1 00:00:00,520 --> 00:00:02,000 This film takes you on a journey… 2 00:00:02,000 --> 00:00:04,520 …a journey through time and space. 3 00:00:36,680 --> 00:00:40,840 I want to tell you the story of an instrument that has vastly improved our view of the skies, 4 00:00:40,840 --> 00:00:43,240 sharpening our perception of the Universe, 5 00:00:43,240 --> 00:00:48,600 and penetrating ever deeper toward the furthest edges of space and time. 6 00:02:03,320 --> 00:02:06,400 Looking at the night sky we see the familiar twinkle of starlight. 7 00:02:06,920 --> 00:02:10,160 Light that has travelled enormous distances to reach us. 8 00:02:10,160 --> 00:02:13,400 But we are not seeing the stars themselves flicker… 9 00:02:16,920 --> 00:02:20,000 The universe is gloriously transparent. 10 00:02:20,000 --> 00:02:25,760 The light from distant stars and galaxies can travel unchanged across space for thousands, 11 00:02:25,760 --> 00:02:28,160 millions, even billions of years. 12 00:02:34,320 --> 00:02:38,520 But then, in the last few microseconds before that light reaches our eyes, 13 00:02:38,520 --> 00:02:41,920 the accurate view of those stars and galaxies is snatched away. 14 00:02:43,080 --> 00:02:48,320 This is because, as light passes through our atmosphere, the ever changing blankets of air, 15 00:02:48,320 --> 00:02:53,160 water vapour and dust, blur the fine cosmic details. 16 00:02:55,760 --> 00:03:00,000 So, for many years, astronomers around the world longed for an observatory in space. 17 00:03:00,000 --> 00:03:06,400 As early as 1923, the famed German rocket scientist Hermann Oberth suggested a space-based telescope. 18 00:03:06,400 --> 00:03:11,320 However, it was decades before technology caught up with the dream. 19 00:03:11,320 --> 00:03:17,400 The American astronomer Lyman Spitzer proposed a more realistic plan for a space telescope in 1946. 20 00:03:21,920 --> 00:03:28,840 From a position in space, above Earth's atmosphere, a telescope would be able to detect the pristine light from stars, 21 00:03:28,840 --> 00:03:34,840 galaxies, and other objects, well before it was distorted by the air we breathe. 22 00:03:34,840 --> 00:03:41,240 The result: much sharper images than even the largest telescopes on the ground can achieve; 23 00:03:41,240 --> 00:03:45,680 images limited in sharpness only by the quality of the optics. 24 00:03:50,080 --> 00:03:57,000 In the 1970s, NASA - the National Aeronautics and Space Administration - and ESA - the European Space Agency - 25 00:03:57,000 --> 00:04:03,600 began working together to design and build what would become the Hubble Space Telescope. 26 00:04:07,520 --> 00:04:12,000 The name is a tribute to Edwin Powell Hubble - the founder of modern cosmology - 27 00:04:12,000 --> 00:04:17,920 who, in the 1920s, proved that not all that we see in the sky lies within the Milky Way. 28 00:04:17,920 --> 00:04:22,080 Instead, the cosmos extends far, far beyond. 29 00:04:23,160 --> 00:04:28,520 Hubble's work changed our perception of mankind's place in the Universe forever and the choice 30 00:04:28,520 --> 00:04:36,600 of naming the most magnificent telescope of all time after Edwin Hubble could not have been more appropriate. 31 00:04:40,160 --> 00:04:44,240 It took two decades of dedicated collaboration between scientists, 32 00:04:44,240 --> 00:04:50,000 engineers and contractors from many countries before Hubble was finally finished. 33 00:04:52,000 --> 00:04:59,080 On April 24, 1990, five astronauts aboard the space shuttle Discovery left on a journey 34 00:04:59,080 --> 00:05:01,680 that changed our vision of the universe for ever! 35 00:05:01,680 --> 00:05:09,400 They deployed the eagerly anticipated Space Telescope in an orbit roughly 600 km above the Earth’s surface. 36 00:05:12,240 --> 00:05:16,680 On Earth, the astronomers waited impatiently for the first results. 37 00:05:17,920 --> 00:05:22,840 But less than two months later it was clear that Hubble’s vision was anything but sharp. 38 00:05:22,840 --> 00:05:26,320 The mirror had a serious flaw… 39 00:05:43,680 --> 00:05:47,600 A defect in the shape of the mirror prevented Hubble from taking sharp images. 40 00:05:47,600 --> 00:05:52,680 The mirror’s edge was too flat, by only a mere fiftieth of the width of a human hair. 41 00:05:52,680 --> 00:05:57,760 But to accomplish its mission, Hubble had to be perfect in every tiny detail… 42 00:05:57,760 --> 00:06:00,320 The disappointment was almost too great to bear. 43 00:06:00,320 --> 00:06:07,520 Not only amongst astronomers, but also for American and European taxpayers… 44 00:06:07,520 --> 00:06:09,920 Nevertheless, over the following two years, 45 00:06:09,920 --> 00:06:12,240 scientists and engineers from NASA and ESA 46 00:06:12,240 --> 00:06:17,600 worked together to design and build a corrective optics package, named COSTAR, 47 00:06:17,600 --> 00:06:22,600 for Corrective Optics Space Telescope Axial Replacement. 48 00:06:22,600 --> 00:06:26,080 Hubble’s masters now faced another tough decision: 49 00:06:26,080 --> 00:06:28,520 which science instrument should they remove 50 00:06:28,520 --> 00:06:30,920 so that COSTAR could be fitted to Hubble? 51 00:06:31,760 --> 00:06:34,400 They eventually chose the High Speed Photometer. 52 00:06:44,680 --> 00:06:49,160 Hubble’s First Servicing Mission in 1993 has gone down in history 53 00:06:49,160 --> 00:06:52,000 as one of the highlights of human spaceflight. 54 00:06:52,000 --> 00:06:56,760 It captured the attention of both astronomers and the public at large to a degree 55 00:06:56,760 --> 00:07:00,400 that no Space Shuttle mission since has achieved. 56 00:07:00,400 --> 00:07:06,000 Meticulously planned and brilliantly executed, the mission succeeded on all counts. 57 00:07:06,000 --> 00:07:12,320 COSTAR corrected Hubble’s eyesight more perfectly than anyone had dared to hope. 58 00:07:15,000 --> 00:07:18,160 When the first images after the servicing came up on the computer screens 59 00:07:18,160 --> 00:07:24,920 it was instantly clear that the glasses taken up by the astronauts were completely correcting Hubble's nearsightedness. 60 00:07:24,920 --> 00:07:27,920 Hubble was finally in business! 61 00:07:46,400 --> 00:07:50,240 That was only the first time the Space Shuttle visited Hubble. 62 00:07:51,320 --> 00:07:57,080 The telescope was designed to be upgraded, to keep utilizing new capabilities. 63 00:07:57,080 --> 00:08:04,600 When more advanced instruments, electrical or mechanical components become available, they could be installed. 64 00:08:04,600 --> 00:08:10,160 Plus, just as your car needs servicing, so Hubble needs tuning-up from time to time. 65 00:08:10,840 --> 00:08:16,760 Engineers and scientists periodically send the Shuttle to Hubble, so that astronauts can upgrade it, 66 00:08:16,760 --> 00:08:21,840 using wrenches, screwdrivers and power tools, just as your mechanic does with a car. 67 00:08:24,320 --> 00:08:34,600 There have been four Servicing missions so far – in 1993, 1997, 1999 and 2002 – all undertaken by astronauts, 68 00:08:34,600 --> 00:08:42,080 transported into space by NASA’s Space Shuttle. The next one was supposed to occur in 2005, 69 00:08:42,080 --> 00:08:48,160 but was unfortunately cancelled in the aftermath of the tragic Columbia crash. 70 00:08:49,920 --> 00:08:51,920 Hubble’s future is uncertain. 71 00:08:51,920 --> 00:08:58,760 It was originally designed to operate for 15 years, but it is now expected thats its life could be extended to 20 years. 72 00:08:58,920 --> 00:09:03,160 Hubble is still producing the most astonishing results that astronomers have ever known. 73 00:09:04,240 --> 00:09:06,760 Hubble's important mission will eventually come to an end. 74 00:09:08,320 --> 00:09:12,920 An unmanned probe will link up with Hubble in orbit and dock with it. 75 00:09:14,920 --> 00:09:19,400 When leaving Hubble, the robot will leave behind a rocket-module so that, 76 00:09:19,400 --> 00:09:21,600 after some more years of fruitful observing, 77 00:09:21,760 --> 00:09:27,000 engineers on the ground can activate these rockets to control Hubble’s final descent 78 00:09:27,080 --> 00:09:31,320 into the atmosphere and to a peaceful final resting place, in the ocean. 79 00:09:37,240 --> 00:09:40,160 However, the retirement of the Hubble Space Telescope 80 00:09:40,160 --> 00:09:46,160 will not signal the end of our unrivalled view of the universe. Rather, it will mark a new beginning, 81 00:09:46,160 --> 00:09:51,320 an era of even more amazing discoveries and images from space. 82 00:09:51,320 --> 00:09:53,160 For Hubble has a successor. 83 00:09:54,400 --> 00:10:02,600 The James Webb Space Telescope is being designed right now and may be launched as early as 2011. 