3. Technology to the rescue 00:00:00:04 00:00:03:24 Just as modern cars don't look like a Model T Ford anymore, so are present... 00:00:04:00 00:00:07:11 ...day telescopes radically different from their classic predecessors... 00:00:07:12 00:00:09:21 ...like the five metre Hale telescope. 00:00:09:22 00:00:13:01 For one thing, their mounts are much smaller. 00:00:13:02 00:00:17:00 The old-style mount is an equatorial one where one of the axis... 00:00:17:01 00:00:20:22 ...is always mounted parallel to the Earth's rotation axis. 00:00:20:23 00:00:24:16 In order to keep track of the sky's motion, the telescope simply... 00:00:24:17 00:00:29:09 ...has to rotate around this axis at the same speed with which the Earth rotates. 00:00:29:10 00:00:32:08 Easy, but space-hungry. 00:00:32:09 00:00:37:05 The modern day altitude azimuth mounts are much more compact. 00:00:37:06 00:00:41:15 With a mount like that, the telescope is pointed much like a cannon. 00:00:41:16 00:00:46:10 One simply chooses the bearing, chooses the altitude, and off you go. 00:00:46:11 00:00:49:20 The problem is to keep track of the sky's motion. 00:00:49:21 00:00:55:10 The telescope pretty much has to rotate around both axis, and at varying speeds. 00:00:55:11 00:01:01:22 Essentially this only became possible once telescopes were computer controlled. 00:01:01:23 00:01:04:00 A smaller mount is cheaper to build. 00:01:04:01 00:01:08:17 Moreover, it fits into a smaller dome which reduces the cost even further... 00:01:08:18 00:01:11:12 ...and it improves the image quality. 00:01:11:13 00:01:14:24 Take the twin Keck Telescopes on Hawaii, for example. 00:01:15:00 00:01:17:19 Although their 10 metre mirrors are twice as large as the one... 00:01:17:20 00:01:21:15 ...of the Hale telescope, they nevertheless fit into smaller domes... 00:01:21:16 00:01:24:10 ...than the one on Palomar Mountain. 00:01:26:05 00:01:28:15 Telescope mirrors have evolved too. 00:01:28:16 00:01:30:07 They used to be thick and heavy. 00:01:30:08 00:01:33:00 Now they're thin and lightweight. 00:01:33:01 00:01:37:24 Mirror shells that can be many metres wide are cast in giant, rotating ovens. 00:01:38:00 00:01:41:12 And they are still less than 20 centimetres thick. 00:01:41:13 00:01:44:04 An intricate support structure prevents the thin mirror... 00:01:44:05 00:01:46:09 ...from cracking under its own weight. 00:01:46:10 00:01:50:07 Computer controlled pistons and actuators also help to keep the mirror... 00:01:50:08 00:01:52:00 ...in perfect shape. 00:01:53:10 00:01:55:14 This system is called active optics. 00:01:55:15 00:01:59:22 The idea is to compensate and to correct any deformations of the main mirror... 00:01:59:23 00:02:04:15 ...caused by gravity, the wind, or temperature changes. 00:02:04:16 00:02:08:07 Now, a thin mirror also weighs much less. 00:02:08:08 00:02:11:12 That means that its whole supporting structure, including the mount... 00:02:11:14 00:02:13:12 ...can also be a lot trimmer and lighter. 00:02:13:13 00:02:15:15 And cheaper! 00:02:15:16 00:02:18:10 Now here's the 3.6 metre New Technology Telescope... 00:02:18:11 00:02:21:20 ...built by European astronomers in the late 1980s. 00:02:21:21 00:02:24:22 It served as a testbed for many of the new technologies... 00:02:24:23 00:02:26:04 ...in telescope building. 00:02:26:05 00:02:31:01 And even its enclosure has nothing in common with traditional telescope domes. 00:02:31:02 00:02:34:07 The New Technology Telescope was a great success. 00:02:34:08 00:02:38:14 It was time to break the six metre barrier. 00:02:38:15 00:02:42:11 Mauna Kea Observatory sits on the highest point in the Pacific... 00:02:42:12 00:02:46:00 ...4200 metres above sea level. 00:02:48:00 00:02:52:04 On the beaches of Hawaii, tourists enjoy the Sun and the surf. 00:02:52:05 00:02:55:14 But high above them astronomers face chilling temperatures... 00:02:55:15 00:03:02:05 ...and altitude sickness in their quest to unravel the mysteries of the Universe. 00:03:02:06 00:03:05:04 The Keck Telescopes are among the largest in the world. 00:03:05:05 00:03:10:04 Their mirrors are 10 metres across, and wafer-thin. 00:03:10:05 00:03:15:02 Tiled like a bathroom floor, they consist of 36 hexagonal segments... 00:03:15:03 00:03:18:13 ...each controlled to nanometre precision. 00:03:18:14 00:03:22:06 These are true giants, devoted to observing the heavens. 00:03:22:07 00:03:25:04 The cathedrals of science. 00:03:25:05 00:03:27:16 Nightfall on Mauna Kea. 00:03:27:17 00:03:32:19 The Keck Telescopes begin collecting photons from the far reaches of the cosmos. 00:03:32:20 00:03:35:14 Their twin mirrors combining to be effectively larger... 