Download Evolution of our Sun

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Objectives
Life of Stars – Part 1
Name the force that tries to compress/collapse a star? Name the process that happens in the
core of a star preventing collapse and powering the star.
What is fusion? Why is it important to a star? What is converted to energy in the fusion
process?
About how long does our star live as a main sequence star?
Explain why a massive star only lives a short time?
What elements are created in a sun-like star? What elements are created in a massive star?
Evolution of the Sun – Part 2
Name and briefly describe the stages that our sun will go through as it ages.
About how long does our sun live as a main sequence star?
About how much longer does Earth have until our sun evolves to a Red Giant?
What is a planetary nebula?
Supernovas – Part 3
Describe a supernova. Name two types (Ia and II) of supernovas and briefly describe the
events that happen in each case.
Name and describe the leftovers from a supernova (expanding gas cloud and neutron star).
What is meant by “standard candle”? Describe a neutron star and a pulsar.
Why are supernovas important? Why can we say that we are made of stardust?
Name and describe the stages in the evolution of a sun-like star.
Name and describe the stages in the evolution of large mass star.
1. Life and Death of Stars
2. Evolution of our Star – the Sun
3. Supernovas
Part 1
Life and Death
of All Stars
(Determined by
MASS of star)
•Gravity pulls in
•Energy from fusion
pushes out
Balance =
Stable star
Balance
How long is a star
balanced?
1 M star ~ 10 Billion yrs
(our Sun)
Know this one
M = One Solar Mass
(Our Sun’s Mass)
16 M star ~ 200 M yrs
100 M star ~ 3 M yrs
Massive Star Life
Massive star  Lots of gravity  Needs lots
of fusion  Burns fuel fast
Massive star lives hard and fast
More massive star  shorter life
Fusion
FUSION IN STAR:
• Powers the star
• loses mass, emits energy
• Balances the star
• fusion and gravity
• Lighter elements combine to make heavier
elements
• Sun-like stars: He, Li, (Be, B, C)
• Heavier stars: He, C, O, Si …Fe
Summary
• Gravity pulls in
• Energy from fusion pushes out
• Star (alive) is balanced
• Fusion: lighter elements  heavier elements + energy
• E = mc2 (mass converted to energy)
• Less massive star – long lived
• Massive star – short lived, because it MAKES HEAVY
ELEMENTS
Star Life Summary
SHORTEST LIFE and LARGEST MASS
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Supergiants – shortest lives; ~3–50 million years
Giants – shorter lives; ~100 million years
Main Sequence – long lives; billions of years
White & Red Dwarfs – longest lives; hundreds of
billions of years or trillions of years (maybe to the life of a
proton 1032 or more)
LONGEST LIFE and SMALLEST MASS
KNOW THE ORDER.
Don’t need to know
numbers.
Part 2
Evolution of our Sun
From cradle to grave
in billions of years
Also evolution of other “average” stars
(~0.5 M  ~3 M)
Summary
Evolution of our Sun
and other average stars
1.
2.
3.
4.
5.
6.
Nebula
Protostar
Main sequence
Red giant
White dwarf
Black dwarf
1. Nebula
1. Nebula
• Large gas and dust cloud
2. Protostar
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Pre-star
Formed from contraction of nebula
~30 million years for Sun-like stars
More massive star evolves faster
15 M ~ 160 000 years
0.2 M ~ 1 billion years
http://apod.nasa.gov/apod/ap130904.html
3. Main sequence star
• Most of stars in universe
• Fusion powered stars
Main Sequence Star
Sun
Main Sequence Stars
Pleides
Other Main Sequence Stars
Balance cannot go on forever
1 M star
~ 10 Billion yrs
4. Red Giant
Sun now
Sun as Red Giant
In ~ 5 Billion yrs
Earth
4. Red Giant
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Lasts ~1 billion years
Core converts H to He
H layered above He core
Fusion starts in H layer
Outer layers expand
Strong stellar winds expel outer layers
– Hiccups – size changes
– Planetary Nebula – gas shell ejected
• H  He  C in core
Orbits before
Red Giant stage
In the
meantime,
what’s
happening
to the
planets?
Orbits at Red
Giant stage
Giants
Ex: Arcturus,
Aldebaran,
Spica
Our star from Earth
4. Red Giant
• He exhausted in core (He  C)
• Carbon core (no more fusion)
• Core collapses to degenerate state
– white dwarf
• Fusion slowing in outer layers
• Star gently switching off
5. White Dwarf
• Collapsed
degenerate core of
sun-like star
• Lasts 10 to 20
billion years for
our sun
(~age of universe)
Ring Nebula
(Planetary
Nebula)
White Dwarf at center
http://apod.nasa.gov/apod/ap060625.html
1500 year intervals
3300 LY away
3 LY across
2300 LY away
18 000 LY away
130 SS wide
15 mi/s
8 000 LY away
6. Black Dwarf
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Cooled off dense cinder
Older white dwarf
None found yet (hypothetical)
Few if any exist (universe not old enough)
http://apod.nasa.gov/apod/ap990604.html
Star Evolution Summary
http://www.nasa.gov/pdf/208668main_Planetary_Nebula_Lithograph.pdf
Part 3
Supernovas
or How some stars go BOOM!
