So, you want to be an astrophysicist? You're an undergraduate, doing astronomy or physics (or possibly engineering, mathematics or computer science, or something), should you go to grad school?
Why is there even a question?
Well, it is several years of your life, earning minimal pay, doing some grind work, including classes (1-2 years at most institutions) and exams (most places have some "admission to candidacy" hoop), with interesting but uncertain career prospects.
And you have to do research. Supervised, but independent and original research.
Not everyone wants to do that.
You can do stuff with a BSc or MSc, like start to earn money, and still be involved in research. In very rare cases you can get promoted through to full professor/senior scientist, and lead major science teams etc, but the odds are bad.
So, go to grad school, go for a PhD.
It is fun.
We'll deal with the practicalities later. First, what is involved.
Well, learn math.
Undergrads tend to be math phobic.
Lack of math preparation is the major reason why interested people find themselves unable to go on to astrophysics (yes, I keep harping on this for a reason!).
Not that you will be a mathematician. They are special...
Mathematics is a tool, and you need the full kit.
There are mathematicians who do physics, mostly in corners of particle theory, or, interestingly, in gravitational physics - relativity or quantum gravity, but physics is not math. Math is tautology, subtle, interesting, useful tautologies [sometimes], physics deals with "reality" with math as a tool of choice.
Now, what is there to do:
1) instrumentation - if you can build bleeding edge, high quality, fragile instruments, go for it. You'll be sought after and hopefully not too under-appreciated. Instrumentalists are always under-appreciated...
If you got the knack, you got the knack.
2) Observations - looking at stuff, using instruments... analysing data, planning observing strategies, and destroying perfectly good theories.
There's people who know about that stuff, they can address it.
Most astronomers are observers of some flavour (and most observers do some theory too).
3) Theory - are you a physicist doing astro (like astrochemist, or astrobiologist)?
Er, well, lets get back to that last one some other time?
Or are you and astronomer doing theory? Yes, one of those.
Lots of places don't even have an astronomy department, you're doing a theoretical physics PhD (like I did!) in an astronomical topic.
Even if there is an astro dept, you can still do that.
It actually doesn't matter much, in most places, whether you are in astro or physics, though it may restrict your choice of advisor a bit, but it is usually not critical.
Astrophysics that is.
Well, astrophysics covers all of physics.
I challenge anyone to come up with a sub-field of physics not relevant to astro.
You personally don't have to do it all; your goal after all is to "know less and less about more and more, until you know absolutely everything about nothing".
But it is a good start, otherwise how do you know what you're missing.
Astrophysics is data driven, there is lots of high quality data. The quality of the data is progressively improving, and there is no end in sight.
Arguably particle theory is now driven by secondary inferences from astronomical data, or astroparticle data, at least until the next generation of colliders comes on line and have some (non)results.
Why, there's even a subset of cosmologists who are really refugees from particle theory, dabbling in beyond standard model physics (with astronomical implications) and having fun tweaking Lagrangians and seeing what happens.
Then go for it.
Next, the practical details (like GRE), and the sub-fields (or some of them).
Then, eventually, what astrophysicists actually DO.
Personally I like to argue that there are several "styles" of theory, and they are complementary.
Some people disagree. Their way is the one true way...
Such is life, and they are wrong.
Thank you for posting this series, I really appreciate it.
Part of this decision involves the sacrifices one might need to make in order to pursue a graduate degree. It is almost guaranteed that one would need to move, usually across country, several times in order to go through grad school and then post-doctoral positions. People who wish to put down roots in a community after receiving an undergraduate degree, to purchase a house and have children, for example, may find that these plans conflict with their graduate education.
I ended up being assigned an advisor whose personal chemistry and mine didn't mix. [That was probably mostly my fault, as isn't uncommon for young physicists to be socially ackward]. It didn't end well for me. So I would consul that care in choosing an advisor is important.
Thanks for letting us know.