1 00:00:00,000 --> 00:00:04,000 Hello and welcome to the first of a very special pair of Hubblecast episodes. 2 00:00:05,000 --> 00:00:12,000 So last month we asked you to send us your Hubble and astronomy related questions and the response we got was incredible! 3 00:00:16,000 --> 00:00:22,000 So what we’ll do is that in this episode we’ll try to answer your questions that were specifically about Hubble itself, 4 00:00:23,000 --> 00:00:26,000 and in the next episode we look at the more science related questions. 5 00:00:44,000 --> 00:00:47,000 Episode 78: Q&A with Dr J part 1 6 00:00:50,000 --> 00:00:54,000 Presented by Dr J, aka Dr Joe Liske 7 00:00:56,000 --> 00:00:59,000 A lot of you wanted to know about Hubble’s general location. 8 00:00:59,000 --> 00:01:06,000 Well, Hubble is of course in orbit around Earth, at an altitude of about 545 kilometres, 9 00:01:07,000 --> 00:01:14,000 and its orbit is inclined with respect to the Earth’s equator at angle of about 28.5 degrees. 10 00:01:14,000 --> 00:01:26,000 Now Hubble zooms along in its orbit at a speed of 28 000 km/h, meaning that it completes an entire orbit in just under 97 minutes. 11 00:01:26,000 --> 00:01:31,000 In other words, Hubble circles the Earth almost 15 times every day! 12 00:01:32,000 --> 00:01:37,000 And yes, you CAN see it, even with the naked eye if you know where to look... 13 00:01:45,000 --> 00:01:49,000 I want to see Hubble in space. How can I do this? 14 00:01:52,000 --> 00:01:54,000 So, where IS Hubble? 15 00:01:56,000 --> 00:02:02,000 Track the location of Hubble, or a host of other satellites and space telescopes, here: 16 00:02:05,000 --> 00:02:08,000 So Hubble isn’t up there all by its lonely self. 17 00:02:08,000 --> 00:02:15,000 Space is actually quite a busy place and there are lots of other active satellites as well as space debris in orbit around Earth. 18 00:02:15,000 --> 00:02:18,000 So how come Hubble doesn’t bump into anything? 19 00:02:20,000 --> 00:02:26,000 How do they keep Hubble in orbit without it crashing into other things? There’s so much stuff up there... 20 00:02:28,000 --> 00:02:35,000 There are not many satellites with similar orbits to Hubble so there is very little risk of a satellite collision. 21 00:02:45,000 --> 00:02:51,000 For the visible space debris which is big enough to cause some damage, the orbits are carefully tracked. 22 00:02:53,000 --> 00:02:59,000 This makes it possible to predict if and when this debris might collide with Hubble. 23 00:03:00,000 --> 00:03:06,000 If a collision is likely Hubble cannot be moved to a different orbit as it has no engine. 24 00:03:07,000 --> 00:03:18,000 But we can change its orientation and if the space junk can’t be avoided, then the sturdier, less delicate, back of Hubble can be turned towards the impact. 25 00:03:20,000 --> 00:03:27,000 A disastrous collision, like the one that ended Hubble at the beginning of the film Gravity, is very, very unlikely. 26 00:03:29,000 --> 00:03:34,000 Now the possibility of a collision with space debris is definitely a downside for space telescopes. 27 00:03:36,000 --> 00:03:40,000 Some of you wanted to know more about the pros and cons of space versus ground-based telescopes. 28 00:03:42,000 --> 00:03:50,000 Do ground-based optical telescopes have similar capabilities, or better, compared to Hubble with the use of adaptive optics? 29 00:03:50,000 --> 00:03:55,000 Will adaptive optics eventually make space-based optical telescopes redundant? 30 00:03:57,000 --> 00:04:04,000 Well, a much younger version of me actually discussed this in some detail back in Hubblecast episode 6. 