Listen&Learn: The Oort Cloud

Learn about the edge of the solar system

Pre-listening vocabulary

• astronomical unit: the average distance between the Earth and the Sun
• disk: a flat, circular object
• comet: a piece of ice that releases a “tail” of gas as it moves through space
• orbit: to travel around a planet or star
• trapped: stuck, unable to escape
• dwarf planet: a round object in space that is too small to be considered a planet

Listening activity

Podcast: Play in new window | Download (Duration: 1:29 — 1.4MB)

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Gapfill exercise

The Oort Cloud is a cloud of small icy objects at the very edge of the solar system. It is of astronomical units away from the Sun. It is made up of an inner disk, called the Hills Cloud, and an outer sphere, which surrounds the entire solar system. Scientists believe that the Oort Cloud formed in the days of the solar system, when the strong of the gas planets pushed other matter far away. The outer Oort Cloud contains the objects that are trapped in the Sun’s gravity. Most of these objects are comets, which can take millions of years to orbit the Sun. However, the Hills Cloud also contains dwarf planets similar to Pluto. One of these dwarf planets, called Sedna, may be the farthest planet-like object in the Sun’s orbit.

Comprehension questions

See answers below

1. The inner disk of the Oort Cloud is also called
   a. the Hills Cloud
   b. the Kuiper Cloud
   c. the Neptunian Ring
   
2. Most of the objects in the Oort Cloud are
   a. asteroids
   b. comets
   c. gas planets
   
3. Sedna is the name of
   a. the moon that orbits Pluto
   b. a far dwarf planet in the inner Oort Cloud
   c. a comet with an orbit of millions of years

Discussion/essay questions

1. Some people make wishes on comets and meteors in the sky. The planets in the solar system are named after ancient gods. Why do you think humans see magic in space?

Transcript

The Oort Cloud is a cloud of small icy objects at the very outer edge of the solar system. It is thousands of astronomical units away from the Sun. It is made up of an inner disk, called the Hills Cloud, and an outer sphere, which surrounds the entire solar system. Scientists believe that the Oort Cloud formed in the early days of the solar system, when the strong gravity of the gas planets pushed other matter far away. The outer Oort Cloud contains the farthest objects that are trapped in the Sun’s gravity. Most of these objects are comets, which can take millions of years to orbit the Sun. However, the Hills Cloud also contains dwarf planets similar to Pluto. One of these dwarf planets, called Sedna, may be the farthest planet-like object in the Sun’s orbit.

Answers to comprehension questions

1a 2b 3b