Stars in the sky above Tenerife
© Gunnar Knechtel

Dark side of the sun


Astronomers around the world are looking forward with excitement to the “eclipse of the century” on August 21. You can see very deep into space at Teide Observatory on the island of Tenerife.

Dr. Miquel Serra’s work day on the island of Tenerife begins at nightfall, with an evening meal of chicken, fries and a glass of water. From the dining room, Serra, 51, looks out onto an arid, volcanic universe 2400 meters above sea level. Black rock, green broom, scree and not a tree in sight, and far below, a layer of cloud. Beyond that, the coast, and in the west, an orange sun sinks into the Atlantic. Earlier in the day, the scientist had taken a look at the current NASA coordinates and checked the weather: perfect visibility, no moon, no dust in the atmosphere. “Fantastic conditions,” says Serra, pushing his plate aside. The sky will soon be full of stars, meaning that Serra will probably get a good look at some asteroids circling somewhere beyond the sun, more than 200 million kilometers away.

The roof of Tenerife is ideal for gazing deep into space. The Observatorio del Teide on the flanks of this Canary island’s volcano is the world’s most famous observatory – along with its sisters in Hawaii and Chile. Stars fill the sky on eighty-five out of a hundred nights here, and low-lying cloud usually deflects all artificial light. Mount Teide is one of the darkest places on earth; the sky above it is even off-limits to aircraft, which means a clear view of space for the scientists.

The observatory on Mount Teide

On Mount Teide, one of the darkest places on earth, scientists have the best view of the stars

© Gunnar Knechtel



  Serra is chief astronomer at the Instituto de Astrofísica de Canarias, his workplace for the past 25 years. He gives lectures all over the world and teaches at the university of La Laguna, but spends most of his time on his own work. His main focus of research are near-earth asteroids (NEAs), which travel through our solar system at very high speeds. Studying them is more than a job to Serra, it’s a passion. He studied physics for ten years before writing his dissertation, Astronomical Applications of Artificial Neuronal Networks, and receiving a professorship. “Just a bunch of theory,” he says off-handedly. Astronomy, he adds, is all about mathematics and statistics, but it also deals in a special way with the real world. “Just look up at the sky, the whole universe out there is real!”

Dr. Serra knows better than to imagine things like that – it could drive him insane

At 9 pm, Serra gets up from the table and steps out into the thin air of the moonscape beneath the pointed cone of the Teide volcano. To the east, Gran Canaria juts out of the clouds, and to the west, there’s the island of La Palma surrounded by blue sea. The sun dips ever lower toward the horizon. Up here, high above the beaches of the popular vacation island, we are in another world. A gentle wind whistles across the landscape; the air tastes cold and fresh. Everywhere, antennae rise from the dark volcanic earth amid domes and white orbs scattered about like giant astronaut helmets. These contain the astronomers’ high-tech telescopes, their mirrors, sensors and cameras all trained on our infinite universe.


Sun, moon and stars

A tropical lagoon, the middle of the desert and a mountaintop are all excellent places from which to look deep into space. The Teide Observatory app permits private viewings on your phone.

Map of hotels that offer a view to the stars

1. USA: Astronomy lectures will be held at the Amangi Hotel in Wyoming during the solar eclipse.
2. Chile: The Elqui Domos hotel offers rooms with a window on the sky, astro tours and an observatory.
3. Switzerland: The Null Stern Hotel has neither walls nor roof. It's a double bed in the mountains – with a butler.
4. Italy: The Carlo Magno Hotel The Carlo Magno is popular with astro-physicists and hosts Astronomy Week in September.
5. Germany: Westhavelland Nature Park in Potsdam became Germany’s first dark sky reserve In 2014.
6. South Africa: Guests at the Kagga Kamma Nature Reserve can gaze at the Milky Way from their beds.
7. Lapland: Glass igloos at the Kakslauttanen Arctic Resort let you watch the Northern Lights from your bed.
8. Maldives: The Soneva Jani resort in the Medhufaru lagoon not only has style, but also its own observatory.
9. Australia: The Magellanic Clouds and Southern Cross are visible in the Outback even when there’s no moon.
10. New Zealand: The aurora australis dances across the southern skies of Dunedin between March and September.


  More than 20 nations operate various different telescopes on the slopes of Mount Teide, engage in research projects and perform experiments aimed at extracting further secrets from space. They conduct seismological studies of the sun, search for exoplanets (planets that revolve around a star) and carry out laser-based satellite communication or radio telescopic measurements to capture leftover radiation from the Big Bang. The research is a complex form of fieldwork; every night, the scientists collect hundreds of terabytes of data with which to study far-off nebula and galaxies. After all, astronomers have no concrete samples at their disposal. All they have to go by is the light and the radiation from the depths of the cosmos.

Chief astronomer Miquel Serra’s standing by his telescope

In search of cosmic knowledge: Chief astronomer Miquel Serra’s tools are telescopes and computers

© Gunnar Knechtel
Scientists at the IAC-80 observatory keep an eye out for approaching asteroids

On guard: Scientists at the IAC-80 observatory keep an eye out for approaching asteroids

© Gunnar Knechtel

  The sky over Tenerife glows blood-red as night creeps up on the island from the east. And now, high up on the mountain, a loud whirring fills the air as the domes rise and their hatches slide apart, making them look like giant clams opening their shells. The telescopes appear, their view of the stars now entirely unobstructed. Serra, an old leather cap on his head, takes a few steps down the slope and spreads his arms wide, saying, “The sea below, the peace up hear, the stars and the telescopes – I love this place!”

