Sjha 6 Sci Chap 2.3

Front 1

star

Back 1

a large sphere of hydrogen gas hot enough for nuclear reactions t occur in its core

Front 2

shine

Back 2

As a star's core heats and the hydrogen gas becomes hot, nuclear reactions begin and energy begins to travel. This is why stars

Front 3

light

Back 3

when measuring distances to stars, astronomers often use a unit based on the speed of ____ rather than astronomical units

Front 4

light year

Back 4

the distance light travels in one year

Front 5

trillion

Back 5

one light year equals 9.46 ____ km

Front 6

FALSE

Back 6

Because it takes time for light to travel, starts are seen as they are right now in the present

Front 7

4.2

Back 7

If Proxima Centauri is the star nearest to the Sun and it is 4.2 light years away, then the light from Proxima Centauri we see today left the star ___ years ago

Front 8

FALSE - some are red, orange and even blue

Back 8

All stars are white

Front 9

Blue

Back 9

The hottest stars are ____

Front 10

Red

Back 10

The coolest stars are ____

Front 11

FALSE

Back 11

True or False - All stars are the same size

Front 12

90%

Back 12

The sun is a yellow star and is larger and more massive than ___ of other stars

Front 13

solitary

Back 13

What type of star is our sun - solitary, binary or multiple star system

Front 14

variable

Back 14

stars that change brightness over time are called ___ stars

Front 15

sun

Back 15

the ___ is the closest star to the earth

Front 16

5 billion

Back 16

scientists estimate that our sun has a lifetime of 10 billion years, meaning it has ___ years left

Front 17

white dwarf star

Back 17

when the sun stop shining it will become a ______

Front 18

randomly scattered

Back 18

stars are [randomly scattered or in fixed location] throughout the universe

Front 19

galaxy

Back 19

a huge collection of stars, gas and dust

Front 20

shape

Back 20

galaxies are classified by their

Front 21

elliptical, irregular and spiral

Back 21

the three types of galaxies are __, ___ and ___

Front 22

billions

Back 22

each galaxy contains hundreds of [millions or billions] of stars

Front 23

spiral

Back 23

Our solar system is part of the Milky Way which is a ____ galaxy

Front 24

elliptical

Back 24

these galaxies are shaped like basketballs or footballs and contain older, redder stars and have little gas or dust; very few young stars

Front 25

irregular

Back 25

oddly shaped galaxies contain large amounts of gas and dust. They have the highest rate of star formation and therefore have many young stars but do not have bright centers

Front 26

spiral

Back 26

these galaxies are shaped like disks and contain dust, gas and young stars in their bluish arms. Older redder stars are in their central bulges; these have older stars

Front 27

gravity

Back 27

this causes galaxies to gather in clusters where they interact and sometimes merge with one another

Front 28

Local Group

Back 28

Milky Way is part of a cluster called the ____ which contains about 30 galaxies

Front 29

super clusters

Back 29

the largest structures in the universe

Front 30

dark

Back 30

astronomers hypothesize that 90 to 95% of the mass in the galaxies is ____ matter or energy

Front 31

13 - 14 billion

Back 31

Most scientist agree that the universe was formed ___ years ago.

Front 32

The Big Bang Theory

Back 32

this theory states that the universe began from one point and has been expanding and cooling ever since.

Front 33

FALSE

Back 33

True or False - Scientists have determined the fate of the universe

Front 34

FALSE

Back 34

True or False - The sun is the largest star in our galaxy