84 00:10:03,840 --> 00:10:05,520 When that day comes, 85 00:10:05,520 --> 00:10:09,760 scientists using the James Webb Space Telescope hope to discover 86 00:10:09,760 --> 00:10:15,760 and understand even more about our fascinating universe. 87 00:10:39,840 --> 00:10:45,960 Hubble is an upgradeable, space-based telescope orbiting at almost 600 km, 88 00:10:45,960 --> 00:10:50,560 placing it well above most of our image-distorting atmosphere. 89 00:10:50,560 --> 00:10:54,160 It takes about 97 minutes to complete each orbit. 90 00:10:54,160 --> 00:11:00,800 It is designed to take high-resolution images and accurate spectra by concentrating starlight 91 00:11:00,800 --> 00:11:09,440 to form sharper images than are possible from the ground, where the atmospheric ‘twinkling' of the stars limits the clarity. 92 00:11:09,440 --> 00:11:12,760 To gather as much light as possible from the faint objects it studies, 93 00:11:12,760 --> 00:11:16,400 any telescope needs the largest mirror it can get. 94 00:11:16,400 --> 00:11:20,360 Despite Hubble’s relatively modest mirror diameter of 2.4 metres, 95 00:11:20,360 --> 00:11:29,440 it is more than able to compete with ground-based telescopes that have mirrors 10 or 20 times larger in collecting area. 96 00:11:31,560 --> 00:11:32,840 Hubble is a large satellite, 97 00:11:32,840 --> 00:11:36,120 about 16 metres long or the size of a small bus. 98 00:11:36,120 --> 00:11:40,040 It is also one of the most complicated pieces of technology ever built. 99 00:11:40,040 --> 00:11:43,360 It contains more than 3000 sensors that continuously read out 100 00:11:43,360 --> 00:11:48,760 the status of the hardware so that technicians on the ground can keep an eye on everything. 101 00:11:48,760 --> 00:11:52,040 Time on the Hubble is a precious commodity. 102 00:11:52,040 --> 00:11:56,040 Astronomers across the world regularly ask for much more time than is available. 103 00:11:56,040 --> 00:11:59,840 Keeping Hubble working 24/7 is no small task. 104 00:11:59,840 --> 00:12:06,600 Not a single second must be lost and all tasks either observations or so-called ‘housekeeping’ tasks, 105 00:12:06,600 --> 00:12:13,080 such as repositioning of the telescope, or uploading new observing schedules are meticulously planned. 106 00:12:15,400 --> 00:12:20,200 For astronomers, the most important components of Hubble are its scientific instruments. 107 00:12:23,440 --> 00:12:28,520 There are two groups of instruments in Hubble, here and here. 108 00:12:30,600 --> 00:12:34,520 The different instruments serve different purposes – some are for making images, 109 00:12:34,520 --> 00:12:43,440 some are designed to dissect the light from the stars and galaxies by spreading it out to form a rainbow-like spectrum. 110 00:12:44,960 --> 00:12:50,360 Hubble’s unique vantage point in space makes it capable of observing the infrared and ultraviolet light 111 00:12:50,360 --> 00:12:56,160 that is otherwise filtered away by the atmosphere before it can reach telescopes on the ground. 112 00:12:59,680 --> 00:13:04,560 These forms of light reveal properties of celestial objects that are otherwise hidden from us. 113 00:13:08,840 --> 00:13:16,400 Some instruments, like ACS – the Advanced Camera for Surveys – are better for visible and ultraviolet observations, 114 00:13:16,400 --> 00:13:24,960 some, like NICMOS – the Near Infrared Camera and Multi-object Spectrograph – are best for infrared observations. 115 00:13:29,520 --> 00:13:34,240 Different mechanical and electrical components keep Hubble functioning. 116 00:13:34,240 --> 00:13:40,640 The power for Hubble comes from solar panels on the side, which convert sunlight into electricity. 117 00:13:42,920 --> 00:13:50,960 Gyroscopes, star trackers and reaction wheels keep Hubble steady and pointing in the right direction – not too close to the Sun, 118 00:13:50,960 --> 00:13:55,360 Moon or Earth as they would destroy the light-sensitive instruments – 119 00:13:55,360 --> 00:14:00,360 and accurately towards the objects being studied for hours or days at a time. 120 00:14:01,920 --> 00:14:06,840 Hubble has several communication antennae on its side that are necessary for sending 121 00:14:06,840 --> 00:14:08,840 observations and other data down to Earth. 122 00:14:10,000 --> 00:14:15,040 Hubble sends its data first to a satellite in the Tracking and Data Relay Satellite System, 123 00:14:15,040 --> 00:14:20,120 which then downlinks the signal to White Sands, New Mexico. 124 00:14:22,320 --> 00:14:32,160 The observations are sent from NASA in the United States to Europe where they are stored in a huge data archive in Munich. 125 00:14:35,960 --> 00:14:40,400 No single nation could undertake such an enormous project. 126 00:14:40,400 --> 00:14:44,320 Hubble has been a major collaboration between NASA and ESA, 127 00:14:44,320 --> 00:14:48,560 the European Space Agency from an early stage in its life. 128 00:14:52,560 --> 00:14:56,440 Hubble has been of paramount importance to European astronomy. 129 00:14:56,440 --> 00:15:02,120 European astronomers regularly win more than 15% of the observing time with Hubble, 130 00:15:02,120 --> 00:15:06,200 resulting in several thousand scientific publications over the years. 131 00:15:07,560 --> 00:15:10,240 Two groups of European specialists work with Hubble. 132 00:15:10,920 --> 00:15:17,240 There are 15 people from ESA currently working at the Space Telescope Science Institute in the USA, 133 00:15:17,240 --> 00:15:24,200 and 20 others make up the Space Telescope-European Coordinating Facility in Munich, Germany. 134 00:15:44,680 --> 00:15:47,240 There are no boundaries in space. 135 00:15:47,920 --> 00:15:54,000 In this vast Universe, our closest relatives are the objects within the Solar System. 136 00:15:55,760 --> 00:16:00,760 We share the same origin and the same destiny… 137 00:16:04,520 --> 00:16:09,080 Our Solar System was formed about four and a half billion years ago from a huge gas cloud. 138 00:16:10,320 --> 00:16:13,840 Ironically, it could have been the deadly force of a thermonuclear blast 139 00:16:13,840 --> 00:16:18,400 from an exploding star in the vicinity that triggered our creation… 140 00:16:24,400 --> 00:16:30,680 The devastating force of the blast may have disturbed the precarious equilibrium of the original gas cloud, 141 00:16:30,680 --> 00:16:37,000 causing some of the matter to collapse inwards, towards the centre, creating a new star, our Sun, 142 00:16:37,000 --> 00:16:46,600 and a minute percentage of the collapsing matter became the multifaceted assembly of planets that we have around us today. 143 00:16:48,680 --> 00:16:53,160 We are, in other words, just the leftovers of our Sun’s birth. 144 00:16:53,840 --> 00:17:00,680 The planets were born in the rotating disk of dust and gas left behind as our mother star was formed. 145 00:17:01,680 --> 00:17:09,840 The rocky planets formed in the inner Solar System while the enigmatic gas giants were formed further out. 146 00:17:09,840 --> 00:17:14,920 And then, when a fierce wind of smashed atoms began to blow from the Sun –, 147 00:17:14,920 --> 00:17:19,240 or perhaps from hot nearby stars or a nearby supernova 148 00:17:19,240 --> 00:17:26,520 only sizable planets could maintain their gaseous surroundings and the last wisps of the tenuous cloud 149 00:17:26,520 --> 00:17:29,680 between the planets was whipped away. 150 00:17:29,680 --> 00:17:36,160 So in our Solar System’s zoo of celestial bodies there are rocky worlds… 151 00:17:40,080 --> 00:17:44,160 … and giant gaseous planets. 152 00:17:49,840 --> 00:17:56,400 Even now, there is no exact estimate of how much matter or even how many planets exist within our Solar System… 153 00:17:56,400 --> 00:18:02,000 Since Pluto’s discovery in the 1930s, and its satellite Charon’s in the 1970s, 154 00:18:02,000 --> 00:18:07,520 astronomers have tried to figure out if there’s anything else out there, beyond the ninth planet. 155 00:18:07,520 --> 00:18:12,760 In 2003, Hubble spotted something moving fast enough across the background 156 00:18:12,760 --> 00:18:17,000 of faraway stars to be an object within the Solar System. 157 00:18:17,000 --> 00:18:24,520 Estimates show that it could be about the size of a planet and it has been named Sedna, after an Inuit goddess. 158 00:18:24,520 --> 00:18:30,840 Sedna may be 1500 km in diameter, that’s about three quarters the size of Pluto, 159 00:18:30,840 --> 00:18:37,160 but so far away that it appears as just a small cluster of pixels even to Hubble. 160 00:18:37,160 --> 00:18:42,760 Nevertheless, it is the largest object discovered in the Solar System since Pluto. 161 00:18:44,080 --> 00:18:47,680 The Sun is about 15 billion km from Sedna 162 00:18:47,680 --> 00:18:51,840 – 100 times further than Earth’s distance from the Sun – 163 00:18:51,840 --> 00:18:56,080 and barely gives out as much light and heat as the full moon. 164 00:18:56,080 --> 00:19:00,760 So Sedna is engulfed in an eternal bleak winter… 165 00:19:03,000 --> 00:19:05,520 Sedna is not the only mysterious object out there. 