He opens a door and enters IAC-80, his telescope facility. A narrow corridor, two offices and beyond them, the control room filled with screens, computers and display boards with flickering coordinates, longs lines of figures, parameters and time periods. These represent the positions of stars and asteroids, computations of their orbits and their relative distance to the sun. Mathematical symbols of space; the astronomers’ language.

We walk up a couple of steps and through another door behind which we find the wired-up “eye” of the dome – a metal structure equipped with mirrors and lenses that capture and condense the light of the stars: It’s the telescope itself. The roof of the dome slides open above our heads. Serra boots up one computer after another, loading files and positions, and aligning the telescope with millimeter precision. On the wall beside his desk, he has photos of galaxies, the Horsehead Nebula and the Rosetta Nebula, mysterious apparitions from the farthest reaches of space. But tonight, Serra is studying something else: the 2014 JO25, an asteroid with a diameter of roughly one kilometer that he’s been tracking for two months. Just now, for a few weeks, it will be passing in orbit at 1.5 times the distance from the earth to the sun before disappearing from sight for another three years.

Today, the angle is perfect for capturing and analyzing the asteroid’s light. What is the asteroid composed of? How fast is it traveling? Could it be entirely silicon or even contain traces of water? These days, such conclusions can be drawn by analyzing the asteroid’s reflections, although it is a Sisyphean task. That’s why the scientists enlist the help of a supercomputer called the “LaPalma node.” Its 512 processors are able to carry out 4.5 billion calculations per second; modern astrophysics requires this kind of help. Astrophysicists study black holes but also scan the skies for orbiting space debris that could collide with the international space station ISS.

Stargazers watching the night approaching on Tenerife Island

When night approaches, stargazers get excited

© Gunnar Knechtel

  Serra focuses primarily on the Asteroid Belt between Mars and Jupiter, which contains over a million chunks of rock, small stars and vagabond debris. Some of these occasionally leave their orbit to hurtle headlong into space. Such mavericks can measure up to ten kilometers across. Some asteroids have even come quite close to earth, passing by only as far away as the moon before whizzing off again. “We are quite familiar with about a thousand of the biggest asteroids,” Serra explains, “and what we aim to do is to characterize these and other asteroids even more precisely.” Robots could be landing on them one day to explore them as sources of energy, for instance. But it’s also a matter of preventing collisions with planet, moons and the earth. What would the consequences of such a collision be? And how can such catastrophes be reliably prevented?

The telescope takes an hour to locate the asteroid. Serra points to one of the screens. There it is! A white dot on a gray background pulling a flimsy trail of light along behind. The telescope takes thousands of pictures, virtually sucking up the light from the celestial body so far away. The images will not be analyzed nor the spectra and wavelengths decoded until later. Now dozens of other white dots are visible beyond the first one. “They’re all galaxies,” says Serra, “and each one has a diameter of at least 200 million light years. Welcome to outer space.” But before long, even the experienced professor starts getting nervous and sends everyone out of the control room, even his assistant. In the next few minutes, he will have to make some important calculations and establish crucial data. He already knows that the asteroid rotates once around its own axis every three hours, but which axes are those? Does it tumble through space? In order to concentrate, Serra needs complete silence. Right now, he’s a physicist utterly absorbed in his chosen universe, an astronomer in a state of bliss.

Young astronomers Paloma Minguez and Lueia Mag­da­lena outside the Pyramid solar lab

On the sundeck: Young astronomers Paloma Minguez and Lueia Mag­da­lena outside the Pyramid solar lab

© Gunnar Knechtel
Stop sign prohibiting access to the Teide Observatory terrain

Next stop, the Milky Way: Teide Observatory accommodates nocturnal telescopes, solar labs and radiation pyrometers

© Gunnar Knechtel

  It’s long past midnight now and just like most nights, Serra will sit with his data, images and coordinates until three or four in the morning. At 1 am, he spots Johnson C/2015 V2, an asteroid with a diameter of ten kilometers, far beyond the sun. Somewhat later, he watches a comet with a long tail melt near the sun. Small fry. In the end, he is also interested in the big picture, looking for answers to big questions. How was the universe formed? What came before it? What lies beyond its limits?

Serra takes a piece of paper and a pencil and writes down the formula: 0 = 1 + (-1). “It’s very simple,” he says. Zero is nothingness, the equals sign is the Big Bang, one is matter, negative one is antimatter. “Everything can be reduced to that,” he adds. The big question is the equals sign, the Big Bang. Why did it happen? Why did everything, the universe that we know and that experts claim has eleven dimensions, arise out of nothing? Many things can be explained mathematically, but Serra knows better than to try to imagine all of that because it could drive him insane. “I stick to my asteroids because I know what I’m dealing with,” he says. Serra steps outside and looks up into the sizzling, blinking, shimmering heavens. The sky over Tenerife is once again teeming with stars.