AS THE sun sets on the 2600-metre Cerro Paranal mountain in Chile, the nightly choreography at the European Southern Observatory begins. The domes housing each of the four 8-metre mirrors that make up the Very Large Telescope spin around almost silently, and mighty doors slide open to give the telescopes their first glimpse of the emerging stars.
I watch in awe and blink furiously as my contact lenses dry out. Staff astronomer Jonathan Smoker had warned me earlier about the effects of working in the Atacama desert, the most parched place on the planet. “If you stay here for long your skin dries out,” he said. “Sometimes it’s so bad that my hands bleed.”
Water vapour in the atmosphere blocks certain wavelengths of light. So the extreme dryness is one reason why Chile is a magnet for astronomers (see “Giants on Chile’s mountains”). Ambitious new observatories are in the works. Cerro Paranal’s altitude above sea level is another – the VLT’s optical and infrared view of the sky is uninterrupted by clouds and the atmosphere is so thin there is not even enough turbulence to make the stars twinkle, pretty for you and me but an annoying source of error for astronomers. The “seeing”, in other words, is just about perfect, and has enabled the observatory to find the oldest star in the universe and to image worlds beyond our solar system. “The VLT produces one peer-reviewed paper per day,” says astronomer Valentin Ivanov.
I don’t even have to look up to appreciate this for myself. The stars stretch across the sky from one horizon to the next, and I finally fulfil my ambition to see the Milky Way in all its glory. Smudges that look like clouds are our neighbouring dwarf galaxies, the Small and Large Magellanic Clouds, visible only from the southern hemisphere.
The stars stretch from one horizon to the next, and I finally get to see the Milky Way in all its glory
Even Cerro Paranal is not high or dry enough to get a good look at the sky at millimetre wavelengths. So an international coalition is building the Atacama Large Millimeter/submillimeter Array (ALMA) at an altitude about twice as high on Chile’s Chajnantor plateau, home to the highest observatories on Earth.
Getting there is no mean feat. From Paranal, it is a 6-hour drive east through mining towns and bleak desert landscapes, where the only sign of colour comes from shrines honouring people killed on the roads.
We get there and stop for a safety briefing on altitude sickness at 2900 metres – the “low site” – before moving on to see ALMA’s current complement of 20 radio dishes at 5000 metres. There the air is so thin my head starts to pound and I cannot think clearly. No one goes there unless they have to – ALMA’s dishes are controlled from the low site. We do not stay long.
ALMA just snapped its first image, showing cold gas in the Antennae galaxies, a pair of colliding spiral galaxies 70 million light years away. Another 46 dishes are being assembled at the low site, and when they are all in place, they should reveal other hidden regions of cold gas and dust where stars and planets form – as well as untold surprises. “It’s all the things we don’t know out there that are going to be interesting,” says ESO astronomer Diego Garcia-Appadoo.
Giants on Chile’s mountains
Chile could one day be home to yet another giant telescope. An hour’s bone-shaking drive away from Cerro Paranal, across a boulder-strewn landscape that looks like the surface of Mars, is Cerro Armazones.
The 3000-metre-high mountain could be home to a behemoth called the European Extremely Large Telescope, measuring 39.3 metres across. Capable of collecting nine times as much light as any other optical telescope, it could discover Earth-like planets in the habitable zones around other stars and search for changes over time in the fundamental physical constants.
If the European Southern Observatory’s 15 member states agree to the project, work will begin next year to blow the top off the mountain so that the 5000-tonne telescope’s foundations can be laid. Stargazing could begin in a decade.