1
00:00:05,457 --> 00:00:08,731
Cloudy skies may be nice from an artistic point of view,

2
00:00:08,731 --> 00:00:11,796
but clouds are an astronomer’s nightmare.

3
00:00:15,697 --> 00:00:20,016
And while illuminated cities are a night-time beacon of modern civilisation,

4
00:00:20,016 --> 00:00:23,313
bright night skies are also a no-go zone

5
00:00:23,313 --> 00:00:26,331
for world-class astronomical observations.

6
00:00:26,564 --> 00:00:29,443
So, in the pursuit of pristine skies,

7
00:00:29,443 --> 00:00:32,508
ESO, the European Southern Observatory

8
00:00:32,508 --> 00:00:35,573
operates its telescopes far beyond Europe,

9
00:00:35,573 --> 00:00:40,217
in the remote and arid landscape of the Atacama Desert in Chile.

10
00:00:44,907 --> 00:00:46,765
This is the ESOcast!

11
00:00:46,765 --> 00:00:49,876
Cutting-edge science and life behind the scenes at ESO,

12
00:00:49,876 --> 00:00:51,873
the European Southern Observatory.

13
00:00:51,873 --> 00:00:58,259
Exploring the ultimate frontier with our host Dr J, aka Dr Joe Liske.

14
00:01:02,299 --> 00:01:06,711
A top-class site for astronomical observations must meet several criteria.

15
00:01:07,361 --> 00:01:10,519
To begin with, of course, you need a sky that is free of clouds

16
00:01:10,519 --> 00:01:12,423
pretty much all year round.

17
00:01:12,423 --> 00:01:13,816
But in addition to that,

18
00:01:13,816 --> 00:01:16,417
you also need excellent atmospheric conditions,

19
00:01:16,417 --> 00:01:21,014
as well as very dry air with as little water vapour content as possible.

20
00:01:21,014 --> 00:01:23,197
And this is exactly the kind of environment

21
00:01:23,197 --> 00:01:26,309
that you find in the Atacama Desert in Chile.

22
00:01:31,487 --> 00:01:33,437
The Chilean Coast Range.

23
00:01:35,364 --> 00:01:38,058
Here, the cold offshore Humboldt current

24
00:01:38,058 --> 00:01:41,216
creates a coastal inversion layer of cool air,

25
00:01:41,216 --> 00:01:43,909
which prevents rain clouds from developing.

26
00:01:46,231 --> 00:01:48,600
Often, a layer of fog is created,

27
00:01:48,600 --> 00:01:52,779
which rapidly disperses in the foothills above the desert.

28
00:01:59,792 --> 00:02:02,996
A view from the Paranal Observatory towards the Pacific Ocean

29
00:02:02,996 --> 00:02:06,108
clearly shows the top of the cloud layer.

30
00:02:08,568 --> 00:02:11,123
In addition to the coastal inversion layer,

31
00:02:11,123 --> 00:02:16,464
a region of high pressure in the south-eastern Pacific Ocean creates circulating winds,

32
00:02:16,464 --> 00:02:18,530
forming an anticyclone,

33
00:02:18,530 --> 00:02:21,920
which helps to keep the climate of the Atacama dry.

34
00:02:21,920 --> 00:02:27,354
The Andes lie to the east,

35
00:02:27,354 --> 00:02:30,976
acting as a natural barrier for clouds coming from this direction

36
00:02:30,976 --> 00:02:35,713
— so all the possible paths for moisture to reach the Atacama Desert

37
00:02:35,713 --> 00:02:37,989
are literally blocked.

38
00:02:39,591 --> 00:02:43,306
This results in extremely dry air and clear blue skies.

39
00:02:43,306 --> 00:02:46,975
Ideal conditions for astronomical observations.

40
00:02:49,993 --> 00:02:53,476
But we’re not done yet with our checklist of ideal observing conditions.

41
00:02:54,057 --> 00:02:56,565
In addition to cloudless and dry skies,

42
00:02:56,565 --> 00:02:59,444
astronomers need dark sites and unpolluted air

43
00:02:59,444 --> 00:03:01,534
in order to make the best observations.

44
00:03:08,128 --> 00:03:12,308
In most places, the world at night is far from being a dark place

45
00:03:12,308 --> 00:03:17,323
and the light pollution caused by modern civilisation can easily be spotted.

46
00:03:19,784 --> 00:03:23,593
However, light pollution hinders astronomical observations,

47
00:03:23,593 --> 00:03:25,729
as it brightens the night sky

48
00:03:25,729 --> 00:03:29,212
and makes faint celestial objects undetectable.

49
00:03:32,672 --> 00:03:35,504
Only in places that are far from any cities

50
00:03:35,504 --> 00:03:38,105
— like some regions in the Atacama Desert —

51
00:03:38,105 --> 00:03:40,381
— is the night sky pitch-black.

