What can you see in the sky over San Pedro de Atacama in winter?
Winter is the season of the Milky Way
Many of the people who come to San Pedro de Atacama to look at the stars arrive with an image in mind: the Milky Way crossing the sky from end to end. That image has its season. It is winter.
If we had to choose one time of year for looking at the sky in San Pedro de Atacama, it would be this one. Not because the others aren't worth it, since every season has something of its own, but because between June and August the Milky Way is in its best position for observing early in the night.
Different stretches of the Milky Way's band are visible throughout the year, at different hours. But in the southern-hemisphere winter months, the central region of our galaxy rises above the horizon early, at the hour when you naturally go out to look at the sky. And that is precisely the hour at which we hold our observations.
The result is that in winter you don't have to wait until the early morning to see the Milky Way at its finest. It is there, overhead, from nightfall.
The constellations of the winter sky
The sky is not the same in June as in August. Over the course of the winter, the constellations shift night by night, and the set visible early in the evening at the start of the season is not the one visible at its end.
Early winter
On the ecliptic, the path travelled by the Sun, the Moon, the planets and the zodiac constellations, the stars of Leo, Virgo, Libra, Scorpius, Sagittarius and Capricorn will be visible.
To the south, the Southern Cross is in a privileged position: at the beginning of winter it stands upright as soon as night falls. Above it is the constellation of Centaurus and, west of the south celestial pole, the Argo Navis group begins its descent.
To the north, from our latitude it is still possible to see the main stars of the Great Bear, a constellation many associate with the northern hemisphere and don't expect to find here. Hercules is also beginning to rise.
Late winter
The sky changes over the weeks.
On the ecliptic, the zodiac constellations visible early in the night will be Virgo, Libra, Scorpius, Sagittarius, Capricorn and Aquarius.
To the south, the Southern Cross is no longer upright: each night it appears a little more tilted towards the west. East of the south celestial pole, the constellations of the southern birds and the Small Magellanic Cloud have begun to rise, and west of the south celestial pole, Centaurus begins to fall.
To the north, what the northern hemisphere calls the Summer Triangle starts to appear: the three brightest stars of Lyra, Aquila and Cygnus, announcing the change of season.
The other sky: the dark constellations
There is something we often share during our winter observations that doesn't appear on Western star charts.
In the southern hemisphere, where we are fortunate enough to have the Milky Way overhead in the winter months, the ancient inhabitants of the Andes did not see figures in the stars alone. There is a group of constellations called Yana Phuyu in Quechua: dark clouds set within the whiteness of the Milky Way.
Among these constellations, various animals have been identified: the llama Yakana, the fox Atoq, the toad Hamp'atu and the tinamou Yutu. There is no way of knowing when the constellation of the tinamou was born, but it is already named in the seventeenth- and sixteenth-century chronicles describing the customs of indigenous Peru. In the body of Quechua myths and legends known today as Gods and Men of Huarochirí, the extirpator of idolatries Francisco de Ávila names it just after telling the story of the principal dark constellation.
"They say that this Yakana we have named is like a shadow of the llama, a double of that animal, which walks through the middle of the sky. We too see it come this way, dark. It is very large, and blacker than the night sky. At night it advances with its long neck and its two eyes. It is the Yakana. "They say that Yakana comes down at midnight, when no one can feel it or see it, and drinks the water of the sea. They say that if it did not drink that water, the whole world would be flooded. The dark patch that goes a little ahead of this shadow we call Yakana is given the name Yutu, the tinamou. They also say that it has young, and that when they begin to suckle, it wakes."
The sky through the telescope
Among the objects we usually show in this season:
The Butterfly Cluster and the Ptolemy Cluster, in the region of Scorpius.
The Jewel Box Cluster, beside the Southern Cross.
Omega Centauri, the largest and brightest globular cluster in the whole night sky.
47 Tucanae, the second largest known globular cluster in our galaxy, towards the end of the season.
Antares, the supergiant in Scorpius.
Alpha Centauri, the stellar system closest to our own.
The Carina Nebula, a vast star-forming region.
Vega, one of the brightest stars in the sky, which begins to appear towards the end of the season.
Is it worth the cold?
Winter nights in the desert are cold. Towards the end of the tour, the temperature can approach 0°C. It is worth it. We say so from experience. The winter Milky Way is among the most beautiful things you can see in the sky, and it makes up for the cold. And so that the cold is not a problem but part of the experience, we have fleece blankets, we light a fire, and hot drinks — coffee, tea, chocolate — become especially comforting when you drink them under the stars.
There is something about looking at the most intense sky of the year while warming your hands by the fire.
Every winter observation cycle is a chance to see the Milky Way at its best. If you are going to be in San Pedro de Atacama between June and August, we invite you to see the sky with us.
Comments