Chapter 2 Vocabulary: Stars, Galaxies, & the Universe

Galaxy

a huge collection of stars

Spiral Galaxy

a galaxy shaped like a pinwheel; a large flat disc with arms radiating out

Elliptical Galaxy

a galaxy shaped like a sphere, egg, or football

Irregular Galaxy

a galaxy with no definite shape

Dark Matter

matter that emits no light at any wavelength

Light-year

the distance light travels in one year; 10 trillion km

Constellation

a pattern or group of stars that astronomers use to divide the night sky into 88 regions

Parallax

the apparent change in position of an object by looking at it from two different locations

Spectroscope

a tool that spreads light into different wavelengths

Doppler Shift

the shift to a different wavelength on the electromagnetic spectrum

Astronomical Unit

a unit of measurement equal to the average distance from the center of the

Earth to the center of the Sun; 149.6 million kilometers

Astronomy

the study of space and celestial objects, including stars, planets, moons, and galaxies

Telescope

a tool used to make distant objects appear more visible using a variety of lenses and mirrors

Universe

all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy

Planet

objects in space  orbiting a star, and that are massive enough to be rounded by its own gravity, and has cleared its own orbital path

Star

a large ball of gas held together by gravity with a core so hot that nuclear fusion occurs

Gravity

an attractive force that exists between all objects that have mass