Chapter 15: Universe

science 8th grade

eletromagnetic radiation

energy that can travel through space in the form of waves

visible light

all the colors you can see

wavelength

the distance between the crest of one wave and the crest of an other

septrum

range of different colors with different wavelength

optical telescope

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

refracting telescope

uses a convex lens to gather and focus light

convex lens

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

reflecting telescope

uses a mirror to collect and focus light

radio telescope

a device used to detect radio waves from objects in space

observatory

a building that contains one or more telescopes

constellations

imaginary patterns of stars

spectrograph

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

apparent brightness

brightness seen from Earth

absolute brightness

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

light-year

the distance that light travels in one year

parallex

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

hertzspung Russel diagram

a graph

nebula

a large cloud of gas and dust spreed out in a immense volume

protostar

a contracting cloud of gas and dust with enough mass to form a star

planetary nebula

glowing cloud of gas

white dwarf

when the core of a star cools

neutron stars

remains of high mass stars

pulsars

spinning neutron stars

black whole

an object with gravity so strong light can’t escape

binary stars

star system that have 2 stars

eclipsing binary

1 star periodically blocks the light from another

open cluster

loose appearance no more than 1,000 stars, super giants, gas, dust

globular cluster

older stars more than million

galaxy

group of single stars, star system, star clusters, dust, gas held by gravity

quasars

active young galaxies with black holes in the middle

spiral galaxies

bugle in the middle and arms that spiral out

elliptical galaxy

shape is round has billions of stars, little gas, and dust, star no longer able to form

irregular galaxies

smaller than others, bright young stars, lots of gas and dust next to large galaxies

universe

space and everything in it

big bang

the universe exploded

Hubble’s law

farther away galaxy is the faster it is moving away from us

cosmic background ration

left over thermal energy from the big bang

solar nebula

a large cloud of gas and dust that formed our solar system

planetesimals

outer part of the disk gas and dust formed small asteroid- like and comet-like bodies

dark matter

matter that does not give off electromagnetic radiation

dark energy

a mysterious new force