Supernova
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Huge explosion of a star
Quick (seconds to minutes)
Energetic (~200 million suns)
Can outshine a galaxy
Light fades quickly (weeks)
Supernova 1006
http://apod.nasa.gov/apod/ap030328.html
Supernova
1994D
http://apod.nasa.gov/apod/ap981230.html
SN 2004dj
www.randybrewer.net
M74
Feb 2002
www.rochesterastronomy.orgy.org
M101
Aug 2011
Supernova Types
• Type I – no hydrogen lines in spectra
– Type Ia – white dwarf in binary system explodes
– Type Ib – massive star loses outer layers
• Type II – have hydrogen lines in spectra from
massive star explosion
Type 1a supernova
• Binary system
• One is white dwarf
• Mass pulled onto white dwarf –
explosion
• Used as standard candles to
measure large distances
– standard candle = known luminosity
– billions of light-year distances
L
Bk 2
D
Type II Supernova
Massive star explodes
Video animation of Crab Supernova explosion and remnant
http://www.spacetelescope.org/videos/html/heic0515a.html
Type II Supernova
• Massive star > ~8 M
• Core collapses and explodes because..
• Successive shells of heavier elements in core
H  He  C  O  Si  Fe
Type II supernova
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H  He  C  O  Si  Fe
Fe is the end of the road
Core collapses suddenly (implodes)
Rebounds and huge shock wave
races outward
• Blows up star
Supernova Ball Bounce
Demostration
• NASA Afterschool Universe: Supernova Ball
Bounce (1:32)
• https://www.youtube.com/watch?v=e-91PbbaKI8
• Stacked Ball Drop by Physics Girl (3:33)
• https://www.youtube.com/watch?v=2UHS883_P
60
Supernova remnants (SNR)
1. Rapidly
expanding
shell of gas
2. Core?
SNRs (SuperNova Remants)
Vela SNR
800 LY away
~10 000 yrs ago
Video
http://hubblesite.org/newscenter/archive/relea
ses/2007/10/video/a/
X-rays
Tycho’s SNR 1572
8000+ LY away
35 LY across
http://apod.nasa.gov/apod/ap090317.html
SNR 15 000 yrs ago
2600 LY away
Importance of SN
1. Standard candles to measure distance
2. Expanding gas (H, He, C, O...Fe)
– Enriches gas clouds with heavy elements
– Where did heavy elements on Earth come from?
• Iron in Iron Range
• Meteorite material
3. Shock waves can trigger star formation
4. Massive explosion produces even heavier
elements (beyond iron)
5. We are made of star stuff!
Star Stuff
• “The nitrogen in our DNA, the calcium in
our teeth, the iron in our blood, the carbon
in our apple pies were made in the
interiors of collapsing stars. We are made
of star stuff.”
• Carl Sagan famously said in his 1980
series Cosmos.
Strange Parts of SN
• Type Ia - blows star to bits
• Type II - sometimes find core
– Some of those are 2 to 3 M squashed
into ~10 miles
• 1 tsp weighs 100 million tons
– Neutron star
Type II Supernova
Death of a big mass star
Super
red giant
Supergiant
Sometimes beam sweeps past Earth and we
see…
A Pulsar
is
• A neutron star (small, massive, dense)
• With extremely rapid rotation
– Slowest: Once every 3 s
– Fastest: 716 times/s
• And extremely strong magnetic field
• That emits precise “signals”
• Like a lighthouse beacon
Pulsar
Jocelyn Bell
Puppis A
X-rays
Neutron star at 600 mi/s
IC433, 5000 LY, 65 LY,
Blue = radio
Red = optical
Green = x-ray
http://antwrp.gsfc.nasa.gov/apod/ap06
0602.html
Crab Nebula
7000 LY
6 LY
http://www.spacetelescope.org/news/html/heic0515.html
Crab Nebula Supernova history
http://www.astronomy.pomona.edu/archeo/outside/chaco/nebula.html
Pulsar in Crab Nebula
Pulsar Sounds
http://www.jb.man.ac.uk/~pulsar/Education/
Sounds/sounds.html
OR
https://www.youtube.com/watch?v=gb0P6x_
xDEU
http://antwrp.gsfc.nasa.gov/apod/ap090216.html
http://apod.nasa.gov/apod/ap080617.html
Mass of the star determines its fate
Supernovas
• Exploding stars
• Luminous
• Types 1a (Binary), Type II (Massive)
• Remnants (SNR) – Expanding gas, core
• Importance
• Neutron stars and pulsars
• Black holes next lecture
Homework & Updates
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Take time to register for fall classes.
D2L Quiz 9 & Sun Quiz available
No Lab or Lecture on Tuesday, 4/11.
No Lab this week. Thursday lab students: Lab Exam 1 on
4/13. Tuesday lab students: Lab Exam 1 on 4/18.
• Observations: Star Gazing, Telescopes & Moon Craters (60
pt.)
• (Tonight) April 6, Thursday, Jackson Middle School, Champlin, MN
• April 7, Friday, Bell Museum, University of MN, Minneapolis, MN
• Times and directions on class website
• Observation Option: Univ. of MN Public Lectures – Only Do 1!
• Thur, Apr 20, 7pm, Ted Mann Concert Hall, A Deeper Understanding
of the Universe from 1.2 miles Underground (find Raquel for 10 points).
No credit given if you went to the lecture on 4/4/17.