1 00:00:00,041 --> 00:00:01,709 (intricate instrumental music) 2 00:00:01,709 --> 00:00:04,745 - [Narrator] NASA's Jet Propulsion Laboratory presents: 3 00:00:04,745 --> 00:00:08,349 the von Karman Lecture, a series of talks by scientists 4 00:00:08,349 --> 00:00:11,185 and engineers who are exploring our planet, 5 00:00:11,185 --> 00:00:14,756 our solar system, and all that lies beyond. 6 00:00:27,368 --> 00:00:29,503 - Good evening, ladies and gentlemen. 7 00:00:29,503 --> 00:00:30,504 How's everyone tonight? 8 00:00:30,504 --> 00:00:32,239 (applause) 9 00:00:32,239 --> 00:00:34,108 Thank you very much for coming out on this rather 10 00:00:34,108 --> 00:00:36,377 soggy evening and fighting the LA traffic. 11 00:00:36,377 --> 00:00:39,113 We're really grateful for your attendance, for sure. 12 00:00:39,113 --> 00:00:40,714 So let's jump right in, shall we? 13 00:00:40,714 --> 00:00:43,116 The Nuclear Spectroscopic Telescope Array, 14 00:00:43,116 --> 00:00:46,654 or NuSTAR, which launched in June of 2012, 15 00:00:46,654 --> 00:00:51,125 is the first telescope in orbit to focus X-ray light. 16 00:00:51,125 --> 00:00:52,960 Compared to the previous generation 17 00:00:52,960 --> 00:00:56,230 of non-focusing observatories, working in this energy band, 18 00:00:56,230 --> 00:00:58,265 this change in technology provides NuSTAR 19 00:00:58,265 --> 00:01:00,501 with a 10-times sharper images, 20 00:01:00,501 --> 00:01:03,738 and 100-times improved sensitivity. 21 00:01:03,738 --> 00:01:05,873 High energy X-ray light provides a unique probe 22 00:01:05,873 --> 00:01:08,876 of the most energetic phenomena in the Universe. 23 00:01:08,876 --> 00:01:10,945 From flares on the surface of the sun, 24 00:01:10,945 --> 00:01:13,847 to the explosions of stars, to the extreme environments 25 00:01:13,847 --> 00:01:16,350 around neutron stars and black holes. 26 00:01:16,350 --> 00:01:18,252 This talk will present some of the recent highlights 27 00:01:18,252 --> 00:01:20,854 from the NuSTAR mission and describe how they are changing 28 00:01:20,854 --> 00:01:23,157 our picture of the extreme Universe. 29 00:01:23,157 --> 00:01:26,326 Tonight's guest earned his AB in physics and Princeton, 30 00:01:26,326 --> 00:01:29,830 in 1991, and went on to earn his PhD in astrophysics 31 00:01:29,830 --> 00:01:32,166 from UC Berkeley in 1999. 32 00:01:32,166 --> 00:01:34,335 He came straight from Berkeley to JPL, 33 00:01:34,335 --> 00:01:37,304 initially as a post-doc, to work with Peter Eisenhower, 34 00:01:37,304 --> 00:01:40,307 but switched to the Spitzer Space Telescope science staff 35 00:01:40,307 --> 00:01:41,842 about 18 months later. 36 00:01:41,842 --> 00:01:44,111 Since then, he's worked on WISE, Euclid, 37 00:01:44,111 --> 00:01:48,483 W-FIRST, a CubeSat, the Habitable Exoplanet Imaging Mission, 38 00:01:48,483 --> 00:01:51,252 and several other missions and mission concepts. 39 00:01:51,252 --> 00:01:52,653 But his main job, currently, 40 00:01:52,653 --> 00:01:55,122 is as the NuSTAR project scientist. 41 00:01:55,122 --> 00:01:56,857 Scientifically, his main interests are 42 00:01:56,857 --> 00:02:00,394 observational cosmology, and extra-galactic astrophysics. 43 00:02:00,394 --> 00:02:02,963 But he's had a sideline, finding the most distant objects 44 00:02:02,963 --> 00:02:07,134 of various source classes, including the most distant object 45 00:02:07,134 --> 00:02:10,838 like, period, (laughing) the most distant galaxy, 46 00:02:10,838 --> 00:02:14,441 the most distant radio galaxy, the most distant quasar, 47 00:02:14,441 --> 00:02:16,410 the most distant galaxy cluster, 48 00:02:16,410 --> 00:02:18,512 and the most distant supernova. 49 00:02:18,512 --> 00:02:20,347 He's also very interested in fields 50 00:02:20,347 --> 00:02:22,649 where infrared satellites and X-ray satellites 51 00:02:22,649 --> 00:02:24,519 make important contributions. 52 00:02:24,519 --> 00:02:26,687 Specifically, distant galaxy clusters 53 00:02:26,687 --> 00:02:29,256 and obscured black holes are both well-served 54 00:02:29,256 --> 00:02:31,692 in observations in those two wavelengths. 55 00:02:31,692 --> 00:02:34,962 As one might expect, he's a very enthusiastic observer, 56 00:02:34,962 --> 00:02:38,632 having logged more than 500 nights at telescopes worldwide 57 00:02:38,632 --> 00:02:40,534 over the past 20 years. 58 00:02:40,534 --> 00:02:42,269 Ladies and gentlemen, please help me welcome 59 00:02:42,269 --> 00:02:44,438 tonight's guest, Dr. Daniel Stern. 60 00:02:44,438 --> 00:02:46,708 (applause) 61 00:02:50,277 --> 00:02:51,779 - Thank you. 62 00:02:51,779 --> 00:02:54,582 Thank you for braving the weather and coming out for this. 63 00:02:54,582 --> 00:02:56,850 I'm excited to have the opportunity to talk to you 64 00:02:56,850 --> 00:02:59,686 about some recent highlights from the NuSTAR mission. 65 00:02:59,686 --> 00:03:03,056 Here is an artist's conception of NuSTAR, 66 00:03:03,056 --> 00:03:04,992 and I'll talk about spinning black holes, 67 00:03:04,992 --> 00:03:08,295 exploding stars, and hyperluminous pulsars. 68 00:03:08,295 --> 00:03:10,765 And I list a couple other missions that I'm involved in, 69 00:03:10,765 --> 00:03:14,768 if people have questions afterwards about those. 70 00:03:14,768 --> 00:03:16,403 So, diving in a little bit. 71 00:03:16,403 --> 00:03:19,873 So, NuSTAR is the Nuclear Spectroscopic Telescope Array. 72 00:03:19,873 --> 00:03:21,809 Our little tagline is: 73 00:03:21,809 --> 00:03:24,545 bringing the high-energy Universe into focus. 74 00:03:24,545 --> 00:03:27,915 We were the, not quite right in that tagline. 75 00:03:27,915 --> 00:03:31,252 We're not the first to focus X-ray light, period. 76 00:03:31,252 --> 00:03:33,821 We're the first to focus high-energy X-ray light. 77 00:03:33,821 --> 00:03:35,589 The more energetic X-rays. 78 00:03:35,589 --> 00:03:37,557 And we have a change in technology that brought 79 00:03:37,557 --> 00:03:39,993 about a factor of 200 gain in sensitivity, 80 00:03:39,993 --> 00:03:42,696 compared to what has flown before us. 81 00:03:42,696 --> 00:03:44,866 We're a NASA small explorer mission 82 00:03:44,866 --> 00:03:47,802 that's a line of missions that cost about 150 million. 83 00:03:47,802 --> 00:03:50,570 It's about as small as NASA goes into space, 84 00:03:50,570 --> 00:03:53,340 typically, for, in astrophysics. 85 00:03:53,340 --> 00:03:55,843 About, you know, more expensive than an indie film 86 00:03:55,843 --> 00:03:57,878 but less expensive than a blockbuster. 87 00:03:57,878 --> 00:04:00,280 I think we've gotten good value out of it. 88 00:04:00,280 --> 00:04:03,250 Giving into the LA context. 89 00:04:03,250 --> 00:04:05,886 We launched in June, 2012. 90 00:04:05,886 --> 00:04:08,589 We were initially designed for a two-year mission, 91 00:04:08,589 --> 00:04:10,891 but everything's been going swimmingly, 92 00:04:10,891 --> 00:04:14,061 and we then continued on for continued funding, 93 00:04:14,061 --> 00:04:15,996 and so now we're a couple years past that, 94 00:04:15,996 --> 00:04:19,800 in this extended mission, since August, 2014. 95 00:04:19,800 --> 00:04:22,736 The principle investigator, or PI, is Fiona Harrison, 96 00:04:22,736 --> 00:04:24,871 who's the Cal Tech physics professor, 97 00:04:24,871 --> 00:04:26,774 and now the chair of physics, math, 98 00:04:26,774 --> 00:04:29,377 and astronomy at Cal Tech. 99 00:04:29,377 --> 00:04:32,879 She, we were the first mission that NASA selected 100 00:04:32,879 --> 00:04:36,283 with a female PI, which is both very exciting 101 00:04:36,283 --> 00:04:38,819 and also kinda embarrassing, because about 50 years 102 00:04:38,819 --> 00:04:42,056 into NASA's history, before that had happened. 103 00:04:42,056 --> 00:04:45,492 Another mission selected after us actually launched 104 00:04:45,492 --> 00:04:48,329 before us with a female PI, so we weren't the first 105 00:04:48,329 --> 00:04:50,430 in orbit with a female PI. 106 00:04:50,430 --> 00:04:53,033 I'm the project scientist; I'm a JPL employee. 107 00:04:53,033 --> 00:04:54,668 I spend a lot of time at Cal Tech. 108 00:04:54,668 --> 00:04:57,204 And the NuSTAR mission's been a really fun project. 109 00:04:57,204 --> 00:05:00,207 It's about 150 scientists on the science team, 110 00:05:00,207 --> 00:05:01,709 around the world. 111 00:05:01,709 --> 00:05:04,611 We have the Italian Space Agency has a big role in it. 112 00:05:04,611 --> 00:05:07,514 The Danish Technical University in Copenhagen 113 00:05:07,514 --> 00:05:10,484 had a big role, and then here's Columbia University, 114 00:05:10,484 --> 00:05:14,288 Berkeley, I guess, so it's been a fun ride. 115 00:05:14,288 --> 00:05:16,224 With a nice, good team. 116 00:05:18,358 --> 00:05:21,662 I mentioned that we were a NASA small explorer. 117 00:05:21,662 --> 00:05:24,631 Just to explain to you, in the astrophysics, 118 00:05:24,631 --> 00:05:27,601 so everything that NASA studies outside of our solar system 119 00:05:27,601 --> 00:05:30,671 counts as astrophysics, and the smaller line 120 00:05:30,671 --> 00:05:32,205 of that are these explorers. 121 00:05:32,205 --> 00:05:34,174 We have the mid-sized explorers, 122 00:05:34,174 --> 00:05:35,876 and then the small explorers, 123 00:05:35,876 --> 00:05:37,944 and then sometimes these mission of opportunities, 124 00:05:37,944 --> 00:05:40,481 which will often be NASA building an instrument 125 00:05:40,481 --> 00:05:44,252 on a foreign instrument, a foreign telescope. 126 00:05:45,619 --> 00:05:48,756 And so, there's NuSTAR, one of the more recent 127 00:05:48,756 --> 00:05:51,892 small explorers, and then I circled a couple other ones 128 00:05:51,892 --> 00:05:55,028 that came out of Pasadena that you might have heard of. 129 00:05:55,028 --> 00:05:58,332 WISE and GALEX and ACE, and so it's a really exciting line. 130 00:05:58,332 --> 00:06:01,135 It's had really exciting discoveries. 131 00:06:01,135 --> 00:06:03,637 And these missions are relatively small, for NASA. 132 00:06:03,637 --> 00:06:05,606 So it's a relatively small teams 133 00:06:05,606 --> 00:06:09,477 and relatively quick timelines, from selection to launch. 