Astrophysics winter trimester  2009

 syllabus   &  course expectations
safety, tardy, classroom computer use, and honesty

 Astronomy Picture of the Day        the latest astrophysics discoveries
  what's up in the 
sky this week

February 15
February 16

make sure that you have green book in class today

final exam sometime today

make sure that you have checked the exam schedule so that you know where it is

you can use YOUR notes (in your handwriting), your past assignments (homework and labs),
any official handouts (green book, particle sheet)

bring your textbook, but you will likely not be using it

amnesty hour is 10 - 11 am

you can bring in assignments
(labs and homework) that were done sort of on time
but were not turned into the black box before grading started
(this does not include assignments that were not done until today)
(always done
before class)
nothing new
we didnt finish last friday's stuff

things you should know the answer to before coming to class
see friday questions

(written assignments

to be turned in)

absolute last chance to turn in any assignments is today

web stuff

star formation:

star formation propagation
(grav collapse induced by shock wave from O/B stellar winds)

M16 before hubble
 Star-Birth in M16
the Eagle in 2005

shock-wave triggered starbirth
Hubble presents a family portrait of a parent and 6 offspring

star death/supernova:

Cygnus loop shock wave

spiral shock waves in galaxies:

M51 as seen by Hubble 2005

M83's emission nebulae and its spiral arms

  cloud-cloud collisions:

a bow shock near LL Orionis

the Antennae, a galaxy-galaxy collision

molecular clouds & cooling

molecules in space

how stellar disks form and evolve
(theory in pictures)

the first observations of jets and disks during stellar birth 

stellar Disks and Jets

  12-c-yr long jets

Stellar Disks Set Stage for
Planet Birth in New Hubble Images

disks without jets: planet building?:

10 years ago we had 1; now,  hundreds

the original discovery of proplyds in the

Orion Nebula

Orion Nebula Mosaic and
Protoplanetary Disks


news, discoveries
 of the week

February 8
February 9
February 10
February 11
February 12

short classes
last (or 2nd last?) jit of the trimester is now available in moodle...
due by 1 pm

remember that you are to use no other source besides articles contained within the JIT or the text

make sure that you haev your green book & calculator

(always done before class)

21(3), especially figure 21-9

pp. 407 - 408
& the atmospheric-neutrino article


did you do tuesday's reading?  21(3)


things you should know the answer to before coming to class

see the questions in last friday's slot....
we didnt make much progress

how do astronomers KNOW (with observational evidence to back it up) that massive main-sequence stars live less long than less massive stars?

you (with your table partner) will get to calculate the red giant lifetime based on the calculation we did in class friday (for main-sequence lifetime)    be prepared!
it's a quiz!

how can tell the age of a star?

how would we calculate lifetimes of other phases of a star's life?
(we've already done main sequence and red giant in class)

have we proved that chemical burning cannot have powered the sun for its lifetime?

questions imspired by yesterday's class:

so what is the charge of the weak force?
(what is that you have to have to participate?)

how did Mr. Davis collect the handful of Ar atoms from the huge chlorine tank?  not something i want you to look up, but use your chemistry knowledge:
what bonds best with argon?

look again at the  3 tables we looked at in class today on page 21 green book:

why is it that one of the reactions in the middle table, has a target area (cross sectional area) of zero?
how can that be?
(hint: the answer is in the 3rd table!)

the big question:
what are the 3 generic explanations for why experiments on earth have not detected the expected number of solar neutrinos?

how are the atmospheric neutrinos (in the weighing the neutrino article) produced?  what process makes them?

stellar birth questions:

what are some on the objects out there that seem to be in the process of star making?
what's in the interstellar medium?

what are the 3 types of nebulas present?
how do each of them show themselves?

how do we know they are there?:

what are 3 pieces of evidence for the presence of interstellar dust?

ditto for interstellar gas?

what condition(s) would require a star to contract?  to expand?
(hint: it's an inequality!)

what controls each side of the inequality?

(written assignments
to be turned in)

"your fusion" reaction assignment due

sign up for your reaction on the bulletin board OUTSIDE the physics hallway (just around the corner from the elevator)
[the sign-up sheet is page 25 in your green book;  follow exactly the procedure i showed you in class!

