Download Stars Chapter 21

Stars
Chapter 21
The Branches of Earth Science
• Astronomy: The
study of the
planets, stars,
and other objects
in space.
The Branches of Earth Science
• Lithosphere: the land masses
of earth
•
Litho means rock
The Branches of Earth Science
• Hydrosphere: waters of the
earth
– Hydro means water
The Branches of Earth Science
Atmosphere: The
envelope of
gases that
surround the
Earth as well as
space and stars.
Tools Used to Study Stars
• Spectroscope: Breaks
light from a distant star
into its characteristic
color
• SPECTRUM: the band of
colors that forms as light
passes through a prism
• Used to see if galaxies are moving
away or toward the earth
Tools Used to Study Stars
• Types of Telescopes
Telescopes: device
– Optical
that makes distant
– Radio
objects appear
– X-Ray
closer
– U-V
– Infrared
Constellations
Constellations:
group of stars
that formed
patterns
How do They Get Their Name?
• Different cultures
gave different
names to the
constellations
For Example: The
Greeks named
constellations
according to myths
•
The same
constellation can
have different
names in different
cultures
Greek  Orion
Sumerian  Sheep
China  Three
Why are Constellations
Important?
• Navigation
– Sailors use
Polaris (North
Star)
– Important in
space navigation
• Used to predict
the weather.
Best Known Constellations
• Big Bear or Ursa
Major
• Very similar to Big
Dipper
– Has pointer stars to
Polaris
• Little Bear or Ursa
Minor
• Very similar to Little
Dipper
What are Stars Like?
• Stars are
made up of
mostly
hydrogen
• Stars produce
energy
through
nuclear
fusion.
Characteristics of Stars
• There are 4
major
characteristics of
starts that
scientists use to
classify stars
• Color &
Temperature
• Size
• Composition
• Brightness
Color & Temperature
• Stars are very Patriotic
• A stars color
when it comes to color
reveals its surface
Coldest
Red
temperature
– The surface
White
temperature is
lower than the
core temperature
Hottest
Blue
due to nuclear
fusion.
5 Categories of Sizes
Smallest
Neutron (16-20 km diameter)
White dwarf (size of Earth)
Medium Size (the sun) *MOST
STARS*
Giant
Largest
(10-1000 x’s the sun)
Super Giant (1000 x the diameter of the
sun)
The Sizes of Super Giant Stars
Look at the size of the sun compared to the stars, it is almost invisible
Composition
(Chemical Makeup)
• Most stars have the same general
composition
– 73% Hydrogen
(Most Common)
– 25% Helium
(2nd most common)
– 2% Other Elements
Composition Continued
• Scientists use a spectroscope to
identify characteristics
–Characteristic: Something that
identifies an object
–Elements have “Fingerprint”
color characteristics
• They have a unique set of lines
in the spectrum
Brightness
(Also called Magnitude)
Depends on… •
• Temperature
• Size
•
• Distance
Apparent Brightness:
the brightness of a
star as it appears on
Earth.
Absolute Magnitude:
The amount of light
the star actually gives
off
Measuring Distance to Stars
• Light Year- Astronomers use light
years to measure the distances
between stars
–A light year is the distance that light
travels in one year
• 9,460,730,472,580.8 km
• 5,878,630,000,000 miles
Parallax
• Parallax- the apparent change in
the position of a star in the sky.
–The change is due to the change
in the Earth’ position as the
Earth revolves around
the sun.
Parallax
Hertzsprung-Russell Diagram:
(H-R Diagram)
• It is a scatter plot
• Shows the relationship between absolute
brightness and surface temperature
• This is the single most important diagram
that astronomers use
• Uses of H-R Diagram
– Classify Stars
– Understand how stars change over time
H-R Diagram
Brightest
Absolute
Magnitude
Dimmest
Hottest
Surface Temp
Coolest
H-R Diagram
H-R Diagram
• Main sequence: the area where the
most stars are located
• Extends from the upper left corner to
the lower right corner
• 90% of stars are located here
Life Cycle of a Star
• All stars start with a NEBULA
–Nebula is a large cloud of gas and
dust that forms protostar with
gravity
• Then Nuclear Fusion occurs (atoms
combine to form heavier atoms)
• The star takes 2 different paths
depending on their size
Life Cycle of Stars
Lower Mass Stars
• Giant Star: outer layer expands
–White Dwarf: extremely dense
–Black Dwarf: dead
Life Cycle of Stars
• Higher Mass Stars
–Super Giant: Fusion continues until
iron is formed
–Explosion Occurs: No more nuclear
fusion
• Super Nova: Star breaks apart
–Neutron Star
–Black Hole
Death of Star
• When a star begins to run out of fuel,
its core shrinks and its outer portion
expands
–White Dwarf
–Neutron Star
–Black Hole
Multiple Star Systems
• Multi Star System: Star system with
one
or more companion stars
–Most stars have companions but
not all stars
• The sun does not have a
companion
Multiple Star System
• Example of multi star system: ALPHA
CENTURI: a three star system that is the
CLOSEST star to the sun.
– Proxima Centuri
– Alpha century A
– Alpha Century B
Multiple Star Systems
• Binary Stars: Star systems with 2 stars
• Bi = 2 (remember bicycle)
• Eclipsing Binary Star System
–The larger companion blocks the
smaller companion
Star Clusters
Star Clusters:Large Groupings of Stars
Open Cluster
• Loose and disorganized appearance
• Contain 100- 1000 stars
• young stars
Star Clusters
Globular Cluster
• more common round, densely packed
stars
• 100,000 to 1,000,000
• older stars
Galaxies
• Galaxy is a huge collection of stars
bound by gravity
– Contain various star groups
• Billions of galaxies in the universe
• 3 Types of Galaxies
Spiral Galaxy
Elliptical Galaxy
Irregular Galaxy
The Milky Way
• The galaxy we live in
• Spiral shaped
• Looks like a milky or whitish band in the
sky
•Sun is located in one of the spiral arms
•It has 400 billion
stars
Milky Way Galaxy
•It takes the sun and planets over 200
million years to move around the center
of the milky way
Big Bang Theory
• Theory is an idea that is supported by evidence
• The universe began to expand with the
explosion of concentrated matter and energy
and has been expanding ever since