134 00:06:09,477 --> 00:06:12,646 And in fact, by the end of this month, 135 00:06:12,646 --> 00:06:14,180 or maybe by the end of next month, 136 00:06:14,180 --> 00:06:17,051 the next SMEX will be selected. 137 00:06:17,051 --> 00:06:19,186 They do a multiple-stage down-select. 138 00:06:19,186 --> 00:06:20,420 So at this point, 139 00:06:20,420 --> 00:06:22,789 there's three missions competing for one slot. 140 00:06:22,789 --> 00:06:24,825 One of those three is called SPIREX that comes 141 00:06:24,825 --> 00:06:26,894 out of Cal Tech and JPL, so hopefully, 142 00:06:26,894 --> 00:06:29,130 maybe the next week we'll find out 143 00:06:29,130 --> 00:06:32,199 that the next SMEX will be coming out of JPL, as well. 144 00:06:32,199 --> 00:06:33,466 And you'll be able to hear a talk 145 00:06:33,466 --> 00:06:36,604 about that in a couple of years. 146 00:06:36,604 --> 00:06:37,872 Our outline for the talk: 147 00:06:37,872 --> 00:06:39,506 I'll start off with a little bit of overview 148 00:06:39,506 --> 00:06:41,008 of what the NuSTAR mission is like. 149 00:06:41,008 --> 00:06:43,611 You know, the engineering of it, the launch of it. 150 00:06:43,611 --> 00:06:45,946 And then I'll hit on those three science topics, 151 00:06:45,946 --> 00:06:47,647 from the title of the talk. 152 00:06:47,647 --> 00:06:50,117 And here's the website, and here's the artist's conception 153 00:06:50,117 --> 00:06:52,719 of what NuSTAR looks like. 154 00:06:52,719 --> 00:06:55,856 We work in the high-energy X-ray regime. 155 00:06:55,856 --> 00:06:58,358 So this is the same energy X-rays, 156 00:06:58,358 --> 00:07:01,428 or energy light, that doctors and dentists use 157 00:07:01,428 --> 00:07:04,098 to study your body, that airport security use 158 00:07:04,098 --> 00:07:06,800 to study your luggage; these are very penetrating light. 159 00:07:06,800 --> 00:07:09,403 They're able to go through material. 160 00:07:09,403 --> 00:07:11,705 We're not sending out X-rays and then studying, 161 00:07:11,705 --> 00:07:14,208 you know, X-ray images, the way doctors do. 162 00:07:14,208 --> 00:07:15,976 Instead, we study some of the most energetic, 163 00:07:15,976 --> 00:07:19,947 powerful phenomena in the Universe that create X-rays, 164 00:07:19,947 --> 00:07:23,117 like supernovae, the sun, black holes, 165 00:07:24,518 --> 00:07:28,088 and use that to understand the extreme Universe. 166 00:07:28,088 --> 00:07:31,458 We work in the high-energy, or hard X-ray regime. 167 00:07:31,458 --> 00:07:32,959 I'll try not to use the term "hard", 168 00:07:32,959 --> 00:07:35,562 but that's the technical term. 169 00:07:35,562 --> 00:07:38,232 We're the first mission to focus X-rays 170 00:07:38,232 --> 00:07:40,534 in this high-energy X-ray regime. 171 00:07:40,534 --> 00:07:42,269 There've been several missions that have done this, 172 00:07:42,269 --> 00:07:44,772 similar things, in the low-energy X-rays. 173 00:07:44,772 --> 00:07:48,308 I have a picture here of Europe's XMM Newton Satellite. 174 00:07:48,308 --> 00:07:50,277 You might also have heard of NASA's 175 00:07:50,277 --> 00:07:52,413 flagship Chandra X-ray Observatory, 176 00:07:52,413 --> 00:07:54,648 that works in a similar energy regime. 177 00:07:54,648 --> 00:07:57,018 Those missions launched about 15 years ago 178 00:07:57,018 --> 00:07:59,486 and are continuing and doing really exciting work 179 00:07:59,486 --> 00:08:01,421 in the lower-energy X-rays, and we actually 180 00:08:01,421 --> 00:08:03,924 partner up a lot with those missions. 181 00:08:03,924 --> 00:08:08,095 So we got a full X-ray study of interesting objects. 182 00:08:10,297 --> 00:08:13,133 NuSTAR, I keep saying that we're focusing optics, 183 00:08:13,133 --> 00:08:14,635 so I'll describe that a little bit. 184 00:08:14,635 --> 00:08:17,972 We're the first focusing X-ray satellite in orbit. 185 00:08:17,972 --> 00:08:21,708 Previous generations of X-ray satellites use something 186 00:08:21,708 --> 00:08:23,777 called "coded aperture optics", which are like 187 00:08:23,777 --> 00:08:26,246 a pinhole camera or, I like to think of it as, 188 00:08:26,246 --> 00:08:29,750 kind of have a lead screen with lots of holes in it, 189 00:08:29,750 --> 00:08:32,119 and then the satellites looming across the sky, 190 00:08:32,119 --> 00:08:33,921 just rotating around, and you watch how 191 00:08:33,921 --> 00:08:36,056 the shadow pattern changes and you're able to 192 00:08:36,056 --> 00:08:39,793 figure out where the X-rays are coming from in the sky. 193 00:08:39,793 --> 00:08:43,630 And so that sort of design, this coded aperture optics, 194 00:08:43,630 --> 00:08:45,765 by nature, gets you blurry images, 195 00:08:45,765 --> 00:08:47,301 you need really big detectors, 196 00:08:47,301 --> 00:08:49,803 you need this big lead shielding thing, 197 00:08:49,803 --> 00:08:52,673 and so it ends up being a very heavy satellite. 198 00:08:52,673 --> 00:08:55,309 I have a picture here of the European INTEGRAL satellite, 199 00:08:55,309 --> 00:08:58,078 and NASA also has a coded aperture satellite 200 00:08:58,078 --> 00:09:00,414 up in orbit right now, called the BAT, 201 00:09:00,414 --> 00:09:04,551 the BAT Alert Telescope on the Swift Satellite. 202 00:09:04,551 --> 00:09:06,620 Those sort of designs are pretty heavy, 203 00:09:06,620 --> 00:09:09,756 and if you, if you're a NASA person, 204 00:09:09,756 --> 00:09:11,792 you know heavy means expensive. 205 00:09:11,792 --> 00:09:13,460 Costs a lot to launch things into space, 206 00:09:13,460 --> 00:09:16,863 so you try to make them as light as possible. 207 00:09:16,863 --> 00:09:19,666 NuSTAR instead does focusing optics. 208 00:09:19,666 --> 00:09:21,668 And X-ray focusing is a little bit tricky, 209 00:09:21,668 --> 00:09:25,105 because if you had, like, your usual antennas like we see 210 00:09:25,105 --> 00:09:27,540 here or like radio dishes you see, 211 00:09:27,540 --> 00:09:29,777 or normal, optical telescopes, 212 00:09:29,777 --> 00:09:31,544 X-rays tend to like to go 213 00:09:31,544 --> 00:09:33,880 right into it and penetrate through. 214 00:09:33,880 --> 00:09:35,682 And so when you wanna focus X-ray light, 215 00:09:35,682 --> 00:09:37,951 you have to do grazing incidence optics, 216 00:09:37,951 --> 00:09:40,053 so the X-rays come and you kind of nudge them, 217 00:09:40,053 --> 00:09:42,823 almost like a rock on a lake. 218 00:09:42,823 --> 00:09:45,626 And so our design is something called Walter One Optics, 219 00:09:45,626 --> 00:09:49,229 we have two bounces to the X-rays, 220 00:09:49,229 --> 00:09:51,765 and then it sends them down, focuses them on where 221 00:09:51,765 --> 00:09:53,900 we have our detectors. 222 00:09:53,900 --> 00:09:56,537 The optics end up, so, rather than looking like a dish, 223 00:09:56,537 --> 00:09:59,939 it's a cylinder, nudging the light in, 224 00:09:59,939 --> 00:10:03,344 and in fact, what we do is we have 133 shells, 225 00:10:03,344 --> 00:10:06,546 concentric shells, almost like Russian nesting dolls, 226 00:10:06,546 --> 00:10:08,448 that make up our optics. 227 00:10:08,448 --> 00:10:10,183 So our optics are about yay big, 228 00:10:10,183 --> 00:10:13,120 they weight about 50 kilograms. 229 00:10:13,120 --> 00:10:15,689 And they focus the light in. 230 00:10:15,689 --> 00:10:18,525 Here's a picture from a Scientific American article 231 00:10:18,525 --> 00:10:20,260 about a year before we launched, a year and a half 232 00:10:20,260 --> 00:10:22,095 before we launched, where they took pictures 233 00:10:22,095 --> 00:10:23,931 of different parts of NuSTAR being built. 234 00:10:23,931 --> 00:10:26,233 And this shows you the top-end view of the optics, 235 00:10:26,233 --> 00:10:29,136 so you have these concentric shells, 133 of them, 236 00:10:29,136 --> 00:10:31,738 with the little, graphite spacers. 237 00:10:31,738 --> 00:10:34,407 This was a big effort to build this thing. 238 00:10:34,407 --> 00:10:36,443 And we actually built, we built three of them. 239 00:10:36,443 --> 00:10:39,880 We launched two of them on the satellite. 240 00:10:41,314 --> 00:10:44,184 So this change in technology buys NuSTAR a huge gain. 241 00:10:44,184 --> 00:10:47,421 We're about 10-times or even more than 10-times 242 00:10:47,421 --> 00:10:50,791 sharper images, about 200-times more sensitive images, 243 00:10:50,791 --> 00:10:53,593 and actually, because we weigh so much less 244 00:10:53,593 --> 00:10:56,329 than the other design, we're about a quarter of the cost 245 00:10:56,329 --> 00:10:59,032 of the INTEGRAL satellite, for example. 246 00:10:59,032 --> 00:11:03,403 So this is just a game-changer in high-energy astrophysics. 247 00:11:03,403 --> 00:11:06,840 Here's an example, showing you what that change buys you. 248 00:11:06,840 --> 00:11:09,209 Here's an optical image of a nearby galaxy, 249 00:11:09,209 --> 00:11:11,978 NGC 1365, it's a barred-spiral galaxy. 250 00:11:11,978 --> 00:11:15,248 The pretty picture is a ground-based, optical image. 251 00:11:15,248 --> 00:11:17,952 And then, what I'm showing you here is the beam size, 252 00:11:17,952 --> 00:11:20,687 or essentially, the pixels for some of the other 253 00:11:20,687 --> 00:11:22,789 high-energy satellites in orbit. 254 00:11:22,789 --> 00:11:25,225 So, INTEGRAL has this big circle, here. 255 00:11:25,225 --> 00:11:28,562 Swift's pixels are about the size of the full moon. 256 00:11:28,562 --> 00:11:31,264 Roughly about 20 arcminutes versus 30 arcminutes, 257 00:11:31,264 --> 00:11:35,102 and the NuSTAR's beam size is about the size of Mars. 258 00:11:35,102 --> 00:11:37,137 And so we get much, much sharper images. 259 00:11:37,137 --> 00:11:39,606 We're able to, whereas Swift and INTEGRAL 260 00:11:39,606 --> 00:11:43,209 might have said NGC 1365 has a lot of high-energy X-rays 261 00:11:43,209 --> 00:11:45,078 coming out of it, with NuSTAR, 262 00:11:45,078 --> 00:11:46,980 we're actually able to map it. 263 00:11:46,980 --> 00:11:49,483 And so here's an example of another nearby galaxy, 264 00:11:49,483 --> 00:11:53,653 IC 342, again, the background image is an optical image, 265 00:11:53,653 --> 00:11:56,957 from the ground, of this nearby spiral galaxy, 266 00:11:56,957 --> 00:12:00,160 the purple is the NuSTAR image of it, 267 00:12:00,160 --> 00:12:01,895 and we actually see three sources. 