Download Stars and Galaxies PP 2013

HOW WAS THE UNIVERSE
FORMED?
• The BIG BANG THEORY states that
billions of years ago the universe
exploded and expanding energy
became matter over time.
WHAT IS A GALAXY?
• A collection of billions of stars,
gas, and dust that orbit each
other around a center.
• They are not all the same size.
Some may be 20 LY across, some
may be 100 LY across.
WHAT IS A GALAXY?
• Stars in galaxies revolve around
the center of the galaxy (like
planets around the sun).
• Scientists believe at the center
of each galaxy is a black hole.
WHAT ARE THE 3 TYPES OF
GALAXIES?
1.Spiral
2.Elliptical
3.Irregular
WHAT IS A SPIRAL GALAXY?
• Shaped like a
pinwheel. It
usually has a
large, flat disk.
• Contain a lot of
interstellar
matter (gas and
dust) and young
star clusters.
WHAT IS A SPIRAL GALAXY?
• Rotates clockwise
around the center.
• Our sun is one of
several 100 billion
stars in a spiral
galaxy, the Milky
Way
• Spiral galaxies can
also be barred.
WHAT GALAXY IS OUR
SOLAR SYSTEM IN?
Our sun
and solar
system is
in the
Milky Way
Galaxy
in the
Orion Arm
WHAT IS AN ELLIPTICAL
GALAXY?
• Elliptical galaxies
are oval in shape
• They do not
rotate
• Contain very little
or no gas and dust
(interstellar
matter).
• Consists mainly of
old stars. No new
stars are forming.
WHAT IS AN IRREGULAR
GALAXY?
• No definite shape
(contains star
clusters, clouds,
dust and gas).
• Not very common
• Often due to
distortion by the
gravitation of
other galaxies.
WHAT IS A STAR?
• A bright, hot, dense ball of gas
(hydrogen and helium) held together by
its own gravity.
• Stars radiate light
and heat and are
the only source of
light in the universe.
WHAT IS NUCLEAR FUSION?
• Stars create energy in the form of
light and heat through nuclear fusion.
• Hydrogen is the main component of
stars. Hydrogen fuses with another
Hydrogen to create Helium and
release energy.
H + H  He
HOW ARE DISTANCES
BETWEEN STARS MEASURED?
• Distances between stars are measured
in light years.
• 1 light year = the distance light travels
in 1 year. Light is the fastest thing in
the Universe.
• The speed of light = 300,000 km/sec
That’s 9,467,280,000,000 km/year
(9 ½ trillion).
STARS AND THEIR DISTANCES
FROM EARTH
• Alpha Centauri………………………………4 light years
• Sirius………………………………………………8 light years
• Polaris (north star)……………………..400 light years
• Andromeda galaxy……………………….2 million light years
WHAT IS THE SUN?
•
What are the Parts of a Star?
Radiative
Zone
Chromosphere
Convective
Zone
Corona
Photosphere
Sun Spot
Core
Solar Flare
PARTS OF THE SUN
(THE INTERIOR)
1. Core:
The center of the sun. Where
fusion occurs and the sun’s
energy is produced.
2. Radiative Zone:
Very dense region.
3. Convective Zone:
Gases circulate in convection
currents. Hot gases sink and
cool gases rise.
PARTS OF THE SUN
(THE ATMOSPHERE)
4. Photosphere:
Surface of the sun. Where light radiates (photo =
light)
5. Chromosphere:
thin region below the corona. Gives the star its color
(chromo = color) Only visible during a total solar
eclipse.
6. Corona:
The sun’s outer atmosphere.
WHAT LAYER OF THE SUN IS
ONLY VISIBLE DURING A SOLAR
ECLIPSE?
•
FEATURES OF THE SUN
• Sun Spot: dark, cooler
areas on the sun that
move around every 11
years. Usually in pairs.
Sunspot up close…it’s way
bigger than the Earth

FEATURES ON THE SUNS
SURFACE
• Prominence:
Loop extending from the
sun’s photosphere. Link
sunspots together.
• Solar Flare:
Explosion extending from
connected sun spots.
Releases large amounts
of energy.
HOW ARE STARS CLASSIFIED?
• Size (magnitude)
• Temperature
• Color
WHAT IS A HERTZPRUNGRUSSEL DIAGRAM
• Luminosity (brightness) increases from
bottom to top. Brightness is affected
by the temperature of the star
• Temperature increases from right to
left. Temperature depends on the
elements of the star-what is the star
made of.
• Magnitude (size) increases from
bottom to top.
H-R DIAGRAM
Luminosity (brightness)
100,000
10,000
1,000
1
1/100
1/10,000
Increasing Temperature
HOW DOES THE TEMPERATURE OF
A STAR RELATE TO ITS COLOR?
H-R DIAGRAM
STARS
STARS
• The life cycle of a star!
Star Life Cycle
Nebula
Large, dense, cloud of
interstellar dust (like
carbon) and gas (mostly H
and He). This is the area
where stars are born.
Star Life Cycle
Protostar
A baby star. Gravity pulls
gases together, it
contracts into a clump of
matter and becomes more
dense. When hot enough,
it starts nuclear fusion
and the star is born.
Star Life Cycle
Main Sequence
Most of a stars life.
Smaller cooler stars are
on the right, bigger hotter
stars on the left. Hotter
stars have very short life
span, cooler stars have a
long life span.
Star Life Cycle
GIANT
Low mass stars
become giants. The
star runs out of
hydrogen, the core
shrinks and the outer
layers expand. Starts
to cool down.
SUPERGIANT
High mass stars
become supergiants.
The star runs out of
hydrogen, the core
shrinks and the outer
layers expand. Starts
to cool down.
Star Life Cycle
White Dwarf
Red giant looses its
atmosphere leaving a
small, very hot core.
These are old stars about
to die. Our sun will
become a white dwarf.
What is a Star’s life cycle?
Neutron Star
High mass supergiants may undergo a
supernova, where the core suddenly
collapses and explodes. A neutron star
is what remains after the supernova.
It is composed mainly of neutrons and
is very dense. If it spins and releases
radiation it is called a pulsar.
What is a Star’s life cycle?
Black Hole
The biggest mass stars (10-1,000,000
times the sun) will undergo a supernova
and will contract into a black hole.
It is not really a hole. It has so much
gravity that not even light can escape
it. They can not be seen directly.
STARS
• Stars have long lives compared to us
STARS
SO LET’S SEE IF
LIGHT
CHANGES DUE
TO
COMPOSITION!!!
ELECTROMAGNETIC SPECTRUM BY TEMPERATURE
Radio
• Radio
• Microwave
Gamma
less than 3K
3 to 30K
Cool
• Outer Space
• Infrared
30 to 4100K
• Humans
• Visible
4100 to 7300K
• Our star!
• UV
7300 to 3,000,000K
• Hottest Stars
• X-ray
• Gamma Ray
Hot
3,000,000 to 300,000,000K
beyond 300,000,000K
ELECTROMAGNETIC SPECTRUM
• Light travels in the universe and
atmospheres absorb wavelengths
• We can figure out what elements the
star is made of by the color of it’s
wavelength.
H
hydrogen