A Modern View of the Universe

Flashcards of key vocabulary terms from Chapter 1 Lecture: A Modern View of the Universe.

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.

Astronomical Unit (AU)

Average distance between the Earth and the Sun (150 million kilometers = 93 million miles).

Light-year (ly)

The distance that light can travel in 1 year, about 10 trillion kilometers (6 trillion miles).

Star

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

Planet

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

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.

Earth's Rotation

The rate at which Earth rotates around its axis.

Earth's Revolution

The orbit of Earth around the Sun.

Direction in Space

The direction specified by stating toward the center (or away from the center) of an object, e.g., the Earth, Sun, Galaxy

Sun

The name of our central star.

Milky Way Galaxy

The galaxy containing our solar system.

Big Bang

The expansion began, referred to as the Big Bang

Cosmic calendar

A scale on which we compress the history of the universe into 1 year.

Our cosmic address

Earth is part of the solar system

What is our place in the universe?

The solar system, which is the Milky Way Galaxy

Earth orbits around the sun

The average distance between the Earth and the Sun is 1 AU = 150 million kilometers.

Stars in the Local Neighborhood

Objects move randomly relative to one another and orbit the center of the Milky Way in about 230 million years.

Heavier elements

Stars undergo nuclear fusion.

How do galaxies move within the Universe?

All galaxies beyond the Local Group are moving away from us with expansion of the universe: the more distant they are, the faster they're moving.

Astronomy in human history

Through history, astronomy has provided an expanded perspective on Earth that has grown hand in hand with social and technological developments.