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Darkness in the Atacama: An Eclipse Adventure

An article I wrote shortly after the total solar eclipse in November, 1994, sent to the newsletter of the astronomy club I attended at the time.

When you see the Southern Cross for the first time, you understand just why you came this way. -- Crosby, Stills, and Nash

One of the most unusual places on the Earth is a narrow strip of land running along the South American coast and Andean foothills in southern Peru and northern Chile. Known as the Atacama Desert, it is one of very few places on the planet where some places have recorded no rain since being settled hundreds of years ago. In many places, nothing lives, except for people who know how and where to irrigate the land. The dryness and thin population, however, make it a haven for astronomers, who have placed major observatories -- Cerro Tololo, La Silla, and a new eight-meter telescope in construction near Antofagasta, Chile -- in the dry, clear air of the desert. More recently, however, it was a haven for astronomers of a different sort -- on November 3, 1994, much of central South America, including a stretch of the Atacama Desert, was darkened briefly by a total eclipse of the sun.

Reports during total or deep partial eclipses often mention the strange behavior of animals during the darkest phases; insects return to their hives, roosters begin crowing, and so on. Without a doubt, this list of animals must be headed by Homo sapiens, for who else would deliberately seek out the Atacama for three minutes of semi-twilight? In any event, last year I registered with a tour group going to Tacna, a city in southern Peru nestled against the foothills of the Andes mountains, and just a few kilometers from the centerline of the eclipse. Bringing a pair of 10x70 astronomical binoculars -- large enough to show impressive details on astronomical subjects, but not so large that traveling with them is awkward -- I began my adventure in the Atacama.

Tacna itself is a fairly large city -- two hundred thousand people, many of whom live in hastily constructed brick or concrete-block houses in and about the foothills north of the center of town. Being hundreds of miles from Lima and the tourist centers of Arequipa,Cuzco, and Machu Picchu, Tacna is well off the usual tourist itinerary. What does it feel like to be in a Latin American town with essentially no tourist infrastructure? For one thing, the four years of secondary-school Spanish I had didn't make life all that much easier, even though immersion in the language rapidly removed the decade-long patina of disuse. When one is a Southern Hemisphere virgin, however, these little details do not matter, so long as one is able to get to a clear enough site to do some observing.

The night before the eclipse was dedicated to a Southern Hemisphere observing session in the foothills. Around midnight, my group boarded two buses and headed along a narrow dirt road (in Peru and Bolivia, this is a major international highway!) up into the ridges north of the city. At our first site, twenty-three kilometers from Tacna, we disembarked -- into persistent fog that had the appallingly bad taste to top out perhaps thirty meters above our heads. Nevertheless, the skies were good enough to make out major constellations, and I wasted no time in getting out the binoculars and exploring. The first order of business, of course, was getting oriented. Seeing Orion and Canis Major standing on their heads is slightly confusing at first, but after a few minutes I made the adjustment and began delving into the southern sky. Finding south was no major problem; I just found the two big bright patchy things Magellan and other explorers saw, and which have no northern analogues.

With time short and interrupted occasionally by foggy spells, I wasted no time in exploring the southern skies. I got lost in the two Magellanic Clouds several times; the Large Magellanic Cloud was so large only the central portion fit into my binoculars, and with the unaided eye the outer portions spanned perhaps ten degrees, about the size of a hand held at arm's length. Inside the LMC are literally dozens of small, local clusters of stars or nebulous regions. Ofthese, the largest is the Tarantula Nebula, a huge nebulous mass in the binoculars and dimly visible without them. The Tarantula is, in fact, the largest known emission nebula in any galaxy, even ones much larger than the LMC (e.g. the Andromeda galaxy and our own Milky Way). Were it to replace the Orion Nebula, it wouldn't resemble a fuzzy patch in the Sword of Orion; it would be a bright cloud encompassing the whole constellation.

Near the Small Magellanic Cloud is a globular cluster, 47 Tucanae, that is worth any five northern globulars put together. Observers in the club will be familiar with M13 and M5, probably the best examples of this class of objects north of the celestial equator. On a dark, clear night in the United States, these appear as dim stars to the unaided eye. On this foggy night in the Atacama, 47 Tuc appeared as a bright star near the SMC; in my 10x70's, it partially resolved. Unfortunately, I was unable to find an observer with a fully set up telescope; I can only imagine what it looks like at 50x or 100x.

