HR Diagram

http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html

Low and High Mass Evolution

The stellar wind
causes mass loss
for AGB stars. This
loss is around 10-4
solar masses per
year, which means
that in 10,000 years
the typical star will
dissolve, leaving
the central, hot core
(the central star in a
planetary nebula).

http://abyss.uoregon.edu/~js/ast122/lectures/lec16.html


High Mass Evolution

If the star is larger
than 8 solar
masses, then the
core continues to
heat. Carbon and
Text oxygen fuse to
form neon, then
magnesium, then
silicon. All forming
into burning shells
surrounding an
iron ash core.

http://abyss.uoregon.edu/~js/ast122/lectures/lec16.html


Type-II
Supernova

http://www.williams.edu/
astronomy/Course-Pages/111/
Images/SN/sn_explosion.gif


Supernova 1987a

http://cse.ssl.berkeley.edu/bmendez/ay10/2000/cycle/snII.html

Type-II Supernova

http://ircamera.as.arizona.edu/NatSci102/NatSci102/movies/suprnova.mpg


Supernova Light Curves

http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/supernovae.htm


Supernova 1987a

http://www.stsci.edu/~mutchler/ http://apod.nasa.gov/apod/
images/clouds_ctio.jpg ap020331.html


Supernova 1987a

http://www.sﬂorg.com/spacenews/sn022207_02.html

Novae and Type-Ia Supernovae

http://antwrp.gsfc.nasa.gov/apod/ap060726.html


Novae and Type-Ia Supernovae
Spectacular explosions keep occurring in the binary star
system named RS Ophiuchi. Every 20 years or so, the red giant star
dumps enough hydrogen gas onto its companion white dwarf star to set
off a brilliant thermonuclear explosion on the white dwarf's
surface. At about 2,000 light years distant, the resulting nova
explosions cause the RS Oph system to brighten up by a huge factor and
become visible to the unaided eye. The red giant star is depicted on the
right...while the white dwarf is at the center of the bright
accretion disk on the left. As the stars orbit each other, a stream
of gas moves from the giant star to the white dwarf.
Astronomers speculate that at some time in the next 100,000 years,
enough matter will have accumulated on the white dwarf to push it over
the Chandrasekhar Limit, causing a much more powerful and ﬁnal
explosion known as a supernova.

http://antwrp.gsfc.nasa.gov/apod/ap060726.html


Type Ia and Type II Supernovae

http://www.ifa.hawaii.edu/~barnes/ast110_06/tooe/1314a.jpg

Type-I vs. Type-II Supernovae

http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap21/FG21_08.jpg

Stellar Evolution: [Nova]

Low vs. High Mass

http://
www.redorbit.com/
education/
reference_library/
universe/
stellar_evolution/246/
index.html


Enrichment of the ISM
when the stellar core
becomes solid iron, there is
no fusion reaction available to
produce energy to keep the
core hot and maintain the
pressure that resists gravity

the iron core collapses in just a few seconds to a
neutron star (or black hole).

http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/supernovae.htm


Enrichment of the
Interstellar Medium

Gas is recycled in the Galaxy.
It goes into forming stars and
is returned during the death
throws of stars enriched with
heavy elements for the next
generation of stars. It is a
giant cycle of life.
http://cse.ssl.berkeley.edu/bmendez/ay10/2002/notes/lec16.html


High Mass and Binary System
Stellar Evolution
LACC §: 22.1, 22.2, 23.5
• High Mass (>~10 Msolar) Stars: fuse all the way
up to Fe, iron; Type-II Supernovae (sometimes
Gamma-Ray Bursters) fuse past Fe, iron
• Binary Systems: Novae, Type-Ia Supernovae,
X-ray Binaries, X-ray Bursters)
• Enrichment of the ISM: Stars convert H into
elements up to Fe: He, C, O, Ne, Mg, Si, Fe;
Supernovae create elements heavier than Fe
An attempt to answer the “big questions”: What is
out there? Where did I come from?

LACC HW: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.