166 00:19:05,520 --> 00:19:11,000 Debris from the formation of the planets is still floating everywhere in the form of asteroids 167 00:19:11,000 --> 00:19:13,680 and comets of various shapes and sizes. 168 00:19:13,680 --> 00:19:18,240 Sometimes their orbits can lead them on catastrophic courses … 169 00:19:19,160 --> 00:19:24,520 The Hubble Space Telescope witnessed the final journey of the comet Shoemaker-Levy 9… 170 00:19:24,520 --> 00:19:34,000 It was torn into numerous pieces by Jupiter's gravitational pull when it passed the massive planet in the summer of 1992. 171 00:19:34,000 --> 00:19:41,000 Two years later, these fragments returned and drove straight into the heart of Jupiter’s atmosphere. 172 00:19:41,000 --> 00:19:49,920 Hubble followed the comet fragments on their last journey and delivered stunning high-resolution images of the impact scars. 173 00:19:49,920 --> 00:19:56,080 Our Earth could easily fit into any of these black bruises… 174 00:20:58,080 --> 00:21:04,240 Space probes with sophisticated instruments are frequently sent to the planets of our Solar System. 175 00:21:04,240 --> 00:21:09,000 They provide close-up investigations of these distant places. 176 00:21:09,000 --> 00:21:18,400 Hubble, too, provides its own unique service, by opening a window on our Solar System that is never closed. 177 00:21:32,000 --> 00:21:36,840 We’ve gained unprecedented views of storms on other planets, 178 00:21:36,840 --> 00:21:40,320 … their changing seasons 179 00:22:00,920 --> 00:22:06,680 …and unprecedented views of other atmospheric events, such as aurorae, 180 00:22:06,680 --> 00:22:10,600 known on Earth as the northern and southern lights. 181 00:22:21,920 --> 00:22:26,600 Even though the solar system clearly has many more surprises in store for us, 182 00:22:26,600 --> 00:22:32,520 Hubble has also turned its eye out towards other stars, looking for planetary systems. 183 00:22:33,600 --> 00:22:37,840 Astronomers are beginning their search for life elsewhere in the Universe. 184 00:22:37,840 --> 00:22:42,920 To start with, they are concentrating on finding earth-like planets. 185 00:22:47,320 --> 00:22:51,840 In 2001, Hubble made the first direct detection of the atmosphere 186 00:22:51,840 --> 00:22:55,840 of an extra-solar planet and partially determined its composition. 187 00:22:55,840 --> 00:23:01,240 Measuring the chemical makeup of extra-solar planetary atmospheres will one day 188 00:23:01,240 --> 00:23:07,760 allow us to search for the markers of life beyond Earth. All living things breathe 189 00:23:07,760 --> 00:23:13,000 and this changes the composition of the atmosphere in readily detectable ways. 190 00:23:15,000 --> 00:23:19,760 Astronomers believe there are many planetary systems similar to ours, 191 00:23:19,760 --> 00:23:23,600 orbiting other stars throughout the Galaxy. 192 00:23:23,600 --> 00:23:33,400 The birth, life, death and rebirth of stars continues in an unending cycle, in which stars, 193 00:23:33,400 --> 00:23:37,400 born of gas and dust, will shine for millions or billions of years, 194 00:23:37,400 --> 00:23:42,400 die and return as gas and dust to form new stars. 195 00:23:42,400 --> 00:23:50,520 The by-products of this continual process include planets and the chemical elements that make life possible. 196 00:23:52,080 --> 00:23:59,600 So through the entire vastness of space the eternal ebb and flow of life continues… 197 00:24:18,520 --> 00:24:23,680 Our Sun, that vital source of energy for life on Earth, is a star. 198 00:24:23,680 --> 00:24:26,360 A totally unexceptional star, 199 00:24:26,360 --> 00:24:30,880 just like billions of others that we can find throughout the Galaxy. 200 00:24:35,160 --> 00:24:37,360 A star is nothing but a sphere of glowing gas. 201 00:24:37,360 --> 00:24:43,920 It forms out of a compressed cloud of gas and releases energy steadily, throughout its life, 202 00:24:43,920 --> 00:24:47,760 because a continual chain of nuclear reactions takes place in its core. 203 00:24:47,760 --> 00:24:54,120 Most stars combine hydrogen atoms to form helium through the process called nuclear fusion 204 00:24:54,120 --> 00:24:57,640 - the same process that powers a devastating hydrogen bomb. 205 00:24:57,640 --> 00:25:05,320 In fact, stars are nuclear factories that convert lighter elements into heavier elements in a series of fusion reactions. 206 00:25:05,320 --> 00:25:08,800 They will keep glowing until they run out of ‘fuel’. 207 00:25:08,800 --> 00:25:15,240 And that’s it - a star’s life: a quiet beginning and a steady progress to a sometimes violent end. 208 00:25:15,240 --> 00:25:24,200 But how can we be certain of this picture when an individual star like our sun outlives humans by a factor of a few hundred million? 209 00:25:26,120 --> 00:25:30,040 To investigate the lifecycle of a particular organism on Earth, 210 00:25:30,040 --> 00:25:34,440 we don’t have to track an individual specimen’s entire life. 211 00:25:34,440 --> 00:25:39,000 Instead, we can observe many of the organisms at once. 212 00:25:39,000 --> 00:25:43,200 This will show us all the different phases of its life cycle. 213 00:25:43,200 --> 00:25:49,800 For example, each stage of a person’s life is a snapshot of the human experience. 214 00:25:49,800 --> 00:25:52,760 And so it is with stars... 215 00:25:52,760 --> 00:25:56,680 Stars live and die over millions, or even billions, of years. 216 00:25:56,680 --> 00:26:00,160 Even the most reckless stars live for at least one million years 217 00:26:00,160 --> 00:26:03,160 – longer than the entire history of mankind! 218 00:26:03,160 --> 00:26:08,160 And that’s why it is extremely unusual to be able to track age-related changes in individual stars. 219 00:26:08,160 --> 00:26:10,040 To learn more about stars, 220 00:26:10,040 --> 00:26:15,440 we must sample different stars at every stage of life and piece together 221 00:26:15,440 --> 00:26:17,520 the whole cycle from birth to death. 222 00:26:17,520 --> 00:26:22,920 Hubble’s vivid images have documented the tumultuous birth of stars and delivered many, 223 00:26:22,920 --> 00:26:26,400 astonishing pictures in colourful detail. 224 00:26:39,840 --> 00:26:46,160 The birth of stars in neighbouring stellar ‘maternity wards’ can be used as a time machine 225 00:26:46,160 --> 00:26:50,760 to replay the events that created our Solar System. 226 00:26:50,760 --> 00:26:56,960 Hubble has often had to work hard for this information because these important clues 227 00:26:56,960 --> 00:27:09,320 about our genesis lie hidden behind the veil of gently glowing, dust-laden molecular clouds where stars are formed. 228 00:27:49,560 --> 00:27:53,320 Right now there are stars forming everywhere in the Universe. 229 00:27:53,320 --> 00:27:57,840 Enormous glowing pillars of dusty hydrogen gas stand sentinel over their cradles, 230 00:27:57,840 --> 00:28:02,000 basking in the light of nearby, newly-formed stars. 231 00:28:08,280 --> 00:28:12,840 Hubble’s ability to observe infrared light enables it to penetrate the dust and gas 232 00:28:12,840 --> 00:28:16,840 and reveal the newly born stars as never before. 233 00:28:24,000 --> 00:28:28,160 One of the most exciting of Hubble’s many discoveries was the observation of dust disks 234 00:28:28,160 --> 00:28:33,240 surrounding some newborn stars, buried deep inside the Orion Nebula. 235 00:28:33,240 --> 00:28:38,280 Here we are actually seeing the creation of new Solar Systems where planets will eventually form. 236 00:28:38,280 --> 00:28:45,800 Just as they did in our own Solar system four and a half billion years ago. 237 00:28:51,560 --> 00:28:56,680 In the first stages of their lives, stars can stock up on gas from their original birth cloud. 238 00:28:56,680 --> 00:29:01,040 Material falling into the star creates bubbles or even jets 239 00:29:01,040 --> 00:29:10,080 as it is heated and blasted along a path that follows the star's rotation axis, like an axle through a wheel. 240 00:29:16,640 --> 00:29:19,840 Often many stars are born from the same cloud of gas and dust. 241 00:29:19,840 --> 00:29:25,200 Some may stay together through their whole lifetime, keeping step as they evolve, 242 00:29:25,200 --> 00:29:29,800 like childhood friends that you keep for life. 243 00:29:34,800 --> 00:29:41,120 The stars in a cluster will all have the same age, but will have a range of different masses. 244 00:29:41,120 --> 00:29:46,280 And this means that very different destinies await them. 245 00:29:52,360 --> 00:29:57,440 Human existence is the mere blink of an eye compared with the life of a star. 246 00:29:59,120 --> 00:30:08,000 So the direct observation of a transition between different stages of a star’s life can only come about by lucky chance. 