The document discusses the galactic matter cycle and star formation. It describes how dying stars replenish the interstellar medium with gas and dust, and how massive stars enrich it with heavy elements. Gas and dust in the interstellar medium concentrate under gravity to form dense clouds where stars form. The life cycles of both low-mass and high-mass stars are presented.

1. The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
The Galactic Matter Cycle and Star Formation
ISM
Galactic Matter
Cycle
Dying Stars
Randolf Klein
low-mass
high-mass
Summary
Space Sciences Laboratory & Dept. of Physics
UC Berkeley
Star Formation
Summary
July 4, 2010
Galaxy Forum USA
The Tech Museum
San Jose, CA

2. The Galaxy
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
Dark clouds in front of the Galactic Center from wikipedia – Milky Way

3. A small dark nebula: Barnard 68
The Galactic
Matter Cycle Looking through an isolated dense core in the near infrared.
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

4. Orion in the Far Infrared
The Galactic
Matter Cycle
and Star The constellation
Formation
Randolf Klein Orion harbors many
ISM bright and dark
Galactic Matter
Cycle nebulae.
Dying Stars
low-mass
high-mass
They are another
Summary
Star Formation
telltale sign for matter
Summary between the stars.
But the whole picture
emerges at far infrared
wavelengths . . .
c T. Credner & S. Kohle, AlltheSky.com

5. Orion in the Far Infrared
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

6. The Interstellar Medium – ISM
The Galactic
Matter Cycle
and Star A few facts:
Formation
Randolf Klein The space between the stars is filled with gas and dust.
ISM The average density is one atom per cm3 .
Galactic Matter In this room, there are 6 · 1019 atoms per cm3 .
Cycle
Dying Stars
The average temperature is a few 1000 Kelvin (similar to
low-mass stellar surfaces). But the temperature ranges from a few
high-mass
Summary million Kelvin down to 10 Kelvin.
The gas con be ionized (H+ ), neutral (H), or molecular (H2 )
Star Formation
Summary
depending on the temperature.
About one percent in mass of the ISM are very fine (∼ 1µm)
dust grains. The composition is similar to sand and soot.
This little amount of dust is very important for the optical and
chemical properties of the ISM.

7. The Galactic Matter Cycle
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
Question?
ISM Where does the gas and dust
Galactic Matter
Cycle
Dying Stars
come from?
low-mass
high-mass
Summary
Stars fuse hydrogen and helium into heavier
Star Formation
Summary
elements, but how do these elements end up
between the stars.

8. The Galactic Matter Cycle
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
Question?
ISM Where does the gas and dust
Galactic Matter
Cycle
Dying Stars
come from?
low-mass
high-mass
Summary
Stars fuse hydrogen and helium into heavier
Star Formation
Summary
elements, but how do these elements end up
between the stars.
But where do stars come from?

9. The Galactic Matter Cycle
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
Question?
ISM Where does the gas and dust
Galactic Matter
Cycle
Dying Stars
come from?
low-mass
high-mass
Summary
Stars fuse hydrogen and helium into heavier
Star Formation
Summary
elements, but how do these elements end up
between the stars.
But where do stars come from?
Let’s look at the Galactic Matter Cycle. . .

10. The Galactic Matter Cycle
The Galactic
Matter Cycle Stellar and interstellar Matter get recycled
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
http://hea-www.cfa.harvard.edu/CHAMP/EDUCATION/PUBLIC/starlifecycles pics.html
Left: low-mass/sun-like stars – planetary nebulae
Right: high-mass stars – supernovae

11. Dying Low-Mass Stars
The Galactic
Matter Cycle The Fate of the Sun:
and Star
Formation
In a few billion
Randolf Klein
years, the sun’s
ISM
core will run out
Galactic Matter
Cycle of hydrogen.
Dying Stars
low-mass
The nuclear fire
high-mass
Summary
will continue to
Star Formation burn in a shell
Summary causing the sun
to swell
enormously.
The outer layers
will be blown
into space.

12. Dying Low-Mass Stars
The Galactic
Matter Cycle
and Star
The Next Stage: a Proto-Planetary Nebula
Formation
Randolf Klein
ISM
Galactic Matter
Here, a sun-like
Cycle star illuminates
Dying Stars
low-mass
the shedded
high-mass
outer layers as it
Summary
Star Formation
contracts and
Summary heats up.
It will become a
Planetary
Nebula.

13. Planetary Nebulae Gallery
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

14. Planetary Nebulae Gallery
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

15. Planetary Nebulae Gallery
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

16. Planetary Nebulae Gallery
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

17. Dying High-Mass Stars
The Galactic
Matter Cycle η Carinae,
and Star
Formation
This very massive
Randolf Klein
star (100 M ) is
ISM
running out of
Galactic Matter
Cycle hydrogen and starts
Dying Stars to fuse heavier
low-mass
high-mass elements.
Summary
Star Formation It burns in many
Summary shells violently
bursting off its outer
layers.
And the end is also
much more
violently. . .

