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visible light

light you can see

elecromagnetic radiation

energy that can travel through space in the from of waves


distance between the crest of one wave and the crest of the next wave


range of different colors with different wavelengths that you can see if you shine white light through a prism

electromagnetic spectrum

radio waves, infrared radiation, visible light, ultraviolet radiation, x-rays, gamma rays


instrument that collects and focuses light and other forms of electromagnetic radiation

optical telescope

telescope that uses lenses or mirrors to collect and focus visible light

refracting telescope

uses convex lenses to gather and focus light

convex lens

piece of transparent glass, curved so that the middle is thicker than the edges

reflecting telescope

uses a curved mirror to collect and focus light

radio telescope

used to detect radio waves from objects in space


building that contains one or more telescopes


imaginary patterns of stars

star characteristics

color, temperature, size, compostition, brightness


device that breaks light into colors and produces and image of the resulting spectrum

size and temperature

what the brightness of a star depends on

apparent brightness

a star's brightness as seen from earth

absolute brightness

brightness the star would have if it were at a standard distance from Earth

light year

the way scientists use to measure distances between stars


apparent change in position of an object when you look at it from different places

H-R diagram

diagram used to classify stars and to understand how stars change over time

main sequence

diagonal area in H-R diagram


earliest stage of a star's life


large cloud of gas and dust that spread out in an immense volume


depends on how long a star lives

white dwarf

blue-white core of the star that is left behind and cooled, from a low-medium mass star


explosion of a high mass star

neutron stars

remains of high-mass stars


spinning neutron stars

black hole

object with gravity so strong that nothing, not even light, can escape

binary stars

star systems that have two stars

eclipsing binary

a system where one star periodically blocks the light from another, dim star revolves around bright star

open clusters

cluster with loose, disorganized appearance, no more than a few thousand stars

globular clusters

large groupings of older stars, round, densely packed

spiral galaxies

galaxy that appears to have a bulge in the middle and arms that spiral outward


huge group of single stars, star sytems, star clusters, dust, and gas bound together by gravity

elliptical galaxies

look like circles, old stars, contain billions of stars, little gas and dust between stars

irregular galaxies

irregular shapes, new stars, smaller than other galaxies


active young galaxies with giant black holes at their centers

scientific notation

way that scientist use to write really long numbers

big bang theory

theory that the universe formed in an instant, billions of years ago, in an enormous explosion

hubble's law

states that the farther away a galaxy is, the faster it is moving away from us

cosmic background radiation

leftover thermal energy from the big bang

solar nebula

large cloud of gas and dust such as the one that formed our solar system


small, asteroid-like, comet-like bodies

dark matter

matter that does not give off electromagnetic radiation

dark energy

mysterious new force that is causing the expansion of the universe to accelerate

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