## Saturday, December 3, 2011

### Interview with Dr. Anneila Sargent

Recently, wanting to learn more about the career path of astronomy (and as a class assignment), I went (with two classmates Juliette and Iryna) and did an interview with Dr. Anneila Sargent, the Benjamin M. Rosen Professor of Astronomy at Caltech.  We ended up talking for more than an hour, and here are some of the highlights:

[me] How did you become an astronomer?

My career path was very irregular, but it shows you that it doesn't really matter.  I think I've made the most of opportunities that came my way, but I also think that if you do what you want to do, and especially if you do what you feel passionate about then you'll probably do better than if you just take some job because you have to make some money. There were points of my life where I did things because I had to just make money but mostly I did what I wanted to do and that was really great. I've always had what I now see at this stage of my life as the luxury of being able to be completely honest and not compromise myself and that was important too.

I grew up in Scotland in a very small town of 19,000 people, near Edinburgh. I was good at science. Well actually I was quite good at history and English

[me] Everything?

Oh no, I was not good at Latin; I was really not good at Latin

[me] I took some Latin and I thought it was very formulaic and well suited to scientific minds.

Not my mind. I’m not a very linear thinker.

[me] how did you start to study astronomy?

I did science, I went to Edinburgh, and I did a degree in physics. By chance I went to a summer astronomy course at the Royal Greenwich Observatory and then I went to work there and met my husband who is also a professor at Caltech now. He suggested I go to graduate school in the United States where he had been offered an assistant professorship at UCSD. Within a year, he was lured away by Caltech and I became a graduate student here. I dropped out to have two kids and then thought "I think I'd like to finish my PhD" so then I went back and finished at Caltech.

[me] How did you decide on the field you are in?

When I went back, astronomy at millimeter wavelengths had started and that was lucky for me.  I was able to pick up in a field that was new so that most people were as new in the field as me.  In a way, you could point your telescope, find something interesting, and then think, "What the heck does it mean?" I started in millimeter astronomy looking at clouds of gas and dust in the interstellar medium around stars. For my thesis I mapped clouds forever.  At first it seemed a bit dull and then gradually, various aspects became more and interesting. Science can be like that

[me] What was one of your most exciting projects?

A friend called one day as he was coming back from observing in Hawaii and said "You know  we just found this star with peculiar  infrared emission, you should look at it with your telescope [points at picture of OVRO]" and I said, "oh, that's a good idea."  And we went from there.  The first observations were not really very exciting but we did find enough to write a paper about them

[me] There's something up there?

Well, there was something, but as I say, it wasn't very exciting.  We thought a bit about it and decided to look for a rarer isotope of the molecule we were observing. Instead of looking at 12C16O we looked for 13C16O, which is much less abundant, down by a factor of almost 100 in the interstellar medium. The time allocation committee for the Owens Valley array was not enthusiastic but eventually agreed to allocate some time. It took months of before all the observations were complete. The night before I finished the data reduction was I was really worried and thought I might have wasted 40 hours of telescope time.  But next morning to my great surprise, there I saw a structure around the star that was very thin and narrow like a disk – as we had hoped. The truth is sometimes you have to have a feeling that what you're doing is the right thing, and you have to believe in yourself. That's somehow one of the most exciting things about being a scientist. You can’t do this lightly but have to work though the problem, while combining it with a gut feeling.

[me] You have been at Caltech a long time.

I stayed here because my husband had a professorship here. We also had kids in school here. I was on the research ladder for quite a while as a result. But that meant I was free to take on other interests because I didn’t have the responsibilities of an assistant professor working towards tenure.  I did research that I wanted to do, gave presentations at astronomy meetings took on astronomy service tasks in the community, advisory committees and so on. Along the way I got professorial offers from other places but Caltech always made it more attractive for me to stay here.

[me] What was your position before you were Vice President for Student Affairs?

Before I had this job I was the director of Caltech’s radio observatory for 11 years. I've loved being an astronomer but I also loved the experience of expanding the Caltech array into a larger facility, the Combined Array for Research in Millimeter Wave astronomy. Some of the advisory committees were also fantastically interesting. For example, as the chair of a NASA advisory committee I had to testify in front of congress.  It was fascinating to understand decisions about NASA and NSF funding are made.

[me] Have you always worked in millimeter astronomy?

I'm a kind of restless person and astronomy lets you try different observational techniques. I started in optical astronomy then moved into infrared and millimeter. One of the more unusual experiences was balloon borne astronomy.  At that time the launches were from Palestine, Texas, which was very different from the kind of world, I knew in California.

