Origin Of the Universe
The scientific explanation that the universe began as an extremely hot, dense state and has been expanding over time.
Big Bang Theory
The distance light travels in one year; used to measure large distances in space.
Light-year
The distance between successive wave peaks.
Wavelength
The study of light to determine the composition, temperature, motion, and density of objects in space.
Spectroscopy
The longest stage of a star’s life, where it fuses hydrogen into helium.
Main Sequence
All of space, time, matter, and energy that exists.
Universe
A massive system of stars, gas, dust, and dark matter held together by gravity.
Galaxy
The number of waves that pass a point in a given amount of time.
Frequency
A spectrum with dark lines where specific wavelengths have been absorbed by cooler gas.
Absorption Spectrum
A powerful explosion marking the death of a high-mass star.
Supernova
Faint radiation left over from the early universe that provides strong evidence for the Big Bang.
Cosmic Microwave Background (CMB)
The average distance between Earth and the Sun, used to measure distances within the solar system.
Astronomical Unit (AU)
The full range of electromagnetic radiation, from radio waves to gamma rays.
Electromagnetic Spectrum
A spectrum with bright lines produced when excited atoms emit light at specific wavelengths.
Emission Spectrum
An object with gravity so strong that not even light can escape.
Black Hole
The stretching of light to longer wavelengths when an object in space is moving away from Earth.
Redshift
A group of galaxies held together by gravity.
Galaxy Cluster
The highest-energy form of electromagnetic radiation, produced by extreme cosmic events.
Gamma Ray
Unique lines in a spectrum that identify specific elements.
Spectral Lines
The small, dense remains of a low-mass star after it sheds its outer layers.
White Dwarf
The observation that more distant galaxies move away faster, showing that the universe is expanding.
Hubble’s Law
The curved path an object follows as it moves around another object due to gravity.
Orbit
The small portion of the electromagnetic spectrum that humans can see.
Visible Light
The unique pattern of spectral lines that identifies an element.
Elemental Fingerprint
An extremely dense stellar remnant made mostly of neutrons.
Neutron Star