Astrophysics falltrimester  2006

 syllabus   &  course expectations

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

November 13
November 14
November 15
November 16

news about
graded work
starbirth  homework is graded and can be picked up in the black box

hopefully the interstellar matter  (Palomar print) lab
will be graded by 6 pm today
 interstellar matter graded;
lab books can be picked up from box

block D: spectra lab has been grade; you can LOOK at your grade (individual and group) but DO NOT remove from box

final exam
tutorial from 4 - 6 pm today
Bryan 439

alternative exam time for people not taking the exam tuesday morning
(room to be decided; meet on the 4th floor Bryan)
 amnesty hours:
today 4 - 6 pm
if your lab book wasnt graded for a previous lab (because it wasnt in the box, or wasnt finished or whatever)

there sure are a lot of graded papers in the "stray paper" envelope.... if yours are still there tomorrow morning, there will be a class commitment penalty
new physics you (could have) learned in astro...

this chould help you be prepared and able to do well on
the SAT

sunspot observing 3 - 4 pm today

November 6
November 7
November  8
November 9
November 10
come to block C and watch SI present his solution to the differential equation for free-fall collapse time

(always done before class)



more about post-main-sequence

things you should know the answer to before coming to class
why the sun (or any main-sequence star) leaves the main sequence and how the changes in L, R, and T that result when a star becomes a red giant happen

why clusters are important

why do the outer layers of a star leave in the late red giant phase? what pushes it off?

why do the outer layers of a star leave in the late red giant phase? what pushes it off?
(the outer layers do not escape
solely because they are hot!)

 what are the important features of a white dwarf?

how does it evolve with time?

(perhaps, but perhaps not, we will get to discuss
a) what is this course about?

b) how is/was this course different from the intro physics course?)
(written assignments
to be turned in)
1) find, by dimensional analysis, the formula for free-fall collapse time of a star of mass M and initial radius R
(you MUST show all work starting from the equation we wrote down in class, match the units on both sides by writing down three equations in three unknowns, and then solving them.... you get minimal credit by solving them by "inspection")

2) using your dimensionally-correct formula, find the numerical value for the sun's free-fall collapse time
(assume it formed from a Bok globule)

3) in class friday, we came up for a formual for the gravitational lifetime of a cloud, by using the usual formula for lifetime ( = (grav energy lost)/luminosity);
using appropriate numerical values, find the gravitational lifetime of the sun
(which should, of course, match the value in the book)
1) email me:
how do we KNOW
(i.e., what's the OBSERVATIONAL EVIDENCE) that massive stars leave the main sequence first?

(after all, we humans  have never seen a star leave the main sequence during the time we have been doing astronomy!)

so what's the evidence?
(hint: what kind of astrophysics situation must we have that would allow astronomers to be convinced that  the more massive stars always leave first?)

2) find the RATIO of the red giant lifetime to the main sequence lifetime for the sun
(but no numbers till the end!)

in the red giant phase, the core burns
He --> C (someone in your class should have the efficiency)
the envelope burns H--> He

3) find the maximum time for a transit of Mercury.... I think you should be able to find all data needed in the Appendices
(you may make reasonable simplifying assumptions; just let me know what they are)

web stuff

red giant and planetary nebula evolution

learn even more about planetary nebulas:


magnitude lab due
of the week

a rare transit of Mercury
simulated transit of Mercury
movies and pictures
of the Mercury transit


October 30
October 31
November 1
November 2
November 3

students return from extended

faculty have countless meetings
 see yesterday's reading


(always done before class)
once you return Monday night, it would be nice if you could spend 15 minutes

matching the steps on page 25 (green book) to

1) those pictured in the
starbirth summary table


2) the figures in Chapter 20 of the text


and pages 172, 177
 see yesterday's reading

the origin of the spiral shock wave in galaxies

things you should know the answer to before coming to class

see above

figures in chapter 20
and pages 172, 177

& those listed on page 25 of green book matched to the 5 starbirth steps ("step 6" could be main sequence stars with, perhaps, planets)
in the starbirth summary table

what two "things" can a non-contracting, non-expanding  interstellar cloud do
(or have done to it) so that its energy (presently zero) can become negative and therefore begin collapsing?
(looking at the terms in the calculation of total energy should immediately tell you!
further hint: if the cloud were an isolated, closed system, its energy would remain the same
(i.e., be conserved) and thus not change its expanding/constracting/sitting still status....
therefore these two "things" must involve an interaction with the outside world)

how in practice do these two "things happen" ?  I want details!
why do starbirth objects end up shaped like disks?

why do they produce jets?

what are the sources of shock waves that squeeze the clouds?

what is the energy source of protostars?

how long do the various phases of starbirth last and how do we know?

see yesterday's questions


what does the H-R diagram of a young cluster (with star birth still going on) look like?

what is the difference between protostars
pre-main-sequence stars?
(behavior?  state of matter? appearance?)

(written assignments
to be turned in)


bring to class
(on paper, ready to hand in at the beginning of class),
a) the name of your "starbirth-related" object

b) its properties
(T, M, R, and composition)
including page number references to text ore elsewhere and/or how they were calculated

c) the kinetic energy

d) the gravitational

e) the total energy

f) whether it is collapsing or expanding & why

g) does the theoretical calculations you did fit expectations?

last chance for corrections to your board presentations on starbirth objects
(there are still some incorrect entries on the board)
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

interstellar and circumstellar molecules

the GMC at the heart Of Orion

Milky Way Molecule Map

Dark Bok Globules in IC 2944

JPL press release on first GMC caught in the act of collapse
( the NY Times article Oct. 10, 1995)

Stellar Disks Set Stage for
Planet Birth in New Hubble Images


the original discovery of proplyds in the

Orion Nebula


interstellar sugar provides clue to origin of life

 palomar print
interstellar lab due
news & discoveries
comet Swan visible in evening

 stellar sorting in a globular cluster

HII regions and star clusters in the Antennae

peeling back layers in
Cas A
 dead star creates havoc

Hubble views rare light echo
the amazing Hubble telescope
(NY Times editorial)

Hubble will be fixed
(yes, NASA finally decides in favor of science!)

october pages for astro 06
   september pages for astro 06