Stars 1. Patterns of stars – - PowerPoint Presentation

Slide1

StarsSlide2

1. Patterns of stars –

constellations

a. Ancient cultures used

mythology

or everyday items to name constellationsSlide3
Slide4
Slide5

2. Modern astronomy studies

88

constellations

3. Some constellations are not

visible

all year because Earth revolves around the Sun

4.

Circumpolar constellations

in the northern sky appear to circle around Polaris and are visible all yearSlide6

The central part of the Milky Way with summer constellations Scorpius and Sagittarius shine above Bryce Canyon National Park in southern Utah, USA.Slide7
Slide8

B. Star

magnitude

Absolute magnitude—

measure

of the amount of light a star actually gives off

2.

Apparent magnitude—

measure of the amount of a star’s light received on EarthSlide9
Slide10

Sirius appears to be a much brighter star than Rigel. However, the opposite is true. Sirius only appears brighter because it is one hundred times closer to Earth than Rigel. Slide11

C. Space

measurement

Astronomers measure a star’s

parallax

—shift in its position when viewed from two different angles

2. Distance is measured in

light-years

—the distance light travels in a yearSlide12

http://hypnagogic.net/sim/Sim/new-parallax/Parallax.htmlSlide13

D. Star

properties

Color indicates

temperature

Hot stars are

blue-white

b. Cool stars look

orange or red

c.

Yellow

stars like the Sun are medium temperatureSlide14

2. A spectroscope breaks the visible light from a star into a

spectrum

a. Spectrum indicates

elements

in the star’s atmosphereSlide15

The Sun’s Energy (WTD)

The energy of the Sun is derived from the fusion of H into He***

The Sun is about halfway through it’s life cycle with another 5 billion yrs left to go Slide16
Slide17

Sun’s

layers

—energy

created in the core

moves outward through

the radiation zone

and the convection zone

and into the Sun’s atmosphere

B. Sun’s

atmosphere

1.

Photosphere

—lowest layer gives off light and is about 6,000 KSlide18

2.

Chromosphere

is the next layer about 2,000 km above the photosphereSlide19

3. Extending millions of km into space, the 2 million K

corona

releases charged particles as solar windSlide20

C. Surface

features

Sunspots

—dark

areas cooler than

their surroundings

Temporary

features

which come and go

over days, weeks,

or months

b. Increase and decrease in a 10 to 11 year pattern called

solar activity cycle

2. Sunspots are related to

intense magnetic fields

Videos\Sun Set GOOD.flvSlide21

Solar Eclipse Corona Slide22

Magnetic fields may cause

prominences

—huge, arching gas columns

b. Violent eruptions near

a sunspot are called

solar flares

Slide23

3. Bright

coronal mass ejections

(CMEs) appear as a halo around the Sun when emitted in the Earth’s direction

http://www.tomwujec.com/?page_id=1105Slide24

a. Highly charged

solar wind particles

can disrupt radio signalsSlide25

b. Near Earth’s polar areas solar wind material can create light called an

auroraSlide26

D. Sun is mostly

average

Middle-aged

star

2. Typical

absolute magnitude

with yellow light

3. Unusual—Sun is

not part

of a multiple star system or cluster (most of stars are binary systems) WTDSlide27

Stellar EvolutionSlide28

How I Wonder What You Are ...

Stars have

D

i

f

f

e

r

e

n

t

c

o

l

o

r

s

Which indicate different temperatures

The hotter a star is, the faster it burns its life away.

Write all this down (WTD)

Slide29

A. Classifying stars—Ejnar Hertzsprung and Henry Russell graphed stars by temperature and absolute magnitude in a H-R

diagramSlide30

1.

Main Sequence

—diagonal band on H-R diagram

a. Upper left—hot,

blue

, bright stars

b. Lower right—

cool

, red, dim stars

c. Middle—average

yellow

stars like the Sun

2.

Dwarfs and giants

—the ten percent of stars that don’t fall in the main sequenceSlide31

http://hypnagogic.net/sim/Sim/hr3/HRdiagram.htmlSlide32

A

B

C

D

B.

Fusion

of hydrogen occurs in star cores releasing huge amounts of energy

http://hypnagogic.net/sim/Sim/fusion/Fusion.htmlSlide33

C.

Evolution

of stars

A

nebula

contracts and breaks apart from the instability caused by gravity

Temperatures

in each nebula chunk increase as particles move closer together

b. At 10 million K

fusion

begins and energy from a new star radiates into spaceSlide34

2. The new main sequence star

balances

pressure from fusion heat with gravity

Balance is lost when core hydrogen fuel is

used up

b. Core contracts and heats up causing outer layers to

expand

and cool

c. Star becomes a

giant

as it expands and outer layers cool

d. Helium nuclei fuse to form core of

carbonSlide35

3. A

white dwarf

forms from the giant star

a. Helium is exhausted and outer layers escape into space

b. Core contracts into hot, dense, small starSlide36

4. In massive stars fusion causes higher temperatures and greater expansion into a

supergiant

a. Eventually fusion stops as iron is formed

b. The core crashes inward causing the outer part to explode as an incredibly bright

supernovaSlide37

5. The collapsed core of a

supernova

may form a neutron star of extremely high densitySlide38

6.

The mass of a tremendously big supernova core can collapse to a point, forming a

black hole

Gravity

is so strong not even light can escape

b.

Beyond a black hole’s

event horizon

gravity operates as it would before the mass collapsedSlide39

7. Matter emitted by a star over its life time is recycled and can become part of a new

nebulaSlide40

Galaxies and the UniverseSlide41

Galaxy

—gravity holds together a large collection of stars, gas, and dust

Earth’s galaxy is

Milky Way which

is part of a galaxy

cluster named

the

Local GroupSlide42

2.

Spiral galaxies

—spiral arms wind out from inner section; some have barred spirals with stars and gas in a central barSlide43

3.

Elliptical galaxies

—large, three-dimensional ellipses; most common shapeSlide44

4.

Irregular galaxies

—smaller, less common galaxies with various different shapesSlide45

B. The Milky Way Galaxy—classified as a

spiral galaxy

1. May contain one

trillion

stars

2. About 100,000 light-years

wide

3. Sun orbits galaxy’s core every 225 million yearsSlide46

C. Theories on the

origin

of the universe

1.

Steady state theory

—universe has always existed just as it is now

2.

Oscillating model

—universe expands and contracts repeatedly over timeSlide47

D. Universe is

expanding

1.

Doppler shift

—light changes as it moves toward or away from an object

a. Starlight moving toward Earth shifts to

blue-violet

end of spectrum

b. Starlight moving away from Earth shifts to

red end

of spectrum

2. All galaxies outside the Local Group indicate a red shift in their spectra indicating they are moving

away

from EarthSlide48

E.

Big Bang Theory

—holds that universe began 13.7 billion years ago with huge explosion that caused expansion everywhere at the same timeSlide49

Galaxies more than 10

billion

light-years away give information about a young universe

2. Whether the universe may

eventually stop

expanding and begin

contracting

is unknown