Chapter 1: A Modern View of the Universe Vocabulary

Vocabulary practice flashcards generated from Chapter 1 of The Essential Cosmic Perspective Ninth Edition.

Cosmic Address

The multi-tiered sequence specifying Earth's location in space: Earth, Solar System, Milky Way Galaxy, Local Group, Local Supercluster, Universe.

Star

A large, glowing ball of gas that generates heat and light through nuclear fusion.

Planet

A moderately large object that orbits a star and shines by reflected light; it may be rocky, icy, or gaseous in composition.

Moon (or Satellite)

An object that orbits a planet.

Asteroid

A relatively small and rocky object that orbits a star.

Comet

A relatively small and icy object that orbits a star.

Solar (Star) System

A star and all the material that orbits it, including its planets and moons.

Nebula

An interstellar cloud of gas and/or dust.

Galaxy

A great island of stars in space, all held together by gravity and orbiting a common center.

Universe

The sum total of all matter and energy; that is, everything within and between all galaxies.

Light-Year

The distance light can travel in $1\text{ year}$, which is about $10\text{ trillion kilometers}$ ($6\text{ trillion miles}$).

Speed of Light

The finite speed at which light travels through space, equal to approximately $300,000\text{ km/s}$.

Cosmic Calendar

A scale model on which the entire history of the universe is compressed into a single $1\text{-year}$ calendar.

Ecliptic Plane

The flat plane defined by Earth's orbital path around the Sun, relative to which Earth's rotational axis is tilted by $23\frac{1}{2}^\text{o}$.

Expansion of the Universe

The cosmological process in which space expands uniformly, causing all galaxies outside our Local Group to move away from us at speeds proportional to their distance.