247 00:30:08,000 --> 00:30:15,720 In fifteen highly productive years, Hubble has allowed us to observe some stars ageing in real time. 248 00:30:15,720 --> 00:30:19,600 The telescope has produced startling “movies” that allow us to witness 249 00:30:19,600 --> 00:30:28,120 how some of them DO modify their appearance over this minute span of astronomical time. 250 00:30:29,520 --> 00:30:33,520 The stars containing the most mass end their lives cataclysmically, 251 00:30:33,520 --> 00:30:39,760 destroying themselves in titanic stellar explosions known as supernovae. 252 00:30:39,760 --> 00:30:46,000 For a few glorious months, each becomes one of the brightest objects in the entire Universe, 253 00:30:46,000 --> 00:30:51,680 outshining all the other stars in its parent galaxy. 254 00:30:51,680 --> 00:30:59,520 Since its launch in 1990, Hubble has watched the drama unfold in supernova 1987A, 255 00:30:59,520 --> 00:31:03,680 the nearest exploding star in modern times. 256 00:31:03,680 --> 00:31:08,520 The telescope has been monitoring a ring of gas surrounding the supernova blast. 257 00:31:08,520 --> 00:31:15,760 Hubble has observed the appearance of bright spots along the ring, like gemstones on a necklace. 258 00:31:15,760 --> 00:31:25,040 These cosmic pearls are now beeing lit by supersonic shocks unleashed during the explosion of the star. 259 00:31:27,160 --> 00:31:30,640 The ruins of an exploding star can hide a powerful engine. 260 00:31:30,640 --> 00:31:36,120 Hubble has probed the mysterious heart of the Crab Nebula, the tattered remains of an exploding star, 261 00:31:36,120 --> 00:31:43,120 vividly described by Chinese astronomers in 1054, and has revealed its dynamic centre. 262 00:31:43,120 --> 00:31:48,680 The innermost region of this nebula harbours a special type of star, a pulsar. 263 00:31:48,680 --> 00:31:54,080 Like a beacon, this star rotates, emitting light and energy in a beam. 264 00:31:54,080 --> 00:31:58,640 And it powers the vast nebula of dust and gas surrounding it. 265 00:31:58,640 --> 00:32:02,040 However, not all stars end their lives so violently. 266 00:32:02,040 --> 00:32:05,800 Sun-like stars cool down once they run out of hydrogen. 267 00:32:05,800 --> 00:32:10,240 The centre collapses in on itself and the heavier elements are burnt, 268 00:32:10,240 --> 00:32:14,280 causing the outer layers to expand and leak slowly into space. 269 00:32:14,280 --> 00:32:18,600 At this stage in a star’s life, it is called a “red giant”. 270 00:32:18,600 --> 00:32:22,320 Our Sun will become a “red-giant” in a few billion years. 271 00:32:22,320 --> 00:32:29,320 At that time, it will expand so much that it will swallow Mercury, Venus and our planet, too. 272 00:32:29,320 --> 00:32:34,080 But these stars are not finished quite yet. They can still become something extraordinary… 273 00:32:35,880 --> 00:32:44,880 Just before they breathe their last breath, stars like our Sun go out in a final blaze of glory. 274 00:32:44,880 --> 00:32:50,120 In its final stages of nuclear fusion, stellar winds blow from the star, 275 00:32:50,120 --> 00:32:54,320 causing the red giant to swell to an enormous size. 276 00:32:54,320 --> 00:32:59,720 At the heart of this expansion, the exposed heart of the star floods 277 00:32:59,720 --> 00:33:05,360 the gaseous envelope with powerful ultraviolet light, making it glow. 278 00:33:07,000 --> 00:33:09,440 Because to early telescopic astronomers, 279 00:33:09,440 --> 00:33:14,200 these amazing constructions looked a bit like the newly discovered planet Uranus, 280 00:33:14,200 --> 00:33:17,520 they became known as planetary nebulae. 281 00:33:17,520 --> 00:33:24,920 Hubble's keen perception shows that planetary nebulae are like butterflies: no two are alike. 282 00:33:32,120 --> 00:33:36,920 Hubble’s dazzling collection of planetary nebulae show surprisingly intricate, 283 00:33:36,920 --> 00:33:44,840 glowing patterns: pinwheels, swirling jets, elegant goblet shapes, 284 00:33:44,840 --> 00:33:51,720 barrel shapes, or even rocket engine exhausts. 285 00:34:13,000 --> 00:34:18,080 From its unique position high above the distorting atmosphere Hubble is the only telescope 286 00:34:18,080 --> 00:34:24,160 that can observe the swollen outer envelope of these dying stars in full detail. 287 00:34:24,160 --> 00:34:32,280 Here we flip back and forth between Hubble images from 1994 and 2002. 288 00:34:32,280 --> 00:34:38,000 One of the greatest mysteries in modern astrophysics is how a simple, 289 00:34:38,000 --> 00:34:44,320 spherical gas ball such as our Sun, can give rise to these intricate structures..!! 290 00:34:44,320 --> 00:34:50,320 For some planetary nebulae it is as if a cosmic garden sprinkler created the jets 291 00:34:50,320 --> 00:34:54,920 that stream out in opposite directions. 292 00:34:54,920 --> 00:34:59,160 …Or could these amazing patterns possibly be sculpted by the magnetic field 293 00:34:59,160 --> 00:35:03,040 of a companion star that funnels the emitted gas into a jet? 294 00:35:08,720 --> 00:35:15,600 Whatever their cause, in only ten thousand years these fleeting cosmic flowers disperse in space. 295 00:35:15,600 --> 00:35:20,920 Just as real flowers fertilize their surroundings as they decompose, 296 00:35:20,920 --> 00:35:27,560 the chemical elements produced inside the star during its life are dispersed by the planetary nebula 297 00:35:27,560 --> 00:35:33,760 to nourish the space around it, providing the raw material for new generations of stars, 298 00:35:33,760 --> 00:35:36,600 planets and possibly even life. 299 00:35:36,600 --> 00:35:40,520 Because they disappear so quickly on a cosmic timescale 300 00:35:40,520 --> 00:35:47,520 there are never more than about 15000 planetary nebulae at any one time in our Milky Way. 301 00:35:47,520 --> 00:35:54,800 A more lasting monument to the dead star, is the tiny heart it leaves behind. 302 00:35:54,800 --> 00:36:00,360 Known as a white dwarf, each of these exceptionally dense, Earth-sized stars 303 00:36:00,360 --> 00:36:06,600 are fated to spend the rest of eternity gradually leaking their residual heat into space, 304 00:36:06,600 --> 00:36:17,000 until eventually, in many billions of years, they approach the frigid –270 degrees centigrade of space. 305 00:36:33,640 --> 00:36:38,800 We live inside a huge star system, or galaxy, known as the Milky Way. 306 00:36:38,800 --> 00:36:46,040 Seen from outside, the Milky Way is a gigantic spiral, consisting of a central hub embraced by long arms. 307 00:36:46,040 --> 00:36:53,080 The whole system slowly rotates. Between the stars there are vast amounts of gas and dust 308 00:36:53,080 --> 00:36:59,120 - that we can see - and some unknown material called “Dark Matter” that is invisible to us. 309 00:36:59,120 --> 00:37:05,240 Far from the centre, out in one of the arms, the suburbs of the Milky Way, 310 00:37:05,240 --> 00:37:10,240 there’s a tiny star system, our home, the Solar System. 311 00:37:29,000 --> 00:37:35,120 When we look upon a clear night, we can see about 5000 of the closest stars. 312 00:37:36,640 --> 00:37:43,080 Our eyes struggle to see beyond a thousand light-years because of the dust that blankets space 313 00:37:43,080 --> 00:37:45,160 and dims the distant starlight. 314 00:37:45,160 --> 00:37:52,680 So without a telescope we can only see a minute portion of the entire 100000-light-year-wide Milky Way. 315 00:37:53,680 --> 00:38:00,360 For the Milky Way contains several hundred billion stars, many like our own Sun!! 316 00:38:00,360 --> 00:38:08,400 Although several hundred thousand million is an almost unfathomable number, it is only the beginning. 317 00:38:08,560 --> 00:38:16,000 Astronomers believe there are more than a hundred billion galaxies in the Universe. How many stars would that be? 318 00:38:27,160 --> 00:38:31,800 In a handful of sand there can easily be 50,000 individual grains of sand. Even so, on an entire beach 319 00:38:31,840 --> 00:38:37,280 there are only just enough grains of sand to represent each star in the Milky Way. 320 00:38:40,120 --> 00:38:46,400 There are so many stars in the Universe that we would need to count every grain of sand on every beach 321 00:38:46,400 --> 00:38:51,520 on the entire Earth to get anywhere near the right number! 322 00:38:53,960 --> 00:39:00,680 Let’s take a grain of sand, 1 mm across, and place it here to represent the size of the Sun. 323 00:39:01,360 --> 00:39:07,000 If we started walking towards the nearest star it would take us the better part of a day to complete the journey 324 00:39:07,000 --> 00:39:10,440 because the star would be nearly 30 kilometres away. 325 00:39:30,920 --> 00:39:34,880 So, galaxies are mostly large collections of emptiness. 