18. Supernovae
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
c NSF

19. Supernovae Remnants
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

20. Supernovae Remnants
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

21. Supernovae Remnants
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

22. Summary of Stellar Evolution
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM Dying stars
Galactic Matter replenish the
Cycle
interstellar
Dying Stars
low-mass medium with
high-mass
Summary
gas and dust.
Star Formation
Massive stars
Summary
enrich it with
heavy elements.
http://chandra.harvard.edu/edu/formal/stellar ev/

23. The Galactic Matter Cycle
The Galactic
Matter Cycle
and Star
Formation
Question?
Randolf Klein What happens to the gas and dust?
ISM
Galactic Matter
Cycle
Gravity
Dying Stars
low-mass
high-mass
Summary Under its own gravity, the gas and dust
Star Formation
concentrates in clouds.
Summary
The gas cools and becomes molecular.
More cooling by dust and molecular radiation
allows the gas to collapse more and more.
Stars form in the densest cloud cores.

24. How to form a low-mass star?
The Galactic
Matter Cycle
and Star
Formation Dense cores Gravitational collapse
Randolf Klein in molecular cloud
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
1 pc 10 000 AU
Design: Michiel Hogerheijde (nach Shu, Adams & Lizano 1987, ARAA 25, 23)
t = 0 yr

25. How to form a low-mass star?
The Galactic
Matter Cycle
and Star Embedded protostar Pre−main sequence star
Formation
Accretion, Jet, Outflow Jet, Outflow
Randolf Klein . ¨
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
Core ~ 8000 AU
Disk ~ 80 AU
100 AU
4 5 5 6
t ~ 10 −10 yr t ~ 10 −10 yr
Design: Michiel Hogerheijde (nach Shu, Adams & Lizano 1987, ARAA 25, 23)

26. How to form a low-mass star?
The Galactic
Matter Cycle
and Star Pre−main sequence star Main sequence star
Formation
Planet formation in disk with planetary system
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
100 AU 50 AU
6 7 7
t ~ 10 −10 yr t >10 yr
Design: Michiel Hogerheijde (nach Shu, Adams & Lizano 1987, ARAA 25, 23)

27. Disks around Young Stars
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary

28. Disks launch Jets
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter
Cycle
Dying Stars
low-mass
high-mass
Summary
Star Formation
Summary
scale bar = 1000 AU

29. Star and Planet Formation
The Galactic
Matter Cycle
and Star
Formation The forming stars radiate
Randolf Klein energy gained mainly from
ISM contraction.
Galactic Matter
Cycle They are contracting till
Dying Stars their central temperature
low-mass
high-mass reaches 10,000,000 K.
Summary
Star Formation
Then hydrogen fusion
Summary
starts and a normal, a
Star formation is very inefficient. main-sequence star star is
Only a few percent of the gas in a born.
molecular cloud is converted into
The cycle is closed.
stars and planets.

30. Summary
The Galactic
Matter Cycle
and Star
Formation
The space between the stars is filled with gas and dust:
Randolf Klein the Interstellar Medium or ISM.
ISM The ISM can be studied at other wavelengths than the
Galactic Matter visible light.
Cycle
Dying Stars The life of stars cycles matter in and out of the ISM.
low-mass
high-mass Dying stars inject a (large) fraction of their mass into the
Summary
Star Formation
ISM.
Summary Massive stars enrich the ISM with heavy elements.
In the densest molecular clouds, a few percent of the
ISM gets transformed into stars and planets.
We are all made of star dust!
Then jets, outflows, and supernovae disperse the cloud.

31. What is more: Massive Star Cluster
The Galactic
Matter Cycle
and Star We further know:
Formation
Randolf Klein All stars form in
ISM clusters.
Galactic Matter
Cycle
While the sun
Dying Stars formed a
low-mass
high-mass
Supernova went off
Summary
close by – < 1.6 pc
Star Formation
away. (Looney at al. 2006)
Summary
The Sun forming
close to massive
stars is likely, but
makes things
complicated.
Rosette
Nebula

32. Massive Star Cluster
The Galactic
Matter Cycle
and Star
Formation
Randolf Klein
ISM
Galactic Matter Strong stellar
Cycle
Dying Stars
winds erode the
low-mass molecular cloud the
high-mass
Summary massive star
Star Formation formed from and
Summary
other dense cores
around it.

33. Simulation of a Turbulent Cloud Collapsing
The Galactic
Matter Cycle
and Star
Formation
Mass 50 M
Randolf Klein Size 0.3 pc
ISM
Duration 266,000 yr
Galactic Matter
Cycle
Forms 50 stars and Brown
Dying Stars
low-mass
Dwarfs
high-mass
Summary
Star Formation 100000 CPU hours on up
Summary to 64 processors.In total
1016 FLOP.
Matthew Bate, University
of Exeter (2002)