• Ch. 22, pp. 509-511: 8 (Speciﬁcally, what is the cause of
each: Nova, Type Ia Supernova, Type II Supernova)

Due ﬁrst class period of the next week (unless
there is a test this week, in which case it’s due
before the test).
AstroTeams, be working on your Distance Ladders


Stellar Remnants
LACC §: 22.1, 22.2, 23.5

• White Dwarfs
• Neutron
• Black Holes

An attempt to answer the “big questions”:
What is out there? Where did I come from?


Stellar Remnants

neutron degeneracy
electron degeneracy pressure pressure
http://www.maa.mhn.de/Scholar/Starlife/evolutnc.html


White Dwarf:
Mass-Radius Relationship

About 15 km

About 10,000 km
http://ircamera.as.arizona.edu/NatSci102/lectures/whitedwrf.htm


Stellar Remnants
Density: ~0.5 tons/cc

About 15 km

About 10,000 km
Density: ~100,000,000 tons/cc

http://astro.ucc.ie/research/intro/index.html

Stellar Remnants: Black Hole

Note that the Schwarzschild radius scales with the mass of
the black hole. The Schwarzschild radius of a 1 solar mass
black hole is 3 x 105 cm [3 km, less than 2 miles].

http://www.astro.cornell.edu/academics/courses/astro201/bh_structure.htm

Neutron Stars / Pulsars
What a star becomes
when it dies depends on
the mass left when all
possible nuclear fuels are
exhausted and the star
has lost some of its
original mass by ejecting
it:

M <= 1.4 M -----> white
dwarf (planetary nebulae)

1.4 M <M < ~3 M -->
neutron stars/pulsars
(type II supernova)

M > ~ 3 M ---->
supernovae/black holes
(type II supernova)
Pulsar Animation

http://ircamera.as.arizona.edu/NatSci102/lectures/whitedwrf.htm


The Crab Nebula/
Pulsars
http://hera.ph1.uni-koeln.de/
%7Eheintzma/NS1/SN1054.htm

This picture shows a time sequence for the pulsar in the Crab nebula, shown in context
against an image.... Both the nebula and its central pulsar were created by a supernova
explosion in the year 1054 A.D. The enlarged region is a mosaic of 33 time slices,
ordered from top to bottom and from left to right. Each slice represents approximately
one millisecond in the period of the pulsar.

What would a naked black hole
look like? Maybe...
“A (simulated)
Black Hole of
ten solar
masses as
seen from a
distance of
600 km with
the Milky Way
in the
background
(horizontal
camera
opening angle:
90°).”
http://www.tutorgig.com/ed/black_hole


http://www.spitzer.caltech.edu/Media/happenings/20050526/

Gamma-Ray Bursts
James Annis, an astrophysicist at
Fermilab, near Chicago, has speculated
that such events could sterilize
entire galaxies, wiping out life-forms
before they had the chance to evolve to
the stage of interstellar travel. 1 "If one
went off in the Galactic center," he
wrote, "we here two-thirds of the way
out of the Galactic disk would be
exposed over a few seconds to a wave
of powerful gamma rays." It would be
enough, according to Annis, to
exterminate every species on Earth.
Even the hemisphere shielded by the
planet's mass from immediate exposure
would not escape, he claimed, since
there would be lethal indirect effects
such as the demolition of the entire
protective ozone layer. The rate of
GRBs in the universe today
appears to be about one burst
per galaxy per several hundred
million years.
http://www.daviddarling.info/encyclopedia/G/gamma-ray_burst.html