326 00:39:34,880 --> 00:39:39,000 If we could squeeze together all the stars in the Milky Way, 327 00:39:39,000 --> 00:39:44,080 they would easily fit into the volume of space between our Sun and the nearest star. 328 00:39:44,880 --> 00:39:47,000 In fact, to completely fill that volume, 329 00:39:47,000 --> 00:39:53,160 we would have to pack in all the stars from all the galaxies in the entire Universe!! 330 00:40:01,920 --> 00:40:05,880 When looking at the night sky, the universe seems motionless. 331 00:40:05,880 --> 00:40:12,920 This is because our life spans are nothing but brief drops in the universal ocean of time. 332 00:40:12,920 --> 00:40:20,640 In fact, the universe is in constant motion, but we would need to watch for vastly longer than a lifetime 333 00:40:20,640 --> 00:40:23,400 to perceive that motion in the night sky. 334 00:40:23,400 --> 00:40:28,000 Given enough time, we would see stars and galaxies move. 335 00:40:28,800 --> 00:40:35,000 Stars orbit the centre of the Milky Way and galaxies are pulled together by each other’s gravity. 336 00:40:35,000 --> 00:40:42,320 Sometimes they even collide. Hubble has observed numerous galaxies crashing together. 337 00:41:26,520 --> 00:41:32,840 Like majestic ships in the grandest night, galaxies can slip ever closer 338 00:41:32,840 --> 00:41:40,880 until their mutual gravitational interaction begins to mould them into intricate figures that are finally, 339 00:41:40,880 --> 00:41:51,920 and irreversibly, woven together. It is an immense cosmic dance, choreographed by gravity. 340 00:42:08,640 --> 00:42:14,200 When two galaxies collide, it’s not like a car crash or two billiard balls hitting each other, 341 00:42:14,200 --> 00:42:17,520 it is more like interlocking your fingers. 342 00:42:17,520 --> 00:42:22,720 Most of the stars in the galaxies will pass unharmed through the collision. 343 00:42:22,720 --> 00:42:28,800 At worst, gravity will fling them out, along with dust and gas to create long streamers that 344 00:42:28,800 --> 00:42:34,560 stretch a hundred thousand light-years or more. The two galaxies, 345 00:42:34,560 --> 00:42:39,160 trapped in their deadly gravitational embrace, will continue to orbit each other, 346 00:42:39,160 --> 00:42:46,720 ripping out more gas and stars to add to the tails. Eventually, hundreds of millions of years from now, 347 00:42:46,720 --> 00:42:51,920 the two galaxies will settle into a single, combined galaxy. 348 00:42:51,920 --> 00:42:56,400 It is believed that many present-day galaxies, including the Milky Way, 349 00:42:56,400 --> 00:43:01,240 were assembled from such a coalescence of smaller galaxies, occurring over billions of years. 350 00:43:03,640 --> 00:43:07,760 Triggered by the colossal and violent interaction between the galaxies, 351 00:43:07,760 --> 00:43:15,800 stars form from large clouds of gas in firework bursts, creating brilliant blue star clusters. 352 00:43:19,720 --> 00:43:25,240 Our own Milky Way is on a collision course with the nearest large galaxy, the Andromeda galaxy. 353 00:43:25,240 --> 00:43:31,320 They are approaching each other at almost 500000 kilometres per hour and, in three billion years, 354 00:43:31,320 --> 00:43:34,040 will collide head-on. 355 00:43:34,040 --> 00:43:40,360 The direct collision will lead to a magnificent merger between the two galaxies, 356 00:43:40,360 --> 00:43:45,920 during which the Milky Way will no longer be the spiral galaxy we are familiar with. 357 00:43:45,920 --> 00:43:50,160 Instead, it will evolve into a huge elliptical galaxy, 358 00:43:50,160 --> 00:43:55,520 containing all of its own stars and all those of the Andromeda galaxy too. 359 00:43:56,200 --> 00:44:00,680 Seen from the Earth the collision will look something like this. 360 00:44:01,880 --> 00:44:05,440 Although this will not happen for a very long time, 361 00:44:05,440 --> 00:44:13,640 there are other dark forces of nature in play everywhere around us, even as we speak… 362 00:44:32,600 --> 00:44:40,960 Black holes are the enigmatic villains of the Universe: swallowing all that comes their way, allowing nothing to escape. 363 00:44:40,960 --> 00:44:45,880 So for astronomers, the centre of a black hole is the ultimate unknown... 364 00:44:45,880 --> 00:44:50,880 No information can escape from within a black hole’s gravitational stronghold. 365 00:44:50,880 --> 00:44:54,120 There is no way to find out what is in there. 366 00:44:54,120 --> 00:44:59,840 Not even light can escape. So how do we know that they are even there? 367 00:45:05,320 --> 00:45:07,280 Black holes themselves cannot be observed directly. 368 00:45:07,760 --> 00:45:10,960 However, astronomers can study the indirect effects of Black Holes 369 00:45:11,240 --> 00:45:13,680 because the one thing they have in abundance is gravity. 370 00:45:15,040 --> 00:45:19,960 Hubble’s high resolution has revealed the dramatic distorting effects of black holes on their surroundings. 371 00:45:20,880 --> 00:45:25,320 And not just gravity, astronomers have found that when material is packed tightly enough 372 00:45:25,880 --> 00:45:27,680 around a black hole it can ring like a bell. 373 00:45:28,960 --> 00:45:34,000 This is the actual note produced by a black hole 250 million light years from Earth. 374 00:45:35,680 --> 00:45:37,880 It reverberates through the disc of matter surrounding the black hole and has been altered 375 00:45:38,880 --> 00:45:45,680 to bring it within the range of human hearing. In reality it is a B flat, 57 octaves below middle C. 376 00:45:49,440 --> 00:45:54,040 Astronomers believe that black holes are singularities – simple points in space. 377 00:45:54,040 --> 00:45:58,200 No volume, no extension, but infinitely dense! 378 00:45:58,200 --> 00:46:04,800 Black holes can be created during the final collapse of a massive star, many times the size of the Sun. 379 00:46:04,800 --> 00:46:12,000 The stellar corpse left over from the demise and collapse of a massive star can be so heavy that no force in nature 380 00:46:12,000 --> 00:46:17,040 can keep it from crumpling under its own weight into an infinitely small volume. 381 00:46:17,040 --> 00:46:22,040 Although the matter has apparently disappeared, having been compacted into nothingness, 382 00:46:22,040 --> 00:46:29,440 it still exerts a powerful gravitational pull and stars and other objects that come too close can be pulled in. 383 00:46:33,440 --> 00:46:38,000 For any black hole there is a point of no-return, called the “event horizon”. 384 00:46:38,000 --> 00:46:45,880 Once something – a nearby star say - is pulled in past this point it will never been seen again. 385 00:46:45,880 --> 00:46:53,080 On its way towards the event horizon, the doomed star will begin to follow a fatal, spiralling orbit. 386 00:46:53,080 --> 00:46:56,920 As the star approaches the black hole still further, 387 00:46:56,920 --> 00:47:01,320 the matter closest to the hole feels a greater attraction than the rest of the star, 388 00:47:01,320 --> 00:47:05,880 sucking and stretching the star out towards the hole until… 389 00:47:05,880 --> 00:47:11,000 … the immense tidal forces pull it to pieces and devour it. 390 00:47:20,600 --> 00:47:23,760 There are quirkier aspects to these objects too, 391 00:47:23,760 --> 00:47:29,520 a twisting of space and time that warps and slows even the passage of time. 392 00:47:29,520 --> 00:47:38,120 All objects with a mass deform the very fabric of space and time, but black holes do this to an extreme degree. 393 00:47:38,120 --> 00:47:42,800 According to Einstein’s famous theory of general relativity, 394 00:47:42,800 --> 00:47:46,960 an intrepid traveller who could visit a black hole and hang above the event horizon 395 00:47:46,960 --> 00:47:54,000 without being swallowed would eventually return to find himself younger than the people he had left behind. 396 00:48:05,560 --> 00:48:10,600 Perhaps the most curious objects astronomers have hypothesized about are wormholes. 397 00:48:10,600 --> 00:48:18,240 A wormhole is essentially a "shortcut" through space time from one point in the universe to another point in the universe. 398 00:48:18,240 --> 00:48:25,560 Maybe wormholes, if they exist, will some day allow travel between regions in space faster 399 00:48:25,560 --> 00:48:29,520 than it would take light to make the journey through normal space. 400 00:48:35,600 --> 00:48:39,440 Hubble has shown that black holes are most likely to be present at the centre of all galaxies. 401 00:48:39,440 --> 00:48:42,880 There is one at the centre of our Milky Way - a giant, 402 00:48:42,880 --> 00:48:50,000 super-massive Black Hole, perhaps a million times bigger than those created from the collapse of massive stars. 