Unit 5 - Stars

Learning Goals:
 How do stars differ from moons and
planets, and from one another?
4. Complex Knowledge:
demonstrations of
learning that go
aboveand above and
beyond what was
explicitly taught.
 How does the classification of stars
help us understand how they evolve
over their lifetimes?
3. Knowledge: meeting
the learning goals and
expectations.
 What are the different types of
2. Foundational
knowledge: simpler
procedures, isolated
details, vocabulary.
stars?
 What happens when different types
of stars die?
 Why is it important for us to
understand stars?
1. Limited knowledge:
know very little details
but working toward a
higher level.
Bell Work
3-13-16
 How can you tell how a star will change
throughout it’s life cycle? (what characteristic(s))
Test on the Friday after we get back
Tomorrow (Tuesday) is the LAST day to turn
in an assignment that is late.
THE LAST DAY
Calculate – lifetime of a star
 The lifetime of a star is inversely
proportional to its initial mass.
 Bigger Stars = Shorter Lives
 Smaller Stars = Longer Lives
 L~ 1/ M2.5
 L= Lifetime in solar lifetimes (10billion years)
 M= Mass in solar masses
 L~ Lifetime = 1/ M2.5
 M~0.5 solar masses
 M~20 solar masses
5.66 solar lifetimes or 56-57 billion years
.00056 solar lifetimes or 5.6 million years
Variable Stars
 Intrinsic
 Pulsating Variables
 Consistent - Cepheid and RR Lyrae Stars
 Galactic Measuring Tape
 Semi regular
 Eruptive
 Type 1 supernova
 Nova
 Extrinsic
 Eclipsing binaries
 Rotating variables
Variable Stars
 The time it takes to complete a cycle of
maximum brightness to minimum
brightness then back to maximum is
called the period of the variable star.
 Plotting the period produces a light
curve, which can be studied to
determine
 Magnitude of stars
 Distance from earth
Variable
Stars
1. what are the
periods of the
four stars?
If an astronomer observed a Cepheid star with
period of 34 days, comparing to previously
measured Cepheids, its absolute magnitude is
-5.65. If its apparent magnitude was +23.0, the
astronomer could use the distance modulus
equation:
m - M = 5 log d - 5
rearranged:
d = 10(m - M + 5)/5 parsecs
to find the distance to the Cepheid:
d = 10(23 - -5.65 + 5)/5 parsecs
d = 106.73 parsecs
d = 5.4 × 106 parsecs
Death Star
New Topic
I mean…
Death OF A Star!
what happens to the core? –
cosmic balancing act
 Star core < 1.4 solar masses (Chandrasekhar Limit)




Planetary Nebula
Electron degeneracy
1 tablespoon of matter = 10 tons
Becomes white dwarf
 Star core > 1.4 but < 4.5 solar masses




Supernova
Neutron degeneracy
1 tablespoon of matter = 250,000 tons
Becomes neutron star
 Star core > 5 solar masses
 Supernova
 Becomes a black hole
Planetary Nebulae
 Planetary Nebulae  are the remnants of stellar death.
 can be uniform and spherical or more
complicated structures
 Form when a star expands too much, and
gravity drops and isn’t strong enough to hold
on to the outer layers of the star.
(paraphrase)
 The gas is ionized by the star’s radiation, so
it glows
 Have a white dwarf star core
Green Bubble Nebula
https://www.youtube.com/watch?v=3k6AMA
mLmK4
Planetary Nebulae Exit Ticket
 1. Cat’s Eye
 2. Helix
 3. Ring
 4. Ant
 5. Hourglass
 6. Bug
 7.Dumbbell
 8. Eskimo
Create an information
page about your
nebula.
Include:
•1 picture/sketch
•2 facts about your
nebula in particular
•2 general facts about
planetary nebulae