X-ray binaries & X-ray bursters

http://www.roe.ac.uk/roe/support/pr/pressreleases/050608-ultracam/index.html


Millisecond Pulsars
This animation attempts to condense the
billion year evolutionary history of such a
binary system into a few tens of seconds.
It begins with two stars, one more
massive than the other, in a tight orbit.
The massive star evolves ﬁrst and
swallows up its companion, which spirals
into it forming an even tighter binary system. The core of the massive
star produces a supernova and leaves behind a neutron star. The
neutron star's companion eventually begins to lose mass and forms an
accretion disk around the neutron star. The accretion of material
onto the neutron star causes it to spin faster and faster,
eventually reaching a spin period of a few milliseconds. The accreted
material produces X-rays which in turn can begin vaporizing the
companion. All that remains at the end is a highly compact, rapidly
rotating neutron star which produces a pair of radio beams and may be
observable as a millisecond radio pulsar. http://heasarc.gsfc.nasa.gov/docs/
xte/Snazzy/Movies/millisecond.html


Stellar Remnants
LACC §: 22.1, 22.2, 23.5
• White Dwarfs (Chandrasekhar mass limit = 1.4 M ):
the dead carbon cores (<~1.4 M ) of low mass stars
(<~10 M ) left behind after a Planetary Nebulae

• Neutron Stars and Pulsars: neutron degenerate
remnants (1.4 < 3 M ) of high mass stars (>~10 M )
left behind after a Type-II Supernovae

• Black Holes (>3 M ): ∞ dense remnants of high
mass stars (>~10 M ) after a Type-II Supernovae
An attempt to answer the “big questions”: What is out
there? Where did I come from?


LACC HW: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.

• Ch. 23, p. 532: 4.

Due at the beginning of next class period.
Test covering chapters 14-23 next class period.


Review for Test (4 of 5): Stars
[10 pts] The Sun [10 pts] Nebulae, Binary Systems & Stellar Remnants
• proton-proton chain (hydrogen nucleus, proton, positron, • nebulae: molecular clouds, HII regions (star forming
gamma rays, helium nucleus), the neutrino problem regions, planetary nebulae, supernova remnants),
• interior → atmosphere: core, radiation zone, convection reflection nebulae, supernova remnants
zone, photosphere, chromosphere, corona, solar wind • nova and type-I supernova: binary system with a white
• solar phenomena (solar magnetic field): granules dwarf, light curves; X-ray binaries and X-ray bursters:
sunspots, flares, prominence/filaments, coronal mass binary system with a neutron star or black hole; accretion
ejection, aurora and geomagnetic storms (on Earth) disks
• stellar remnants: masses, sizes, densities of white dwarfs
[10 pts] Stars vs. neutron star vs. black holes; pulsars; black holes
• stellar spectra: temperature, spectral class, radial velocity (singularity, Schwarzschild radius, event horizon)
(red-shift vs. blue shift), composition, cluster age (main
sequence turn-off) [10 pts] Identify from an Image or Chart
• determining distances: (radar (closest planets/asteroids • solar surface features: sun spots (umbra, penumbra),
only)), stellar parallax, standard candles--e.g. main granules, prominence, flare, coronal mass ejection;
sequence fitting, RR Lyrae and Cepheid variables nebulae: molecular clouds, star forming HII region,
• other properties: proper motion, luminosity, apparent planetary nebulae, reflection nebulae
brightness/magnitude vs. absolute brightness/magnitude, • HR Diagram: regions--main sequence, white dwarfs,
spectroscopic or eclipsing binaries to determine mass giants, supergiants, spectral class, luminosity class; axes--
x-axis = temperature, spectral class; y-axis = luminosity,
[10 pts] Stellar Evolution absolute magnitude; mass & age & main sequence--high
• HR Diagram: x-,y-axes, evolutionary tracks mass at top left, short lifetimes; low mass at lower right,
• low mass evolution: Hayashi track, main sequence (H long lifetimes; main sequence turn-off point gives a star
core burning), red giant branch (H shell burning), helium cluster’s age
flash (He core ignition), horizontal giant branch (He core • Make use of a chart containing the following stellar data:
burning), asymptotic giant branch (He shell burning), apparent magnitude (mv), absolute magnitude (Mv),
planetary nebulae (envelope ejection), white dwarf spectral class, luminosity class
• high mass evolution: similar to low mass stars, but keep
fusing elements up to iron, type-II supernova (gamma ray
burst), neutron star (pulsar) or black hole


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