A1 18 Stellar Evolution

Typical Stellar Evolution
LACC §: 20.2, 21.4, 21.5

• Red Giant Branch
• Horizontal Giant Branch
• Asymptotic Giant Branch

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

Thursday, April 29, 2010 1

HR Diagram

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

Low Mass Evolution

http://www.physics.uc.edu/~hanson/ASTRO/LECTURENOTES/W07/Death/Page1.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


Low M Evolution: 1 vs. 5 M

Notice how much
mass is lost:

1 M to .065 M :
a loss of 35%

5 M to 1.34 M :
a loss of 73%

http://zebu.uoregon.edu/~imamura/122/images/1_5.gif


Low Mass Evolution

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


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

HR Diagram and Mass

http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter17.html

Typical Stellar Evolution
LACC §: 20.2, 21.4, 21.5
• Red Giant Branch: H → He in shell; star expands and
surface cools (but core temperature increases)
• Horizontal Giant Branch: preceded by a Helium ﬂash;
He → C in core, H → He in shell; like a 2nd (brief,
semi-return to the) main sequence
• Asymptotic Giant Branch: He → C in shell, H → He in
shell; star expands and surface cools (but core
temperature increases)
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 20, pp. 461-462: 13.

• Ch 22: Tutorial Quizzes accessible from: http://
www.brookscole.com/cgi-brookscole/course_products_bc.pl?
ﬁd=M20b&product_isbn_issn=9780495017899&discipline_number=19

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.


Low Mass Stellar Evolution
LACC §: 20.2, 21.4, 21.5

• Hayashi Track
• Typical Evolution
• Planetary Nebula


Star Birth -- Hayashi Track

Infrared energy
emissions
result from the
gravitational
collapse of the
protostar

http://www.physics.uc.edu/~sitko/Spring00/4-Starevol/starevol.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


Low Mass Evolution

http://www.physics.uc.edu/~hanson/ASTRO/LECTURENOTES/W07/Death/Page1.html


Planetary Nebulae
With some complications
glossed over, the envelope
and as much as 50% of
the stellar mass is
detached from the
star and expelled into
space leaving the AGB star
very hot core exposed.
The high temperature of the "central star" (it is not REALLY a star as
there is no fusion energy source) means it has a Planck [or thermal
spectrum] curve that peaks way out in the UV and produces many UV
and even soft X-ray photons. These collide with the H, He, C and O
atoms in the former envelope that we now call a PN. These atoms get
ionized, and on recombination the e- drop through the energy levels
giving off various lower energy photons (that add up in energy to the
original UV or X-ray ionizing photon) as they head for the ground state.
http://www.ucolick.org/%7Ebolte/AY4_00/week7/low-mass_deathC.html


Planetary Nebulae

http://rst.gsfc.nasa.gov/
Front/pne.jpg

Planetary Nebulae: Spectrum

http://mais-ccd-spectroscopy.com/Planetary%20Nebula.htm


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

Planetary Nebulae: A Dying
Low Mass (<~10 Msun) Star

http://oposite.stsci.edu/pubinfo/pr/96/13/Helix.mpg


Low Mass Stellar Evolution
LACC §: 20.2, 21.4, 21.5

• Hayashi Track: for all stars--low and high
mass; gravitation contraction heats protostar
• Typical Evolution: Main Sequence → Red
Giant → Helium Flash → Horizontal Giant
Branch → Asymptotic Giant Branch →
• Planetary Nebula with White Dwarf


LACC HW: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.
• Ch 21, p. 485-486: 2 (I want a one word answer), 4&5
(Mention how and where the thermal energy is coming from for each
stage: protostar, main sequence, red giant, helium flash, horizontal giant
branch, asymptotic giant branch)

• Ch 23: Tutorial Quizzes accessible from:
www.brookscole.com/cgi-brookscole/course_products_bc.pl?
http://

fid=M20b&product_isbn_issn=9780495017899&discipline_number=19

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.


A1 18 Stellar Evolution

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