In Search of Pure Dark Skies

Watch in 1080p! From ESOCast with the famous Dr. J. In the pursuit of pristine skies, the European Southern Observatory operates its telescopes in the remote and arid landscape of the Atacama Desert in Chile.

A top-class site for astronomical observations must meet several criteria. To begin with, of course, you need a sky that is free of clouds pretty much all year round. But in addition to that, you also need excellent atmospheric conditions, as well as very dry air with as little water vapor content as possible. And this is exactly the kind of environment that you find in the Atacama Desert in Chile.

The Chilean Coast Range. Here, the cold offshore Humboldt current creates a coastal inversion layer of cool air, which prevents rain clouds from developing. Often, a layer of fog is created, which rapidly disperses in the foothills above the desert. A view from the Paranal Observatory towards the Pacific Ocean clearly shows the top of the cloud layer.

Chilean coastal range Coastal clouds gathering at the foothills. In addition to the coastal inversion layer, a region of high pressure in the south-eastern Pacific Ocean creates circulating winds, forming an anticyclone, which helps to keep the climate of the Atacama dry.

The Andes lie to the east, acting as a natural barrier for clouds coming from this direction - so all the possible paths for moisture to reach the Atacama Desert are literally blocked. This results in extremely dry air and clear blue skies. Ideal conditions for astronomical observations.

But we're not done yet with our checklist of ideal observing conditions. In addition to cloudless and dry skies, astronomers need dark sites and unpolluted air in order to make the best observations. In most places, the world at night is far from being a dark place and the light pollution caused by modern civilization can easily be spotted. However, light pollution hinders astronomical observations, as it brightens the night sky and makes faint celestial objects undetectable.

Only in places that are far from any cities - like some regions in the Atacama Desert - is the night sky pitch- black. Furthermore, because Chile's cities are relatively far apart, the air in the Atacama Desert is almost completely free of pollutants and is extraordinarily transparent.

Now, astronomical observations are disturbed by the turbulent motions of pockets of air in the atmosphere. Essentially this turbulence blurs our images of the night sky. In addition, the atmosphere also absorbs and scatters light. In order to minimize these effects an observatory should be located in an area with a calm atmosphere above it and on top of a high mountain, in order to reduce the amount of atmosphere between your telescope and the stars. Once again, the high-altitude of Atacama Desert fits this description perfectly.

The Atacama Desert offers many sites at high altitude, ranging from extended plateau in the Altiplano highlands to high mountain tops close to the Pacific Coast. The Chajnantor plateau, at an altitude of 5000 meters, offers ideal conditions for observing in the millimeter and submillimeter wavelength domain. This is where ESO, together with its partners, has chosen to construct the Atacama Large Millimeter/submillimeter Array, or ALMA for short. At such high altitudes there is very little water vapor in the air and the disturbing effects of the atmosphere are kept to a minimum.

Cerro Paranal is an isolated mountain top in the Atacama Desert, only 12 kilometers inland from the Pacific Coast. This is the home of ESO's Very Large Telescope, which makes good use of Cerro Paranal's approximately 320 cloud-free nights each year.

Further inland, within sight of Paranal, another mountain has been identified as an ideal place to conduct astronomical observations: Cerro Armazones. This will be the future site of ESO's Extremely Large Telescope, or the E-ELT, for short.

The Mars-like landscape of the Atacama Desert is really a wonderful gift of nature. Its unique climate makes it a first-class location for ESO's powerful telescopes so that night after night ESO's astronomers can observe the crystal clear skies.

Category:

Science & Technology

Tags:

• astronomy
• space
• sky
• photography
• night
• universe
• south america
• milky way
• black hole
• supernova
• galaxy
• nasa
• eso
• esa
• Dr. J
• solar system
• sun
• moon
• stars
• hubble
• telescope
• earth
• mars
• saturn
• jupiter
• m87
• orbit
• light
• speed of light
• 1080p
• high definition
• hi-def
• hi def
• aliens
• ufo
• quality
• flying
• shuttle
• planet

[lgalicki]

Are you guys polluting these video comments with your religion again? And then you want us not to bash religion? Leave us alone!

[stiimuli]

@jonnyjones62 "I mean don’t you every wonder what happens after we die?"

Without indication that consciousness continues after biological death the question is meaningless. I know its difficult to comprehend an end to yourself. This is a major reason religions came about in the first place.

But we can live on through the mark we leave and the knowledge we spread....and the atoms in our bodies will always be.

Aristotle and Ghandi are both dead but they are not gone.

[lukeseti]

@NailArtSalon I hope your kidding. Their planes. :\

[1111DestroSuper]

Sangat Baik

[SuperDestro1111]

Mengagumkan

[DevilOnHog]

the video title would make a nice heavy metal song title

[NailArtSalon]

that was alot of shooting stars



[Skullking489]

This guys accent made me want rip someones head off. His voice should be played to boxers right before a fight to just to piss them off and get them incredibly angry.

[SLewis958]

@xy274 I hear you. Since I live in the city there are only a couple of stars that I can see, and Venus of course.

But...If there is ever a blackout where you live, you will be amazed. After Katrina, the sky over N.O. was crazy awsome.

[dec041]

Where do they get electricity from for the site? Do they produce it locally? if yes how? or do they run cables from the closer city?

[sam9072000]

@damnyourpasswords you got a point..., what do you think they're doing then except biebering?

[damnyourpasswords]

@sam9072000 maybe more important is that Males watch this.. what about Females? are they in Justin Beaber videos? are they chatting about clothes and boys? what the F are THEY doing?