52
00:03:42,888 --> 00:03:46,696
Furthermore, because Chile’s cities are relatively far apart,

53
00:03:46,696 --> 00:03:51,317
the air in the Atacama Desert is almost completely free of pollutants

54
00:03:51,317 --> 00:03:54,429
and is extraordinarily transparent.

55
00:03:57,308 --> 00:03:59,398
Now, astronomical observations are disturbed

56
00:03:59,398 --> 00:04:02,927
by the turbulent motions of pockets of air in the atmosphere.

57
00:04:03,368 --> 00:04:07,409
Essentially this turbulence blurs our images of the night sky.

58
00:04:07,409 --> 00:04:11,310
In addition, the atmosphere also absorbs and scatters light.

59
00:04:12,029 --> 00:04:13,390
In order to minimise these effects

60
00:04:13,390 --> 00:04:18,252
an observatory should be located in an area with a calm atmosphere above it

61
00:04:18,252 --> 00:04:20,389
and on top of a high mountain,

62
00:04:20,389 --> 00:04:25,543
in order to reduce the amount of atmosphere between your telescope and the stars.

63
00:04:26,147 --> 00:04:28,841
Once again, the high-altitude of Atacama Desert

64
00:04:28,841 --> 00:04:30,791
fits this description perfectly.

65
00:04:39,638 --> 00:04:43,167
The Atacama Desert offers many sites at high altitude,

66
00:04:43,167 --> 00:04:46,883
ranging from extended plateaux in the Altiplano highlands

67
00:04:46,883 --> 00:04:50,551
to high mountain tops close to the Pacific Coast.

68
00:04:54,452 --> 00:04:58,585
The Chajnantor plateau, at an altitude of 5000 metres,

69
00:04:58,585 --> 00:05:01,813
offers ideal conditions for observing in the millimetre

70
00:05:01,813 --> 00:05:04,274
and submillimetre wavelength domain.

71
00:05:06,178 --> 00:05:08,686
This is where ESO, together with its partners,

72
00:05:08,686 --> 00:05:14,282
has chosen to construct the Atacama Large Millimeter/submillimeter Array,

73
00:05:14,282 --> 00:05:16,418
or ALMA for short.

74
00:05:18,346 --> 00:05:22,897
At such high altitudes there is very little water vapour in the air

75
00:05:22,897 --> 00:05:26,983
and the disturbing effects of the atmosphere are kept to a minimum.

76
00:05:33,439 --> 00:05:37,804
Cerro Paranal is an isolated mountain in the Atacama Desert,

77
00:05:37,804 --> 00:05:41,891
only 12 kilometres inland from the Pacific Coast.

78
00:05:44,514 --> 00:05:47,672
This is the home of ESO’s Very Large Telescope,

79
00:05:47,672 --> 00:05:55,196
which makes good use of Cerro Paranal’s approximately 320 cloud-free nights each year.

80
00:05:59,143 --> 00:06:01,883
Further inland, within sight of Paranal,

81
00:06:01,883 --> 00:06:05,343
another mountain has been identified as an ideal place

82
00:06:05,343 --> 00:06:08,083
to conduct astronomical observations:

83
00:06:08,083 --> 00:06:09,987
Cerro Armazones.

84
00:06:09,987 --> 00:06:14,724
This will be the future site of ESO’s Extremely Large Telescope,

85
00:06:14,724 --> 00:06:18,671
or the E-ELT, for short.

86
00:06:21,156 --> 00:06:23,478
The Mars-like landscape of the Atacama Desert

87
00:06:23,478 --> 00:06:25,892
is really a wonderful gift of nature.

88
00:06:25,892 --> 00:06:30,583
Its unique climate makes it a first-class location for ESO’s powerful telescopes

89
00:06:30,583 --> 00:06:32,208
so that night after night

90
00:06:32,208 --> 00:06:35,273
ESO’s astronomers can observe the crystal clear skies.

91
00:06:35,923 --> 00:06:38,338
This is Dr J signing off for the ESOcast.

92
00:06:38,338 --> 00:06:41,473
Join me again next time for another cosmic adventure.

93
00:06:45,072 --> 00:06:48,694
ESOcast is produced by ESO, the European Southern Observatory.

94
00:06:48,694 --> 00:06:52,694
ESO, the European Southern Observatory, is the pre-eminent intergovernmental science and technology organisation in astronomy,

95
00:06:52,694 --> 00:06:55,707
designing, constructing and operating the world’s most advanced ground-based telescopes.

96
00:06:57,355 --> 00:07:02,589
Transcription by ESO ; translation by —

97
00:07:13,772 --> 00:07:17,209
Now that you've caught up with ESO,

98
00:07:18,927 --> 00:07:22,363
head 'out of this world' with Hubble.

99
00:07:24,662 --> 00:07:31,814
The Hubblecast highlights the latest discoveries of the world´s most recognized and prized space observatory,

100
00:07:33,741 --> 00:07:37,363
the NASA/ESA Hubble Space Telescope