Travelogue: Random Moments from Conference Week

Cheetah Encounter: Sunday afternoon, heading towards the harbor, I was walking with a few other people and we decided to take a bit of a shortcut, that they had taken earlier. It was early enough in the week that we didn't actually know the long way around, in fact - I was just following the crowd. But our way was blocked off, by, of all things, a Cheetah. Yes, there was a live cheetah blocking our path. Sitting on a table, on a leash, held by 2 handlers, looking quite bored, and possibly tranquilized somewhat. Apparently there was another conference going on, and they had a live cheetah as some sort of entertainment, and they were holding an event right in the hotel plaza where we wanted to cut. They eventually let us by, holding the cheetah back, but I got within about 2 meters of it. NOT what I expected to encounter in the Cape Town harbor...

Kicked out of the Aquarium: The conference reception was held Sunday evening at the aquarium in the harbor, and we had a great open view into the shark tank, and around the lobby. There was also a set of unlocked doors that led into the rest of the building. So I, and several other astronomers including my advisor, naturally wanted to explore the rest of the aquarium. And it was super cool - the lights were all dim, including in most of the tanks, and we could wander around the floor looking at giant crabs, jellyfish tanks, and so on. Until we were informed that no... we weren't actually supposed to be in there. Oops! Who knew a closed door meant "do not enter"?

Local Cuisine: There has been a surprising lack of distinct South African cuisine around here, though I've had a few things that are apparently local. The dried fish that I've mentioned, a couple desserts (a gingery pudding, brandy sticks), something called Bobotie, which is like a shepherd pie only with a egg custard top. Probably the most different thing I've tried, however, is a local meat that has popped up several places. It's generally not cooked in any particular style, but the meat itself is local: Springbok. I'd never HEARD of springbok, so naturally I ordered it at first opportunity. Its a (very cute) type of antelope, which are very common in the area. I haven't seen any live ones, but they're pretty tasty. The meat is a little tough, so they tend to be braised or roasted for long periods of time. Kind of like a tough venison, is the closest taste I can describe. Not bad, certainly worth a try. Hopefully I'll find some other local cuisine soon - there are some local curries, for example, which I've been wanting to try... but haven't found any place that serves them.

Robben Island

Robben Island: Of course, I had to go for a bit of the historical side of Cape Town and South Africa, definitely a region with a lot of it. Wednesday afternoon was given off to all of us, and we were given the option to take a tour of Robbin island, the prison island where Nelson Mandela (and other political prisoners) were incarcerated. This was a boat ride across the water to the island, followed by a bus tour around it: stopping at a scenic overlook where we had a great view of the city and Table Mountain, one of the prison yards, the quarry where people were doing their hard labor (as well as secretly teaching and talking with each other). And finally, one of the ex-prisoners there gave us a tour of the prison itself, pointing out Nelson Mandela's cell and the garden where he hid his writings, and telling us about details of prison life (for example, that your food rations depended on your skin color/ethnicity). Overall, a very interesting trip.

