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Stars and the Universe

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Cassie Grether

on 29 August 2016

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Transcript of Stars and the Universe

Stars & the
Universe

Life Cycle of a Star
IV. The Nebular Hypothesis
III. The Past
A. Our sun is a
star.
B. This means it uses
nuclear fusion
reactions that take
hydrogen
atoms and fuse them into
helium
atoms.
E. The brightest stars in our galaxy are the most massive and hottest. They are using their fuel much faster. but the largest stars have the ability to make larger elements.
Why Does the Sun Shine?
II. The Life Cycle of a Star
A. The life-cycle path depends on the star's
size.
Stars begin the same way with a stellar nebula.
Each star begins as a
stellar nebula
that clumps together to form a protosun
star -
nuclear fusion at the core
When it runs out of hydrogen in its core, a smaller star like our sun will then swell to a...
red giant
A massive star, however, will:
red supergiant
supernova
Lastly, a massive star will either become a:
neutron star or black hole
C. Star formation: Why is it relevant to us?
1. In the beginning of the Universe there was mostly hydrogen and helium.
2. So where do all of the other elements come from?
A. Nebular Hypothesis describes the
formation of a solar system.
B. Steps of the Nebular Hypothesis:
1. All solar systems begin as star dust and gas also known as a nebula.
2. The nebula will collapse and form a protostar.
5. Heavier elements such as carbon, silicon, iron and others from a disk closer to the sun.
6. Lighter elements, such as hydrogen, helium, and molecules like methane and water are shot farther out away from the spinning protosun.
F. This spinning disk of gas and dust surrounding the protosun is called the
accretion disk.
What causes the star and the planets to form? Why does this dust collect anyhow?
H. Composition of the inner and outer planets:
1. Inner planets and Asteroid belt - mostly rock.
2. Outer planets - mostly gasses.
V. Nebular Hypothesis
Evidence!
1. observations of newly forming stars with telescopes
Accretion disks
accretion disks with protoplanets and dust.
Nebular Hypothesis
Evidence!
2. Solar system structure due to gravity. Lighter element has less of a gravitational force and spread out farther.
Nebular Hypothesis
Evidence!
3. motion of the solar system
all the planets, asteroid belt Kuiper belt orbit the sun in the same direction.
4. Radiometric dating puts age of planetary rocks and of meteorites are all same age (about 4.6 billion years old). This suggests they formed at the same time.
Nebular Hypothesis
Evidence!
Inside Our Sun - a Deeper Look
I. Star facts
What is nuclear fusion?
Important Term
C. nuclear fusion:
a nuclear reaction in which atoms or their components combine to make larger atoms. This process can produce or absorb energy.
D. A star is
incandescent
. It glows because it is so hot - like a heating element on a stove.
What is left is a
white dwarf
which slowly cools over time and finally becomes a sad, lonely and dark black dwarf.
Red giant: a very large bright star which uses elements larger than hydrogen for fuel.
white dwarf: a small very dense "star" the size of a planet. It glows because it is hot and has no nuclear fusion still occurring.
black dwarf: a dark, cold, dense core of a dead star that gives off no energy or light.
supernova: death of a star; a star that explodes and becomes extremely luminous in the process
neutron star: gravitational collapse of a star after a supernova where everything is so dense that all that exists is neutrons.
Black hole: the collapse of a star where everything is so compacted that nothing, not even light can escape the gravity.
a) Nuclear fusion in the sun take hydrogen atoms together and fuse them into helium.
b) helium then fuses to create nitrogen;

c) These processes continue until iron is created in the core.

d) As a massive star
supernovas
the energy required to fuse larger elements like
uranium,
lead
, gold, iron and
others exists. These elements are then blasted into the cosmos.
3. At the center
: The Milky Way
a) at the center of our Milky Way Galaxy is a massive gravitational anomaly we can't see. It is a massive black hole.
Black Holes
How we know its there and what is it?
Geocentric vs. Heliocentric
1543 Nicholas Copernicus
Polish Roman Catholic
mathematician
astronomer
Galileo Galilei
E. It was
Galileo Galilei's
observation of the
moons of Jupiter
that showed objects in the solar system could orbit things other than the Earth.
His fate: arrested on heresy by the Inquisition.
Italian physicist, mathematician, astronomer, and Roman Catholic
C. Ptolemy's theory put the Earth at the center of the Universe. This was called the geocentric model. (geo = Earth; centric = centered)
The Earth stood still while everything else orbited around us.
D. Long after Ptolemy died, Nicholas Copernicus discovered the Sun was at the center of the Universe. This was called the heliocentric model. (helio=sun; centric = centered)
F. Even though the heliocentric view of the solar system was right it took many many years for people to accept the truth. Why?
Galileo and Copernicus' ideas conflicted with the understood beliefs at the time.
3.
Once the protostar gains enough mass, the internal pressure and heat will cause nuclear fusion and a star is born.
Crab Nebula
Stable stage
Dying Star
After the star uses up all of its fuel and has produced iron in its core it implodes and becomes a
planetary nebula
(star blasts off outer shells)
Start at the top track of your notes
1054 AD
6,523 light years
4. Planets form from the accretion disk (dust and gases spinning around the star).
Full transcript