1 00:00:00,000 --> 00:00:06,000 We live in a Universe of unimaginable scale and almost incomprehensible beauty. 2 00:00:06,000 --> 00:00:14,000 How is the light from stars, galaxies and nebulae fashioned into the spectacular images that have so inspired us over the years? 3 00:00:37,000 --> 00:00:39,000 This is the Hubblecast! 4 00:00:39,000 --> 00:00:48,000 News and Images from the NASA/ESA Hubble Space Telescope. Travelling through time and space with our host Doctor J a.k.a. Dr Joe Liske. 5 00:00:49,000 --> 00:00:51,000 Welcome to the Hubblecast! 6 00:00:51,000 --> 00:00:55,000 Do you ever look at these beautiful Hubble images and wonder how they were made? 7 00:00:55,000 --> 00:00:59,000 What exactly happens after the faint light from distant objects is detected by Hubble? 8 00:00:59,000 --> 00:01:08,000 How are these cosmic photons captured in space transformed into the glorious colour images down here on your wall or on computer screen? 9 00:01:08,000 --> 00:01:14,000 On a clear night when we look up into the heavens we can see the light from thousands of stars. 10 00:01:14,000 --> 00:01:19,000 Our eyes are fantastic detectors but in reality are actually very limited. 11 00:01:19,000 --> 00:01:22,000 They aren’t sensitive enough to peer out very far into space. 12 00:01:22,000 --> 00:01:29,000 Also we can only see visible light, but not ultraviolet or infrared light like Hubble can. 13 00:01:29,000 --> 00:01:35,000 That’s why for professional astronomers the Hubble Space Telescope is such an exciting tool to probe the Universe 14 00:01:36,000 --> 00:01:42,000 Sitting at its vantage point 600 km above the Earth, Hubble is a window on the Universe. 15 00:01:42,000 --> 00:01:48,000 The journey to make a Hubble image begins when light from a distant object starts on its way towards us. 16 00:01:48,000 --> 00:01:55,000 After travelling across the vast distances of space it is captured by Hubble with its 2.4 metre wide mirror. 17 00:01:55,000 --> 00:02:05,000 The light is then sent to one of Hubble’s several cameras where the photons are turned into an electrical charge by a CCD chip rather similar to the ones in digital cameras. 18 00:02:05,000 --> 00:02:11,000 The Advanced Camera for Surveys, for example, contains over 16 million picture elements or ‘pixels’. 19 00:02:11,000 --> 00:02:15,000 These act as miniature ‘buckets’ to collect the light. 20 00:02:15,000 --> 00:02:23,000 The camera then reads out how much light has been captured in each bucket (the charge within each of the pixels) and outputs an image. 21 00:02:23,000 --> 00:02:31,000 This readout is then beamed back to the Earth as a series of encoded numbers that are stored in archives in the US and Europe. 22 00:02:32,000 --> 00:02:38,000 Hubble’s cameras image the Universe through different filters – like this one. 23 00:02:40,000 --> 00:02:50,000 These select specific wavelengths of light that are characteristic of different physical processes which may be going on in different parts of distant galaxies and nebulae. 24 00:02:50,000 --> 00:02:56,000 Each of the filters results in a single greyscale image which is then assigned a colour. 25 00:02:56,000 --> 00:03:04,000 This colour is usually chosen to more or less correspond to the actual colour of the filter, although this is not always true. 26 00:03:04,000 --> 00:03:10,000 Anywhere between two and six of these images are then combined to create the final colour image. 27 00:03:11,000 --> 00:03:14,000 Take this view of the colliding Antennae Galaxies. 28 00:03:14,000 --> 00:03:22,000 Hubble imaged this colliding pair through red, green and blue filters to reveal the different components inside the galaxies. 29 00:03:22,000 --> 00:03:33,000 For example the red light is coming from old stars and glowing hydrogen gas, while the blue light is showing the violent star formation triggered by the cosmic collision. 30 00:03:33,000 --> 00:03:39,000 The red, green and blue images are then combined to create the final multi-colour image. 31 00:03:41,000 --> 00:03:49,000 One of the challenges in making images is that there is a huge range of brightness in nature from faint to bright objects 32 00:03:49,000 --> 00:03:56,000 and astronomical images are so rich in information that our eyes and computer screens cannot show their full content. 33 00:03:56,000 --> 00:04:03,000 Nature can be difficult to capture in a single photograph and most of us have encountered situations like the following. 34 00:04:03,000 --> 00:04:06,000 Imagine you try to take a picture of a landscape. 35 00:04:06,000 --> 00:04:14,000 When you do so you can either capture the bright parts of the sky or the darker parts of the vegetation, but rarely both together. 36 00:04:14,000 --> 00:04:22,000 The job of the image processing specialists is to compress this range of brightnesses together so that we can see all the nuances 37 00:04:24,000 --> 00:04:34,000 Image experts use the program FITS Liberator, pioneered by ESA, ESO and NASA to produce a magnificent rich image which can be interpreted by our eyes. 38 00:05:02,000 --> 00:05:08,000 But is this what we would see with our eyes if we could look through Hubble? Well not really. 39 00:05:08,000 --> 00:05:14,000 Look at this image of the Cigar Galaxy. This is what Hubble sees in visible light. 40 00:05:14,000 --> 00:05:21,000 Our eyes aren’t actually sensitive enough to be able to detect the faint light from this distant object even when looking through a telescope. 41 00:05:21,000 --> 00:05:31,000 The reason why Hubble’s instruments can do it is because they can gather and add up the light over an extended period of time - which is something our eyes can’t do. 42 00:05:32,000 --> 00:05:36,000 Furthermore some telescopes can ‘see’ wavelengths that we can’t see with our eyes. 43 00:05:36,000 --> 00:05:42,000 This multi-wavelength view shows us much more than our eyes, or any one telescope, can see. 44 00:05:42,000 --> 00:05:51,000 Parts of the image were made with the Chandra X-ray Observatory in X-rays and part with the Spitzer Space Telescope in infrared light. 45 00:05:52,000 --> 00:05:57,000 In this episode we have seen how the images that have amazed and intrigued us are created. 46 00:05:57,000 --> 00:06:03,000 You too can have a go at making your own images, just Google for ‘FITS Liberator’. 47 00:06:03,000 --> 00:06:06,000 This is Dr J signing off for the Hubblecast. 48 00:06:06,000 --> 00:06:10,000 Once again nature has surprised us beyond our wildest imagination . 49 00:06:11,000 --> 00:06:17,000 Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany. 50 00:06:17,000 --> 00:06:23,000 The Hubble mission is a project of international cooperation between NASA and the European Space Agency.