spot

---

A giant, persistent high-pressure storm system in Jupiter's atmosphere, characterized by high-speed winds like a terrestrial hurricane.

---

Example: This image shows the planet Jupiter, an outer planet, with an arrow pointing to the Great Red Spot, a massive, long-lasting storm in its atmosphere.

Front

Great Dark Spot Noun

---

[greyt dark spot]

Back

Great Dark Spot

---

A large storm system, similar in nature to Jupiter's Great Red Spot, that was once observed in Neptune's atmosphere.

---

Example: This image shows Neptune, an outer planet, with a large storm system called the Great Dark Spot, similar to Jupiter's Great Red Spot.

Front

Axis (Planetary) Noun

---

[ak-sis (plan-i-ter-ee)]

Back

Axis (Planetary)

---

An imaginary line passing through a planet's center around which it rotates, determining its orientation in space.

---

Example: This diagram shows Earth's planetary axis, the imaginary tilted line it spins around, which causes the cycle of day and night as it rotates.

Front

Period of Rotation Noun

---

[peer-ee-uhd uv roh-tey-shuhn]

Back

Period of Rotation

---

The amount of time a planet takes to complete one full spin on its axis, which determines its day length.

---

Example: This image shows the Earth spinning on its axis, a motion called rotation. The time it takes to complete one full spin, which causes day and night, is its period of rotation (24 hours).