268 00:12:01,895 --> 00:12:04,198 You see two on the, two bright buys in the outskirts, 269 00:12:04,198 --> 00:12:06,033 and there's actually a little bit of high-energy 270 00:12:06,033 --> 00:12:08,635 X-ray light coming from the center of the galaxy. 271 00:12:08,635 --> 00:12:10,437 And so, with Swift or with INTEGRAL, 272 00:12:10,437 --> 00:12:12,639 all of the previous satellites just would have seen 273 00:12:12,639 --> 00:12:14,408 there's X-rays coming from this, 274 00:12:14,408 --> 00:12:16,343 and they wouldn't have know if it was one source, 275 00:12:16,343 --> 00:12:18,646 three sources, coming from the center, 276 00:12:18,646 --> 00:12:21,114 from the outskirts, so it's a total game-changer 277 00:12:21,114 --> 00:12:23,284 in what you're able to do. 278 00:12:24,618 --> 00:12:27,187 A little bit on the technology that allowed it. 279 00:12:27,187 --> 00:12:30,523 So here's the optics, I showed you. 280 00:12:30,523 --> 00:12:32,726 We have two of them, actually, 281 00:12:32,726 --> 00:12:34,795 just to get more collecting area. 282 00:12:34,795 --> 00:12:36,330 Just a fun little story: 283 00:12:36,330 --> 00:12:38,632 they sit in something called the "trashcan", 284 00:12:38,632 --> 00:12:40,834 or we called it the trashcan before launch. 285 00:12:40,834 --> 00:12:42,669 Until the guys who were building it said: 286 00:12:42,669 --> 00:12:44,571 can you stop calling it the trashcan? 287 00:12:44,571 --> 00:12:46,506 (laughter) 288 00:12:46,506 --> 00:12:48,475 Yeah, so the optics are yay big. 289 00:12:48,475 --> 00:12:51,178 They focus the light down on these detectors. 290 00:12:51,178 --> 00:12:53,012 We have two sets of detectors, one for the optics. 291 00:12:53,012 --> 00:12:55,415 They're both pointing at the same patch of sky. 292 00:12:55,415 --> 00:12:58,718 The detectors, whereas your cellphones use a silicon 293 00:12:58,718 --> 00:13:02,089 detector to detect optical light, for high-energy X-rays, 294 00:13:02,089 --> 00:13:03,524 you have to do a little bit of change. 295 00:13:03,524 --> 00:13:06,125 It's cadmium-zinc-telluride detectors. 296 00:13:06,125 --> 00:13:07,794 These detectors were all built 297 00:13:07,794 --> 00:13:09,996 at Cal Tech by Fiona Harrison's group, 298 00:13:09,996 --> 00:13:11,397 which is one of the world leaders 299 00:13:11,397 --> 00:13:13,066 in these high-energy detectors. 300 00:13:13,066 --> 00:13:16,970 And these were built specifically for NuSTAR. 301 00:13:16,970 --> 00:13:19,306 Both the detectors and the optics, 302 00:13:19,306 --> 00:13:22,275 we flew an earlier version of NuSTAR on a balloon 303 00:13:22,275 --> 00:13:24,411 called the High-Energy Focusing Telescope, 304 00:13:24,411 --> 00:13:27,047 or HEFT, which was really a proof of technology, 305 00:13:27,047 --> 00:13:29,282 that the detectors and the optics worked. 306 00:13:29,282 --> 00:13:31,718 It just, you know, flew for a couple of hours, 307 00:13:31,718 --> 00:13:34,521 a couple of days, was able to look at very bright objects, 308 00:13:34,521 --> 00:13:36,823 but this showed to NASA that this worked, 309 00:13:36,823 --> 00:13:39,092 and then allowed us to then propose, 310 00:13:39,092 --> 00:13:41,895 and get accepted as a satellite mission. 311 00:13:41,895 --> 00:13:46,333 And really be able to exploit this energy regime. 312 00:13:46,333 --> 00:13:49,102 And then finally, the third key part of the technology 313 00:13:49,102 --> 00:13:53,239 is that these focusing, high-energy X-ray optics 314 00:13:53,239 --> 00:13:54,841 have very long focal length. 315 00:13:54,841 --> 00:13:56,910 You need a really large separation from your, 316 00:13:56,910 --> 00:13:59,446 essentially, your lens and your film, 317 00:13:59,446 --> 00:14:02,015 or your, you know, your lens and your detectors. 318 00:14:02,015 --> 00:14:05,285 For NuSTAR, this is 10 meters, 30 feet, 319 00:14:05,285 --> 00:14:08,388 or about the length of a school bus. 320 00:14:08,388 --> 00:14:12,226 Chandra and XMM, those flagship, lower-energy missions, 321 00:14:12,226 --> 00:14:16,296 had similar focal lengths for their telescopes, 322 00:14:16,296 --> 00:14:18,865 but they were, you know, billion-dollar class missions. 323 00:14:18,865 --> 00:14:23,002 They were able to launch on a big rocket, fully-extended. 324 00:14:23,002 --> 00:14:25,205 For NuSTAR, we had to extend after launch, 325 00:14:25,205 --> 00:14:28,075 because we had to go on a little, cheap, less-expensive, 326 00:14:28,075 --> 00:14:29,276 (laughter) 327 00:14:29,276 --> 00:14:31,245 launch vehicle. 328 00:14:31,245 --> 00:14:33,547 And so, so we have this extendable mast 329 00:14:33,547 --> 00:14:35,816 that was build in Galleda, California. 330 00:14:35,816 --> 00:14:37,817 Pretty close to Santa Barbara, by a company 331 00:14:37,817 --> 00:14:40,887 that specializes in extendables in space. 332 00:14:40,887 --> 00:14:43,222 They have about, more than 100 things, 333 00:14:43,222 --> 00:14:47,527 some in orbit, some on Mars, with 100 percent success rate. 334 00:14:47,527 --> 00:14:49,562 The design for the one on NuSTAR was based 335 00:14:49,562 --> 00:14:51,864 on something that launched about 20 years ago, 336 00:14:51,864 --> 00:14:55,135 on the shuttle, called the Shuttle Radar Topography Mission. 337 00:14:55,135 --> 00:14:59,506 And so it was a very similar design to that. 338 00:14:59,506 --> 00:15:01,541 And then here's just a sense of scale. 339 00:15:01,541 --> 00:15:03,877 Here's a picture, towards the end of the integration 340 00:15:03,877 --> 00:15:06,279 and testing of NuSTAR. 341 00:15:06,279 --> 00:15:09,116 So there's the two optics modules, 342 00:15:10,483 --> 00:15:12,519 the mast is deployed in there, 343 00:15:12,519 --> 00:15:14,555 and there's a person, just to give you a sense of scale. 344 00:15:14,555 --> 00:15:18,258 So, you know, we're a little bit bigger than a person. 345 00:15:18,258 --> 00:15:21,128 Our launch was this interesting launch called, 346 00:15:21,128 --> 00:15:24,197 the launch vehicle, called the Pegasus Launch Vehicle. 347 00:15:24,197 --> 00:15:26,766 Here's a little video of it. 348 00:15:26,766 --> 00:15:28,701 This actually isn't our launch. 349 00:15:28,701 --> 00:15:32,372 We launched at night, and so this is just archival footage 350 00:15:32,372 --> 00:15:35,409 of a launch, but essentially, they use an L-1011, 351 00:15:35,409 --> 00:15:39,479 a Lockheed 1011 jumbo jet as a first stage, 352 00:15:39,479 --> 00:15:42,716 takes the rocket up to 30,000 feet, 353 00:15:42,716 --> 00:15:45,552 drops it for five seconds, it ignites, 354 00:15:45,552 --> 00:15:48,488 and then takes you up into space. 355 00:15:48,488 --> 00:15:50,157 And so this all happened in June. 356 00:15:50,157 --> 00:15:52,392 The airplane took off from the Kwajalein Atoll, 357 00:15:52,392 --> 00:15:55,528 in the Marshall Islands, and since that point, 358 00:15:55,528 --> 00:15:57,698 NuSTAR has been orbiting the Earth, 359 00:15:57,698 --> 00:16:00,766 basically over the equator every 90 minutes 360 00:16:00,766 --> 00:16:03,670 and taking data the whole time. 361 00:16:03,670 --> 00:16:05,939 I heard on NPR this morning, they launched a, 362 00:16:05,939 --> 00:16:08,007 they did another Pegasus this morning, 363 00:16:08,007 --> 00:16:10,043 if you had heard, with something studying, 364 00:16:10,043 --> 00:16:13,580 something called CYGNSS, studying hurricanes. 365 00:16:13,580 --> 00:16:15,215 But there's beautiful videos of that. 366 00:16:15,215 --> 00:16:17,317 I just was watching that. 367 00:16:18,818 --> 00:16:20,454 So we got into space. 368 00:16:20,454 --> 00:16:22,388 The first thing you do is you deploy your solar panel, 369 00:16:22,388 --> 00:16:24,290 just to stay power-positive. 370 00:16:24,290 --> 00:16:27,261 Exercise that you're able to move the spacecraft around, 371 00:16:27,261 --> 00:16:31,431 and then about a week after launch, we deployed 372 00:16:31,431 --> 00:16:34,234 this extendable mast, so that we could start 373 00:16:34,234 --> 00:16:36,269 focusing the X-ray light. 374 00:16:36,269 --> 00:16:37,771 And so this is the artist's conception 375 00:16:37,771 --> 00:16:39,305 of what that looked like. 376 00:16:39,305 --> 00:16:42,074 There's our two optics modules. 377 00:16:42,074 --> 00:16:44,311 We have two detectors down here, 378 00:16:44,311 --> 00:16:46,512 and basically the launch and then this were 379 00:16:46,512 --> 00:16:49,149 the two really scariest parts of the mission. 380 00:16:49,149 --> 00:16:51,184 This took about 40 minutes. 381 00:16:51,184 --> 00:16:54,488 And just like the launch, it went perfectly. 382 00:16:54,488 --> 00:16:57,658 And so, it just is a very cute design, 383 00:16:58,825 --> 00:17:01,361 that very simple and very compact, 384 00:17:02,562 --> 00:17:05,732 and then it extends out by this 30 feet. 385 00:17:07,334 --> 00:17:10,170 And so, I'll just let that finish. 386 00:17:11,605 --> 00:17:13,306 And so, we're orbiting the Earth every 90 minutes, 387 00:17:13,306 --> 00:17:16,810 taking data; there's the two optics units. 388 00:17:20,713 --> 00:17:24,451 So, with this very successful launch, 389 00:17:24,451 --> 00:17:27,454 ant this great new technology, we've been doing a range 390 00:17:27,454 --> 00:17:30,423 of really game-changing observations. 391 00:17:30,423 --> 00:17:34,194 Talk about first: black hole spin measurements. 392 00:17:34,194 --> 00:17:37,264 So, first off, what's a black hole? 393 00:17:37,264 --> 00:17:40,967 I could give a whole, one-hour lecture on black holes, 394 00:17:40,967 --> 00:17:42,903 do more than that even. 395 00:17:44,271 --> 00:17:46,273 We're not gonna do that today, but just real briefly, 396 00:17:46,273 --> 00:17:49,409 black holes are these sort of crazy things that, 397 00:17:49,409 --> 00:17:51,377 you know, if I take this ball and I throw it up, 398 00:17:51,377 --> 00:17:53,246 it comes back down; if I throw it higher, 399 00:17:53,246 --> 00:17:54,781 it takes longer to come down. 400 00:17:54,781 --> 00:17:58,718 If I threw it really hard, it would go up into space, 401 00:17:58,718 --> 00:18:01,721 and reach, you know, escape velocity and go out into space 402 00:18:01,721 --> 00:18:05,825 and escape the gravitational pull of the Earth. 