31 00:04:08,000 --> 00:04:11,000 Episode 6: A battle of giants - telescopes in space and on the ground 32 00:04:14,000 --> 00:04:16,000 The atmosphere blocks certain wavelengths of light. 33 00:04:16,000 --> 00:04:20,000 Only space telescopes like Hubble, that fly above the atmosphere, 34 00:04:20,000 --> 00:04:25,000 can access the ultraviolet and infrared parts of the spectrum, which are invisible from the ground. 35 00:04:27,000 --> 00:04:32,000 In addition, space telescopes avoid the blurring effects of Earth’s atmosphere. 36 00:04:32,000 --> 00:04:38,000 Having said that, these days, large telescopes on the ground can correct for this blurring, 37 00:04:38,000 --> 00:04:42,000 and can actually make images that are sharper than those by Hubble. 38 00:04:43,000 --> 00:04:50,000 But this does not work in the optical, but only at longer wavelengths and only over relatively small fields of view. 39 00:04:51,000 --> 00:04:58,000 And so, overall, there’s definitely still a need for space telescope — even at those wavelengths that do make it to the ground. 40 00:05:01,000 --> 00:05:05,000 With space telescopes of course, it’s much more of a problem when something goes wrong. 41 00:05:05,000 --> 00:05:08,000 As NASA and ESA found out first hand with Hubble. 42 00:05:12,000 --> 00:05:16,000 Episode 41: Hubble's History Told by Hubble's Scientists 43 00:05:19,000 --> 00:05:24,000 Spherical aberration, a flaw in the main mirror, meant that the telescope could not focus properly. 44 00:05:25,000 --> 00:05:32,000 Where Hubble’s images should have been razor sharp, astronomers instead struggled to make out the fine details of their observations. 45 00:05:34,000 --> 00:05:40,000 Some of you want to know how the effect of the flaw in Hubble’s primary mirror was corrected for. 46 00:05:42,000 --> 00:05:47,000 The main mirror of the Hubble telescope had a flaw. How was this flaw fixed? 47 00:05:49,000 --> 00:05:54,000 Well, essentially, they built Hubble a contact lens called COSTAR. 48 00:05:54,000 --> 00:06:00,000 This piece of corrective optics was installed in place of one of Hubble’s instruments during the first servicing mission. 49 00:06:01,000 --> 00:06:07,000 COSTAR consisted of small mirrors that were inserted into Hubble’s light path, 50 00:06:07,000 --> 00:06:11,000 thereby correcting the beam before it reached the scientific instruments. 51 00:06:12,000 --> 00:06:16,000 Later instruments were designed to correct for the aberration themselves. 52 00:06:17,000 --> 00:06:23,000 Eventually COSTAR was no longer needed and so it was removed during the fourth servicing mission. 53 00:06:26,000 --> 00:06:33,000 I read recently that the US government is making a few of its spy satellites available for astronomers. Is it true? 54 00:06:33,000 --> 00:06:35,000 Yes, this story is true! 55 00:06:36,000 --> 00:06:39,000 Although, the satellites were never actually launched or used by the government. 56 00:06:40,000 --> 00:06:44,000 One of these Hubble-like telescopes may be launched for scientific purposes. 57 00:06:51,000 --> 00:06:54,000 We also received several questions about Hubble data. 58 00:06:55,000 --> 00:07:01,000 Something that interests me about Hubble is the amount of data. How many gigabytes of data does it produce? 59 00:07:02,000 --> 00:07:06,000 How is the great amount of Hubble data stored and processed? 60 00:07:08,000 --> 00:07:12,000 The amount of data produced by Hubble isn’t actually all that much. 61 00:07:12,000 --> 00:07:17,000 It sends back about 120 GB of data to Earth every week. 62 00:07:17,000 --> 00:07:19,000 That’s about 26 DVDs. 63 00:07:20,000 --> 00:07:23,000 The data are first sent to New Mexico, 64 00:07:23,000 --> 00:07:26,000 then to NASA’s Goddard Space Flight Center, 65 00:07:26,000 --> 00:07:34,000 and finally to the Space Telescope Science Institute in the USA and to several institutes across Europe where the data are processed and archived. 