Over the next hour or so, our group gradually lost the battle with the fog -- the clouds thickened and banished all but the brightest stars. Fortunately, like all good explorers and expeditions, we had contingency plans. After reboarding the buses, our tour leaders took us to a second site, forty kilometers from Tacna, reached only by the same narrow dirt road we took earlier. An hour and several harrowing switchbacks later, we arrived at the backup site, over two kilometers above sea level and safely above the fog banks that plagued us earlier. In the meantime, the Southern Cross and the glorious southern Milky Way in Carina, Vela, Crux, and Centaurus had risen.

With less than an hour till morning twilight, I wasted little time. I soaked up about a dozen brilliant open clusters in the binoculars, and marveled at the stream of first- and second-magnitude stars that seems to run along the Milky Way through the southern constellations. I could almost imagine the old ship Argo (what these stars belonged to in this region before it became Carina and the rest) sailing through the sky, leaving these stars and clusters as its wake. Though lacking a cluster as conspicuous as the Pleiades or Hyades, Carina and Vela make up for it with numbers and brilliance. I saw five or six clusters which were very prominent naked-eye objects in these two constellations alone; adding in Puppis, Crux, and Centaurus would surely increase the numbers further. In the Southern Cross, Kappa Crucis, the "Jewel Box", was a small but beautiful group of strongly colored stars, with a range of reds and pale blues -- color contrasts unusual in an open cluster. Further away from the Milky Way there remained many other sights to behold; the Magellanic Clouds were still prominent, and I could finally trace Eridanus for all of its length, from its headwaters near Rigel to the brilliant blue star Achernar not far from the Southern Magellanic Cloud.

Shortly later, dawn broke -- the eastern horizon brightened, and the stars began to fade. Eclipse day had arrived. People completed their set-ups, began taking pictures, and eagerly awaited the arrival of the Sun -- so that they might see it disappear briefly again. Some modest scientific experiments were being set up; several people had brought thermometers to take temperature measurements during the various phases of the eclipse, one person brought an eyechart-like diagram to help characterize visibility and light levels, and a number of people brought along white bedsheets to hunt for "shadow bands", faint ripples of light and shadow that sometimes appear just before totality. Dawn grew, but the stars were surprisingly tenacious. It is difficult to appreciate just how bright Sirius really is until it appears nearly overhead; with less than thirty minutes until sunrise, Sirius and Canopus hung nearly overhead as two blazing jewels which seemed to ignore the growing sunlight.

Dawn brought a moonscape. I knew how dry the Atacama was, and how sterile the land seemed to be away from the irrigated regions near Tacna, but the view from the eclipse site was surprising. The desert southwest of the United States is downright fertile in comparison to the Atacama. From the site, I literally saw no living things aside from humans. In one dry river bed, I did see one or two plants -- or more accurately, things that were plants at one time. The foothills were eerily eroded; clearly, rain does fall there, but only infrequently. Finally, the soil in this part of the world is not so much soil as dust -- dust which goes everywhere and gets into everything. People who had brought sheets to sit on and watch shadows with had some explaining to do at the hotel the next day.

An hour after dawn, the first appearance of the Moon became apparent. With the help of a #14 welder's filter, I could see a small indentation appear on the upper limb of the Sun; the beginning of the partial phase of the eclipse. At this point, nothing particularly unusual was running through my mind; after all, I had seen at least eight partial eclipses before, and there was nothing -- yet -- to distinguish this.

As the Moon further covered the Sun, the interesting phenomena began. About fifteen minutes into the partial phase, people who were monitoring temperature began to record a decrease. Shadows and projection devices clearly showed the effects of the asymmetry of the Sun; people's hands seemed to sprout claws. Twenty-five minutes into the eclipse, almost halfway to totality, the temperature drop became apparent even without a thermometer. As the partial phase deepened, the aspect of the sky began to change, subtly at first -- the sky, particularly to the west, became a slightly deeper blue.

Fifty minutes into the eclipse -- ten minutes from totality -- effects were no longer subtle. The western sky had darkened grotesquely, taking on a dark, almost steel-blue, color in places. The darkening of the sky was itself ominous; it was very easy to see why a phenomenon like this would have frightened people millenia ago, before they could understand or at least predict it. Although the Sun was still intensely bright -- much too bright to look at -- the shadows and illumination were bizarre. All sense of normality had vanished long ago from the shadows; instead of being a dark shadow surrounded by a fringe of penumbra, some appeared as a dark shadow topped by a region of penumbra, or some other seemingly unphysical arrangement. The sunlight had become extremely subdued, and took on a curiously yellow color. At one point, I imagined the site was being illuminated not by he Sun but by a distant lamp with a yellowish tinge to it.