403 00:18:05,825 --> 00:18:09,129 So way back, actually, back in the 1700s, 404 00:18:09,129 --> 00:18:11,998 Emanuel Kant kind of did a thought experiment that, 405 00:18:11,998 --> 00:18:13,800 could you imagine if you had something that, 406 00:18:13,800 --> 00:18:16,836 its escape speed was the speed of light, 407 00:18:16,836 --> 00:18:19,572 then not even light would be able to escape from it? 408 00:18:19,572 --> 00:18:21,941 And so Emanuel Kant actually kind of came up with the idea 409 00:18:21,941 --> 00:18:24,577 that black holes might exist. 410 00:18:24,577 --> 00:18:26,546 And it was many centuries later, 411 00:18:26,546 --> 00:18:28,882 before you know, physics started showing that, 412 00:18:28,882 --> 00:18:30,950 yeah, we do predict they might happen, 413 00:18:30,950 --> 00:18:32,752 and that actually, the first black holes 414 00:18:32,752 --> 00:18:35,555 were found by a Cal Tech astronomer, 415 00:18:35,555 --> 00:18:38,925 Martin Schmidt, about 52, 53 years ago, 416 00:18:38,925 --> 00:18:42,495 using the Palomar Telescope with 3C 273. 417 00:18:42,495 --> 00:18:46,933 So these are incredibly odd objects in the Universe. 418 00:18:46,933 --> 00:18:48,835 Very heavy, very dense. 419 00:18:50,436 --> 00:18:52,873 And very fascinating objects. 420 00:18:54,307 --> 00:18:56,709 A couple of things that we know about black holes, 421 00:18:56,709 --> 00:18:58,311 we know that there's a big black hole 422 00:18:58,311 --> 00:19:01,314 in the center of every large galaxy, 423 00:19:01,314 --> 00:19:05,251 weighing millions to billions of times as much as the sun. 424 00:19:05,251 --> 00:19:06,753 We know that there are smaller black holes, 425 00:19:06,753 --> 00:19:08,555 weighing a bit more than the sun, 426 00:19:08,555 --> 00:19:11,124 near 10 or a couple of 10's of times as much 427 00:19:11,124 --> 00:19:13,626 as the sun, peppered throughout galaxies. 428 00:19:13,626 --> 00:19:16,329 There's, you know, thousands in our own galaxy, 429 00:19:16,329 --> 00:19:18,431 and we see them in nearby galaxies. 430 00:19:18,431 --> 00:19:22,736 So astronomers, like, all astronomers know black holes exist 431 00:19:22,736 --> 00:19:25,137 and that there's different types. 432 00:19:25,137 --> 00:19:27,874 Oddly, we don't know, we only know of one, 433 00:19:27,874 --> 00:19:29,776 in this intermediate range, between the small 434 00:19:29,776 --> 00:19:32,545 and the big, and that's a big issue 435 00:19:32,545 --> 00:19:35,314 that I'll talk about a little bit later. 436 00:19:35,314 --> 00:19:38,885 Highlighting some more Southern California astronomy, 437 00:19:38,885 --> 00:19:43,823 one of the best studies of the nearest big black hole to us 438 00:19:43,823 --> 00:19:46,592 comes out of Andrea Ghez's group at UCLA. 439 00:19:46,592 --> 00:19:48,461 And they've been using, for the last 440 00:19:48,461 --> 00:19:50,763 15, 20 years, very advanced techniques 441 00:19:50,763 --> 00:19:53,466 on the biggest ground-based telescopes, 442 00:19:53,466 --> 00:19:57,604 to watch stars moving in the center of our galaxy. 443 00:19:57,604 --> 00:19:59,639 There's a couple dozen stars that they've now 444 00:19:59,639 --> 00:20:02,542 been tracking for 20 years, and they find 445 00:20:02,542 --> 00:20:05,277 that they're all orbiting around a single point. 446 00:20:05,277 --> 00:20:07,246 You can use just high school level physics 447 00:20:07,246 --> 00:20:10,350 to figure out how much that single point must weigh, 448 00:20:10,350 --> 00:20:12,919 and it's about four million times as much as the sun. 449 00:20:12,919 --> 00:20:16,356 It's very dim; you see it flaring every once in a while. 450 00:20:16,356 --> 00:20:18,324 And there's basically, physics tells you 451 00:20:18,324 --> 00:20:20,960 that the only thing that could be that heavy 452 00:20:20,960 --> 00:20:24,030 and that dense is a black hole. 453 00:20:24,030 --> 00:20:26,098 And so this is, you know, one of the best-studied 454 00:20:26,098 --> 00:20:30,036 black holes, is that one in the center of our own galaxy. 455 00:20:30,036 --> 00:20:32,138 Over the last 15 years, we've come to appreciate 456 00:20:32,138 --> 00:20:35,008 that probably all big galaxies have something 457 00:20:35,008 --> 00:20:37,276 that weighs millions to billions of times 458 00:20:37,276 --> 00:20:39,579 as much as the sun, at their center. 459 00:20:39,579 --> 00:20:41,915 And they, about one half of one percent of the mass 460 00:20:41,915 --> 00:20:45,986 of a galaxy is in the central, little black hole. 461 00:20:47,420 --> 00:20:50,423 Things that we don't know about black holes is, 462 00:20:50,423 --> 00:20:52,959 there's really extreme physics happening, 463 00:20:52,959 --> 00:20:54,694 right near the black hole. 464 00:20:54,694 --> 00:20:57,764 It's, space and time is being torn apart, 465 00:20:57,764 --> 00:21:02,502 as you might have seen in the Interstellar movie. 466 00:21:02,502 --> 00:21:04,905 The, really strong magnetic fields, 467 00:21:04,905 --> 00:21:08,108 crazy high temperatures, creating X-rays, for instance. 468 00:21:08,108 --> 00:21:09,575 And so there's a lot of work going on, 469 00:21:09,575 --> 00:21:11,243 trying to understand the detailed physics 470 00:21:11,243 --> 00:21:13,946 of what's going on near black holes. 471 00:21:13,946 --> 00:21:16,349 The cosmic history of how black holes 472 00:21:16,349 --> 00:21:20,520 form and grow over time is a big area of study, right now. 473 00:21:21,954 --> 00:21:24,624 We see black holes weighing a billion times as much 474 00:21:24,624 --> 00:21:28,428 as the sun, less than a billion years after the Big Bang. 475 00:21:28,428 --> 00:21:31,831 And basically, theorists say that shouldn't exist. 476 00:21:31,831 --> 00:21:35,100 They, that the models have a really hard time creating 477 00:21:35,100 --> 00:21:37,170 things that big, that quickly, 478 00:21:37,170 --> 00:21:39,673 and then the observers find them. 479 00:21:39,673 --> 00:21:42,241 And then the other thing is we think that black holes 480 00:21:42,241 --> 00:21:45,311 are really important in how galaxies form 481 00:21:45,311 --> 00:21:47,647 and evolve over time, and that's a big area 482 00:21:47,647 --> 00:21:49,182 of study right now. 483 00:21:50,182 --> 00:21:52,452 So where does NuSTAR come in? 484 00:21:52,452 --> 00:21:56,122 So black holes, at some level, are very simple things. 485 00:21:56,122 --> 00:21:58,558 They're really, mathematically, very pure. 486 00:21:58,558 --> 00:22:03,129 There's only three parameters that define a black hole: 487 00:22:03,129 --> 00:22:06,466 its mass, its spin, and then its charge. 488 00:22:08,801 --> 00:22:10,903 But any astrophysical black hole should 489 00:22:10,903 --> 00:22:13,239 essentially have zero charge, so we really kind of think 490 00:22:13,239 --> 00:22:16,276 of just two parameters, the mass and the spin. 491 00:22:16,276 --> 00:22:19,079 Masses, we've been measuring for the last 20 years, 492 00:22:19,079 --> 00:22:21,380 like that study by Andrea Ghez, you watch things 493 00:22:21,380 --> 00:22:23,950 orbiting the black hole, you can figure out how big it is. 494 00:22:23,950 --> 00:22:27,086 The spin of the black hole has been harder to measure. 495 00:22:27,086 --> 00:22:29,789 And that's where NuSTAR came in. 496 00:22:29,789 --> 00:22:31,491 Being able to measure the spin tells you 497 00:22:31,491 --> 00:22:33,560 about the environment around the black hole. 498 00:22:33,560 --> 00:22:35,695 A little bit about how the black hole forms. 499 00:22:35,695 --> 00:22:39,099 But one of the big issues is, before NuSTAR, 500 00:22:39,099 --> 00:22:41,434 there'd been this longstanding debate 501 00:22:41,434 --> 00:22:43,536 in the high-energy X-ray community 502 00:22:43,536 --> 00:22:45,972 about if you could even measure how fast black holes 503 00:22:45,972 --> 00:22:48,207 are spinning, and if you went to a conference 504 00:22:48,207 --> 00:22:51,044 before NuSTAR launched, somebody would give a talk about, 505 00:22:51,044 --> 00:22:52,978 you know, we measure the spin of this black hole 506 00:22:52,978 --> 00:22:55,048 to be blah-blah-blah, and then the next person 507 00:22:55,048 --> 00:22:57,717 would come up and say: you can't measure the spin 508 00:22:57,717 --> 00:23:00,153 of a black hole, here's our model that tells you, 509 00:23:00,153 --> 00:23:02,355 we can take that same data and tells you nothing 510 00:23:02,355 --> 00:23:04,523 about how fast the black hole is spinning. 511 00:23:04,523 --> 00:23:06,659 So you have these two, like, warring camps 512 00:23:06,659 --> 00:23:09,729 at conferences, and then most of the community 513 00:23:09,729 --> 00:23:12,899 was just sitting on the fence, unsure. 514 00:23:14,301 --> 00:23:18,838 And the way the people who are thinking they were 515 00:23:18,838 --> 00:23:21,074 measuring the spin of the black holes were doing it, 516 00:23:21,074 --> 00:23:24,043 is that one of the strongest features that you see 517 00:23:24,043 --> 00:23:26,779 in the X-rays from a black hole is a strong 518 00:23:26,779 --> 00:23:29,949 emission line of iron, you get very hot iron, 519 00:23:29,949 --> 00:23:31,817 very close to the black hole, 520 00:23:31,817 --> 00:23:35,221 and so it basically comes from the region 521 00:23:36,388 --> 00:23:39,359 closest to the black hole, and that region 522 00:23:39,359 --> 00:23:41,294 closest to the black hole, would depend 523 00:23:41,294 --> 00:23:44,063 on how fast the black holes is spinning. 524 00:23:44,063 --> 00:23:47,133 If the black hole is spinning very, very fast, 525 00:23:47,133 --> 00:23:50,503 the disc of material around the black hole gets 526 00:23:50,503 --> 00:23:54,940 brought in very, very close to the black hole, and so this, 527 00:23:54,940 --> 00:23:59,479 the iron, is moving at incredibly fast speeds. 528 00:23:59,479 --> 00:24:02,282 It's so close to the black hole that you have light bending 529 00:24:02,282 --> 00:24:05,417 going on, and the emission line, this iron line, 530 00:24:05,417 --> 00:24:10,356 gets really spread out and has this really extreme profile 531 00:24:10,356 --> 00:24:14,360 that's from light bending and relativistic effects. 532 00:24:14,360 --> 00:24:16,028 In the middle, I have a picture 533 00:24:16,028 --> 00:24:18,231 of a black hole that's not spinning. 