How to Become an Astronomer, the Basics

Being (most likely) the only person in my astronomy class that does not have any plans to be a professional astronomer, I think I can offer a unique perspective on the career path of a professional astronomer, but I can also talk about my own career goals as a chemist.  I'll start with the basics of what I think it takes to be a professional astronomer.  So here's what I think you need to do:

First, at some point, probably during high school, you need to develop a passion for math and physics.  This could be casual or maybe you get into advanced classes.  If this is during high school, doing these activities can really help your college application for getting into a top tier school. If you have the time and such, you can even start looking into astronomy, learning about the constellations and anything else you can. And then of course get into a school where you can continue your developed passion and learn more about math, physics, and/or astronomy.  You would need to decide specifically that you are interested in astronomy, take some courses, and make sure that you enjoy the work that you will need to be doing.  While you don't need to major in astro or astrophys, it can be quite helpful for showing a specific interest in the field.  Showing this interest is very important for your next step.

Applying to graduate programs can be an arduous task, but one that is vital to becoming a career astronomer, at least as I see it.  Though you may be able to find some positions as a researcher, lab tech, staff member, or something similar in academia or a related industry with only an undergraduate degree, I don't know that I would consider those as career astronomy positions.  So, grad school it is.  Of course to get in, a few really good recommendations, good grades, good test scores, and well written essays are all very helpful, and I am sure there are many things written online about how to go about getting all of those.  You'll need to find schools with PhD (or masters, I suppose) degrees offered in astro, or whatever astro related field you are interested in.  To do this, check online and ask around at your school about what schools offer good programs in what you are interested in pursuing.  Once you've found some schools, research the professors and programs there because actually knowing about the school and some things going on there can help you show a genuine interest in their program and ultimately help you to be admitted.  Then, all you have to do is fill out the applications, take the tests, write the essays, and then wait (and while you're at it, probably fill out some fellowship applications).

Assuming you get in somewhere and decide to attend a PhD program, then go to school.  This (being something I have yet to do) is where my knowledge gets much fuzzier.  Depending on the school and program, you may have a year or less working with different groups/professors on campus looking for something that fits your personality and will be something you enjoy doing for the next several years.  This can be a very important decision because if you choose something uninteresting, it will be hard to stay motivated.  If you don't fit in well, you could hate going to work every day.  Luckily, most people (from what I hear) find somewhere they really like working with research they really like doing.  From that point, just get to work.  It will probably take several years to get through a PhD program, but that's the way it is.

After that, I now get to start making guesses.  Considering the term "post doc," go for that next.  These tend to be positions where you are generally still in an academia setting, somewhere between a grad student and a professor.  You'll work under a professor still but you'll also enjoy greater standing than most grad students.  It seems that during this period of your life, it's just your job to pump out as much work, research, and papers as you can, boosting your résumé (or CV really) for your next post doc position, and then eventually applying for faculty positions at universities.  I think in a tenure track faculty position, you start as an associate professor, then move to assistant professor.  At this point, if you like the school you are at and want to work there indefinitely, you can go before the tenure committee and try to become a full professor at the school.  From what I think I recall hearing at some point, (at least here at Caltech) you have 3 years (I think) before you have to try to become tenured, during which time you need to try to produce as much visible work as possible to help you with the tenure committee.  Assuming you then get tenure, hey you're now tenured faculty at a university! Congrats!

I don't know which step, but somewhere along the way, you became an astronomer.  Not only looking up at the stars in wonder any longer, you now know a whole lot about something going on up there, or at least somebody thinks you do.  You developed a passion for something and changed that into a career learning more about the universe around us.

Now being a chemist, personally, as far as I know, my career path will be very similar except of course I have developed a passion for chemistry, not phys or astro, and I will be seeking my PhD in chemistry.  I'm guessing that there are many more commercial/industrial/corporate positions for chemists, so I may end up leaving academia at some point, and in fact next year I am planning on taking some time off of school to work in the so-called real world.  As long as I get to be doing interesting work, hopefully on some boundary of knowledge, I will be happy with where I am.  This may be easiest to maintain in academia, but it definitely exists outside of that also.  Ultimately, I hope to make it back to school so that I can make all my friends call me doctor because isn't that all we really want anyway?