1) name & show the three integer conservation laws

2) calculate the KE/light released (or absorbed?) in Mev in the nuclear reaction,
following the same steps we did in class

3) calculate the efficiency of the reaction

if any of your nuclei are not in Appendix F in Walker,
find the mass (in u) here
(type your isotope, for example C-12, in the box at the upper left)

start EARLY, so that if you end with questions, you can come get help!

show and tells we would really like to see answers to before the course ends:

how hot does it have to be for fusion in the sun?
we know the energy of the coulomb barrier at the protons' closest approach to each other.... how much KE is needed to get over it?

how long could the sun have lasted on all the gravitational energy it has released in its lifetime?

how long can the sun last on chemical energy?

how big is the orbit of Nemesis,
the sun's possible companion?
would it be visible in binoculars?
a small telescope?

bring to class

a circular cutout representing your extrasolar palnet

with diameter = 10 cm*(Myp/MJ)

with color of the cutout determined by the temperature of your planet
black = 0 - 300 K
violet = 300-500K
blue = 500 - 700 K
green = 700-900 K
yellow = 900 -
1100 K
orange = 1100 -
1300 K
red > 1300 K

also write on your circle:

1) your extrasolar planet's orbit radius in au

2) your extrasolar planet's star's luminosity relative to the sun

web stuff

the first neutrino image of the sun

Super-Kamiokande and its photomultipliers surrounding the water (before it was destroyed in a chain reaction)
are periodic extinctions really caused by a companion to the sun?
A Scientific American debate

A UC-Berkeley discussion

binary star lab due

have you entered you star radii in moodle?
(moodle slots opens at 6 am saturday)

of the week


February 1
February 2
February 3
February 4
February 5
also, bring to class TOMORROW (wednesday)  a printed copy of your extrasolarplanet's (starr's) radial velocity curve

start early, because some curves are harder to find than others

as instructions say, first try clicking on the data links to your extrasolar planet star in either of the two encyclopedias...

if that doesnt work, there is always google

if after 15 minutes, you still havent found it, write me
(although not later than 9 pm tonight)....
jit is now available in moodle due by 10:45 am

for the rest of the trimester:
please do not come to class without a calculator or your green book....
if you do, you will be sent back and an automatic tardy or severely tardy will be assessed

in addition to your green book & calculator, make sure you  have your particle physics handout AND your radial velocity curve

bring to class today your  binary star lab book which contains everything up through part C of the lab (radii of the two stars)

also, please think carefully about (because no one came up with the correct answer last time)

the deeper eclipse is always the eclipse of the __________ star
by using the star cutouts and thinking carefullly about the answer to the question:
in which eclipse (primary = deeper or secondary) is more area covered?
(are you using your star cutours?)

(always done before class)
the search for dark matter

moodle readings include
a different search for dark matter article
(Scientific American
March 2003)


The Universe's Invisible Hand
on dark energy
(Scientific American
February 2007)


Did Dark Matter Power Early Superstars?
(Sky and Telescope
March 2010)

a new topic:
the interior of stars,
particularly the sun

Walker 15(2 on Pascal's principle.... how does pressure vary with depth?)

Walker bottom of p. 549-551
on the derivation of the perfect gas law
18(1) for the JIT

18(2) since we didnt get to it yesterday

18(4)  and pages

things you should know the answer to before coming to class

the first questions I will ask in class:

how does pressure vary with depth in an incompressible fluid?

where does the perfect gas law come from?
why does pressure depend on temperature and on particle density?

see questions
what is the strong force's strength
(relative to the electric force)?  what tells us?

from Universe:

how did the temperature get to be so high at the center of the sun so that fusion could start?

what if fusion slowed down in the sun (compared to its present rate); what would happen?

what if fusion sped up and produced more energy than presently; what would happen?
(for both questions, connect the dots) 

why doesn't the sun collapse under its own gravity?

why does the gas pressure increase with depth in the sun?

why does the gas temperature increase with depth in the sun?

why does high density and high temperature produce high pressure?
(what's the physics?)

how does the energy released in fusion get to the surface?
by what processes?

from the end of yesterday's class

what were the 3 mistakes we made in sun's main-sequence lifetime calculation that we did right at the end of yesterday's class
(in making each mistake, we allowed the sun to live longer than it actually does)

new questions from the new reading:

what are the 2 or 3 DIFFERENT ways that we can detect neutrinos?

what is the flux of solar neutrinos at earth?

why isn't it easy to detect neutrinos?

questions we didnt get to yet:

how did the temperature get to be so high at the center of the sun so that fusion could start?

what if fusion slowed down in the sun (compared to its present rate); what would happen?

what if fusion sped up and produced more energy than presently; what would happen?
(for both questions, connect
the dots

how does the energy released in fusion get to the surface?
by what processes?

(written assignments
to be turned in)

have you selected your extrasolar planet and posted your choice in moodle?

extrasolar planet homework
(start early... it's fairly long)

moved to friday--->

web stuff

European catalog of extrasolar planets

Princeton catalog of extrasolar planets
for help in your homework due thursday

here's another extrasolar planet catalog I found that has more direct links to the original data and is organizable (clickable) by different parameters (period, orbit size, mass, etc) by clicking on the column headings at the top of the page


binary star lab due monday
of the week

january pages
december pages
november pages