Classifica
tion
HR
diagram
Star
clusters
Terms
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Life cycle Black holes
Life Cycles
2
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Temperature
The star's color index is a
quick way of determining its
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Sun
The most famous G type star
is:
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In the middle of the main sequence
Where does our sun lie on the
HR diagram
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It’s mass
What is the single most
important characteristic in
determining the course of a star's
evolution?
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Type G2 star, middle of HR diagram-average size
and luminosity, end of life will be white dwarf,
only known star to support a planet with life.
Why is our star (the sun) frequently referred to
as an “average” star? Compare the important
physical characteristics of the Sun with the most
common types of stars.
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About the middle of the main sequence
On the HR Diagram, the sun
lies where?
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At the top right of the diagram
Where on the H-R diagram,
are red giants like
Betelgeuse?
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In the lower left of the diagram
On the HR diagram, white
dwarfs are where?
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White Dwarf
Stars that have masses similar to the
sun but sizes similar to Earth are:
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Above and to the right of the main sequence.
On an H-R diagram where would a
protostar lie in comparison to the main
sequence?
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The stars are in old age (Red Giants) and
there are hundreds of thousands to millions
of stars in a cluster.
Describe globular star
clusters
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Massive blue main sequence stars
The brightest stars of a young
open cluster will be
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Red Giants
In globular clusters the
brightest stars will be
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Stars that are in clusters are of similar age,
(also composition and distance) from Earth.
Why are star clusters a great
way for us to study star
evolution?
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Collisions and physical interactions that can
include mergers of object.
What can occur in star
clusters because of the
number of stars that are close
together.
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Brown Dwarfs
Objects which have contracted, but are
too little mass to ignite nuclear reaction
are called
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Red Giant
Stars that leave the main
sequence because they run out
of hydrogen in their cores and
eventually become white
dwarfs are:
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Gravitation
What is the force that keeps a
main sequence star from
blowing apart?
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Radiation pressure
What is the force that keeps a
main sequence star from
collapsing on itself?
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A star is only stable when the pull of
gravity is equal to the pressure of
radiation. (When balanced it is in
hydrostatic equilibrium)
Why can we say a star spends
its life trying to maintain
equilibrium?
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The igniting of nuclear fuel at 10 millionK
What process marks the birth
of a new star (protostar to an
actual star) ?
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Stars live too long to be observed from birth
to death
Why is it hard to study the
life cycle of one star?
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It fragments into smaller clouds that form
into many stars
How does an interstellar gas
cloud first begin to form
hundreds of stars
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Once it is heated up enough, nuclear fusion
ignites and radiation pressure stabilizes.
Why does gravitational contraction halt in
collapsing protostars?
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An interstellar cloud is disturbed and begins to
gravitationally collapse, fragments,It heats up and
spins faster. When the core temperature reaches 10
mill K, nuclear fusion begins (H into He). When
outward pressure equals inward pressure the star
enters the main sequence.
Outline the process of star
formation from interstellar
cloud to main sequence
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Black hole
A “failed” supernova undergoes
core collapse but instead of
forming a neutron star like a Type
II supernova it forms a black hole.
A hypernova ends up as a
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More slowly
As a spaceship nears an event
horizon, a clock on the spaceship
will go more quickly or more
slowly?
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In the center of galaxies
Where do we most often find
massive black holes
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Look for effects on nearby objects
How are black holes identified
(“seen”)?
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The point of no return
What is the event horizon?
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Shock waves from
supernovae
Star formation may be triggered by __________
which help gravity through compression of
interstellar clouds to greater densities.
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T Tauri
Strong winds develop
during which phase of
a protostar?
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When a protostar in about
to become a main
sequence star
When does the T Tauri
star occur?
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They are young enough to not have most
of their hydrogen not fused into helium.
They do not evolve off until helium is
built up. Most of stars life time is spent
as a main sequence star.
Why is the largest group of stars the
main sequence stars?
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Inward force of gravity is equal to the outward force of radiation
energy due to nuclear fusion
What is meant by a star being in equilibrium