4th Period PS Stars, Galaxies, & the Universe Test Review

Constellations

pattern of stars in the sky that have been given a name

Electromagnetic spectrum

the type of electromagnetic radiation (radio waves, infrared, visible light, UV rays, X-Rays, Gamma rays)

Electromagnetic radiation

energy that can travel through space in the form of waves.

Telescope

collects and focus different types of electromagnetic radiation; device that makes distant objects appear to be closer.

refracting telescope

uses 2 convex lenses to gather a large amount of light & focus it onto a small area

reflecting telescope

collects & focuses light using mirrors. The biggest visible light telescopes are mostly this type. Larger mirrors capture more light.

radio telescope

most have a curved surface 305 meters in diameter; the larger the telescope the more waves it can collect

Spectroscope

used to analyze properties of light, can be used to identify elements; ; breaks light from an object into colors & photographs the resulting spectrum.

Satellites

Earth's atmosphere blocks out most of the short wavelengths on the electromagnetic

spectrum such as UV, X-Ray, & Gamma Rays; This type of telescope detects these forms of radiation & give very detailed images

Observatory

a building that contains one or more telescopes; most are built on mountain tops

Spectrum

when white light is shined through a prism, the light spreads out to make a range of different colors

with different wavelengths

wavelength

the distance between the crests of 2 waves.

Spectrograph

breaks light from an object into colors & photographs the resulting spectrum. Scientists use these to get information about stars, including chemical composition & temperature.

Galaxy

structure in space that contains billions of stars

Universe

all of space & everything in space

Parallax

the apparent change in position of an object when you look at it from different places. Is used by astronomers to measure distances to nearby stars (nearby being < 1000 light years)

Characteristics used to classify stars

size, temperature, brightness, color, & composition

Hertzsprung-Russell diagram (H.R. diagram)

was developed to determine if there is a relationship between

a star's temp. & absolute brightness.

red giants, main sequence stars, white dwarfs

the 3 main groups on an H.R. diagram

Giant & Super Giants

very large stars, are 10 - 100 times larger than our sun

Medium Sized Star

our Sun, 60% of the stars in the universe are this size

White Dwarf

small stars about the size of Earth, are in the final stage in the life of low-mass stars like the sun

Neutron Star

are about 20km cubed, the remnant of an exploded star (supernova). Contains the mass of several suns. A thimble full of neutron star weighs 100 million tons

Red Stars

are the coolest stars

White & Blue Stars

are the hottest stars

apparent brightness

the brightness of an object as viewed from Earth

absolute brightness

the brightness a star would have if viewed from a standard distance from Earth.

directly proportional

a star's surface temperature and brightness are

Pulsar

(aka: pulsating radio sources)

Nebula

interstellar clouds composed of hydrogen, helium & cosmic dust. Stars are born here from the condensation of such clouds

Protostar

the earliest stage of a star's life, gravity pulls some of the gas & dust in a nebula together and the contracting gas & dust become so hot that nuclear fusion begins

The stars mass

determines the life span of a star

Red Giants & Super Giants

these stars occur when small to medium stars begin running out of hydrogen fuel.

Supernova

when a dying giant or super giant star suddenly explodes producing a bright light

Black hole

dense object formed from a massive collapsing star; Eventually the gravity is so strong that nothing escapes not even light.

Quasar

aka: quasi-stellar radio source; emit huge amounts of radio waves & light. They also may be the most luminous objects in the universe

Nova

variable stars that give off bursts of energy that make them appear many 1000's of times brighter for days or even years.

star systems

groups of 2 or more stars, more than half of all stars are star systems

binary stars

double stars; star system with 2 stars

eclipsing binary star

double star system where one star is darker than the other and may pass in front of the other blocking the light from the brighter star

triple stars

star systems with 3 stars

Variable star

stars that change in brightness or luminosity. Most stars are of this type.

Spiral Galaxy

consists of a bright core with rotating arms

Elliptical Galaxy

most plentiful galaxies. The core fades almost to the edges of the

galaxies.

Barred Spiral Galaxy

the spiraling arms emerge from a bar that extends beyond the Core.

Irregular Galaxy

least common galaxies. The stars do not rotate about a a central core.

spectrums

these help tell scientists how far away and how fast a galaxy is moving away from our galaxy

Moving away from the Milky Way

most galaxies are moving which way relative the Milky Way?

Big Bang Theory

theory of the origin of the universe

13.7 billion years old

Using data from how fast galaxies are moving away from us and cosmic background radiation, astronomers estimate the age of our Universe is believed to be ?

Local Group

a family of galaxies of which the Milky Way is a member. There are 28

known members.

Charles Messier

this scientist gave M- numbers for galaxies so that they could be better kept track of

Hubble's Law

the farther away a galaxy is, the faster it is moving away from Earth

Cosmic Background Radiation

faint thermal radiation left over from the Big Bang.

solar nebula

a large cloud of gas & dust that gravity slowly pulled together.

Planetesimals

small asteroid-like bodies; they form the building blocks of the planets

Dark Matter

the 90% of matter in galaxies that can't be seen; is matter that does not give off electromagnetic radiation

Dark Energy

the force thought to be the cause of why the universe expansion is accelerating.