Thursday, June 7, 2012

Pulsar Girl

I arrived in Charlottesville on Sunday, HOURS later than expected, because (1) the hot air balloon was going too fast to land, so we ended up bouncing around Pennsylvania for a while, and (2) our GPS died en route so I had to call a friend and get him to navigate us over the phone. Good times were had by all, as you can probably imagine.

Anyway, I got here eventually, and met my house-mates: four of us (all girls, and all summer students at the NRAO) are subletting a house together. They're perfectly nice (and nerdy! yay!) - and they like to cook, which makes me feel very at-home. Between the four of us, there is a constant supply of recently-baked goods on the counter, which makes me feel even more at-home. There is also meat pie and sesame noodles in the fridge, courtesy of moi, which has also done wonders for the at-home-ness. One of the girls, Molly, is also a musical theater person; in the car we listen to Book of Mormon and Avenue Q, and sing really loudly. :)

Now. Pop quiz. What are all of these buildings?

Museums? NO! Mansions for rich Charlottesville aristocrats? NO!

These are frat houses. Mind-blowingly fancy shmancy frat houses. I took those pictures en route from home to work, since apparently I live in the middle of UVA Frat Boy City. Lots of guys in polos and khakis around. It's very peculiar. But yeah, seriously - SUCH FANCY FRAT HOUSES! I can't get over it.

Anyway, enough about the frat boys, and more about THIS AWESOME PLACE:

I started work on Monday, and at this point have a pretty good sense of how each day is going to go. I work from ~9-5 or 10-6, depending on when I manage to drag myself out of bed. The NRAO is super-chill and it's totally up to us when we arrive - some of the astronomers don't show up until after 10. I walk to and from work (it's about half an hour each way), because Charlottesville is gorgeous and otherwise I would get fat.

Lunch is at noon - all the summer students + some of the scientists and staff congregate in the library to eat together. Occasionally, I eat lunch at my desk, because it can be hard to tear myself away from a calibration, but I realize that that's super-lame and try to avoid it.

Astronomers are awesome people. My supervisor is a rock-climbing beast with two adorable children (one of them is graduating from middle school tomorrow, so he's going to be late for our group meeting. I suggested that we conduct the group meeting at the graduation. He lol'd because he thought I was joking. Clearly he doesn't know me very well.)

Now. Let me tell you about pulsars.

This little guy is named Terzan 5. He's a globular cluster (and male, I've decided) which basically means that a bunch of stars are attracted to each other, and orbit the galactic center as one happy family. At least 34 of these "stars" are millisecond pulsars, which is my supervisor's area of specialty. For those of you who don't know, a pulsar is a dead, spinning remnant of a star. When a star of a particular size supernovas, it leaves behind a ball of neutrons ~the size of Manhattan called a "neutron star" (a misnomer, since the fusion party is long over.) Physically, it's a spinning spherical dipole. Its magnetic field somehow generates a jet of electromagnetic radiation that happens to fall in the radio spectrum (because of the rotation period). Millisecond pulsars are so-named because their periods are on the order of milliseconds. The whole business looks something like this (picture stolen from the NRAO website):

...Aaand now, congratulations! You know almost as much as pulsars as anyone, since scientists don't know a whole lot more than what I just described. We don't even know the details of how they generate that magnetic field, or how said magnetic field generates the jet of electromagnetic radiation. There are only about 1600 pulsars known, which is why Terzan 5 was such a goldmine. One of my projects this summer is to go through some brand new Terzan 5 data and find more pulsars.

Another project is to deal with something called Faraday rotation. Turns out that the Milky Way has a magnetic field of its own, which, as you can probably imagine, is troublesome for the whole radiation-traveling-through-space-in-a-reliable-fashion thing. Pulsars emit linearly polarized radiation, which acquires a phase shift due to the Milky Way's magnetic field before it gets to our telescopes on Earth. We call the phase shift a "rotation measure", and it's something we can (sort of) calculate.