A follow up to Y Dwarfs

Below is a little thing that approximates what it would look like on a telescope to have two objects really close together in the sky with different intensities. You can slide the slider to change the relative intensity between 50 and 300. As you can see, even if the brighter spot is only 300 times the darker spot, it is very difficult to see the less intense object in the diffraction pattern of the brighter object. If you recall or look back, we found the relative intensity to be 40,000:1 for a Sun-like star compared to a Y Dwarf both around 30 ly away, so if they were as close as shown here from our point of view, they would most likely be impossible to distinguish without other methods.

Viewing this will require installing the free Wolfram CDF viewer available here.

Created with Wolfram Mathematica 8.0

Observing a Y Dwarf

Today, let' s look at a type of astrophysical object known as a Y dwarf.
Y dwarfs (n.b. not dwarves) are a recently discovered subclass of brown dwarfs that have an apparent temperature of around 350 K.
In this case we will be looking at one close to a Sun-like star to see how difficult it might be to detect one of these.

Using the blackbody curve for an object at 350 K,
${\lambda }_{\max }=\frac{b}{T}$ Where b = $2.8977685\left(51\right)\times {10}^{-3}$ m·K
∴ ${\lambda }_{\max }=8.28\times {10}^{-6}m=8280\mathrm{nm}$   which is in the far infrared
This is around the wavelength you would want to be looking at to detect this type of object.

Now, we want to think about how many photons we could actually see from the Y dwarf compared to the Sun-like star.
Let’s assume that the star has a radius equal to the Sun’s and that the dwarf has a radius equal to Jupiter’s.  Also, let’s say that these objects are both about 30 light years from where we will detect them.
To figure this out, we will need to use Planck’s Law:
$B_{\lambda }\left(T\right)=\frac{2hc}{{\lambda }^5}\frac{1}{e^{\frac{hc}{\lambda kT}}-1}$    where B is the spectral irradiance in units of ergs per steradian per ${\mathrm{cm}}^2$per wavelength in cgs, h is Planck’s Constant, k is Boltzmann’s Constant, and c is the speed of light
Using this, at ${\lambda }_{\max }$a Y dwarf has a spectral irradiance of
$B_{{\lambda }_{\max }}=$$2.15\times {10}^8$ergs ${\mathrm{sr}}^{-1}{\mathrm{cm}}^{-2}$
To find the number of photons per ${\mathrm{cm}}^2$ per second at a distant of 30 ly we need to multiply by the visible surface of the Y dwarf, then multiply by the solid angle subtended by 1 ${\mathrm{cm}}^2$ at 30 ly, then divide by the energy per photon at this wavelength:
$N_{\mathrm{photons}}=2.15\times {10}^8*\left(\pi {R_{\mathrm{Jupiter}}}^2\right)*\left(\frac{1}{4{\pi \left(30\mathrm{ly}*9.46\times {10}^{17}\frac{\mathrm{cm}}{\mathrm{ly}}\right)}^2}\right)*\left(\frac{1}{\frac{hc}{{\lambda }_{\max }}}\right)=14\mathrm{photons}{\mathrm{cm}}^{-2}{s}^{-1}$
This is clearly not very many photons
Doing the same calculation for the Sun-like object at 5777 K (but still at the same wavelength):
$N_{\mathrm{photons}}=552000\mathrm{photons}{\mathrm{cm}}^{-2}{s}^{-1}$

Looking at these numbers, it is easy to see why it would be very difficult to detect a Y dwarf next close to a Sun-like star (especially when you consider uncertainty in detection and possible error).  The ratio of photons at our detector is 41,000:1; that’s 40,000 photons from the Sun-like star to every photon from the Y dwarf, every second.

This was worked on in class with Cassi, Lauren, and Joanna.

Created with Wolfram Mathematica 8.0