403 00:48:50,000 --> 00:48:57,600 It could be the result of the merger of many star-sized black holes that were formed during the remote history of the galaxy. 404 00:48:59,880 --> 00:49:06,400 When two galaxies collide, the black holes at each of their centres will perform an elaborate dance. 405 00:49:06,400 --> 00:49:10,520 Long after the two galaxies have merged into one, 406 00:49:10,520 --> 00:49:15,120 their central black holes continue to orbit each other for hundreds of millions of years 407 00:49:15,120 --> 00:49:20,160 before their final violent merger into a single, weighty black hole. 408 00:49:21,520 --> 00:49:28,240 This final process is so powerful that it changes the fabric of spacetime enough that we may be able to observe 409 00:49:28,240 --> 00:49:35,960 it from the Earth with a new breed of gravitational-wave telescopes or from special spacecraft in orbit. 410 00:49:35,960 --> 00:49:41,080 However, compared with the millions of years it takes for galaxies to merge, 411 00:49:41,080 --> 00:49:49,080 the final cataclysm at the cores would be relatively brief. So the odds of seeing such an event are small. 412 00:49:50,760 --> 00:49:55,680 Until as recently as 50 years ago, astronomers thought the universe was a mostly peaceful place. 413 00:49:55,680 --> 00:49:57,760 But this is far from the truth… 414 00:49:57,760 --> 00:50:04,080 Space is often shaken by violent events: cataclysmic explosions of supernovae, 415 00:50:04,080 --> 00:50:08,360 collisions of whole galaxies and the tremendous outpouring of energy 416 00:50:08,360 --> 00:50:11,160 due to the large amount of matter crashing into Black Holes… 417 00:50:11,160 --> 00:50:15,960 The discovery of quasars gave us the first clear glimpse of this turmoil … 418 00:50:18,720 --> 00:50:22,120 To ground-based telescopes, quasars look like normal stars. 419 00:50:22,120 --> 00:50:27,840 And that is exactly what astronomers first thought they were, naming them “Quasi stellar” objects. 420 00:50:27,840 --> 00:50:32,440 But Quasars are in fact much brighter and further away than stars… 421 00:50:32,440 --> 00:50:38,720 They can shine more brightly than 1000 normal galaxies and are powered by supermassive Black Holes. 422 00:50:39,400 --> 00:50:47,960 Stars that orbit too close are pulled apart, draining into the quasar like water into an enormous cosmic sink. 423 00:50:47,960 --> 00:50:55,440 The spiralling gas forms a thick disk, heated to a high temperature by its free-fall motion towards the black hole. 424 00:50:55,440 --> 00:51:02,360 The gas blasts its energy into space above and below the disk in colossal jets. 425 00:51:04,240 --> 00:51:08,800 Quasars are found in a wide range of galaxies, many of which are violently colliding. 426 00:51:08,800 --> 00:51:13,400 There may be a variety of mechanisms for igniting quasars. 427 00:51:13,400 --> 00:51:17,840 Collisions between pairs of galaxies could trigger the birth of quasars, 428 00:51:17,840 --> 00:51:23,000 but Hubble has shown that even apparently normal, undisturbed galaxies harbour quasars. 429 00:51:23,000 --> 00:51:27,400 , But quasars are not the only high energy objects astronomers have found…. 430 00:51:28,120 --> 00:51:32,000 A serendipitous discovery is something you find while you’re looking for something else. 431 00:51:32,000 --> 00:51:35,120 Such discoveries have often changed the course of astronomy. 432 00:51:35,120 --> 00:51:40,360 Gamma Ray Bursts were discovered serendipitously in the late 1960s by U.S. military satellites 433 00:51:40,360 --> 00:51:42,960 that were on the lookout for Soviet nuclear tests. 434 00:51:42,960 --> 00:51:47,080 Instead of finding the most devastating detonations produced by humans, 435 00:51:47,080 --> 00:51:51,560 some of the most powerful blasts in the Universe itself were spotted… 436 00:51:53,560 --> 00:52:01,080 These astoundingly energetic blasts of gamma rays are detected at least once per day from random directions in the sky. 437 00:52:02,800 --> 00:52:06,280 Although Gamma Ray Bursts last only a few seconds, 438 00:52:06,280 --> 00:52:13,600 the energy they release is equal to the amount of energy radiated by our whole Milky Way over a couple of centuries. 439 00:52:13,600 --> 00:52:19,880 Gamma rays are not visible to the human eye, and special instrumentation is needed to detect them. 440 00:52:19,880 --> 00:52:24,760 For 30 years, no one knew what caused these bursts. 441 00:52:24,760 --> 00:52:31,280 It was like seeing the gamma-ray bullet fly by Earth without ever glimpsing the weapon that fired it. 442 00:52:32,880 --> 00:52:39,360 Together with nearly all other telescopes in the world Hubble looked for the “smoking gun” for many years. 443 00:52:39,360 --> 00:52:47,520 It observed the positions in the sky where gamma ray explosions had been seen, trying to find any object at that location. 444 00:52:47,520 --> 00:52:52,080 But all efforts were in vain, until… 445 00:52:53,120 --> 00:53:02,400 In 1999 Hubble observations were fundamental in determining that these monstrous outbursts take place in far distant galaxies. 446 00:53:08,760 --> 00:53:16,000 The cause could be the blast produced in the final cataclysmic collapse of a massive star… 447 00:53:16,000 --> 00:53:25,240 … or the dramatic encounter of two very dense objects, such as two Black Holes, or a Black Hole and a neutron star. 448 00:53:34,000 --> 00:53:38,680 Black holes are certainly some of the most exotic objects in the Universe. 449 00:53:38,680 --> 00:53:44,000 As well as affecting matter they can also show up in some other spectacular ways 450 00:53:44,000 --> 00:53:49,120 because their enormous gravitational fields can also deflect light. 451 00:53:50,320 --> 00:53:55,520 In fact, rays of light that pass close to a Black Hole will not follow straight lines, 452 00:53:55,520 --> 00:54:04,240 but will be bent onto new paths, creating a natural telescope that can peer further into space than ever thought possible. 453 00:54:23,000 --> 00:54:27,360 Just as a wanderer in the desert sees a mirage when light from remote objects 454 00:54:27,360 --> 00:54:33,440 is bent by the warm air hovering just above the sand, we may also see mirages in the Universe. 455 00:54:35,560 --> 00:54:41,880 The mirages we see with a modern telescope such as the Hubble Space Telescope do not arise from warm air, 456 00:54:41,880 --> 00:54:48,240 but instead from remote clusters of galaxies - huge concentrations of matter. 457 00:54:50,120 --> 00:54:52,720 Long ago some people thought the Earth was flat. 458 00:54:52,720 --> 00:54:58,880 This is in some way understandable - in our daily life we can’t see the curvature of our planet. 459 00:54:58,880 --> 00:55:04,480 Space itself is actually curved, even though we can’t see this for ourselves on a starry night. 460 00:55:04,480 --> 00:55:10,560 But the curvature of space does create phenomena that we can observe… 461 00:55:11,080 --> 00:55:18,240 One of Albert Einstein's predictions is that gravity warps space and therefore distorts rays of light, 462 00:55:18,240 --> 00:55:25,040 in the same way that ripples on a pond create a warped honeycomb pattern of light on the sandy bottom. 463 00:55:25,280 --> 00:55:30,080 Light from distant galaxies is distorted and magnified by the gravitational field 464 00:55:30,080 --> 00:55:33,480 of massive galaxy clusters on its path to Earth. 465 00:55:34,960 --> 00:55:42,000 The effect is like looking through a giant magnifying glass and the result is called gravitational lensing. 466 00:55:44,320 --> 00:55:47,920 The weird patterns that rays of light create when they encounter a weighty object 467 00:55:48,600 --> 00:55:53,720 depend on the nature of the “lensing body”. Thus, the background object can appear in several guises... 468 00:55:54,320 --> 00:55:59,360 …Einstein rings where the whole image is boosted and squeezed in a circle of light… 469 00:56:01,880 --> 00:56:06,080 …multiple images, ghostly clones of the original distant galaxies… 470 00:56:13,960 --> 00:56:16,920 …or distorted into banana-like arcs and arclets. 471 00:56:23,000 --> 00:56:26,840 Though Einstein realized in 1915 that this effect would happen in space, 472 00:56:27,520 --> 00:56:29,240 he thought it could never be observed from Earth. 473 00:56:30,520 --> 00:56:34,920 However in 1919 his calculations were indeed proved to be correct. 474 00:56:35,760 --> 00:56:40,080 During a solar eclipse expedition to Principe Island near the west coast of Africa, 475 00:56:40,080 --> 00:56:43,360 led by the renowned British astronomer Arthur Eddington, 476 00:56:43,360 --> 00:56:47,760 the positions of stars around the obscured solar disk were observed. 477 00:56:47,760 --> 00:56:53,000 It was found that the stars had moved a small but measurable distance outwards on the sky, 478 00:56:53,000 --> 00:56:56,000 compared with when the Sun was not in the vicinity. 