Countryside in the Winelands

Boschendal: For the conference dinner, we went out about an hour outside the city to the wine country, to the vineyard/restaurant Boschendal.  Beautiful countryside, lots of tasty food, and some VERY excellent sauvignon blanc  - I may have to buy some at some point before I leave, if I see it again. But most awesome of all - I hadn't actually thought much about what kind of sky I would see in the south as far as specifics go. I don't know the southern sky very well at all, in fact, so I just thought "oh, I'll learn some southern constellations" and didn't think much more about it. We'd been to tour the SAOO (South African Optical Observatory), but we had to leave before it got truly dark, and that was much closer to the city anyway. But when we went to Boschendal - that's over an hour outside Cape Town, so you could actually see some LOVELY night sky - the Milky Way, for one thing, which is a baseline for how good a sky you've got - if you can see that, it's got to be a pretty decent sky (at least, that is what I think, having lived in NYC and Baltimore). But I ALSO discovered how Large and Cloud-like the Large Magellanic Cloud actually IS. It hadn't crossed my mind, but of course, it IS in the southern sky, and it was known before there were actual telescopes, so it's quite visible by eye down here on a sufficiently dark night. It had to be pointed out to me, because it is very easily be mistaken for a cloud, but it was a little taller and at least 3 times as wide as the full moon would be (though happily it was a moonless night). It's undoubtedly even larger on a darker night, as it gets even more diffuse around the edges. Super cool. I also had some other constellations pointed out to me, most notably the southern cross. I commented it looked more like a small square than a cross (since I'm used to the northern one, which is quite a bit larger and has a central star which serves as a crossing point), but I can pick that one out now. The only constellation I could recognize myself was Orion, which was upside down to what I'm used to seeing! This weekend I'm going to be going on an after-conference tour to SALT (South African Large Telescope) in the Sutherlands, where I hope to see even more of the southern sky, maybe even the SMALL Magellanic Cloud. It will be a lot further from the city, so I have high hopes for a clear and dark night sky.

Actual Astronomy: Of course, I'm at this conference for a reason, not just to play tourist. It's the first all-novae conference in a decade - one of a series, this is the 4th such conference in ~40 years. I'm meeting scientists from around the world, all of whom work on the same type of object that I do. I'm introducing myself and my work to the community, meeting people who may become future collaborators, exchanging ideas, and absorbing all the science I can. And of course, it's my first international conference - I gave my first ever talk at a conference, on radio observations of the nova V1723 Aql, which seemed to go pretty well. I even got several compliments on it! Certainly an interesting topic (in my completely unbiased opinion!). This is an object which by all appearances, when it first went off in 2010, was a completely typical classical nova (at least in optical observations). In fact, the reason our group (see blog post "The Astronomer's Day On") started observing it was in the hopes of getting a good "baseline" for radio behavior. While the late time observations fit predictions pretty well, there was an early time 'bump' in the light curve (here this means the brightness of the nova over time, when observed in radio at various frequencies) which one can't explain at all with the simple model. So my talk described our speculation about the nature of the bump, in addition to the late time fitting to models which estimates the total ejecta mass and showing off our observations in general. Our radio group had quite a good showing at this meeting, and in fact I met people who I've been collaborating with but hadn't physically met before. In addition, I got to talk to many new people, from people whose papers I have read, to those working on topics I didn't know much about at all. About 90 people, from 22 countries, were in attendance; the various venues, activities, and schedules were all well organized; and the talks were by and large quite interesting - all in all, a very good conference!

Me, giving my talk (taken by Allen Shafter!)

The Astronomer's Day On

Me on Mauna Kea (HI), during an observing run last August.
Those aren't the telescopes I was working with - the
SMA is an array of 8 radio dishes, whereas these are all
optical telescopes near the top of the mountain!

As I said in my introductory post, I am an Astronomy PhD student, studying at Columbia University. While the main focus of this blog is what I do when NOT at work, astronomy is a very important part of my life. Last week, I had a thesis committee review: every six months (or so), the panel that will eventually be deciding if I get a PhD meets, and I give an overview of what I've been doing, and what I plan to do. This is all designed to keep my thesis ON TRACK, make sure I'm not floundering, and to give me advice on what they think I need to work on, or keep doing right. So, having just ruminated on my research, where it's going, and what my accomplishments are to prepare for this meeting, it seemed an appropriate time to introduce readers of this blog to my research.

In a word, I study novae. Novae can occur in binary systems where a compact star (most often a white dwarf) accretes mass from its companion. When enough matter builds up on the surface of the star and some critical mass is reached, it triggers a thermonuclear reaction which blows off material from the white dwarf as a shell of plasma. This material is quite hot and luminous, so naturally at this point you will see the star brighten - hence the name, "nova", which means "new star." Depending on the type of nova, this material will brighten and fade on the order of days to weeks to a few months - in the OPTICAL range. However, my research focuses on the RADIO light curves of novae, and how they evolve over time. In the radio regime, the time it takes for the lightcurve to rise and fall is usually on the order of months to years.