534 00:24:18,231 --> 00:24:20,933 And then on the right, I have a picture of a black hole 535 00:24:20,933 --> 00:24:22,869 that's spinning in the opposite direction 536 00:24:22,869 --> 00:24:24,604 of the material around it. 537 00:24:24,604 --> 00:24:26,906 And in those cases, the inner region is farther 538 00:24:26,906 --> 00:24:30,343 from the black hole, and you get less extreme bending 539 00:24:30,343 --> 00:24:33,379 of the light from this iron line. 540 00:24:33,379 --> 00:24:35,514 And so this is all from Sky and Telescope article, 541 00:24:35,514 --> 00:24:38,384 prior to the NuSTAR launch by a post-doc, 542 00:24:38,384 --> 00:24:41,253 Laura Brenneman, who's actually part of the NuSTAR team. 543 00:24:41,253 --> 00:24:42,155 At Harvard. 544 00:24:43,589 --> 00:24:47,560 So that was one idea of what's going on with how 545 00:24:47,560 --> 00:24:49,762 you're measuring the spin of black holes. 546 00:24:49,762 --> 00:24:52,632 Other people said that we can explain these weird shapes 547 00:24:52,632 --> 00:24:55,034 of the iron line by just putting a lot of gas and dust 548 00:24:55,034 --> 00:24:57,703 in front of the black hole, and you can get 549 00:24:57,703 --> 00:24:59,539 these weird shapes from that. 550 00:24:59,539 --> 00:25:01,207 So you kind of had this one model 551 00:25:01,207 --> 00:25:03,676 where you had the spinning black hole, 552 00:25:03,676 --> 00:25:06,012 and you had this weird-shaped iron line, 553 00:25:06,012 --> 00:25:08,448 and then it predicts that at higher energies, 554 00:25:08,448 --> 00:25:11,784 you get this bump, and then this other model says 555 00:25:11,784 --> 00:25:15,054 that's just gas and dust, in front of the black hole, 556 00:25:15,054 --> 00:25:17,590 that's giving that weird shape, that looks basically the 557 00:25:17,590 --> 00:25:20,759 same in the lower-energy X-rays that you could study, 558 00:25:20,759 --> 00:25:24,430 prior to NuSTAR, with Chandra and XMM, but had very 559 00:25:24,430 --> 00:25:26,332 different predictions of what you should see 560 00:25:26,332 --> 00:25:28,501 in the higher energies, which were inaccessible. 561 00:25:28,501 --> 00:25:29,669 Before NuSTAR. 562 00:25:31,104 --> 00:25:33,239 And so one of our first observations was, we went 563 00:25:33,239 --> 00:25:38,044 to NGC 1365, that barred-spiral galaxy I showed early on. 564 00:25:38,044 --> 00:25:41,613 Here's the low-energy X-ray data from the XMM satellite, 565 00:25:41,613 --> 00:25:43,149 with the two different models. 566 00:25:43,149 --> 00:25:46,452 One is the shape of this feature over here is all due 567 00:25:46,452 --> 00:25:48,521 to the spin of the black hole, and you predict 568 00:25:48,521 --> 00:25:51,090 that at higher energies, you should get this big bump. 569 00:25:51,090 --> 00:25:53,693 The other model says this weird shape is all from gas 570 00:25:53,693 --> 00:25:55,761 and dust, and you have a very different shape 571 00:25:55,761 --> 00:25:57,730 predicted in the NuSTAR band. 572 00:25:57,730 --> 00:25:59,398 So one of the early NuSTAR observations 573 00:25:59,398 --> 00:26:02,202 was this joint observation, and bang. 574 00:26:02,202 --> 00:26:06,439 The NuSTAR observation sat exactly on that model. 575 00:26:06,439 --> 00:26:08,374 And so, at this point, almost everyone 576 00:26:08,374 --> 00:26:10,876 has dropped off the fences, agreed that, 577 00:26:10,876 --> 00:26:14,747 you know, you are able to measure the spins of black holes. 578 00:26:14,747 --> 00:26:17,349 There's, I think, two people, maybe three people 579 00:26:17,349 --> 00:26:19,619 left in that camp are still fighting for that, 580 00:26:19,619 --> 00:26:22,021 but it seems very convincing, and there's been a range 581 00:26:22,021 --> 00:26:24,691 of studies from, you know, more than a dozen black holes, 582 00:26:24,691 --> 00:26:26,993 all supporting this, and showing that we're really able 583 00:26:26,993 --> 00:26:29,629 to measure how fast the black hole are spinning, 584 00:26:29,629 --> 00:26:32,097 which tells you how close that material is coming 585 00:26:32,097 --> 00:26:34,367 to that black hole, and coming, you know, 586 00:26:34,367 --> 00:26:36,836 just a few times the Schwarzchild radius away 587 00:26:36,836 --> 00:26:40,039 from the black hole; it's really extreme. 588 00:26:40,039 --> 00:26:44,377 And so just summarizing, oh yeah, another thing, 589 00:26:44,377 --> 00:26:47,714 pardon, is that, with the NuSTAR, with this extra data, 590 00:26:47,714 --> 00:26:50,783 you're able to get a better, more precise measurement. 591 00:26:50,783 --> 00:26:53,152 So not only do you get rid of this ambiguity, 592 00:26:53,152 --> 00:26:56,655 but you also get a more precise measurement with NuSTAR. 593 00:26:56,655 --> 00:26:59,859 And so, what we found for NGC 1365 is the black hole 594 00:26:59,859 --> 00:27:02,761 is spinning at at least 84 percent 595 00:27:02,761 --> 00:27:05,864 of the maximal speed allowed by relativity. 596 00:27:05,864 --> 00:27:08,701 It's a very robust measurement. 597 00:27:08,701 --> 00:27:12,171 The first, really, robust measurement of a black hole spin. 598 00:27:12,171 --> 00:27:14,640 At this point, we have about a dozen 599 00:27:14,640 --> 00:27:17,276 that we've measured, but most of these spins 600 00:27:17,276 --> 00:27:21,013 have been very high, and that kind of fits with, 601 00:27:21,013 --> 00:27:24,984 we kind of have two ideas about how black holes might grow. 602 00:27:24,984 --> 00:27:28,520 One is your little bits of feeding all the time, 603 00:27:28,520 --> 00:27:30,723 and then in that case, you know, some should be 604 00:27:30,723 --> 00:27:33,092 coming from this direction, some from that direction. 605 00:27:33,092 --> 00:27:35,361 And then that result is the black hole shouldn't 606 00:27:35,361 --> 00:27:36,995 be spinning that fast. 607 00:27:36,995 --> 00:27:39,732 Instead, if you imagine that most of the feeding comes from 608 00:27:39,732 --> 00:27:43,769 large accretion events, where a big bunch of material 609 00:27:43,769 --> 00:27:45,905 falls in on the black hole, that will spin up 610 00:27:45,905 --> 00:27:48,140 the black hole almost like a, you know, 611 00:27:48,140 --> 00:27:50,109 an ice-skater bringing in their arms. 612 00:27:50,109 --> 00:27:52,277 It just, if it's all coming in at once, 613 00:27:52,277 --> 00:27:54,613 it just starts spinning up really close 614 00:27:54,613 --> 00:27:56,683 as it gets close to the black hole. 615 00:27:56,683 --> 00:27:58,884 And so this seems like, the fact that we're measuring 616 00:27:58,884 --> 00:28:01,354 high spins, generally, might point to most 617 00:28:01,354 --> 00:28:03,322 of the black hole growth is happening 618 00:28:03,322 --> 00:28:06,559 in this big accretion events. 619 00:28:06,559 --> 00:28:08,828 We're able to start studying the immediate environment 620 00:28:08,828 --> 00:28:11,097 about the black holes, and then the big thing is 621 00:28:11,097 --> 00:28:13,900 we resolved this 15-year debate in the community. 622 00:28:13,900 --> 00:28:16,301 So that was the nice, early result from NuSTAR, 623 00:28:16,301 --> 00:28:18,871 that was published in Nature. 624 00:28:18,871 --> 00:28:22,841 So that's the first big science result from NuSTAR. 625 00:28:22,841 --> 00:28:27,013 The second one I wanna talk about is supernova explosions. 626 00:28:28,981 --> 00:28:32,785 And just to emphasize, again, just like black holes, 627 00:28:32,785 --> 00:28:35,588 we could give a whole one-hour, one-day lecture 628 00:28:35,588 --> 00:28:38,557 about supernovae; they're incredibly important things. 629 00:28:38,557 --> 00:28:41,360 Basically, the Universe started mainly just hydrogen 630 00:28:41,360 --> 00:28:44,296 and helium, and then stars burned that hydrogen 631 00:28:44,296 --> 00:28:46,999 and helium, or fused it into heavier elements, 632 00:28:46,999 --> 00:28:49,868 and everything in our body, like the carbon in our body, 633 00:28:49,868 --> 00:28:53,606 the silicon in our computers, the platinum in our jewelry, 634 00:28:53,606 --> 00:28:56,441 all was formed in stars, and then was spread out 635 00:28:56,441 --> 00:28:58,911 into the Universe in supernovae. 636 00:28:58,911 --> 00:29:01,747 And you might be a little bit confused of how, 637 00:29:01,747 --> 00:29:04,016 how does that happen? 638 00:29:04,016 --> 00:29:06,853 As the stars, living like our sun, 639 00:29:09,121 --> 00:29:12,625 you have gravity pushing in, because the star is very heavy, 640 00:29:12,625 --> 00:29:15,194 and then it's burning material that's pushing out, 641 00:29:15,194 --> 00:29:17,330 and those balance each other, and we have this largely, 642 00:29:17,330 --> 00:29:21,834 you know, stable star in the center of our solar system 643 00:29:21,834 --> 00:29:23,936 that's burning fuel. 644 00:29:23,936 --> 00:29:27,206 In about five billion years, the sun will run out of fuel, 645 00:29:27,206 --> 00:29:30,776 you'll stop having stuff pushing out, gravity will win out, 646 00:29:30,776 --> 00:29:32,945 and the star will collapse. 647 00:29:32,945 --> 00:29:36,015 For the biggest stars, that collapse should, 648 00:29:36,015 --> 00:29:37,950 creates an explosion. 649 00:29:37,950 --> 00:29:41,453 And one way to think of it is, you imagine 650 00:29:41,453 --> 00:29:44,490 that here's the heavy, inner parts of the star, 651 00:29:44,490 --> 00:29:47,326 here's the lighter atmosphere of the star. 652 00:29:47,326 --> 00:29:51,397 Usually, this heavier part's being held up by the burning, 653 00:29:51,397 --> 00:29:55,033 the regions below it, but as you run out of fuel, 654 00:29:55,033 --> 00:29:57,002 nothing's pushing on this, and then gravity 655 00:29:57,002 --> 00:30:00,006 will make the heavy, inner parts of the star fall in, 656 00:30:00,006 --> 00:30:02,608 the lighter atmosphere will follow it, 657 00:30:02,608 --> 00:30:06,144 falling back in, but then it will hit the bottom, 658 00:30:06,144 --> 00:30:08,581 and the outer parts will bounce 659 00:30:08,581 --> 00:30:11,684 off the heavier, inner parts, so. 660 00:30:11,684 --> 00:30:13,386 This is it. 661 00:30:13,386 --> 00:30:15,655 (laughter) 662 00:30:17,122 --> 00:30:17,957 Oops. 663 00:30:19,358 --> 00:30:21,761 We're actually, I'm gonna do one more, just 'cause it's fun. 664 00:30:21,761 --> 00:30:22,628 (laughter) 665 00:30:22,628 --> 00:30:23,563 Oh, thanks. 