[me] So it was pretty early in your career.

Oh, very early, probably around '78-80. I was only a postdoc. But it was my first experience of contributing financially to a collaboration and that gave me my first real feeling of independence professionally.

[me] Why did you become Vice President of Student Affairs at Caltech?

Oh, it was very much a surprise. I didn’t recognize that the committee was interviewing me and then President Chameau asked me to take the job. I thought that it would be “different”, and it is. My husband is also an astronomer, as you probably know but we have never spoken to each other much about our scientific work at home Since I took this job my husband asks "what happened today?" almost immediately because I now see a whole different part of Caltech life. But it is much more time-consuming than I expected and I think I might be more frustrated by the impact it has had on my doing science if I was at an earlier stage of my career.

[me] You talked about a telescope array in Chile was that built already or is it under construction?

It's under construction. It’s called the Atacama Large Millimeter Array, or ALMA, and there will be 54 12-meter dishes at 17,000 feet above the Atacama Desert. That picture shows the first 9 [pointing at picture on the wall]. Currently there are 21 antennas up there.  It's really beautiful. The very first allocations of time with a limited number of the telescopes have now begun. The results will be spectacular.

[me] Have you been there?

Yeah, I was there 3 weeks ago.  This is just a simulation of the telescopes [handing over postcard with a picture on it], but you can see there are even higher mountains around.  It's a spectacular place. In fact, Caltech wants to build a sub-millimeter wave telescope on the top of that mountain that you see [pointing to post card]

[me] Even higher?

Even higher - a single telescope at 5,500 meters that will operate at sub millimeter wavelengths and  look at gas and dust in the interstellar medium.  In particular it will look for gas and dust in galaxies not long after the Big Bang.  It's really exciting because it enables cosmological studies that can’t be carried out at optical wavelengths. Astronomy takes you to telescopes in great
places like Chile and Hawaii.  Have you seen, for example, one of the latest James Bond movies where they blow up a place near a desert: Quantum of Solace.  Have you seen that?

[me] yeah

Well you know at the end, the desert is the Atacama Desert.

[Juliette] Because you mentioned that you had taken time off from working to have kids, I've heard it's difficult to have kids if you're working in academia.

Oh no, I think academia can make it easier because you don't necessarily have regular hours.  So if the kids got sick for example, we'd take turns staying at home.  I didn't have a problem with it, and I actually did my PhD with small children.  They said they didn't like it because they knew I put them to bed then went back to the computer, but I think they actually grew up fairly normal.

[Juliette] It seems like you were on a bunch of committees, I don't know if you can count being the head of an observatory as being on a committee, but you did a bunch of other things than just working here.  Is that common?

Maybe not as much as I did.

[me] Your list is fairly extensive.

My list is a bit ridiculous actually.

[me] I compiled a short list of some of the things you did: so you had the Owens Valley, CARMA, ALMA, you're the president of AAS, the chair of NASA's space science advisory committee

And I was also on the NASA council, which was a revelation, it was quite fascinating

[me] Then chair of the National Research Counsel Board of Physics and Astronomy, recipient of NASA's Public Service Medal, Caltech's Woman of the Year, a fellow of the American Academy of Arts and Sciences, Associate of the Royal Astronomy Society, and then of course the National Science Board nomination, plus I'm sure a lot of other stuff.

I did a lot of these things when I had more time and was not on the professorial faculty. If you have kids and you have a powerful professorship, it can be very hard.  I actually divided my life in a certain sense in that I felt that there were three things you could do.  You could do family, research and/or teaching.  And until my children were grown up, I only ever did two of these at one time.

[me] How do you manage to still get research done?  You're on a paper that was published in January.

Well I have a student and a postdoc and I read the paper, and I'm excited by it but it's pretty vicarious nowadays.  So yes, I can look at the data, and I can help interpret it, and I can give advice but I haven't gone out there and rolled up my sleeves at the telescope for quite a while.

[me] You're in charge of Student Affairs; you're giving back to the students.

Oh, yeah, but in many ways they're giving a lot to me to me.  It’s very energizing.

[me] I have one final question: what do you wish you knew when you were our age, if anything, that you know now?

I don't know. I think what's really most amusing to me is that I could never have imagined that this could have happened to me.  I like to think that I have lived in a terrific age for astronomy: lots of fantastic things happened, lot of things got built, lots of new discoveries, I would wish for everyone that they could work in such exciting times.  I don't know what else I can say.

## Tuesday, November 15, 2011

### 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:

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?

