Prelim Rules

The Prelim is an oral examination conducted by three members of the Department appropriate for the fields in which the student will be examined. The Exam may be taken at any time the student chooses, subject to the regulations listed below. In setting the time of the Exam the student should consult the Department Chair at least one month in advance of the proposed date concerning the topics and the Prelim Committee. The examination will be at the general level of the graduate core courses. Normally, the topics consist of three fields chosen from among the list of courses in the core curriculum. The student may choose to be examined in another topic at a comparable level of difficulty. Typically, the topics of a special topics class (AY 250) may be used as a preliminary exam topic. In the past, other topics have included:

  • Stellar Atmospheres
  • Stellar Structure & Evolution
  • Stellar Dynamics & Galactic Structure
  • The Sun

The prelim is subject to the following rules:

  1. The prelim can be taken at any time before the end of the student's second year. The exam may be re-taken only once. Taking a course in the subject to be examined is not required.
  2. Any faculty member can be asked by a graduate student to administer the prelim exam. Unless that faculty member is on sabbatical or on ASMD (active service modified duties; typically parental leave), they are generally expected to serve. The composition of the prelim committee should be decided in discussions between the student and the relevant faculty, with oversight and advance approval by the head graduate advisor.
  3. A prelim committee member need not have taught the class in the subject the student wishes to be examined in. Furthermore, the faculty member administering the exam is not obligated to model their questions after another faculty member's course. The spirit of this rule is that the Prelim is not just an “oral exam about 3 classes taken.” The exam seeks to assess the ability of the student to conduct an intelligent conversation about astrophysics — e.g., about galaxies, broadly construed. The questions asked can be of a broader scope than the material covered in a particular class. This kind of intellectual stretching is encouraged — to become a capable researcher one has to “go beyond the problem set” and be receptive to all sources of information (e.g., seminars, conversations, and papers that are not formally part of a course but which are still fairly classified under the heading of “galaxies”). It is the responsibility of the prelim committee members, and in particular the chair of a given prelim committee, to decide whether the questions that are asked are fair.
  4. Every graduate student who wants to take the prelim is required to fill out a form listing topics and examiners, to be approved by the head graduate advisor. The idea here is that the head graduate advisor can assess whether the proposed prelim is sensible, and consult the faculty as necessary if questions arise (e.g., whether certain Astro 250 Special Topics are permissible to use as prelim topics; whether certain combinations of topics are permissible; whether certain examiners — non-Senate faculty — can serve; whether an exception to the usual rule of three examiners can be made). This form is available from Dexter and should be completed in consultation with the head graduate advisor, well in advance of the actual exam.
  5. Faculty members on sabbatical or ASMD can be asked to serve on prelim committees, but whether they agree to serve is at their discretion. Note that according to the UC Academic Personnel Manual, “an individual on regular sabbatical leave is excused from all regular duties to enable full-time effort to research and/or study.”
  6. In order to remain in the Department a student must pass the Prelim within six months after the end of the second academic year.
  7. It is recommended, but not required, that the prelim committee members not include the student's research advisor, to avoid conflicts of interest. For example, the research advisor may have an interest in having the student pass, or find it awkward to fail the student; or the student and advisor may have a ready rapport and a practiced means of communication going into the exam, advantages not necessarily enjoyed by other students. However, this is a recommendation, not a requirement, as there are only so many instructors of core graduate classes.
  8. Embargo policy: Questions asked in any given prelim are embargoed (they cannot be shared with other students) for three months following the exam. The purpose of this rule is to lessen the pressure on faculty to devise new questions in a short period of time.
  9. The student must pass all three areas in order to pass the Examination. A pass is equivalent to the level of performance meriting a “B” grade on any of the graduate core courses.
  10. The student selects one member of the committee to serve as the Chair of the Committee. This Chairperson is responsible for timing the examination and any necessary paperwork following the examination. The student selects the order in which the topics are examined.

NOTE: The faculty are modifying the embargo policy. Not set in stone yet (as of 1/19) but the embargo is tentatively going to be a year.

The Student Affairs Officer maintains a comprehensive list of all topics and questions asked during the preliminary examination. Typically, each topic is alotted 40 minutes of questions for a total of two hours.

Upon completion of the prelim, you can earn a master's degree. If receiving the degree immediately is important to you, you will need to file a form with the university at the beginning of the semester you want to receive your degree (e.g. February for a spring degree or September for a winter degree). See the post prelim section at the bottom for more details.

Past Prelims

Click here for prelim questions until 2015.

Click here for prelim questions after 2015.


Click here for advice on how to pass your prelim without going nuts.

Prelim Lore

The prelim is an oral exam generally taken at some point during the second year (can be taken as late as December of your 3rd year). It's roughly a “master's exam,” in that after passing it (and completing the required coursework), you can pick up your MA. (You can even walk in graduation if you like!) The exam covers three astronomy graduate courses of the student's choosing; each subject is given by a professor of the student's choosing and is 40 minutes long, for a 2-hour-long exam.

