Download Stars & Galaxies

Powers of 10
• http://micro.magnet.fsu.edu/primer/java/s
cienceopticsu/powersof10/index.html
Interactive
H-R Diagram
• http://aspire.cosmicray.org/labs/star_life/hr_interactive.html
Stars & Galaxies
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The Universe

Universe is space and everything in it.
How do measure distance in space?
• Light Year- the distance that light
travels in one year through space.
− 1 light year = 9.5 trillion km or 5.9 trillion miles
• (Speed of light is 300 million m / s, or 186,000 miles / s )
How are stars classified?
-Stars are classified by size, temperature, and brightness.
Size: Stars can range from small, medium, giant (huge),
and supergiant.
Temperature: It is opposite!
Blue White Yellow Red-orange Red
HOT-----------------------------------------COLD
Brightness:
Absolute Magnitude: The brightness the star would have if it were at a
standard distance from earth. The actual brightness of a star.
Apparent Magnitude: The brightness of the star as seen from
How bright a star looks.
earth.
H-R Diagram
• A graph that shows the
relationship between a star’s
surface temperature and it’s
absolute magnitude
(luminosity).
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H-R Diagram
A star is born


A star is made up of a large amount of gas in a
relatively small volume.
A nebula, on the other hand, is a large amount of
gas and dust spread out in an immense volume.

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All stars begin their lives as parts of nebulas. Gravity can
pull some of the gas and dust in a nebula together.
The contracting cloud is then called a protostar.
A star is born when the contracting gas and dust
become so hot that nuclear fusion starts.
Lifetimes of Stars



How long a star lives depends on how much
mass it has.
Stars with more mass have shorter lives than
those with less mass.
Small stars use up their fuel more slowly than
large stars, so they have much longer lives.
 Generally,
stars that have less mass than the sun
use their fuel slowly, and can live for about 200
billion years.
 Medium- mass stars like the sun live for about 10
billion years.
Death of Stars



When a star begins to run out of fuel, the center
of the star shrinks and the outer part of the star
expands. The star becomes a red giant or
supergiant.
All main sequence stars eventually become red
giants or supergiants. However, what happens
next depends on the mass of the stars.
When a star runs out of fuel, it becomes a white
dwarf, a neutron star, or a black hole.
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White Dwarf

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
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Small and medium stars become red giants and
then white dwarfs.
Their outer layers expand to become red giants.
Eventually, the outer parts grow bigger still and
drift out into space.
The blue white hot core is left behind causing a
white dwarf.
When there is no more energy it becomes a
black dwarf.

The most massive stars- those
having more than 40 times the
mass of sun- become black
holes when they die.

After this kind of star becomes
a supernova, more than five
times the mass of the sun may
be left.

The gravity of this mass is so
strong that the gas is pulled
inward, packing it into a smaller
and smaller space.
Black Holes
Neutron Stars

A dying giant or supergiant star can suddenly explode.
Within hours, the star blazes millions of times brighter.

The explosion is called a supernova.

After a star explodes, some material from the star is left
behind. This material may become part of a nebula.

This material may form a neutron star.

Neutron stars are even smaller and denser than white
dwarfs.
Galaxies
• A large grouping of stars in space
• Currently over 50 million galaxies in the
universe
• 3 Types
• Spiral
• Irregular
• Elliptical
Spiral Galaxy
• Spiral arms w/ a bulge in the center.
• Milky Way is a spiral galaxy
Elliptical Galaxy
• Elongated shape
• Very bright centers w/ very little dust
or gas
• Contain mostly old stars
Irregular
Galaxy
• Irregular
shape
• Located close
to spiral
galaxies
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“Main Sequence”
Sun-like and Smaller Stars
Due to the mass of the star, fusion occurs (hydrogen is
fused together releasing light and heat)
Stars the size of our sun can undergo fusion for 10 billion
years.
After all of the helium undergoes fusion, it becomes a white
dwarf.
As the fuel continues to dwindle the star eventually
becomes a black dwarf.
As the hydrogen runs out and helium undergoes fusion, the
star turns into a red giant.
“Giants”
Huge Stars
(1.5-3X the mass of the sun)
•
The remnants of the explosion could become a
neutron star
•
Stars this size usually undergo fusion for less
time than the sun-like stars.
•
As a supergiant can suddenly explode into a
supernova.
•
As the hydrogen runs out and helium
undergoes fusion, the star turns into a super
giant.
“Super Giants”
Giant Stars
(over 3X the mass of the sun)
A dying supergiant can explode into a supernova.
As the hydrogen runs out helium and undergoes
fusion, the star turns into a supergiant.
Due to the immense mass, the material may be
pulled by gravity inward, packing the gas so
tightly a black hole is formed.
Quasars


Quasar is a distant
galaxy with a black
hole at its center.
As enormous amounts
of gas revolve around
such objects as a
black hole, the gas
heats up and shines
brightly.