Stellar Evolution
LACC §: 20.2, 21.4, 21.5
• Stellar Evolution: Hayashi Track, Main
Sequence, Red Giant, Horizontal Giant
Branch, Asymptotic Giant Branch
• Stellar Death: Low Mass (planetary nebulae)
vs. High Mass (type-II supernovae, gamma-
ray bursters) vs. Binary Systems: (novae, type-
I 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?
Monday, November 16, 2009 1

HR Diagram
http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html
Monday, November 16, 2009 2

Star Birth -- Hayashi Track
http://www.physics.uc.edu/~sitko/Spring00/4-Starevol/starevol.html
Monday, November 16, 2009 3

Low Mass Evolution
http://www.physics.uc.edu/~hanson/ASTRO/LECTURENOTES/W07/Death/Page1.html
Monday, November 16, 2009 4

Low 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
Monday, November 16, 2009 5

Low M Evolution: 1 vs. 5 M
http://zebu.uoregon.edu/~imamura/122/images/1_5.gif
Monday, November 16, 2009 6

Low Mass Evolution
http://ircamera.as.arizona.edu/NatSci102/movies/suntrackson.mpg
Monday, November 16, 2009 7

Planetary Nebulae
http://rst.gsfc.nasa.gov/Front/pne.jpg
Monday, November 16, 2009 8

Cat’s Eye Planetary Nebula
At an estimated distance of 3,000 light- The Cat's Eye (NGC 6543) is over half
years, the faint outer halo is over 5 light- a light-year across and represents a
years across. More recently, some planetary final, brief yet glorious phase in the
nebulae are found to have halos like this life of a sun-like star. This nebula's
one, likely formed of material shrugged off dying central star may have produced
during earlier episodes in the star's the simple, outer pattern of dusty
evolution. While the planetary nebula phase concentric shells by shrugging off
is thought to last for around 10,000 years, outer layers in a series of regular
astronomers estimate the age of the outer convulsions. But the formation of the
filamentary portions of this halo to be 50,000 beautiful, more complex inner
to 90,000 years. structures is not well understood.
http://antwrp.gsfc.nasa.gov/apod/ http://antwrp.gsfc.nasa.gov/apod/
ap070629.html ap080322.html
Monday, November 16, 2009 9

Planetary Nebulae: Spectrum
http://mais-ccd-spectroscopy.com/Planetary%20Nebula.htm
Monday, November 16, 2009 10

Main Sequence Turn-Off Point
H-R diagrams of two clusters, the open cluster M67 (a young cluster), and the globular
cluster M4 (an old cluster). The main sequence is significantly shorter for the older
cluster; the luminosity and temperature of stars at the 'turnoff point' can be used to
date these clusters.
http://astro.berkeley.edu/~dperley/univage/univage.html
Monday, November 16, 2009 11

HR Diagram and Mass
http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter17.html
Monday, November 16, 2009 12

High Mass Evolution
If the star is larger
than 8 solar
masses, then the
core continues to
heat. Carbon and
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
Monday, November 16, 2009 13

Type-II
Supernova
http://www.williams.edu/
astronomy/Course-Pages/111/
Images/SN/sn_explosion.gif
Monday, November 16, 2009 14

Supernova 1987a
http://cse.ssl.berkeley.edu/bmendez/ay10/2000/cycle/snII.html
Monday, November 16, 2009 15

Supernova 1987a
http://www.stsci.edu/~mutchler/ http://apod.nasa.gov/apod/
images/clouds_ctio.jpg ap020331.html
Monday, November 16, 2009 16

Supernova 1987a
http://www.sflorg.com/spacenews/sn022207_02.html
Monday, November 16, 2009 17

Novae and Type-I Supernovae
http://antwrp.gsfc.nasa.gov/apod/ap060726.html
Monday, November 16, 2009 18

Novae and Type-I 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 of the above drawing, 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
Monday, November 16, 2009 19

Type I and Type II Supernovae
http://www.ifa.hawaii.edu/~barnes/ast110_06/tooe/1314a.jpg
Monday, November 16, 2009 20

Type-I vs. Type-II Supernovae
http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap21/FG21_08.jpg
Monday, November 16, 2009 21

Stellar Evolution:
Low Mass vs. High Mass
http://www.redorbit.com/education/reference_library/universe/stellar_evolution/
246/index.html
Monday, November 16, 2009 22

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
Monday, November 16, 2009 23

Enrichment of the
Interstellar Medium
Binding energy plot: the graph
shows the nuclear binding energy
per nucleon (i.e. per proton or
neutron).... For increasing atomic
number the binding energy
increases (in this plot, downwards),
until it reaches its maximum for
iron-56. The nucleosynthesis from
hydrogen to iron-56 is energetically
favorable and occurs through
consecutive fusion reactions.
If you want to climb the rest of the periodic table, then new
mechanisms...are needed. Note that one can go in the opposite
direction (from heavy to light nuclei) through nuclear fission.
http://www.scienceinschool.org/2007/issue5/fusion
Monday, November 16, 2009 24

LACC HW: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.
• Ch 20, pp. 461-462: 1.
• Ch 21, p. 485-486: 2 (I want a one word answer), 3.
• Ch 22, 23: Tutorial Quizzes accessible from:
http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?
fid=M20b&product_isbn_issn=9780495017899&discipline_number=19
Due at the beginning of the next class period.
Monday, November 16, 2009 25