666 00:30:24,997 --> 00:30:25,832 Okay. 667 00:30:27,533 --> 00:30:29,802 (laughter) 668 00:30:33,406 --> 00:30:35,641 (applause) 669 00:30:39,879 --> 00:30:43,215 So, one little problem in that though, 670 00:30:43,215 --> 00:30:47,587 is that theorists, trying to create these supernova 671 00:30:47,587 --> 00:30:50,956 explosions on their computers, over the last 20 years, 672 00:30:50,956 --> 00:30:53,058 can't get the explosion to happen. 673 00:30:53,058 --> 00:30:55,361 You should get that collapse, you should get 674 00:30:55,361 --> 00:30:58,130 that bounce back, but in the computer simulations, 675 00:30:58,130 --> 00:31:01,300 after about, I don't know, 100 milliseconds, 676 00:31:01,300 --> 00:31:06,072 the bounce back stalls, and the star should stop exploding, 677 00:31:06,072 --> 00:31:08,407 so there's been a slight embarrassment 678 00:31:08,407 --> 00:31:12,711 that the theorists say stars shouldn't actually supernova. 679 00:31:12,711 --> 00:31:15,214 And then the observers are saying, well, we see them. 680 00:31:15,214 --> 00:31:17,216 (laughter) 681 00:31:17,216 --> 00:31:19,785 And so, NuSTAR comes in with a new way 682 00:31:19,785 --> 00:31:21,687 of studying the supernovae. 683 00:31:21,687 --> 00:31:23,589 This is a slightly complicated slide, 684 00:31:23,589 --> 00:31:27,360 but basically, as a star explodes, it creates 685 00:31:29,094 --> 00:31:31,330 a lot of very hot titanium. 686 00:31:32,564 --> 00:31:35,101 Titanium is an unstable element. 687 00:31:35,101 --> 00:31:37,136 It decays, it's a radioactive element, 688 00:31:37,136 --> 00:31:40,072 it decays into calcium, and as it decays, 689 00:31:40,072 --> 00:31:43,475 it creates high-energy photons, X-ray light. 690 00:31:43,475 --> 00:31:46,145 You get two photons that are in the NuSTAR band 691 00:31:46,145 --> 00:31:49,582 at 68 and 78 kiloelectronvolts, there. 692 00:31:49,582 --> 00:31:51,550 You know, that high-energy X-ray light 693 00:31:51,550 --> 00:31:53,085 that NuSTAR can study. 694 00:31:53,085 --> 00:31:55,287 You got a couple other things that are harder to study, 695 00:31:55,287 --> 00:31:58,457 like positrons and even higher-energy photons. 696 00:31:58,457 --> 00:32:01,193 And so the key thing, though, here, 697 00:32:01,193 --> 00:32:04,664 is that previous studies that people have been doing 698 00:32:04,664 --> 00:32:08,868 of supernovae over the last decades have been studying 699 00:32:10,102 --> 00:32:14,072 either hot iron, or hot magnesium, or cold iron. 700 00:32:14,072 --> 00:32:16,642 They're measuring different states of material 701 00:32:16,642 --> 00:32:18,277 that are dependent on the temperature 702 00:32:18,277 --> 00:32:21,780 and the ionization state of that material. 703 00:32:21,780 --> 00:32:24,016 NuSTAR comes in, and we're the first ones able 704 00:32:24,016 --> 00:32:28,186 to study a radioactive element created in the explosion. 705 00:32:28,186 --> 00:32:32,358 And so, all the titanium will go through this decay rate, 706 00:32:32,358 --> 00:32:35,060 will create those high-energy X-ray light, 707 00:32:35,060 --> 00:32:38,364 whereas the iron that had been studied by Chandra, 708 00:32:38,364 --> 00:32:40,699 for example, had to be a certain temperature 709 00:32:40,699 --> 00:32:43,402 and density of iron to actually see it. 710 00:32:43,402 --> 00:32:45,070 It's not nearly as good of a tracer. 711 00:32:45,070 --> 00:32:48,273 So this is like, DNA evidence, and they were using, 712 00:32:48,273 --> 00:32:52,911 I don't know, fingerprints or something not nearly as good 713 00:32:52,911 --> 00:32:56,148 for trying to understand the supernova. 714 00:33:02,888 --> 00:33:04,790 Oh, and then the other thing, pardon, 715 00:33:04,790 --> 00:33:07,859 is that this titanium also gets formed in this region 716 00:33:07,859 --> 00:33:12,031 where in some models, the iron falls back with the remnant, 717 00:33:13,799 --> 00:33:16,335 created by the supernova, and then in other models, 718 00:33:16,335 --> 00:33:19,505 people had that titanium gets thrown out. 719 00:33:19,505 --> 00:33:23,542 So this titanium line is this very good diagnostic 720 00:33:23,542 --> 00:33:26,045 between all the different theoretical models 721 00:33:26,045 --> 00:33:28,247 of what the explosion should be like. 722 00:33:28,247 --> 00:33:30,816 So this was like, kind of a holy grail 723 00:33:30,816 --> 00:33:33,685 to be able to study the titanium emission 724 00:33:33,685 --> 00:33:36,288 from supernova remnants, and that NuSTAR 725 00:33:36,288 --> 00:33:37,823 was the first one really to step up 726 00:33:37,823 --> 00:33:39,992 and be able to do it well. 727 00:33:41,160 --> 00:33:42,961 Before we launched, there was a range 728 00:33:42,961 --> 00:33:44,563 of models of what would happen. 729 00:33:44,563 --> 00:33:46,632 I said how the models basically say 730 00:33:46,632 --> 00:33:49,502 the explosion should stall, and so there were two different 731 00:33:49,502 --> 00:33:52,671 ideas out there of how you might break the stall. 732 00:33:52,671 --> 00:33:54,039 Some people said, you know, 733 00:33:54,039 --> 00:33:55,708 the star should be spinning quickly. 734 00:33:55,708 --> 00:33:57,209 When you have something spinning quickly, 735 00:33:57,209 --> 00:33:58,577 you might get jets forming. 736 00:33:58,577 --> 00:34:00,379 That jet might break the stall. 737 00:34:00,379 --> 00:34:01,981 And so there were some models where, 738 00:34:01,981 --> 00:34:03,815 you know, you might break the stall from the jets. 739 00:34:03,815 --> 00:34:05,651 And they predicted that the titanium 740 00:34:05,651 --> 00:34:09,721 should make this sort of vertical structure, 741 00:34:09,721 --> 00:34:12,325 around the remnant of the star. 742 00:34:13,426 --> 00:34:15,327 Other people had models where, basically, 743 00:34:15,327 --> 00:34:18,297 the stall, you get the explosion would stall, 744 00:34:18,297 --> 00:34:20,332 and then they would say, well, maybe there's some extra 745 00:34:20,332 --> 00:34:22,868 energy input, and they would make up different reasons 746 00:34:22,868 --> 00:34:25,870 of how you would get it, but that would break the stall. 747 00:34:25,870 --> 00:34:27,740 And those models would predict 748 00:34:27,740 --> 00:34:30,609 that you'd get this sort of spherical explosion coming out, 749 00:34:30,609 --> 00:34:33,312 and so the titanium should be in a ring. 750 00:34:33,312 --> 00:34:35,013 And so basically, the theorists were very excited 751 00:34:35,013 --> 00:34:38,484 to see whether we would see a line or a ring with NuSTAR. 752 00:34:38,484 --> 00:34:42,387 And that, here's just a more colorful model, 753 00:34:42,387 --> 00:34:43,689 prior to the NuSTAR launch, 754 00:34:43,689 --> 00:34:46,992 of what you might see with these jets. 755 00:34:46,992 --> 00:34:51,563 Motivating that, if you looked at the silicon/magnesium 756 00:34:51,563 --> 00:34:53,699 in the lower-energy X-rays, with Chandra, 757 00:34:53,699 --> 00:34:56,401 from the Cassiopeia A supernova remnant, 758 00:34:56,401 --> 00:34:59,871 it's a nearby supernova remnant in our galaxy, 759 00:34:59,871 --> 00:35:01,907 there's sort of this structure, 760 00:35:01,907 --> 00:35:04,376 this long structure, which people would point to 761 00:35:04,376 --> 00:35:07,079 and say, oh, it must be the jet that breaks the stall, 762 00:35:07,079 --> 00:35:09,248 and that's the physics that's going on. 763 00:35:09,248 --> 00:35:11,484 If you looked at the iron, though, from that same remnant 764 00:35:11,484 --> 00:35:13,585 it mainly made a ring, and so people would point 765 00:35:13,585 --> 00:35:16,422 to that and say, oh, it's probably mainly this spherically, 766 00:35:16,422 --> 00:35:18,991 symmetric explosion that's happening. 767 00:35:18,991 --> 00:35:20,493 And so, basically, people thought we'd 768 00:35:20,493 --> 00:35:23,829 either see this, or that with NuSTAR. 769 00:35:23,829 --> 00:35:26,665 And this is what we ended up seeing with the titanium. 770 00:35:26,665 --> 00:35:30,302 We saw these bunches of blue knots, 771 00:35:30,302 --> 00:35:32,971 unlike the ring or the line. 772 00:35:32,971 --> 00:35:35,640 And completely unexpected by us, 773 00:35:35,640 --> 00:35:38,810 completely unexpected by what we put in the proposal 774 00:35:38,810 --> 00:35:42,981 when we, you know, wanted to do NuSTAR in the early 2000s. 775 00:35:42,981 --> 00:35:44,950 We proposed the mission. 776 00:35:44,950 --> 00:35:48,587 However, it turned out that, in the time that we 777 00:35:48,587 --> 00:35:50,489 were so busy building those crazy optics 778 00:35:50,489 --> 00:35:52,958 and doing the extendable mast, the theorists 779 00:35:52,958 --> 00:35:55,060 had taken a step forward in their modeling, 780 00:35:55,060 --> 00:35:57,496 and finally gotten to do three-dimensional models, 781 00:35:57,496 --> 00:35:59,631 putting in all the physics, in a three-dimensional 782 00:35:59,631 --> 00:36:02,868 situation, and so actually, even on the third floor 783 00:36:02,868 --> 00:36:06,205 of Cal Tech Astronomy, there was models, 784 00:36:08,707 --> 00:36:12,177 trying to do this three-dimensional version, 785 00:36:12,177 --> 00:36:13,979 and this is what their models would show. 786 00:36:13,979 --> 00:36:17,416 You get that initial collapse, that explosion out, 787 00:36:17,416 --> 00:36:21,687 you get the stall in the explosion at 100 milliseconds, 788 00:36:21,687 --> 00:36:24,923 and that's just sitting there for a while, 789 00:36:24,923 --> 00:36:27,592 and then in the 3D models, you end up starting to get this 790 00:36:27,592 --> 00:36:31,229 sloshing that can happen, that you didn't see 791 00:36:31,229 --> 00:36:34,667 in the two-dimensional or one-dimensional theoretical models 792 00:36:34,667 --> 00:36:38,837 and that basically breaks the stall, almost like 793 00:36:38,837 --> 00:36:40,606 I like to think of like, when you're blowing up a balloon, 794 00:36:40,606 --> 00:36:42,174 and you're blowing it and it gets stuck, 795 00:36:42,174 --> 00:36:43,675 and it gets stuck, and you keep blowing, 796 00:36:43,675 --> 00:36:46,711 and then eventually, part of it gets expanded out, 797 00:36:46,711 --> 00:36:48,380 and it basically breaks that, 798 00:36:48,380 --> 00:36:50,783 and your balloon gets much bigger. 