Chile 2003

In June, 2003 I was given the opportunity to travel to La Serena, Chile to get first-hand experience with observational astronomy using the 1.5m and 4m telescopes at Cerro Tololo Interamerican Observatory (CTIO). This trip was possible due to the generous support of the Mead Endowment, which supplied funding for the journey through an award to my undergraduate adviser Dr. Steve Majewski.

On June 16 I flew from Virginia to Dallas, Texas, where I caught a 10 hour flight to Santiago. Since my flight onwards to La Serena (the coastal Chilean city nearest to the Observatory, click here for a map) wasn't until the next morning, I spent the evening walking around seeing the sights, and spent the night at the Observatory Guesthouse. At right, a very strange statue I found in a park in downtown Santiago: it reminds me of the cover of a Dead Can Dance CD! The next morning, I flew into La Serena and met up with Steve at the CTIO compound. Before heading off to the mountain, we stopped by a good beachside restaurant, which to our surprise had a large sundial built into the ground just in front of it (below).

The drive up to the observatory (at about 7,300 ft) took another 2 hours, but the incredible views of the mountainous terrain with the Andes looming in the distance made the drive seem much shorter. This region of Chile is very dry, and the low Andean foothills were very reminiscent of Eastern California, where the Sierra Nevada Range towers over smaller mountains covered with desert scrub. Chile may look like a thin country on the map, but it wasn't until I was standing on the mountaintop at the Observatory that I realized that I could see across the entire country from the Argentinian border to the Pacific Ocean! This picture is of one of the nearby (and lower) peaks, notice the snow on the higher peaks in the distance.

I decided to work on a Senior Thesis project with Steve Majewski after taking his course in Observational Astronomy, which exposed me to the excitement of observing the sky with professional telescopes and equipment. For my Senior Thesis I developed a computer model of the destruction of the Sagittarius (Sgr) dwarf galaxy by the Milky Way, in collaboration with Steve and Dr. Kathryn Johnston of Wesleyan University. Sgr is actually the nearest galaxy to our Milky Way, and it orbits around our Milky Way as a satellite. Sgr was only first discovered in 1994.

Since then, many people have suspected that this satellite gets close enough to the Milky Way that it should experience substantial shearing from the gravitational field of the Milky Way. The force of this shearing acts to tear stars off the little Sgr dwarf galaxy into "debris arms", which are basically the entrails of the satellite which are becoming part of the Milky Way in a grand act of cannibalization! But it was only in the past year that we published the first hard evidence that these entrail arms wrap completely around the Milky Way.

I created an animated movie of the Sgr dwarf, which is based on the new data and my computer models. The still frame below (at left) shows for the first time our new picture of our own Milky Way, with the remains of the Sgr dwarf galaxy (shown in orange) wrapped around us. The little yellow dot represents the position of the Sun. Interestingly, we have found that some of the remains of the Sgr dwarf galaxy are falling down all around the neighborhood of the Sun!

It is exciting to see that this model is getting a lot of attention. For example, in June I was lucky to present this new model at an international meeting of experts in the Canary Islands, off the coast of Africa. The organizers of the conference, as well as Dean Sofka of the Echols program, actually helped pay my expenses to attend the conference to present these new results! Above right: the beachfront on the island of La Palma, where the conference was held (the conference hotel is just visible at top right).

As another example of this attention is its publication in the August edition of the French popular astronomy magazine Ciel et Espace.

We have been learning a great deal of information about this dwarf galaxy, but the numerical models which I have been developing also promise to help us solve a number of problems about our own Milky Way, for example, to measure its true size, shape and mass, all of which are not well known due to the presence of an unknown amount of the mysterious "Dark Matter".

It was to address these problems that Steve and I were scheduled to use the 1.5m telescope. With a spectrograph attached to the telescope, we can obtain the Doppler velocities of stars in the Sgr debris arms, and, in so doing, not only check my model, but "weigh the Milky Way" through the response of the Sgr stars to the gravitational field of the Milky Way.

Right: a picture of Steve and I in the control room of the 1.5m, busy collecting the spectra containing the precious Doppler velocity data!

This summer I am finalizing the details of my model. In August we will formally submit the results of this work to the Astrophysical Journal.

Steve and I collected data for four nights and were able to observe over 100 target Sgr debris stars, which have already proven to be of great interest in unraveling the streams of tidal debris about our Milky Way Galaxy. Below: Steve and I bring the UVA school flag to the high Andes!

The picture at left is a time-lapse photograph taken of the Southern Sky, which shows the trailing of stars in the sky as the Earth turns throughout the night. The blue/white glow is the Milky Way, which is stunningly beautiful from a site with a sky as dark as at CTIO. It was my first time viewing the far southern sky, and it was a pleasure to pick out the constellations of Crux and Centaurus (especially since my summer research project last year was based upon a large star cluster located in this constellation), in addition to seeing the Magellanic Clouds.

On the right is a picture of a star taken by the telescope guider camera- during an earthquake. The first night we observed, we felt a magnitude 3 earthquake, which shook the camera considerably (causing the normal star image to look like a lot of squiggles in this few second exposure). The next morning after we'd gone to sleep we were awoken by another earthquake, this one of 7th magnitude, located only a few miles away! Steve had some broken glass in his room, and a slightly embarassing run outside in his skivvies! Click here to read the USGS earthquake report.

After the 1.5m observing run was complete, I had two days to spend back in La Serena before beginning a second observing run with the even larger 4m telescope. Aside from catching up on sleep, I also took the opportunity to explore La Serena. This small town has a long beachfront, a central market, and lots of statues. Right, and below: the local scenery.

After the break, I met up with Dr. Carl Grillmair from Caltech (where I will be starting graduate school in a few months), who had kindly agreed to let me help out with his 6-night observing program on the 4m Blanco telescope. This project was a photometric mapping survey of globular star clusters. Our goal was to see if perhaps some of these small satellite star systems of the Milky Way might also show the kind of "debris arms" that we now see on the Sgr galaxy. This observing project particularly interested me, because last summer I tried to look for arms around just one globular cluster Omega Centauri (with the result to be published in the Astronomical Journal in two months time), but now I would have the opportunity to study many more clusters. Below: pictures of the 4m telescope dome, and of the 4m telescope itself.

In all, I was fortunate to have ten nights of clear observing; I understand that this is pretty good weather karma (clouds moved in the day I left)! I would like to thank the Mead Endowment for making this trip to South America possible: it is extremely rare for undergraduate students to have the opportunity to use such world-class telescope facilities, and the practical experience which I have gained will be of great help as I continue my studies in graduate school at Caltech. My interactions and research with UVa faculty member Steve Majewski have carried me from McCormick Observatory at UVa to Connecticut (to work with a new colleague, Kathryn Johnston), to the Canary Islands to present my undergraduate research, and now, thanks to the Mead Endowment, to Chile to further test and develop my models and make what I am told are (and I hope will turn out to be) lasting contributions to science. I'm not sure if such an undergraduate experience would have been possible at any other university, and I am thankful that the UVa community can promote such unique opportunities.