66 00:07:35,000 --> 00:07:40,000 By the way, after one year absolutely ANYONE can download and use the data for free. 67 00:07:44,000 --> 00:07:49,000 Do the colours shown by Hubble actually exist out there? If we were seeing them with the naked eye? 68 00:07:50,000 --> 00:07:53,000 To answer this, you would need a whole Hubblecast. 69 00:07:53,000 --> 00:07:59,000 Just as well that we have one! Try Hubblecast 23: Seeing the invisible. 70 00:08:04,000 --> 00:08:06,000 Many of you were concerned about Hubble’s future. 71 00:08:07,000 --> 00:08:08,000 And rightly so. 72 00:08:22,000 --> 00:08:27,000 Sadly, Hubble has already had its final rejuvenation and will not be serviced anymore. 73 00:08:29,000 --> 00:08:33,000 We explored its fifth and final servicing mission back in Hubblecast 28, 74 00:08:33,000 --> 00:08:38,000 where we also gave some clues as to the final fate of our favourite telescope. 75 00:08:47,000 --> 00:08:51,000 Episode 28: Servicing Mission 4 76 00:08:52,000 --> 00:08:59,000 Astronauts will carry out extra space walks to replace some parts that will keep Hubble flying hopefully into the next decade. 77 00:09:00,000 --> 00:09:11,000 They will also attach a special mechanism that will allow a future robotic spacecraft to dock with Hubble in order to steer it to a peaceful final resting place in the ocean when its time has finally come. 78 00:09:13,000 --> 00:09:22,000 So, Hubble will not last forever and although its fate isn’t 100% certain it will most likely be guided back to Earth. 79 00:09:22,000 --> 00:09:30,000 On its way down, it will partly burn up in the Earth’s atmosphere and eventually it will finish its life somewhere in the Pacific ocean. 80 00:09:32,000 --> 00:09:38,000 But everyone around here says that Hubble will last at least until 2020, maybe even beyond! 81 00:09:38,000 --> 00:09:43,000 And so there are plenty of pictures, science and, of course, Hubblecasts yet to come! 82 00:09:44,000 --> 00:09:46,000 As to what comes next….. 83 00:09:57,000 --> 00:10:00,000 This is the James Webb Space Telescope. 84 00:10:00,000 --> 00:10:06,000 It‘s due to be sent into an orbit 1.5 million kilometres from Earth in 2018. 85 00:10:08,000 --> 00:10:16,000 With a main mirror 6.5 metres in diameter, it will be able to see more distant and fainter objects than Hubble, 86 00:10:16,000 --> 00:10:19,000 and has been dubbed by some as Hubble’s successor. 87 00:10:20,000 --> 00:10:23,000 But are the two telescopes really comparable? 88 00:10:27,000 --> 00:10:29,000 There are actually a lot of differences between the two telescopes. 89 00:10:30,000 --> 00:10:37,000 But that topic deserves a whole Hubblecast episode of its own, which we’ll get to next year — so just wait and see! 90 00:10:38,000 --> 00:10:47,000 And now to finish the part one of our Q&A lets get to some burning questions that we know everyone is dying to know the answers to. 91 00:10:47,000 --> 00:10:50,000 NO, we have not found little green men. 92 00:10:51,000 --> 00:10:53,000 And we have not found Discworld either. 93 00:10:54,000 --> 00:10:56,000 We really DON’T KNOW whether we’re alone or not. 94 00:10:57,000 --> 00:11:01,000 And NO, the pictures are really not fake! 95 00:11:02,000 --> 00:11:08,000 This is Dr J, signing off for the Hubblecast. Once again, nature has surprised us beyond our wildest imagination. 96 00:11:11,000 --> 00:11:16,000 Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany. 97 00:11:16,000 --> 00:11:19,000 The Hubble mission is a project of international cooperation between NASA and the European Space Agency.