Research careers in astronomy and astrophysics require a Ph.D., a course of study which usually extends 4 to 6 years beyond the Bachelor's degree on the average. You will want to seek admission to astronomy graduate schools with research programs or major observatories. After a certain amount of time taking graduate level courses, you will generally become involved with a research program or a particular professor whose research is of interest to you. You may also obtain a research or a teaching assistantship to help you support yourself while you learn. Admission to the most prestigious schools is quite competitive.
Upon graduation, you would seek employment with major universities, observatories or government research laboratories that offer significant opportunities to pursue scientific research. Many astronomers begin their career with "post-doctoral" research positions on their way to more permanent employment.
It should also be noted that many people have found careers for themselves in fields that directly or indirectly support astronomy research by having a particular skill that is needed in a research program. To mention a few examples, a research effort at an observatory may require optical and mechanical technicians to assist in the work, data reduction specialists to help with data analysis, computer programmers and systems analysts and in some cases, draftsmen, writers, and even artists participate in shape the final presentation of results. Thus, a career involved in astronomy need not necessarily start with astronomy per se, it could begin with a skill you possess that is needed by astronomy.
The availability of jobs when you finally enter the employment market is very difficult to predict, since we are now talking about 10 or more years in the future. Few people have the wisdom to make such determinations accurately. Astronomy is still a small enough field in terms of numbers and funds, and so heavily funded by government research grants, that a small shift in government policy towards scientific research has a very large effect on the field. Over the last 30 years, the job market has fluctuated up and down. In the rapidly changing culture we live in, such variations are to be expected and are often the price of progress.
Given such uncertainties, the astronomy department feels that a program that emphasizes breadth of preparation is indicated, to try and obtain a wide range of useful knowledge and skills. This statement holds true at both the undergraduate and the graduate level. Extreme specialization may be appropriate at a postgraduate level, but at the undergraduate level a narrow orientation may leave you without options. Even if a balanced program adds some extra time to your undergraduate career, it may save you time in the long run by increasing your career options.
But finally, and probably most importantly, your primary criterion as a student should be how much you enjoy a certain area of study and how well you do in it. If you do well in a certain area, and enjoy it so much that you work hard at it, you will accomplish a good deal and have a high likelihood of ending up a successful practitioner in your chosen area, even in a competitive market. If future job security is your most important criterion for a career, then you certainly should not choose astronomy.
There are a variety of career possibilities for those students who stop with a Bachelor's degree; these were discussed in the earlier section "Why Major in Astronomy?"
For further discussion of astronomy as a career, a booklet has been prepared by the American Astronomical Society which pursues this subject in greater depth. It is available on-line at http://www.aas.org/education/careers.html