00:03:35:15 00:03:38:12 ...than all earlier telescopes. 00:03:38:13 00:03:41:10 What will be tonight's catch? 00:03:45:17 00:03:50:14 A pair of colliding galaxies, billions of light-years away? 00:03:50:15 00:03:56:09 A dying star, gasping its last breath into a planetary nebula? 00:03:56:10 00:04:02:02 Or maybe an extrasolar planet that might harbour life? 00:04:02:03 00:04:06:24 On Cerro Paranal in the Chilean Atacama Desert - the driest place on Earth - 00:04:07:00 00:04:11:02 we find by far the biggest astronomy machine ever built: 00:04:11:03 00:04:14:15 the European Very Large Telescope. 00:04:27:05 00:04:30:14 The VLT is really four telescopes in one. 00:04:30:15 00:04:33:20 Each sporting an 8.2 metre mirror. 00:04:33:21 00:04:35:04 Antu. 00:04:35:05 00:04:36:06 Kueyen. 00:04:36:06 00:04:37:09 Melipal. 00:04:37:10 00:04:38:20 Yepun. 00:04:38:21 00:04:44:12 Native Mapuche names for the Sun, the Moon, the Southern Cross and Venus. 00:04:44:13 00:04:48:21 The huge mirrors were cast in Germany, polished in France, shipped to Chile... 00:04:48:22 00:04:52:07 ...and then slowly transported across the desert. 00:04:52:08 00:04:56:00 At sunset, the telescope enclosures open up. 00:04:56:01 00:04:59:15 Starlight rains down on the VLT mirrors. 00:05:01:22 00:05:05:00 New discoveries are made. 00:05:08:00 00:05:10:07 A laser pierces the night sky. 00:05:10:08 00:05:12:20 It projects an artificial star into the atmosphere... 00:05:12:21 00:05:15:24 ...90 kilometres above our heads. 00:05:16:00 00:05:19:01 Wavefront sensors measure how the star's image is distorted... 00:05:19:02 00:05:21:06 ...by the atmospheric turbulence. 00:05:21:07 00:05:25:02 Then, fast computers tell a flexible mirror how it has to... 00:05:25:03 00:05:27:23 ...deform itself in order to correct the distortion. 00:05:27:24 00:05:31:02 In effect untwinkling the stars. 00:05:31:03 00:05:34:18 This is called adaptive optics and it's the big magic trick... 00:05:34:19 00:05:36:11 ...of present day astronomy. 00:05:36:12 00:05:40:24 Without it, our view of the Universe would look blurred by the atmosphere. 00:05:41:00 00:05:45:00 But with it, our images are razor-sharp. 00:05:47:14 00:05:51:15 The other piece of optical wizardry is known as interferometry. 00:05:51:16 00:05:55:12 The idea is to take the light from two separate telescopes and to... 00:05:55:13 00:05:58:19 ...bring it together in a single point, while preserving the... 00:05:58:20 00:06:01:11 ...relative shifts between the lightwaves. 00:06:01:12 00:06:05:07 If it is done precisely enough the result is that the two telescopes... 00:06:05:07 00:06:08:18 ...act as if they were part of a single, colossal mirror... 00:06:08:19 00:06:12:01 ...as large as the distance between them. 00:06:12:02 00:06:16:04 In effect, interferometry gives your telescope eagle-like vision. 00:06:16:05 00:06:19:18 It allows smaller telescopes to reveal a level of detail that... 00:06:19:19 00:06:24:14 ...would otherwise only be visible with a much larger telescope. 00:06:24:15 00:06:27:18 The twin Keck Telescopes on Mauna Kea regularly team up... 00:06:27:19 00:06:29:16 ...as an interferometer. 00:06:29:17 00:06:33:14 In the case of the VLT, all four telescopes can work together. 00:06:33:15 00:06:36:22 In addition, several smaller auxiliary telescopes can also... 00:06:36:23 00:06:41:00 ...join the ranks in order to sharpen up the view even more. 00:06:41:23 00:06:45:13 Other big telescopes can be found all over the globe. 00:06:45:14 00:06:49:15 Subaru and Gemini North on Mauna Kea. 00:06:49:16 00:06:54:09 Gemini South and the Magellan Telescopes in Chile. 00:06:54:08 00:06:58:10 The Large Binocular Telescope in Arizona. 00:06:59:18 00:07:02:08 They are constructed at the best available sites. 00:07:02:09 00:07:05:07 High and dry, clear and dark. 00:07:05:08 00:07:08:05 Their eyes are as large as swimming pools. 00:07:08:06 00:07:11:23 All kitted out with adaptive optics to counteract the blurring... 00:07:11:24 00:07:13:16 ...effects of the atmosphere. 00:07:13:17 00:07:17:13 And sometimes they can have the resolution of a virtual behemoth... 00:07:17:14 00:07:20:04 ...thanks to interferometry. 00:07:21:05 00:07:23:09 Here's what they've shown us. 00:07:23:10 00:07:28:01 Planets. 00:07:28:02 00:07:30:21 Nebulae. 00:07:30:22 00:07:35:12 The actual sizes - and squashed shapes - of some stars. 00:07:35:13 00:07:38:17 A cool planet orbiting a brown dwarf. 00:07:38:18 00:07:43:01 And giant stars whirling around the core of our Milky Way Galaxy... 00:07:43:02 00:07:48:07 ...governed by the gravity of a supermassive black hole. 00:07:48:08 00:07:51:23 We've come quite a way since Galileo's day.