799 00:36:50,783 --> 00:36:53,284 And so, in their models, they were able 800 00:36:53,284 --> 00:36:57,422 to break the stall with this sloshing pattern. 801 00:36:57,422 --> 00:37:00,158 And the predictions of their models 802 00:37:00,158 --> 00:37:04,696 say that the titanium should basically be in clumps, 803 00:37:04,696 --> 00:37:08,366 interior to the ring, the symmetric iron ring, 804 00:37:08,366 --> 00:37:11,737 and basically fitting very much what NuSTAR had seen. 805 00:37:11,737 --> 00:37:14,305 Here's the blue is the NuSTAR titanium, 806 00:37:14,305 --> 00:37:17,242 in these clumps, the red is the iron shell, 807 00:37:17,242 --> 00:37:19,310 and that green is a magnesium, 808 00:37:19,310 --> 00:37:22,314 that magnesium linear structure. 809 00:37:22,314 --> 00:37:27,019 And so basically, our observations of the titanium 810 00:37:27,019 --> 00:37:30,722 fit in exactly with what the theorists were predicting 811 00:37:30,722 --> 00:37:33,559 about, you know, just in the months before 812 00:37:33,559 --> 00:37:35,861 we started making these observations. 813 00:37:35,861 --> 00:37:38,130 And so it seems like NuSTAR has solved 814 00:37:38,130 --> 00:37:40,399 this question of how do stars explode, 815 00:37:40,399 --> 00:37:44,669 which is important for everything around you. 816 00:37:44,669 --> 00:37:47,205 So that was another, chalked up good, 817 00:37:47,205 --> 00:37:49,375 nice discovery from NuSTAR. 818 00:37:49,375 --> 00:37:51,709 And then finally, the most recent one 819 00:37:51,709 --> 00:37:54,346 is ultraluminous X-ray sources. 820 00:37:54,346 --> 00:37:56,582 And so, I mentioned before, 821 00:37:57,916 --> 00:37:59,818 or I showed this picture before, 822 00:37:59,818 --> 00:38:02,554 of this nearby galaxy, IC 342. 823 00:38:02,554 --> 00:38:06,458 Most of the X-rays in this galaxy are coming from two knots 824 00:38:06,458 --> 00:38:09,261 in the outer parts of the disc of the galaxy. 825 00:38:09,261 --> 00:38:13,065 When you look at nearby galaxies, it's rare, 826 00:38:13,065 --> 00:38:15,200 but not incredibly rare, that you will see these 827 00:38:15,200 --> 00:38:17,035 really, really bright X-ray sources, 828 00:38:17,035 --> 00:38:18,837 not at the center of the galaxy. 829 00:38:18,837 --> 00:38:20,239 At the center, we think there's a billion 830 00:38:20,239 --> 00:38:21,907 or million solar mass black hole, 831 00:38:21,907 --> 00:38:24,576 and if stuff's falling in on it, it creates a lot of X-rays. 832 00:38:24,576 --> 00:38:26,712 No surprise if you see a lot of X-rays 833 00:38:26,712 --> 00:38:29,180 coming from the center of the galaxy. 834 00:38:29,180 --> 00:38:30,615 But these guys in the outskirts 835 00:38:30,615 --> 00:38:32,884 have been a bit of a mystery. 836 00:38:32,884 --> 00:38:35,420 There's two main ideas that have been going on for them, 837 00:38:35,420 --> 00:38:38,090 prior to NuSTAR to explain them. 838 00:38:38,090 --> 00:38:40,692 One is that maybe they're large black holes, 839 00:38:40,692 --> 00:38:42,761 bigger than the sort of black holes 840 00:38:42,761 --> 00:38:44,529 that can get formed in supernovae, 841 00:38:44,529 --> 00:38:46,298 that weigh you know, a couple dozen times 842 00:38:46,298 --> 00:38:48,867 as much as the sun, not as big as the guys in the center, 843 00:38:48,867 --> 00:38:52,604 so things weighing 1,000, 10,000-times as much as the sun. 844 00:38:52,604 --> 00:38:55,540 And as I said, there's only one of those that's known. 845 00:38:55,540 --> 00:38:58,644 But the Universe has to be full of them. 846 00:38:58,644 --> 00:38:59,944 And so it could be something like that, 847 00:38:59,944 --> 00:39:02,180 just feeding at a typical rate. 848 00:39:02,180 --> 00:39:05,718 The other idea is maybe they're more like those smaller 849 00:39:05,718 --> 00:39:08,053 black holes formed when stars explode, 850 00:39:08,053 --> 00:39:10,856 but feeding at incredibly high rates. 851 00:39:10,856 --> 00:39:13,058 Rates that can't be stable. 852 00:39:13,058 --> 00:39:15,193 We call it Super-Eddington accretion. 853 00:39:15,193 --> 00:39:18,296 It's, in theory, it should be possible, 854 00:39:18,296 --> 00:39:20,598 but it can't be a stable scenario. 855 00:39:20,598 --> 00:39:23,768 But that was another idea of what might be going on. 856 00:39:23,768 --> 00:39:25,337 And then maybe, some people thought, 857 00:39:25,337 --> 00:39:27,205 maybe it's something else, but it was pretty much 858 00:39:27,205 --> 00:39:30,475 one of those two is what people were thinking. 859 00:39:30,475 --> 00:39:33,312 To put it a little bit in context, here's the range 860 00:39:33,312 --> 00:39:37,649 of masses of very compact objects in the Universe. 861 00:39:37,649 --> 00:39:41,086 At the high end, we see these supermassive black holes 862 00:39:41,086 --> 00:39:43,421 at the centers of the galaxies, weighing millions 863 00:39:43,421 --> 00:39:46,492 to billions of times as much as the sun. 864 00:39:46,492 --> 00:39:49,928 We get stellar-mass black holes, formed when stars explode 865 00:39:49,928 --> 00:39:52,498 that weigh a few 10-times as much as the sun. 866 00:39:52,498 --> 00:39:54,599 There's this intermediate mass range, 867 00:39:54,599 --> 00:39:57,669 which is, there's one object. 868 00:39:57,669 --> 00:40:01,140 And then into the lower end, you can get neutron stars. 869 00:40:01,140 --> 00:40:03,541 So, really big stars when they explode, 870 00:40:03,541 --> 00:40:05,611 leave this black hole remnant. 871 00:40:05,611 --> 00:40:08,313 Smaller black holes, er, smaller stars, 872 00:40:08,313 --> 00:40:11,216 when they explode, can leave a neutron star. 873 00:40:11,216 --> 00:40:14,686 And a neutron star is basically a big atom. 874 00:40:14,686 --> 00:40:16,688 It's just protons and neutrons. 875 00:40:16,688 --> 00:40:19,124 It could be on the periodic table. 876 00:40:19,124 --> 00:40:21,292 Relatively simple physics tells you 877 00:40:21,292 --> 00:40:23,262 it's more neutrons than protons. 878 00:40:23,262 --> 00:40:26,397 But something like the sun, if the sun 879 00:40:26,397 --> 00:40:29,501 were a neutron star, would be about the size of Pasadena. 880 00:40:29,501 --> 00:40:32,972 About 10 kilometers in size, so they're also very extreme, 881 00:40:32,972 --> 00:40:36,175 like black holes, but they're made out of things 882 00:40:36,175 --> 00:40:37,909 that we understand: protons, neutrons. 883 00:40:37,909 --> 00:40:40,312 You have electrons around them. 884 00:40:40,312 --> 00:40:44,483 So they're not nearly as weird as the black holes. 885 00:40:45,950 --> 00:40:48,887 So, where did NuSTAR come in? 886 00:40:48,887 --> 00:40:52,458 So, we did a big study of the Cigar Galaxy, 887 00:40:53,625 --> 00:40:56,060 also known as M82, and this is just showing you 888 00:40:56,060 --> 00:40:57,896 a couple pictures of the M82. 889 00:40:57,896 --> 00:41:00,499 On the left-hand side, I have a picture 890 00:41:00,499 --> 00:41:03,468 with Hubble Space Telescope in the visible light, 891 00:41:03,468 --> 00:41:05,370 the sort of light that you can see with your eyes. 892 00:41:05,370 --> 00:41:07,072 And there's sort of this blue cigar 893 00:41:07,072 --> 00:41:12,010 with hydrogen gas coming out, in the top and bottom. 894 00:41:12,010 --> 00:41:14,946 Chandra has also studied this nearby, beautiful galaxy, 895 00:41:14,946 --> 00:41:18,016 and sees a very different picture of this galaxy. 896 00:41:18,016 --> 00:41:19,984 This is, really just beauty shots 897 00:41:19,984 --> 00:41:21,754 to show you that when you look at different parts of light, 898 00:41:21,754 --> 00:41:24,490 you see very different phenomena. 899 00:41:26,558 --> 00:41:30,396 In January, 2014, a supernova went off in M82. 900 00:41:33,165 --> 00:41:35,266 It was, this is a very nearby galaxy, 901 00:41:35,266 --> 00:41:36,935 so this is a bright supernova. 902 00:41:36,935 --> 00:41:39,471 In fact, it was so bright, that it was found by 903 00:41:39,471 --> 00:41:43,909 a college astronomy class at University College, London, 904 00:41:43,909 --> 00:41:47,846 on the rooftop in London, doing their, like, star party. 905 00:41:47,846 --> 00:41:50,315 And one of the students was like, hey, 906 00:41:50,315 --> 00:41:52,384 this isn't in my picture in the book. 907 00:41:52,384 --> 00:41:55,887 And so they were the discoverers of this supernova. 908 00:41:55,887 --> 00:41:59,191 It was the nearest type 1A supernova, 909 00:41:59,191 --> 00:42:01,626 which is one of the subclasses, but a very important 910 00:42:01,626 --> 00:42:03,595 subclass of supernova, so it was 911 00:42:03,595 --> 00:42:06,598 the nearest 1A in 150 years. 912 00:42:06,598 --> 00:42:09,500 So incredibly important source for study. 913 00:42:09,500 --> 00:42:12,070 Basically, every facility on the planet, 914 00:42:12,070 --> 00:42:14,205 and in space, went and studied it. 915 00:42:14,205 --> 00:42:17,942 And this is a Hubble image of that supernova. 916 00:42:17,942 --> 00:42:20,345 NuSTAR jumped on it as well. 917 00:42:20,345 --> 00:42:22,947 And we spent about a month studying this supernova, 918 00:42:22,947 --> 00:42:24,950 because there was all sorts of unique features 919 00:42:24,950 --> 00:42:27,352 for studying supernova, like I talked about a minute ago, 920 00:42:27,352 --> 00:42:30,489 that NuSTAR has unique access to. 921 00:42:30,489 --> 00:42:32,924 I'm not gonna talk about the supernova anymore, though. 922 00:42:32,924 --> 00:42:34,358 We're still working on that. 923 00:42:34,358 --> 00:42:35,426 We have some exciting results, 924 00:42:35,426 --> 00:42:37,796 but we're still working on it. 925 00:42:37,796 --> 00:42:40,164 The big surprise in this study, though, 926 00:42:40,164 --> 00:42:42,734 was that towards the center of the galaxy, 927 00:42:42,734 --> 00:42:46,037 there are some, these ultraluminous X-ray sources 928 00:42:46,037 --> 00:42:50,542 in M82, there's, astronomers are very good at naming things, 929 00:42:50,542 --> 00:42:53,812 so there's M82 X-1 and M82 X-1 and X-2. 930 00:42:55,247 --> 00:42:57,682 Towards the center, they're very bright X-ray sources. 