479 00:57:13,160 --> 00:57:19,960 Nowadays, faint gravitational images of objects in the distant Universe are observed with the best telescopes on Earth, 480 00:57:19,960 --> 00:57:23,280 and, of course, with the sharp-sighted Hubble. 481 00:57:37,440 --> 00:57:41,680 Hubble was the first telescope to resolve details within the multiple arcs, 482 00:57:41,680 --> 00:57:49,160 revealing the form and internal structure of the lensed background objects directly. 483 00:58:06,160 --> 00:58:13,360 In 2003, astronomers deduced that a mysterious arc of light on one of Hubble’s images was the biggest, 484 00:58:13,360 --> 00:58:18,760 brightest and hottest star-forming region ever seen in space. 485 00:58:30,800 --> 00:58:34,040 It takes fairly massive objects, for example, clusters of galaxies, 486 00:58:34,040 --> 00:58:40,440 to make space curve so much that the effect is observable in deep images of the distant Universe 487 00:58:40,440 --> 00:58:43,160 - even with Hubble’s astonishing resolution. 488 00:58:43,840 --> 00:58:48,120 And so far gravitational lenses have mainly been observed around clusters of galaxies, 489 00:58:48,120 --> 00:58:52,120 which are collections of hundreds or thousands of galaxies 490 00:58:52,120 --> 00:58:56,720 and are thought to be the largest gravitationally bound structures in the Universe. 491 00:58:58,280 --> 00:59:04,760 Astronomers know that the matter we see in the Universe is just a tiny percentage of the total mass that must be there. 492 00:59:04,760 --> 00:59:08,000 For matter exerts a gravitational force, 493 00:59:08,000 --> 00:59:12,960 and the visible stuff is simply not enough to hold galaxies and clusters of galaxies together. 494 00:59:13,680 --> 00:59:19,920 Since the amount of warping of the ‘banana’-shaped images depends on the total mass of the lens, 495 00:59:19,920 --> 00:59:27,680 gravitational lensing can be used to ‘weigh’ clusters and to understand the distribution of the hidden dark matter. 496 00:59:33,680 --> 00:59:40,120 On clear images from Hubble one can usually associate the different arcs coming from the same background galaxy by eye. 497 00:59:41,760 --> 00:59:46,840 This process allows astronomers to study the details of galaxies in the young Universe and 498 00:59:46,840 --> 00:59:51,160 too far away to be seen with the present technology and telescopes. 499 00:59:57,400 --> 01:00:03,040 A gravitational lens can even act as a kind of ‘natural telescope’. In 2004, 500 01:00:03,040 --> 01:00:08,240 Hubble was able to detect the most distant galaxy in the known Universe, 501 01:00:08,240 --> 01:00:14,320 using the magnification from just such a ‘gravitational lens’ in space. 502 01:00:33,400 --> 01:00:39,800 Light may travel through a vacuum at the highest speed anything can ever reach, but it is still a finite speed. 503 01:00:39,800 --> 01:00:45,120 This means that it takes a while for rays of light to travel between two points in space. 504 01:00:45,960 --> 01:00:50,560 The speed of light through space is about 300000 kilometres per second. 505 01:00:50,560 --> 01:00:55,200 300 thousand kilometres is nearly the distance from the Earth to the Moon. 506 01:00:55,200 --> 01:00:59,760 So it takes light just over a second to travel from the Moon to the Earth. 507 01:00:59,760 --> 01:01:04,280 When we look at the Moon we see it as it was just over a second ago. 508 01:01:05,040 --> 01:01:09,680 Who hasn’t thought about what it would be like to travel in time? 509 01:01:09,680 --> 01:01:16,360 The finite speed of light enables us to get close by allowing us to look back in time. 510 01:01:16,360 --> 01:01:22,360 When looking out into space, we just need to wait for the light from distant places to reach us, 511 01:01:22,360 --> 01:01:27,160 and it shows how things were when the light began its journey. 512 01:01:27,160 --> 01:01:33,560 Powerful instruments, like Hubble, have made it possible to look farther out and farther back than ever before. 513 01:01:33,560 --> 01:01:39,960 What cosmologists are seeing is simply astounding. 514 01:01:41,560 --> 01:01:47,120 In the 1920s, astronomer Edwin Hubble discovered that most galaxies appear to be moving away from us 515 01:01:47,120 --> 01:01:54,760 at a rate proportional to their distance. The farther away a galaxy is, the faster it appears to be moving away from us. 516 01:01:54,760 --> 01:01:58,320 This is due to the expansion of the Universe. 517 01:02:05,080 --> 01:02:12,200 That expansion began in a titanic explosion, called the Big Bang, many billions of years ago. 518 01:02:13,360 --> 01:02:18,480 The rate of expansion holds the key to estimating the age and size of the universe. 519 01:02:18,480 --> 01:02:22,280 This rate is called the Hubble constant. 520 01:02:23,080 --> 01:02:28,160 The age and size of the universe can be estimated by "running the expansion backwards" 521 01:02:28,160 --> 01:02:35,240 – until everything is compressed into that infinitely small point of energy from which the universe was generated. 522 01:02:36,280 --> 01:02:42,840 The top ranked scientific justification for building Hubble was to determine the size and age of the Universe. 523 01:02:42,840 --> 01:02:47,840 The quest to determine the Hubble constant precisely was headed by the Key Project team, 524 01:02:47,840 --> 01:02:52,760 a group of astronomers who used Hubble to look for remote, accurate "milepost markers", 525 01:02:52,760 --> 01:02:57,080 a special class of stars called Cepheid variables. 526 01:03:33,960 --> 01:03:38,640 Cepheids have very stable and predictable brightness variations. 527 01:03:38,640 --> 01:03:43,640 The period of these variations depends strictly on the physical properties of the star, 528 01:03:43,640 --> 01:03:47,240 which can be used to determine their distance very effectively. 529 01:03:48,360 --> 01:03:52,720 For this reason these stars are better known as ‘standard candles’. 530 01:03:52,720 --> 01:03:59,240 The Cepheids have been used as reliable stepping-stones to make distance measurements for supernovae, 531 01:03:59,240 --> 01:04:04,000 which are much brighter than Cepheids and so can be seen at far greater distances. 532 01:04:07,480 --> 01:04:11,720 Hubble has measured the light from supernova explosions more accurately than any other instrument, 533 01:04:11,720 --> 01:04:14,080 mostly due to its high resolution. 534 01:04:14,080 --> 01:04:20,240 From the ground an image of a supernova usually blends in with the image of its host galaxy. 535 01:04:21,160 --> 01:04:23,960 Hubble can clearly distinguish the light from the two sources. 536 01:04:25,400 --> 01:04:29,760 Cepheids and supernovae have given a measure for the scale of the Universe. 537 01:04:29,760 --> 01:04:34,600 Today we know the age of the Universe to a much higher precision than ever before: 538 01:04:34,600 --> 01:04:39,120 around 14 billion years. 539 01:04:40,920 --> 01:04:46,280 For many years astronomers have discussed whether the expansion of the Universe would stop in some distant future, 540 01:04:46,280 --> 01:04:53,240 making the universe collapse in a fiery "Big Crunch", or whether it would continue to expand ever more slowly. 541 01:04:55,680 --> 01:05:00,960 Combined observations of distant supernovae with Hubble and most of the world’s top-class telescopes 542 01:05:00,960 --> 01:05:04,640 were used to measure distances to remote supernovae. 543 01:05:04,640 --> 01:05:11,040 And it looks like the expansion of our universe is nowhere near slowing down. Instead, it seems to be speeding up. 544 01:05:18,040 --> 01:05:23,240 When Hubble was used to measure how the expansion of the Universe has changed with time, 545 01:05:23,240 --> 01:05:27,960 it turned out, quite surprisingly, that during the first half of cosmic history, 546 01:05:27,960 --> 01:05:33,880 the expansion rate was actually slowing down. Then, a mysterious force, 547 01:05:33,880 --> 01:05:41,080 a sort of "anti-gravity” made the Universe ‘hit the gas pedal’ starting the acceleration we see today. 548 01:05:43,040 --> 01:05:49,200 This suggests an extraordinary fate for the Universe because it implies that the anti-gravity force 549 01:05:49,200 --> 01:05:52,720 is getting stronger all the time. If this continues, 550 01:05:52,720 --> 01:05:59,200 it will eventually overwhelm all gravity and catapult the Universe into a super fast acceleration 551 01:05:59,200 --> 01:06:09,840 that will shred everything into its constituent atoms. Cosmologists have called this nightmare scenario, the Big Rip. 552 01:06:39,700 --> 01:06:43,820 We are collecting unexpected news from deep space. 553 01:06:43,820 --> 01:06:48,020 Just as geologists dig deeper underground to find ever more ancient fossils, 554 01:06:48,020 --> 01:06:56,300 bearing witness to ever more remote epochs, so astronomers ‘excavate’ deeper and deeper towards the beginning of time, 555 01:06:56,300 --> 01:07:00,940 by looking for light coming from fainter, and thus more distant, objects. 