I could talk about this forever, so I will instead switch gears and tell you a little about what I actually do. Astronomy nowadays is a lot of computer and very little telescope. My job involves a lot of UNIX magic (I've become infinitely more competent at making the terminal do my bidding, which isn't saying very much, since I was 0% competent before) and becoming intimate with PSRCHIVE, a piece of pulsar data analysis/calibration software that the postdoc I'm working with helped write.

One particularly cool technique involves a quasar, and a diode (one of the most energetic, mysterious, ancient objects in the universe...and a little piece of electronics! how poetic). To summarize: the telescope picks up the radiation using two orthogonal receivers, in order to get the range of possible polarizations. However, the raw data doesn't come with any useful (physical) units - just relative sizes. We need to calibrate it. There are a bunch of quasars up there that are very well-studied; at this point, we know exactly how much radiation we receive from them. The amount of "noise" emitted by a diode is totally within our control. So! We inject periodic square waves of noise into our pulsar data, using the diode. We do this while looking at the quasar, and then while looking at a neighboring patch of empty sky. We calibrate the diode using the quasar, and calibrate our raw pulsar data using the diode.

...I think.

Also, does it blow anyone else's mind that we are able to receive a distinct signal from a little spinning ball of neutrons that's like...six hundred millions times as far away as the Sun? My brain explodes every time I think about it. We use Fourier transforms to do it! A bunch of information from different sources all mixed together and jumbled up in time - but not in frequency-space! PHYSICS IS GREAT <3

And astronomers are hilarious. They drink a lot of coffee. Not just *a lot* of coffee. A LOT OF COFFEE. I think they each drink something like twice their own body volume in coffee, daily. I am the ONLY PERSON who doesn't drink coffee. Currently, I compensate by drinking ~three times my body volume in hot chocolate, daily.

The office situation is pretty entertaining. The summer students are split into two rooms with six desks each. My office, 205, has four boys + me. The other office, 211, has three girls + one lucky guy. Well done, whoever figured that one out. 205 > 211, though - we have a sign on our door that says AWESOME PEOPLE ARE HERE, which just about settles it.

On a final note, my office-mates have taken to calling me "pulsar girl." I admit it would be pretty cool to be able to spin hundreds of times per second while shooting beams of radio waves at people.

And now, off to sleep! We have our first group meeting tomorrow, and I have to present what I've been up to since I arrived, which will involve showing a very weird result that I don't understand at all (my understanding of all this calibration business is still pretty limited.) I'm terrified that it'll turn out that I actually just made a mistake, and it's not only not weird, but also not particularly interesting.


One last thing (this is actually the last thing) - did anyone get to watch the Venus transit? Charlottesville was clouded out. I was furious.

Vous me manquez beaucoup!

Avec amour,

Pulsar Girl.


  1. Yay Charlottesville! It's a very pretty place, possibly because downtown is mostly dominated by UVA.

  2. I did! I did! (the Venus transit, I mean). We went to the US Space & Rocket Center Venus transit viewing party. It wasn't much of a party. But it was cool.

    your research is awesome. I'm slightly jealous. :)

  3. With respect to Fourier transforms, I think you mean *math* is great! Ben, Adrienne, Lizi, Davie, and I watched the feed from the University of New Mexico to watch the Venus Transit. There was indeed a little black dot moving in front of the sun over the course of several hours.

    So have you come to your senses, realized you want to spend your life doing in physics, and going to apply to Berkeley for grad school?

    Also, just observing, since your cells are at a different electric potential than the surroundings (this is one way sharks find prey in murky water, by sensing this potential difference with Ampullae of Lorenzini) then theoretically, a spinning Anna with limbs properly arranged would radiate and so maybe you are pulsar girl.

  4. I have to admit that the NRAO is making it really difficult for me to imagine a life without doing astrophysics. Right now, I'd give an 80% chance of me going to grad school for physics/astronomy, and not medical school...though that could change with a different research experience, I guess.

    Even if I radiate, the "pulsing" thing wouldn't necessarily happen since it sounds like with that mechanism I'd be radiating evenly in all be a pulsar girl I'd need a single beam. Or a few beams. It's a nice thought though.