1 00:00:02,080 --> 00:00:06,640 Seeing Sharp 2 00:00:08,020 --> 00:00:11,590 Bigger is better - at least when it comes to telescope mirrors. 3 00:00:11,590 --> 00:00:16,670 But larger mirrors have to be thick, so that they don't deform under their own weight. 4 00:00:17,340 --> 00:00:21,610 And really large mirrors deform anyway, no matter how thick and heavy they are. 5 00:00:22,680 --> 00:00:29,360 The solution? Thin, lightweight mirrors - and a magic trick called active optics. 6 00:00:30,330 --> 00:00:33,350 ESO pioneered this technology in the late 1980s, 7 00:00:33,350 --> 00:00:36,040 with the New Technology Telescope. 8 00:00:37,450 --> 00:00:39,710 And this is the state of the art. 9 00:00:39,710 --> 00:00:45,760 The mirrors of the Very Large Telescope – the VLT – are 8.2 metres across... 10 00:00:45,760 --> 00:00:48,500 ...but only 20 centimetres thick. 11 00:00:49,330 --> 00:00:50,330 And here’s the magic: 12 00:00:50,990 --> 00:00:53,330 a computer-controlled support system ensures 13 00:00:53,330 --> 00:00:59,080 that the mirror keeps its desired shape at all times to nanometre precision. 14 00:01:15,640 --> 00:01:18,950 The VLT is ESO’s flagship facility. 15 00:01:18,950 --> 00:01:25,860 Four identical telescopes, joining forces on top of Cerro Paranal, in the north of Chile. 16 00:01:25,860 --> 00:01:28,040 Built in the late 1990s, 17 00:01:28,040 --> 00:01:32,740 they provided astronomers with the best available technologies. 18 00:01:37,580 --> 00:01:42,930 In the middle of the Atacama Desert, ESO created an astronomer’s paradise. 19 00:01:58,240 --> 00:02:00,560 Scientists stay in La Residencia, 20 00:02:00,560 --> 00:02:04,240 a guest house partly buried under the dirt and rubble 21 00:02:04,240 --> 00:02:06,390 of one of the driest places on the planet. 22 00:02:06,870 --> 00:02:12,940 But inside are lush palm trees, a swimming pool, and... delicious Chilean sweets. 23 00:02:16,260 --> 00:02:16,530 Of course, 24 00:02:16,530 --> 00:02:21,020 the unique selling point of the Very Large Telescope is not its swimming pool, 25 00:02:21,020 --> 00:02:24,790 but its unequalled view of the Universe. 26 00:02:29,600 --> 00:02:33,710 Without thin mirrors and active optics, the VLT would not be possible. 27 00:02:34,200 --> 00:02:35,280 But there’s more. 28 00:02:35,280 --> 00:02:40,550 Stars appear blurry, even when observed with the best and largest telescopes. 29 00:02:40,550 --> 00:02:44,590 The reason? The Earth’s atmosphere distorts the images. 30 00:02:49,300 --> 00:02:53,410 Enter the second magic trick: adaptive optics. 31 00:02:55,130 --> 00:03:01,410 On Paranal, laser beams shoot out into the night sky to create artificial stars. 32 00:03:01,410 --> 00:03:05,020 Sensors use these stars to measure the atmospheric distortions. 33 00:03:05,020 --> 00:03:08,150 And hundreds of times per second, 34 00:03:08,150 --> 00:03:12,420 the image is corrected by computer-controlled deformable mirrors. 35 00:03:13,930 --> 00:03:19,690 And the end effect? As if the turbulent atmosphere were completely removed. 36 00:03:20,090 --> 00:03:21,450 Just look at the difference! 37 00:03:28,470 --> 00:03:31,880 The Milky Way is a giant spiral galaxy. 38 00:03:31,880 --> 00:03:36,190 And at its core – 27 000 light-years away – 39 00:03:36,190 --> 00:03:41,630 lies a mystery that ESO’s Very Large Telescope helped to unravel. 40 00:03:43,859 --> 00:03:47,510 Massive dust clouds block our view of the Milky Way’s core. 41 00:03:47,510 --> 00:03:51,560 But sensitive infrared cameras can peer through the dust 42 00:03:51,560 --> 00:03:54,290 and uncover what lies behind. 