Our Place in the Universe

A collection of vocabulary flashcards based on the concepts and terms covered in the lecture regarding astronomy and cosmology.

Planet

A moderately sized object that orbits a star; shines by reflecting a star's light.

IAU Definition of Planet

Definition stating the criteria for a celestial body to be considered a planet: it must orbit a star, have sufficient mass for hydrostatic equilibrium, and be gravitationally dominant in its orbit.

Star

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

Solar System

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

Nebula

An interstellar cloud of gas and/or dust, often referred to as 'stellar nurseries'.

Galaxy

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

Universe

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

Light-Year

The distance light travels in one year, approximately 9.46 x 10^12 km.

Scientific Notation

A method of expressing numbers as a product of a number between 1 and 10 and a power of ten.

Cosmic Calendar

A scale on which the history of the universe is compressed into one year.

Observable Universe

The portion of the universe that can be observed from Earth, limited by the finite speed of light.

Big Bang

The leading explanation for the origin of the universe, marking the moment of cosmic expansion.

Local Group

A collection of galaxies that includes the Milky Way and its nearest neighbors.

Milky Way Galaxy

The galaxy that contains our solar system, composed of billions of stars.

Local Supercluster

A larger group of galaxies that contains the Local Group, including the Milky Way.