## Thursday, November 3, 2011

### 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.

## Wednesday, November 2, 2011

### Observing a Y Dwarf

Y dwarf 2d.cdf (Wolfram Mathematica 8.0 for Students - Personal Use Only : www.wolfram.com)
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,
${\lambda }_{\mathrm{max}}=\frac{b}{T}$ Where b = $2.8977685\left(51\right)×{10}^{-3}$ m·K
${\lambda }_{\mathrm{max}}=8.28×{10}^{-6}m=8280\mathrm{nm}$   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 ${\lambda }_{\mathrm{max}}$a Y dwarf has a spectral irradiance of
${B}_{{\lambda }_{\mathrm{max}}}=$$2.15×{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:
${N}_{\mathrm{photons}}=\text{}2.15×{10}^{8}*\left(\pi {{R}_{\mathrm{Jupiter}}}^{2}\right)*\left(\frac{1}{4{\pi \left(30\mathrm{ly}*9.46×{10}^{17}\frac{\mathrm{cm}}{\mathrm{ly}}\right)}^{2}}\right)*\left(\frac{1}{\frac{hc}{{\lambda }_{\mathrm{max}}}}\right)=14\mathrm{photons}{\mathrm{cm}}^{-2}{s}^{-1}$
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.

## Sunday, October 16, 2011

### A Bastardization of Science

I was just looking around the internet about the Astronomical Unit (AU) thinking about our class lab, and I ran across this internet gem.  Please note the subtitle of the page, a very reassuring "Science in Ancient Artwork."

It started out looking okay (probably because I skipped the first few paragraphs), and the numbers for his argument made sense in the first thing he was saying about Mercury/Sun distance as the AU. Then the arrows came up about some "patterns," if a sane person can really call them that--I feel like he was in a room lined with pictures and clippings on the walls with yarn or string or something sturdily holding his argument together.

Also, ratios don't have units Mr. Charles William Johnson, so I don't really know why you threw that bit in there.  I get that the numbers vary, but it's not at all because of the units they're measured it.  It's either an imprecise conversion being used, or just different numbers.

And one last word, I think you should go meet with my high school freshman science teacher Mr. McKenna about significant figures.  Don't worry, he's a nice guy and won't judge you too much for what you're trying to do with them.

## Tuesday, October 11, 2011

### Oh, that is what you're calling the Transmission function...

Just a quickie: in class the other day we were talking about a slit experiment with an infinite number of infinitesimal slits in a space day.  I didn't understand that the "transmission function" described meant the light right after the slit screen, I assumed it meant the light transmitted to the back screen where it was being measured.  Knowing this, I now have no issues with that conversation because a finite width slit clearly displays interference with itself and it appears in the form of a sinc function.

## Monday, October 10, 2011

### Summer research and distant amino acids

My research this summer was based on terahertz (THz) spectroscopy of molecules in solution.  While my work was not directly relatable to astronomy work at this point, maybe some day it will be as instrument sensitivity goes up.  However, THz spectroscopy in different forms can be used for identification of molecules in space and research towards that took place in the lab along side me.  THz frequency radiation roughly includes light from 300 to 3 micrometers in wavelength (1-100 THz), and it is in this region that many molecules have distinctive absorption bands.  Water first of all has a huge, strong absorption in this region and thus water can be detected by looking at distant objects, checking the spectrum of radiation we receive from them, and comparing it to the known absorption of water.  While this is more planetary science than straight astronomy or astrophysics, it is closer to what I am interested in, academically.  The research that was happening in the Blake lab this summer with me involved taking samples of amino acids and similar interesting compounds, making them with a simple salt known to not absorb in this spectral range, forming a pellet from this mixture using high pressure, then looking at the absorption of THz through it.  The idea here being that if specific absorptions can be identified to uniquely correspond to certain molecules, then this analysis can be applied to radiation from distant objects, with the hope of identifying amino acids in the atmospheres of distant planets.

Just for my own sake, I want to talk briefly about generation of THz frequency waves, and I suppose you get to read along as I do so.  In our lab, the easiest way to generate THz waves is shining our ultrafast pulsed laser on a crystal of ZnTe.  In a simplification of the process, the laser excites electrons in the semiconductor crystal and the consequent motion of these electrons creates THz frequency radiation because of Maxwell's principles.  In other words, I got to play with big, powerful, and very fast (pulses on the order of 10^-14 s) lasers.  My research was essentially doing the same thing except instead of using crystals to generate the THz, we were using solutions of inorganic molecules and trying to detect and interpret terahertz waves given by these samples.

So not exactly related to astronomy, but interesting nonetheless in my opinion.