Preparing for the Prelim

Choosing Topics

The prelim consists of three subjects; these almost always correspond to astronomy graduate courses. Most courses can be used as prelim topics, but there are several exceptions that you should know about. In case of doubt, talk to the Head Graduate Adviser (who, if also in doubt, consults the faculty as a whole). You are, in any case, required to complete a prelim application form and obtain the Head Graduate Adviser's approval of your topics.

Restrictions include:

  • You can't take a prelim in both Radiative Processes (201) and Fluid Dynamics (202), on the grounds that not enough astronomical phenomenology is covered.
  • You can't take a prelim in Numerical Techniques (204) (ditto above)
  • Prelims in Computational Methods (255) and Plasma Astrophysics (267) are discouraged (ditto)
  • You can't take a prelim in both ISM (216) and Star Formation (Steve Stahler's 250) (too much overlap)
  • Most seminars (250 classes) can't be used for prelims
  • Physics courses generally can't be used for prelims, with possible exceptions
  • Starting in 2019, the undergrad course Astro C161 is sufficient background for the cosmology prelim. Physics 229 may also be taken for the cosmology prelim, although it is more advanced and focuses more on research.

Prelim topics do not need to be topics that you plan to concentrate on in your thesis. Some people use the prelim as opportunity to become fluent in their research area, but others use it as a chance to study a topic that they would never otherwise learn in great detail. The choice is yours.

Choosing a Committee

Each professor on the committee is responsible for a single topic. In general, people ask the professor who taught them a subject to administer the prelim for that subject, but this is not required. Any professor can be asked to give any topic, although for a given topic, it makes sense to stick to professors who have taught that course at some point or who work in that area. (There is a UC rule that your research advisor cannot be on your committee; in the Astronomy department, the faculty may strongly encourage you to avoid your research advisor when choosing your committee, out of concerns of fairness, but they will not enforce this rule.)

When choosing a committee, you also have to ask one of the members to be chair. The responsibilities of the chair are:

  • To take care of general administration (this includes picking up your case folder from Dexter's office before the exam, and dropping it off afterward)
  • To make sure that questions are well-posed and fair
  • To enforce time limits (40 minutes per topic)
  • To establish consensus among committee members about the outcome of the exam

While the chair does have the above duties, in practice he or she acts just like the other committee members and has no additional authority.

Organizing the Exam Day

You are responsible for coordinating all the logistics of your exam, which includes asking people to serve on your committee, finding a date and time that works for everyone, and reserving a room. Because professors schedules tend to be rather full, it's worthwhile to begin asking people to serve on your committee 2-3 months in advance and to set up a date as soon as you've chosen your committee. If you plan on taking your prelim during the summer, you should start even earlier than this, since some people go away for large parts of the summer.

Once you've arranged for a date and time, you need to book a room for the exam. This can be done with Mark. Most prelims occur in Room 419, Room 501B, or Room 219. You should book the room for at least an extra half hour after your exam, to give the committee time to talk with you afterwards and to give you time to clean up.

You also need to let Dexter know your prelim date, so that she can prepare the appropriate paperwork. She will put an assessment sheet inside your file, for your committee to sign after the exam. After the exam, she will send you a paper that needs to be filed with the university in order to be issued the masters degree.

The only paperwork you need to complete before the exam is the prelim application form which can be found here.

Study Materials

Most people study from some combination of the following: class notes, flash cards, and previous prelim questions. Class notes are especially useful if the professor administering a certain topic is the same one who taught you that topic. If not, it is also useful to borrow class notes from someone who did take the course with that professor. Flash cards can be helpful as well, since during the prelim, you'll be expected to have most constants and equations at your fingertips. You should definitely look at previous prelim questions while studying. Dexter has two binders of these in her office (going back to the 1970s!). These can be borrowed essentially indefinitely. A wiki version is under construction. Studying generally occupies the better part of the month prior to the exam. Click here for tips and advice from specific students.


Your fellow grad students are happy to help you prepare for the prelim! Most people take a practice prelim, with a fake committee composed of post-prelim grad students; this helps prepare for both the material and the format of the prelim. The practice prelim is generally taken a few days to a week in advance of the actual prelim. It is identical to the prelim except that the committee is composed of grad students and the results don't count.

The practice prelim can be organized only a week or two in advance, but make sure to leave enough time for your fake committee members to make a good list of questions. Your fake committee should be as close to your actual committee as possible; for each professor and topic, you should try to get a grad student who works in that area (with that professor, if possible) and who has taken that course (as a prelim subject, if possible). Most people find the comments of the fake committee extremely useful in preparing for the actual exam.

Your fake committee may include students whose prelim questions are still under the three-month embargo, provided that they don't ask any embargoed questions during your practice prelim.