A lot of my work is based on the fact that different frequencies of light travel through plasma differently (like X-rays travel through your hand, making it possible to image bones, but you can't see through your hand in visible light). Therefore, if you look at the plasma ejected from a nova in two different frequencies, you'll get two separate brightnesses. So you can watch a nova in multiple frequencies and watch how it changes in each one, put it all together, and using some simple models and assumptions, make estimates about various properties of the ejecta (and thus the star and explosion as well). One of the things I really like about novae is that they occur on a time scale that we can NOTICE and KEEP TRACK OF. A new nova can go off at any time, and people all converge on it at once. You can clearly see the time evolution of these objects, and have a list of novae which are doing interesting things.

 But... sometimes the models don't quite work. Our assumptions are too broad, or there is some extra factor we overlook, or we get an answer which flies in the face of current nova theory. One of these issues is going to be the basis of my thesis: we're finding too much mass. Based on standard nova theory, we can estimate how much mass should be ejected in a nova shell. But when we do our model fits with observations, we seem to get masses over an order of magnitude (ie 10x) greater than what we expect. So is the problem with theory, or with our model fit assumptions? We've been making more and more detailed observations of novae, and we're still getting these large masses, even when taking in some additional factors in our model fit - because you can only stretch parameters so far and still keep your assumptions reasonable.

One of the assumptions we generally make in our models of novae is that the material ejected is spherically symmetric. Now, we KNOW that isn't true - nova ejecta is known to have clumps, or jets, or other asymmetries - but its a useful first-order approximation to make. So I'm also interested in jets and outflows in general, and what they imply about the system. Jets appear on multiple size scales in the universe: they can appear in outflowing systems from white dwarves to active galactic nuclei. So, in addition to novae, I have interest in other systems with varying brightness due to accretion, with outflows - like cataclysmic variables in general (where variation is due to accretion between two stars), and symbiotic stars (white dwarf/red giant binary system). I also have a fondness for neutron stars, though I don't really study them specifically at the moment. So really, binaries, jets, and compact stars in general hold my interest!

Some of the VLA telescopes
(in it's SMALLEST configuration)

I'm working with a collaborative group (the e-Nova project) looking at a number of different novae in radio, optical, and X-ray. The majority of our observations come from the Karl G. Jansky Very Large Array near Socorro, New Mexico.  This is an array of 27 individual antenna, working together as one (very large) radio telescope. I've been out there three times; however, these have generally been to learn how to do radio data reduction and analysis, not for observations themselves. When you get time on the VLA, you can input your operating instructions in the online system, and the operators out in New Mexico take care of the observing for you. The only observing I've done personally has been one trip out to MDM at Kitt Peak, AZ, two years ago, and one trip last August to the Sub Milli-meter Array (SMA) on Mauna Kea, Hawaii. The first of those trips was with a class on observational astronomy, where students got sent to the telescope (of which Columbia owns a share) to get experience with optical observing. The second, however, was directly related to my research: in order to obtain time on the SMA, you are required to send out an observer for a week to assist the local operators. So, when we wanted time for high-frequency radio observations of a few young novae, I got tapped to go. It was a pretty awesome experience... though sitting for a control room over a long night actually gets rather dull after a while.

Anyway, my collaboration has recently submitted two papers on which I'm a co-author. They are still undergoing the referee process, so they're not "published" yet and will undoubtedly change a bit before final publication, but they've been listed on the Astro-ph archives. I'm 9th and 10th author on these - it's a large collaboration - so I didn't actually do much of the writing, my contributions were more on the data side, as well as in editing and general discussion. But if you are interested in a bit more technical detail about what I've been working on, you can find those papers here.