Astronomy 16: Modern Astrophysics

Prof. David Cohen

Fall 2014
Tu., Th. 9:55 to 11:10
SC 113 (seminar room)


Omega Cen Pleiades Arp 188 Eagle Nebula





posted 10/29

There are some stellar spectra and binary orbit simulators, below, for you to look at in preparation for Thursday's class (along with finishing up reading Ch. 13).

posted 10/25

The homework is due on Tuesday in class, and there will be an SA session on Monday, in SC 102, from 7:30 to 9:30, as well as office hours on Monday afternoon (posted on the right). Update 10/26 note that the full homework assignment is now available.

There will be no lab meeting this week, but I will be taking data for each of you, based on the objects you've chosen to observe. Stay tuned for that, and also stay tuned for a new reading assignment (but to begin Tuesday's class, we'll finish up the material in Ch. 14, especially focusing on the HR Diagram).

Archive of old announcements.


posted 10/29

In preparation for (and follow-up after) Thursday's class, spend a few minutes building binary systems and seeing how their properties affect their observables: eclipsing binaries and their light curves; spectroscopic binaries and their radial velocity curves. You will need a working version of Java on your computer to use that second one. Also, take a look at these examples of stellar spectra of different spectral types and also look at these detailed stellar spectra, comparing zoomed in portions of the Sun's spectrum to the spectrum of the hotter star, Vega. Finally, here are quite a few examples of real stellar spectra that cover most of the full visible range. Can you see the extent to which these spectra resemble blackbodies and the ways in which they deviate from a perfect Planck function?

posted 10/26

A shorter-than-usual reading assignment for the week is now available. Binary stars and stellar masses is the new stuff, but the HR diagram and the magnitude system, already assigned last week, is what we'll spend most of Tuesday's class on.

Also, take a look at this annotation of Fig. 13.11 - the mass-luminosity relationship, which we looked at in class on Thursday, and from which we fit a power-law with index 4. If you want to reinforce your understanding of how that's done, have a look at mine. And take another look at the spectral type sequence, including the description underneath the image and look back over the corresponding information in the textbook (Sec. 14.2).

spectral type sequence

posted 10/25

Our fifth homework assignment is partially available. Two more problems will soon be added. It's due on Tuesday, October 28, at the beginning of class. Update 10/26 The full assignment includes two additional problems, on the magnitude system, which was in last week's assigned reading, and which we'll go over in class on Tuesday.

Following up on our lab meeting last week, you should each send me the name of an object you'd like to observe, as well as an airmass plot for it and an annotated finding chart. Here are the resources I've posted over the last week or two: this short article with many pictures about M17; the airmass plotter (the airmass is the cosecant of an object's altitude); and the tool for making finding charts.

Archive of old assignments.

Upcoming Events

Check the departmental colloquium schedule. You should come to these talks. They are typically Friday at 12:30 in Rm. 199, and include pizza.

There are telescope public viewings the second Tuesday of each month, at the Peter van de Kamp Observatory on the roof of the Science Center. The next one is on November 11, at 8 PM. Astro 16 students are welcome to come and help out. It is also an excellent opportunity to show your friends the observatory and the view of astronomical objects through our telescope.


Class Information

Read the class announcement [pdf]

A syllabus [pdf] (Updated 10/14) is available
note that it will be periodically updated

office hours for week 8


Astronomy Picture of the Day

Messier 42; with links to articles about each Messier object

Physical constants and astronomical constants from the appendix of our textbook

what's up in the sky this week

Stellarium software for making sky maps

gravity simulator

Planet Crash

using your hands to measure angles

sky and weather information

observatory website

department website



This page is maintained by David Cohen
cohen -at-

Last modified: October 29, 2014