Don't forget to book a room. And to bring food for your fake committee.

The Day Before

The day prior to your exam there are three things you should do: remind your committee, buy food, and ask Amber to put your folder together. Your committee members will likely not remember the exact date, time, and location of your prelim, so you can avoid a little confusion by sending them a subtle reminder email. It's also nice to ask if they have any specific food preferences. (You can also ask your fake committee for professor-specific food recommendations.) Don't forget to get/make food for your committee; they expect to be fed! Most people bring snack food, healthy and otherwise, and some juice. Also email Amber to let her know that you're taking your prelim so she can put your folder for the chair.

During the Exam

The Exam Process

You should arrive for your prelim a few minutes early, to test that all the white-board markers work and to set out the food. With a little luck, your committee will all arrive on time, and the chair will bring your file. Your file contains your transcript and any other official documents relevant to your progress as a grad student thus far. The committee will then send you out of the room for a few minutes to look over your file and discuss you. They'll call you back in, and then the fun starts!

You get to choose the order of your prelim topics. Conventional grad student wisdom is to put your second best subject first, your worst subject second, and your best subject third. You will tell your committee of the exam order right before the exam starts.

Each professor has 40 minutes to examine you on their subject. Occasionally, the other members will interject with additional questions. You'll be expected to give some qualitative answers and also to do some math and/or plotting on the board. While each professor questions you, one of the other committee members will be recording their questions. In general, nobody makes notes on your performance during the exam.

At the end of the prelim, the committee will again send you out of the room while they decide whether or not you pass. If you let your fellow grads know the time of your prelim, they will show up to cheer you on while you wait. The committee sometimes discusses for only a few minutes, sometimes for much longer. The length of time they talk has very little to do with your competence or performance.

The committee will then call you back in, to tell you whether you passed and their general thoughts on your performance in the exam and as a grad student in general. You can pass or fail all three subjects independently. If you pass all three, they will all sign the assessment paper in your file and return the file to Dexter. If you fail any or all of the three subjects, you can retake the exam in those subjects; you're expected to wait about a month before retaking the exam. Failing happens occasionally, but in current grad student memory, everyone who's failed the prelim the first time has passed the second time. Once your committee has finished chatting with you, you clean up the food and the boards, and then you're done!

A Little Prelim Wisdom

Everyone has their own prelim wisdom, and it's helpful to ask around to get those gems of knowledge. Here's a little list of things that others have found useful:

  • Talk first, write later. If possible, give a concise, conceptual answer to each question before you turn around and start writing on the board. Professors care much more about your conceptual understanding of the topics than they do about your facility with math. Frequently they'll be satisfied with a two-sentence oral answer and will ask you to go on without writing anything down at all!
  • However, you shouldn't be afraid of writing on the board, and don't be afraid of taking time to work through calculations. When you do write on the board, write neatly, starting on the top left side of the board, and keep your writing organized. This will help you to successfully identify the inevitable algebra mistakes that you will make.
  • A sneaky way to buy some time while thinking about a question is to wait to erase the board until after a question is asked (as opposed to erasing it between questions).
  • Avoid the statement “I don't know”. Instead, when stumped, talk through your thought process; detail what you do know and what you're stuck on. This gives your committee a better idea of your understanding and usually opens a window for further questions that lead you to the answer.
  • Don't confuse the above advice with a license to BS. If you have no idea what you're talking about you should not talk for the sake of talking or avoiding saying “I don't know”. The point is to show them what you DO know, even if it's not precisely what they asked, so that they can nudge you in the right direction.
  • Make sure you understand the question. Ask for clarification if you're not sure. It's very easy to misinterpret a basic question as something fantastically arcane and then go babbling on about something unrelated to avoid saying “I don't know”.
  • Upon answering a question correctly do not proceed to volunteer additional information to make yourself look smart. This will inevitably lead to trickier questions and more detailed nitpicking. Plus, you can very easily be wrong!
  • Bring a water bottle. Talking for two hours makes you thirsty.


Click here for personalized prelim wisdom from grad students who have made it through the fiery hoop.


Once you passed your prelim, there are just a few things that you need to do. The first is compile the questions you were asked. Your committee will give you their hand-written notes from your exam; these should be typed up and given to Dexter to add to the binders of prelim questions. You should also add them to the wiki once the 3 month embargo is up.

Dexter will also send you a form that should be filed with the university (via Dexter); this form lets the university know when you expect to earn your masters degree. Degrees are issued in both December and May. The form needs to be filed at the beginning of the semester in which you plan to earn the degree. If, for example, you take the prelim at any point during the spring semester and getting the degree asap is important to you, you should file this form in mid-February. If getting the degree asap is not a priority, just fill out this form once you've passed the prelim and your masters will be available at the end of the following semester. For more information, visit

Now take a vacation; you deserve it!