THE UNIVERSE

CHAPTER 20

THE UNIVERSE

• UNIVERSE – everything physical in __________ and ____________

– Includes all space, matter, and energy that has existed, now exists, and will exist in the future.

– How did our universe form, how did evolve to what it is today, and what will it be doing in the future???

BIG BANG THEORY

• The most widely accepted theory of the universe today is the BIG BANG THEORY!

BIG BANG THEORY: • Occurred _________ billion years ago • All energy and matter was compressed into a

single point that was infinitely dense and small • That point began to

________________extremely rapidly in a “big bang”

BIG BANG THEORY

• IMMEDIATELY AFTER THE “BIG BANG” – The universe existed of pure energy

– The universe was extremely _________ and ____________________quickly

– The universe began to ____________ allowing sub-atomic particles to form

– _________________ pulled atoms together into gas clouds that eventually formed stars, which eventually formed galaxies

– The universe is still __________________ today

EVIDENCE FOR BIG BANG THEORY • ________________________

• Edwin Hubble – 1929 – Stated the universe is

expanding

– Studied spectra “color” from galaxies

– He saw galaxies appeared to be red

– _______________= galaxies moving away from Earth

EVIDENCE FOR BIG BANG THEORY • ________________ BACKGROUND RADIATION

– Field of microwave radiation that comes from everywhere in the sky

– Discovered in 1965

– Scientists believe the microwave radiation found to be everywhere in the sky are dim remnants of radiation produced during the big bang.

QUIZ • How old is the universe believed to be? • Immediately after the big bang, did the universe expand

or contract? (is it still doing this today?)

• What force pulled atoms together as well as gas and dust to form stars and galaxies?

• What are the two pieces of evidence for the big bang theory?

• What does Hubble mean by a “red shift”?

STARS

• Star – huge spheres of very hot plasma that give off ________________and other types of radiation – The sun is our largest star – much closer to earth than

any other star

• Light-year – used to describe distances in space – One light-year is the distance light travels in one

___________ – One light-year = 9.5 trillion km/year

STAR FORMATION • Most stars begin as ______________, with

clouds of gas and dust mainly containing hydrogen and helium

• Hydrogen and helium are pulled together by ___________________

• The gravitational pull creates very high pressure and very high temperatures causing nuclear ______________ to begin which converts matter into energy – Stars give off this energy as heat, light, and other

forms of electromagnetic radiation

STAR CLASSIFICATION - BRIGHTNESS

• Stars are classified by their:

– Color

– Size

– Brightness

– Mass

STAR CLASSIFICATION – COLOR AND TEMPERATURE

• COLOR OF A STAR DETERMINES THE _____________________________ OF A STAR!!! – This is because the temperature of a star determines

the colors of light it gives off

– The hotter the star, the ____________ it appears

– The cooler the star, the ____________ it appears • Our sun is a moderately cool star, it gives off mostly yellow

light

– Temperature also affects __________________ • Hotter stars give off more intense light than cooler stars

STAR CLASSIFICATION - BRIGHTNESS

• BRIGHTNESS – _______________________

• Stars that are far away appear dimmer than closer stars that are the same size and temp.

– _______________________ • Cooler stars appear dimmer than hotter stars that are

the same size and distance from Earth

– _________________ • Small stars appear dimmer than larger stars that are the

same temp. and distance from Earth

HERTZSPRUNG – RUSSELL DIAGRAM

• _____________________ – Shows how the temperature and brightness of a star

are related – Graphs ____________________ vs. absolute

magnitude – Use to learn how stars change as they ___________

– As stars age and pass through different stages in their

life cycles, their positions on the diagram change – Most stars appear on a diagonal line in the diagram

called the __________________________

QUIZ • What is a light-year?

• Stars consist of what two elements that allow nuclear

fusion to occur?

• The color of a star tells you what about the star?

• What 3 factors affect the brightness of a star?

• What does an H-R diagram show you about a star?

• On what part of an H-R diagram is the sun found?

GALAXIES

• Galaxy – group of _________________ of individual stars, star, systems, star clusters, dust and gas bound together by gravity – More than ____________ billion galaxies in the

universe – The closest galaxy to Earth is millions of light years

away – Galaxies are moving _______________ from Earth

(Red Shift) • Galaxies that are farther away have a greater red shift

GALAXIES

• Galaxies are classified based on:

– Size

– Shape

• 3 main types:

– Spiral

– Elliptical

– irregular

______________ – have spiral arms of gas, dust, and stars

______________ – contain little gas or dust and have round or oval shapes

________________ – do not have any particular shape

OUR GALAXY! THE MILKY WAY

• ________________ galaxy

• More than 100 billion stars

• Diameter more than 100,000 light years

• At the center is a bulge of stars, and then spiral arms of gas, dust, and young stars

QUIZ

• How many galaxies are believed to be in our universe?

• Do galaxies experience a “red shift” or a “blue shift”?

• How are galaxies classified?

• What are the 3 types of galaxies?

• What type of galaxy is the our galaxy? What is its name?