43 00:04:00,220 --> 00:04:05,560 Assisted by adaptive optics they reveal dozens of red giant stars. 44 00:04:05,870 --> 00:04:09,500 And over the years, these stars are seen to move! 45 00:04:09,500 --> 00:04:14,270 They orbit an invisible object at the very centre of the Milky Way. 46 00:04:16,040 --> 00:04:21,670 Judging from the stellar motions, the invisible object must be extremely massive. 47 00:04:22,440 --> 00:04:29,000 A monstrous black hole, weighing in at 4.3 million times the mass of our Sun. 48 00:04:29,730 --> 00:04:33,760 Astronomers have even observed energetic flares from gas clouds 49 00:04:33,760 --> 00:04:35,510 falling into the black hole. 50 00:04:35,510 --> 00:04:40,460 All exposed by the sheer power of adaptive optics. 51 00:04:42,340 --> 00:04:47,050 So thin mirrors and active optics make it possible to build giant telescopes. 52 00:04:47,050 --> 00:04:50,050 And the adaptive optics take care of the atmospheric turbulence, 53 00:04:50,050 --> 00:04:53,430 providing us with extremely sharp images. 54 00:04:54,210 --> 00:04:56,260 But we're not done yet with our magic tricks. 55 00:04:56,260 --> 00:05:00,440 There's a third one. And it's called interferometry. 56 00:05:03,080 --> 00:05:06,030 The VLT consists of four telescopes. 57 00:05:06,030 --> 00:05:12,170 Together, they can act as a virtual telescope measuring 130 metres across. 58 00:05:14,730 --> 00:05:20,350 Light collected by the individual telescopes is channelled through evacuated tunnels 59 00:05:20,350 --> 00:05:23,460 and brought together in an underground laboratory. 60 00:05:25,220 --> 00:05:31,280 Here, the light waves are combined using laser metrology and intricate delay lines. 61 00:05:36,160 --> 00:05:41,070 The net result is the light-gathering power of four 8.2-metre mirrors, 62 00:05:41,070 --> 00:05:47,370 and the eagle-eyed vision of an imaginary telescope as large as fifty tennis courts. 63 00:05:50,240 --> 00:05:54,010 Four auxiliary telescopes give the network more flexibility. 64 00:05:54,010 --> 00:05:57,340 They may appear tiny next to the four giants. 65 00:05:57,340 --> 00:06:01,990 Yet, they sport mirrors 1.8 metres across. 66 00:06:01,990 --> 00:06:07,580 That’s bigger than the largest telescope in the world just a hundred years ago! 67 00:06:09,300 --> 00:06:12,070 Optical interferometry is something of a miracle. 68 00:06:12,070 --> 00:06:16,270 Starlight magic, wielded in the desert. 69 00:06:16,270 --> 00:06:20,270 And the results are impressive. 70 00:06:22,380 --> 00:06:26,850 The Very Large Telescope Interferometer reveals fifty times more detail 71 00:06:26,850 --> 00:06:28,920 than the Hubble Telescope. 72 00:06:31,990 --> 00:06:36,220 For instance, it gave us a close-up of a vampire double star. 73 00:06:38,180 --> 00:06:41,050 One star is stealing material from its companion. 74 00:06:45,690 --> 00:06:50,470 Irregular puffs of stardust have been detected around Betelgeuse — 75 00:06:50,470 --> 00:06:54,430 a stellar giant about to go supernova. 76 00:06:56,770 --> 00:07:02,020 And in dusty discs surrounding newborn stars, astronomers have found ... 77 00:07:03,010 --> 00:07:06,370 ... the raw material of future Earth-like worlds. 78 00:07:07,100 --> 00:07:12,710 The Very Large Telescope is mankind’s sharpest eye on the sky. 79 00:07:13,400 --> 00:07:16,780 But astronomers have other means to expand their horizons 80 00:07:16,780 --> 00:07:18,890 and broaden their views. 81 00:07:18,890 --> 00:07:21,720 At the European Southern Observatory, 82 00:07:21,720 --> 00:07:27,610 they have learned to see the Universe in a completely different kind of light.