556 01:07:01,940 --> 01:07:10,220 Hubble started a new era we could call ‘astroarcheology’ and it began during Christmas, 1995… 557 01:07:13,980 --> 01:07:21,340 Pointing the world’s most sophisticated telescope at the same piece of sky for ten days in a row may sound a bit strange. 558 01:07:21,340 --> 01:07:28,140 And this was what many astronomers thought when they tried it for the first time at the end of 1995. 559 01:07:30,820 --> 01:07:35,620 Deep field observations are long-lasting exposures pointing at a particular region of the sky. 560 01:07:35,900 --> 01:07:42,220 They aim to reveal faint objects by collecting as much light as possible over a long period of time. 561 01:07:43,020 --> 01:07:47,060 The ‘deeper’ an observation goes, the fainter are the objects that become visible. 562 01:07:48,260 --> 01:07:55,940 Objects in the sky can either look faint because their natural brightness is low, or because their distance is great. 563 01:07:56,660 --> 01:07:59,140 “When this experiment was first proposed, 564 01:07:59,140 --> 01:08:06,100 nobody really knew if this would lead to any interesting scientific results. 565 01:08:06,100 --> 01:08:13,660 But when we first looked at the image we were astonished! We could see more than 3000 galaxies in this small field.” 566 01:08:15,980 --> 01:08:19,500 The observed region of sky in Ursa Major, the Big Dipper, 567 01:08:19,580 --> 01:08:25,740 was carefully selected to be as empty as possible so that Hubble would look far beyond the stars 568 01:08:25,780 --> 01:08:30,220 of our own Milky Way and out past nearby galaxies. 569 01:08:30,820 --> 01:08:36,500 The thousands of galaxies observed in the first Deep Field were at various stages of evolution 570 01:08:36,580 --> 01:08:39,780 and were strung out along a corridor of billions of light-years. 571 01:08:41,540 --> 01:08:45,860 This allowed astronomers to study the evolution of these objects through time, 572 01:08:45,860 --> 01:08:51,020 glimpsing different galaxies at different stages of their lives. 573 01:08:54,500 --> 01:08:59,420 After the first deep field, another long exposure was taken in the Southern sky. 574 01:09:00,180 --> 01:09:07,940 Together, the Hubble Deep Field North and South gave astronomers peepholes to the ancient Universe for the first time. 575 01:09:09,420 --> 01:09:14,820 Some of the objects viewed on the images were so dim that seeing them would be as difficult as discerning 576 01:09:14,820 --> 01:09:17,700 a flashlight on the Moon from Earth. 577 01:09:20,380 --> 01:09:25,900 “We could definitely tell that the Hubble Deep Field opened a whole new era of observational cosmology. 578 01:09:26,100 --> 01:09:29,380 It formed our view of the distant universe”. 579 01:09:31,260 --> 01:09:34,540 The Hubble Deep Fields have caused a real revolution in modern astronomy. 580 01:09:35,780 --> 01:09:41,060 After the first Deep Field, almost all ground- and space-based telescopes were pointed to this same area 581 01:09:41,060 --> 01:09:48,140 for long periods. Some of the most interesting results in astronomy emerged from this fruitful synergy 582 01:09:48,140 --> 01:09:54,740 between instruments of different sizes, in different environments and with sensitivity to different wavelengths. 583 01:09:56,180 --> 01:10:00,260 They gave us the first clear picture of the rate of star formation throughout the Universe. 584 01:10:00,460 --> 01:10:06,860 Astonishingly, it showed that star formation peaked within a few billion years of the Universe’s creation. 585 01:10:06,980 --> 01:10:11,340 At that time, stars were forming at over 10 times the rate they are today. 586 01:10:19,420 --> 01:10:23,900 Once they had begun to discover the most distant universe ever seen, 587 01:10:23,980 --> 01:10:28,500 Hubble astronomers tried to push their observations even farther back in time. 588 01:10:30,580 --> 01:10:35,900 In 2003 and 2004, Hubble performed its deepest exposure ever: 589 01:10:35,980 --> 01:10:41,220 the Hubble Ultra Deep Field. It is a 28 day-long exposure, 590 01:10:41,260 --> 01:10:46,580 going much deeper than the earlier Hubble Deep Fields North and South. 591 01:10:53,780 --> 01:11:01,780 The Hubble Ultra Deep Field reveals the first galaxies to emerge from the so-called "dark ages" 592 01:11:01,780 --> 01:11:07,220 - the time shortly after the big bang when the first stars reheated the cold, dark universe. 593 01:11:09,500 --> 01:11:16,260 Just after the Big Bang, in the newborn fast-expanding Universe – before the era of the stars and galaxies - 594 01:11:16,260 --> 01:11:19,380 the distribution of matter was fairly smooth. 595 01:11:22,780 --> 01:11:29,500 As time went on, the king of all forces – gravity – started acting. Slowly, but steadily… 596 01:11:43,500 --> 01:11:47,380 Under the influence of gravity from the mysterious dark matter, 597 01:11:47,380 --> 01:11:54,460 small clumps of normal matter started to coalesce in regions where the density was slightly higher than average. 598 01:11:58,100 --> 01:12:02,900 With no stars to light up space, the universe was in its dark age. 599 01:12:04,900 --> 01:12:09,460 Where the density of the clumps became higher, even more matter was attracted, 600 01:12:09,460 --> 01:12:14,180 and a competition between the expansion of space and gravity took place. 601 01:12:15,180 --> 01:12:20,660 Where gravity won, regions stopped expanding, and started to collapse in on themselves. 602 01:12:22,340 --> 01:12:24,180 , The first stars and galaxies were born. 603 01:12:40,140 --> 01:12:46,140 Where the matter density was highest – at the intersections between the large web-like structures of matter 604 01:12:46,140 --> 01:12:50,500 - the largest structures we know were formed: clusters of galaxies. 605 01:13:16,220 --> 01:13:22,700 The Deep Field images are studded with a wide range of galaxies of various sizes, shapes, and colours. 606 01:13:23,700 --> 01:13:29,500 Astronomers will spend years studying the myriad shapes of the galaxies in this image to understand 607 01:13:29,580 --> 01:13:33,380 how they formed and have evolved since the Big Bang. 608 01:13:35,220 --> 01:13:41,060 In vibrant contrast to the image's rich harvest of classic spiral and elliptical galaxies, 609 01:13:41,060 --> 01:13:48,420 there is also a zoo of oddball galaxies littering the field. Some look like toothpicks; 610 01:13:48,420 --> 01:13:54,860 others like links on a bracelet. A few appear to be interacting with each other. 611 01:13:54,860 --> 01:14:02,420 Their strange shapes are a far cry from the majestic spiral and elliptical galaxies we see today. 612 01:14:02,420 --> 01:14:08,140 These oddball galaxies chronicle a period when the Universe was more chaotic, 613 01:14:08,140 --> 01:14:12,700 when order and structure were just beginning to emerge. 614 01:14:14,660 --> 01:14:18,140 One of the great things about Hubble is that there are many instruments onboard 615 01:14:18,140 --> 01:14:20,020 that can make different observations at the same time. 616 01:14:20,500 --> 01:14:25,100 The Hubble Ultra Deep Field is actually two separate images taken by two instruments: 617 01:14:25,100 --> 01:14:31,060 Hubble's ACS camera and the NICMOS instrument. NICMOS sees even farther than the ACS. 618 01:14:31,500 --> 01:14:36,780 It detects infrared light, and so it’s able to reveal the farthest galaxies ever seen 619 01:14:36,860 --> 01:14:41,580 because the expanding universe has stretched and weakened the light from these objects so much that, 620 01:14:41,580 --> 01:14:44,740 they’re now only visible at infrared wavelengths. 621 01:14:47,180 --> 01:14:53,660 The Hubble Ultra Deep Field is likely to remain the deepest image of the Universe for the next decade or so, 622 01:14:53,700 --> 01:15:00,060 until an ESA Ariane rocket launches the James Webb Space Telescope in 2011. 623 01:15:00,260 --> 01:15:07,940 Up until today, during the first 15 years of its life, Hubble has orbited the Earth 80,000 times. 624 01:15:08,500 --> 01:15:14,700 This is the same as three and a half billion kilometres or 24 times the distance from the Earth to the Sun. 625 01:15:16,260 --> 01:15:22,500 Hubble has taken more than 500000 exposures of the Universe and created a visual heritage 626 01:15:22,540 --> 01:15:26,980 that has shaped the way humanity looks at the Universe today. 627 01:15:58,634 --> 01:16:05,674 But Hubble’s perhaps greatest legacy has been to open our eyes to the incredible beauty of nature. 628 01:16:06,540 --> 01:16:14,180 Not only ‘out there’ in the depths of cosmos, but also everywhere around us in our daily lives. 629 01:16:17,187 --> 01:16:19,923 And it’s no where finished yet…