As the minutes rolled by, the changes accelerated rapidly. Three minutes before totality, the Sun had been reduced to a tiny sliver in my welder's filter, and the shadows, which were so prominent (and bizarre) just moments before, were becoming more and more indistinct. With a minute or so to go before totality, the light changes were becoming so rapid they could be followed as they occurred. The Sun's light was falling as though one were turning it down with a dimmer switch. I had long since added a jacket; the temperature folks were reporting temperatures around 10 °C, a drop of ten degrees C from the time of first contact. About thirty seconds before totality, I noticed that although clouds to the north were still white, a group of clouds in the western sky (which by now was very dark and unearthly) had become black; evidently, the shadow had reached them. I turned to the Sun, filter in hand, to watch the last beads of sunlight retreat behind the Moon. The sliver of light broke up into the famous Baily's beads, and with seconds left, these vanished, leaving behind one single bead, shining with the brilliance of the uneclipsed Sun...

Then, bang -- the lights went out. The filter came down, the corona appeared in its full glory, and Venus, less than five degrees from the Sun and completely invisible just seconds earlier, shone with insane brilliance just above the Sun. Shadows vanished almost entirely, as the eclipse site was bathed in the diffuse white light of the solar corona and a few stars and planets.

There was no way to prepare in advance for what I saw in the first few moments. The corona itself was vastly more intricate than I had suspected it would be to the naked eye. Broadly, there were three large, roughly triangular projections from the lunar disk, two on the upper limb and one below; additionally, there were two rough semicircles on the sides. It's hard to describe exactly what this looked like; at one point, I imagined a giant wolf's-head mask. The largest coronal projections extended more than a Moon's diameter from the disk; since this was a total solar eclipse, this meant those arcs were extending over more than a solar diameter into space -- one and a half million kilometers or more. Whether because of contrast effects or other sources, I do not know, but the corona seemed to be the closest thing to pure white light that I have ever seen. In the 10x70's, several prominences peeked over the Moon's disk, in a pure and intense red light, against the backdrop of the corona. The combination of the brilliantly white corona, the jet black disk of the Moon, and the deep red glow of the prominences can only be described as unearthly; I know of no other natural phenomena that produce color combinations that simultaneously are so strongly contrasting and eerie -- and still indescribably beautiful. Even more fascinating, however, was the corona itself. Already intricately detailed with the unaided eye, the extra magnification of the binoculars brought out innumerable fine strands, resembling light and dark threads running from pole to pole, perhaps following magnetic field lines. These do not show up on any visible-light photograph of a total eclipse that I have been able to locate; the detail is simply too fine.

During the total phase, fascinating phenomena occurred well away from the Sun as well. The horizon showed sunset colors all around, with the foothills in the distance bathed in pale red and orange light. The brightest stars had come out, and though many of them were hiding behind high thin clouds, I was able to find Sirius and Canopus, the two brightest in the sky.

As totality progressed, I was able to find more prominences; this time, on the other side of the Moon's disk, meaning that we were more than halfway through and the Sun would soon return. As I moved the binoculars away from the Sun, I could see that the western horizon was brighter than the rest of the landscape -- and brightening fast. The total phase would soon be over. With uncanny rapidity, the western hills brightened, and a moment later, the Sun reappeared and shadows returned. The totality was over.

The thought on everyone's mind, of course, was something like "OK, where's the instant replay?" Or perhaps "Can we do this again?" Nobody is quite the same after an experience like this, and even if one does not break down crying, go slightly bonkers, or even make plans to go visit the next one, there's always a set of strange feelings, some subtle, some intense, thereafter. In my case, there was a period when I wasn't entirely sure whether I had dreamt the entire thing (crashing aboard the return bus from lack of sleep probably contributed to this), and for a while I tried to sort out exactly what I did see, since much of it simply doesn't reproduce well, either on photographs or in other people's descriptions of the event.

For many people, total eclipses provoke a response similar to one borrowed for baser purposes by a potato chip manufacturer: You can't stop with just one. Eclipse chasing, solely the province of professional astronomers and a few junkies not so long ago, appears to have gotten more respectable with the great eclipse of 1991 in Hawaii and Mexico. Already, on the return flights, people in my group were discussing possible itineraries in the future -- perhaps Venezuela or Panama in 1998, or maybe England or France in 1999 -- trying to get their next sight of lunar shadow. For me, I do not know if I will be chasing, but the experience is certainly memorable, and I definitely encourage others to experience it if possible.

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