42 ) mcdonagh mit physics annual 2003

o many of us at MIT, the January Independent Activities

Period (IAP) signifies freedom. Freedom to learn to juggle

four balls at a time, to take a cooking class, to catch up on a semes-

ter of lost sleep. I chose to travel. During the third week of IAP,

while New Englanders shivered in the grip of one of the coldest

spells on record, I had the chance to savor the warmth of the

Chilean summer and visit Las Campanas Observatory. This home

to seven telescopes sits on a remote mountain ridge in the Atacama

Desert, some 200 miles north of Chile’s capital city, Santiago.

Sorcha McDonagh

T

Under the Southern Sky

IWAS A GUEST OF

MIT professor ofastrophysics Paul Schechter, who

allowed me to accompany him on hisobserving “run”to learn how observatories

operate, how astronomers work, and to witness the teething pains of a telescopethat has been “doing science” for just a few months. The telescope in question isknown as Clay, and it is one of the twin Magellan telescopes that were funded bya consortium which includes MIT, Carnegie Institution of Washington, Harvard,and the Universities of Michigan and Arizona.

It took 24 hours to get from Cambridge to the mountaintop. The final two hoursof the journeywere the most spectacular, as we drove along the Pan-American High-way through vast, rolling mountains, the soil tinted by different minerals—purplemanganese, rust-red iron, greenish copper. I thought about the week ahead: goingto bed at six in the morning, rising at two in the afternoon, a schedule made forstarlight. “I think of it as being in monastic mode,” an astronomer from theUniversity of Sheffield told me. “Except instead of doing manuscripts, you’restudying stars. It has its own rhythm.” Watching the sun set seems to be theastronomer’s equivalent of clocking in. We watched it at about 8:50 each evening,a ritual, waiting to see the “green flash” that was lovingly explained to me by anastronomer early in the week. In six sunsets I saw the flash just once, the simmer-ing orange globe turning yellow as it lowered behind the western mountains, finallygiving off a brilliant emerald glint as it disappeared. The green flash happens becauseof refraction of the sun’s light by earth’s atmosphere. Green light, with its shorter

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44 ) mcdonagh mit physics annual 2003

wavelength, is bent more than red light. As thesun sets, you will see its red image set first, thenits yellow image, and seconds later—if the skyis clear and the horizon distant enough—you willsee the sun’s green image, just as it falls below thehorizon. (The last visible colors in the spectrum,blue and violet, are scattered by the atmosphere.)

“Let’s do some science,” Schechter said whenthe sun had set. We went into the telescope controlroom that housed a bank of about 15 computerscreens, each displaying the vital signs of the tele-scope and its various instruments. It is in thisroom that the astronomers pick over the heavens.The light captured by the telescope’s 6.5-meterprimary mirror is reflected into cameras thatrecord digital images of the stars. Most astronomersinvert the image colors so the stars are black andthe sky is white; it is like looking at fuzzy blackand white close-ups of freckles or a child’s splashpainting. To me, these computer-screen imagesfelt abstract, far removed from the stars, even thoughwe were peering deep into space and history,even though astronomers have been seeing the skythis way since the 1980s.

Now, we watch the universe on a screen.When we searched through hundreds of objectsfor gravitational lenses, “prospecting for gold insand,”as Schechter put it, we worked rapidly, taking

a 30-second exposure every minute. But then we switched gears and took long expo-sures of neutron stars, heavy jewels nested in the galactic plane. The control roombecame quiet; we had more time to notice how tired we felt. “But boring is good,”Schechter said. “We like boring.”

One night, at 4:15 a.m., I went outside for some unassisted stargazing, toappreciate why the observatorywas in this remote location in the southern hemi-sphere. I fumbled, waiting for my eyes to adjust, the Magellan telescopes’ domesmoving deliberately nearby, their aluminum skins reflecting starlight in softdaubs. The Southern Cross and an upside-down Orion stood out immediately and,after a few minutes, the dimmer stars and the thick white band of the MilkyWaycame into view. Then, the Magellanic clouds: two galaxies, small and large, likewhispers of light. These stellar treasure troves are only visible from the southernhemisphere. I stood in the quietness, watching the slow revolution of a sky sprayedwith stars, more than I had ever seen.

Inside the dome of the Baade 6.5-m telescope.

Frank

Perez

I was quiet during my first few days on the mountain. The talk in the observ-ing room and at meals was so thick with jargon that it was as impenetrable to meas Urdu. I felt like the odd-one-out, the beggar who sneaked into the banquet. Itwas the sort of setting I had never imagined being in: a mountaintop populatedby astrophysicists and shimmering, complex machinery trained on distant quasars.

When I arrived back in Cambridge, I stood outside on my deck, looking forstars I knew I would never find. Here, an orange-rose veil hangs between us andthe night sky as atmosphere scatters the city lights. This light pollution washes outthe night sky, concealing the stars. True darkness never falls.

I was privileged to visit one of the darkest places in the world, but even closeto home, away from city lights, there are plenty of places to be immersed in thestars. In the thick of the spring semester, when it seems like the pressure is too much,I’ll try to find my way out to the darkness to watch the ancient light emanatingfrom countless points in space.

sorcha mcdonagh recently earned a Master’s Degree from the MIT Graduate Programin Science Writing. She is grateful to Professor Paul Schechter for his tutoring and company.

An earlier version of this article originally appeared in the February 2003 issue of the MITGraduate Student News, reprinted here by kind permission of the author.

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Baade and Clay: the twin Magellan telescopes at Las Campanas Observatory, Chile.

Frank

Perez