Chapter 3

Stars and Galaxies

Section 1:Tools of Astronomy

Electromagnetic Spectrum Includes radio waves, infrared radiation,

visible light, ultraviolet radiation, x-rays, and gamma rays

Ranges from long wavelength to short wavelength

                                                                                       

         

                                          

    

Visible light : Complementary Colors

Blue and Green lights make the color _________

Visible Light Telescopes Refracting

telescope Uses convex

lenses to focus on a small area

Reflecting telescope Built by Issac

Newton Uses a mirror

instead of lenses

Radio Telescopes Used to detect

radio waves

Let’s review !!

Spectrographs Breaks light from

an object into colors and photographs of resulting spectrum

Get information about chemical composition and temperatures of stars

Types of visible Spectrum Continuous - Formed

by white light Includes all colors of

spectrum (ROY G BIV) Dark-line – white

light passes through a cool gas

Bright-line (emission) – due to a gas that has been heated.

Classifying Stars Stars – sphere of glowing gas due to

fusion Classify stars by:

size, temperature Brightness (magnitude)

Sizes of Stars Supergiant –

Largest – 1000x as big as the sun

Giant Medium sized –

most stars White dwarf Neutron stars -

smallest

Color and Temp of Stars Hottest – Blue

(35,000 C) White Yellow Red-orange Coldest – Red

(3000 C)

The H-R diagram Shows the

relationship between surface temperature of a star and brightness

Lives of Stars Nebula – large

amount of gas an dust over a large area

Birthplace of stars

Lifetime of Stars How long a stars

lives depends on its size.

Stars that have more mass than the sun have shorter lives.

Stars that have less mass live longer.

Death of Stars Once fuel is gone:

White dwarf star (when small or medium stars die)

A neutron star (form when giant stars die)

Black hole – form when massive stars die)

Black hole

Constellations Not really a group

of stars – just looks that way

88 constellations

Circumpolar constellations Seen all night long

in the northern hemisphere

Orion

Ursa Major

Ursa Minor (little bear)

Cassiopeia

Cepheus

Draco

Galaxies A giant structure in

the universe that contains millions of stars

Milky Way the galaxy our sun is in

Three types of galaxies: Spiral galaxies Center of Milky

way is about 25,000 light years away.

Elliptical Galaxies “flattened balls” Contains old stars Not a lot of gas

and dust

Irregular Galaxies No real shape