931 00:42:57,682 --> 00:43:00,085 M82 X-1 is actually a candidate 932 00:43:00,085 --> 00:43:03,054 for this intermediate mass black hole. 933 00:43:03,054 --> 00:43:04,989 Not one that everyone believes, 934 00:43:04,989 --> 00:43:06,925 but it's one of the relatively good candidates 935 00:43:06,925 --> 00:43:08,093 for something like that. 936 00:43:08,093 --> 00:43:10,595 M82 X-2 wasn't nearly as well-studied. 937 00:43:10,595 --> 00:43:14,399 The blue light, here, is the Chandra image 938 00:43:14,399 --> 00:43:18,370 of the center of that galaxy, and then the pink is NuSTAR. 939 00:43:18,370 --> 00:43:20,905 And so basically, NuSTAR is seeing mainly X-rays 940 00:43:20,905 --> 00:43:23,808 coming from M82 X-2, so from the 941 00:43:23,808 --> 00:43:26,678 second ultraluminous X-ray source. 942 00:43:26,678 --> 00:43:29,981 And so we spent about a month staring at this galaxy. 943 00:43:29,981 --> 00:43:32,083 This is probably the longest observation 944 00:43:32,083 --> 00:43:34,585 that NuSTAR has done of a single object. 945 00:43:34,585 --> 00:43:37,321 Studying the supernova, but as we were analyzing the data, 946 00:43:37,321 --> 00:43:40,458 we saw M82 X-2, so we started looking at that. 947 00:43:40,458 --> 00:43:45,030 We did something else, and so there's an Italian post-doc, 948 00:43:45,030 --> 00:43:48,700 Matteo Bacetti, who's doing some timing analysis, 949 00:43:48,700 --> 00:43:52,437 and what he found was that, not for the whole month, 950 00:43:52,437 --> 00:43:55,473 but for like, more than a week of that month, 951 00:43:55,473 --> 00:43:59,878 M82 X-2 was pulsating; it would get brighter and dimmer, 952 00:43:59,878 --> 00:44:01,412 brighter and dimmer. 953 00:44:01,412 --> 00:44:04,783 This is something that no ultraluminous X-ray source 954 00:44:04,783 --> 00:44:07,285 had ever been seen to do. 955 00:44:07,285 --> 00:44:11,289 And what we think is happening is that it's a pulsar. 956 00:44:11,289 --> 00:44:14,126 It's, basically, it's like a lighthouse. 957 00:44:14,126 --> 00:44:16,961 You have a, black holes can't do this, 958 00:44:16,961 --> 00:44:18,764 only neutron stars can do this, 959 00:44:18,764 --> 00:44:20,431 because black holes don't have edges, 960 00:44:20,431 --> 00:44:22,500 and they're weird things and they can't have charge, 961 00:44:22,500 --> 00:44:25,169 so only neutron stars can do this, 962 00:44:25,169 --> 00:44:27,105 and it's essentially, it's spinning. 963 00:44:27,105 --> 00:44:31,276 It's got, as it's spinning, light's coming out of the edges. 964 00:44:32,443 --> 00:44:34,345 Pardon, along the spin axis, and as that light 965 00:44:34,345 --> 00:44:36,982 points towards you, it's like a lighthouse, 966 00:44:36,982 --> 00:44:39,050 where it gets brighter and dimmer, 967 00:44:39,050 --> 00:44:41,086 brighter and dimmer. 968 00:44:41,086 --> 00:44:44,155 And so, M82 X-1 was pulsating, I think, 969 00:44:44,155 --> 00:44:48,759 every 4.2 seconds, for about a week of those observations, 970 00:44:48,759 --> 00:44:52,464 and immediately, we knew like, that meant, 971 00:44:52,464 --> 00:44:54,665 it's not a black hole, it's not a big black hole, 972 00:44:54,665 --> 00:44:57,102 it's not a small black hole, it's a pulsar. 973 00:44:57,102 --> 00:45:00,405 And it's way brighter, 200-times brighter 974 00:45:00,405 --> 00:45:04,843 than any pulsar anyone has ever seen before. 975 00:45:04,843 --> 00:45:06,477 It was a new class of object 976 00:45:06,477 --> 00:45:08,479 that hadn't even been dreamt of. 977 00:45:08,479 --> 00:45:10,348 You know, a new denizen of the Universe 978 00:45:10,348 --> 00:45:13,784 that you know, had no idea that these things existed. 979 00:45:13,784 --> 00:45:15,286 It was brighter and more distant 980 00:45:15,286 --> 00:45:18,223 than any pulsar that had ever been seen before. 981 00:45:18,223 --> 00:45:22,761 Pulsars, or neutron stars, have a fixed size. 982 00:45:22,761 --> 00:45:25,229 They can't get more massive than a certain amount, 983 00:45:25,229 --> 00:45:26,965 or else they turn into black holes. 984 00:45:26,965 --> 00:45:29,300 So this thing had to be accreting at this extreme, 985 00:45:29,300 --> 00:45:33,472 Super-Eddington rate, you know, 200-times the, 986 00:45:33,472 --> 00:45:35,940 essentially, the speed limit of how fast you're allowed 987 00:45:35,940 --> 00:45:38,743 to accrete, this thing had to be accreting at. 988 00:45:38,743 --> 00:45:42,247 Incredible surprise; theorists confounded. 989 00:45:43,581 --> 00:45:45,149 And you know, so I've observed I've been making fun 990 00:45:45,149 --> 00:45:47,051 of theorists a couple times tonight, 991 00:45:47,051 --> 00:45:50,155 so for this, immediately theorists starting writing papers, 992 00:45:50,155 --> 00:45:52,157 you know, some groups said, oh, we can explain it, 993 00:45:52,157 --> 00:45:53,892 the way you could get this to happen is, 994 00:45:53,892 --> 00:45:56,728 it's gotta have super, really high magnetic fields, 995 00:45:56,728 --> 00:45:58,697 and that's the way you could get this happening. 996 00:45:58,697 --> 00:46:00,198 And then, you know, another group somewhere else 997 00:46:00,198 --> 00:46:01,632 on the planet: oh, we can explain it. 998 00:46:01,632 --> 00:46:02,834 The only way you could get it is 999 00:46:02,834 --> 00:46:04,169 it's got really low magnetic fields. 1000 00:46:04,169 --> 00:46:07,205 And that's the way it's able to accrete so fast. 1001 00:46:07,205 --> 00:46:10,675 Jury's out, we're still trying to understand it. 1002 00:46:10,675 --> 00:46:13,077 This first one was found in 2014, 1003 00:46:13,077 --> 00:46:16,114 and then for a long time we're like, 1004 00:46:16,114 --> 00:46:17,782 is this the only one? 1005 00:46:17,782 --> 00:46:20,886 Maybe all ultraluminous X-ray sources are pulsars. 1006 00:46:20,886 --> 00:46:22,420 We don't know. 1007 00:46:22,420 --> 00:46:24,389 You know, we've been doing timing studies of a bunch. 1008 00:46:24,389 --> 00:46:26,491 And then it was a bit like waiting for a bus 1009 00:46:26,491 --> 00:46:29,527 that, you know, for two years or a year and a half, 1010 00:46:29,527 --> 00:46:31,462 we're waiting to see if there are any more. 1011 00:46:31,462 --> 00:46:33,731 And then in a single week, our group 1012 00:46:33,731 --> 00:46:38,036 and a group in Europe simultaneously found two more, 1013 00:46:38,036 --> 00:46:40,205 using different data sets. 1014 00:46:41,372 --> 00:46:43,908 So now there's three of these that are known. 1015 00:46:43,908 --> 00:46:45,710 And the other ones are, in some ways, 1016 00:46:45,710 --> 00:46:47,612 better to study, because there isn't another one, 1017 00:46:47,612 --> 00:46:50,015 another ultraluminous source, right next door. 1018 00:46:50,015 --> 00:46:52,717 So it's, you know, we're in the early days. 1019 00:46:52,717 --> 00:46:54,519 So there's all sorts of studies we're trying to do 1020 00:46:54,519 --> 00:46:56,654 to both get more information about them, 1021 00:46:56,654 --> 00:46:58,522 and then theorists are trying to come up 1022 00:46:58,522 --> 00:47:01,759 with the models to explain them. 1023 00:47:01,759 --> 00:47:06,164 So, summary, NuSTAR is the first focusing hard X-ray 1024 00:47:06,164 --> 00:47:09,034 satellite, or high-energy X-ray satellite in orbit. 1025 00:47:09,034 --> 00:47:11,669 Very low backgrounds, very compact detector. 1026 00:47:11,669 --> 00:47:14,272 200-times gain in sensitivity. 1027 00:47:14,272 --> 00:47:16,007 It's been a really fun ride. 1028 00:47:16,007 --> 00:47:19,778 We're up to more than 250 published papers 1029 00:47:19,778 --> 00:47:21,946 out of the NuSTAR mission, at this point. 1030 00:47:21,946 --> 00:47:23,415 On a whole range of studies. 1031 00:47:23,415 --> 00:47:25,417 We've studied the sun, we've studied black holes, 1032 00:47:25,417 --> 00:47:28,286 big black holes, small black holes, neutron stars. 1033 00:47:28,286 --> 00:47:30,789 It's been a really exciting ride. 1034 00:47:30,789 --> 00:47:34,726 And I'm glad to have taken you over on part of it. 1035 00:47:34,726 --> 00:47:37,161 Here's technical details for the X-ray astronomers. 1036 00:47:37,161 --> 00:47:39,364 And then as I was digging through the slides, 1037 00:47:39,364 --> 00:47:43,701 I found, from the launch day, a picture of Fiona's daughter 1038 00:47:43,701 --> 00:47:45,703 and then my kids and my wife. 1039 00:47:45,703 --> 00:47:49,607 And unfortunately, my son's playing piano 1040 00:47:49,607 --> 00:47:51,977 at a school event that I'm missing tonight, 1041 00:47:51,977 --> 00:47:55,547 but they'll be at tomorrow's lecture. 1042 00:47:55,547 --> 00:47:58,316 And then, final, for more information, 1043 00:47:58,316 --> 00:48:00,418 you can email me, or here's some websites. 1044 00:48:00,418 --> 00:48:02,654 (applause) 1045 00:48:10,929 --> 00:48:12,497 Happy to take questions. 1046 00:48:12,497 --> 00:48:15,700 There's a mic over there, that they prefer 1047 00:48:15,700 --> 00:48:18,470 if you go there to ask questions. 1048 00:48:24,141 --> 00:48:25,910 - Is there any limitation to how long 1049 00:48:25,910 --> 00:48:27,244 that it can stay up there and work? 1050 00:48:27,244 --> 00:48:28,846 Is there a fuel or a pointing or anything, 1051 00:48:28,846 --> 00:48:30,414 the cooling, anything like that? 1052 00:48:30,414 --> 00:48:31,917 - Yeah, so we, ah, 1053 00:48:34,519 --> 00:48:36,788 three ways we could lose the mission. 1054 00:48:36,788 --> 00:48:38,690 One is it could break. 1055 00:48:38,690 --> 00:48:40,158 So far, things are going very well. 1056 00:48:40,158 --> 00:48:42,794 We've lost like one pixel in four years. 1057 00:48:42,794 --> 00:48:44,528 So that's going really well. 1058 00:48:44,528 --> 00:48:46,197 The lasers are slowly degrading, 1059 00:48:46,197 --> 00:48:48,800 but not at any level that we're worried about. 1060 00:48:48,800 --> 00:48:51,569 The orbit decays slowly. 1061 00:48:51,569 --> 00:48:54,305 We drop about a kilometer per year. 1062 00:48:54,305 --> 00:48:56,407 That goes with the solar cycle, 1063 00:48:56,407 --> 00:48:59,410 but we expect to get at least 10 to 15 more years 1064 00:48:59,410 --> 00:49:02,046 before the orbit brings us too far down. 1065 00:49:02,046 --> 00:49:03,415 And then when you get too low, 1066 00:49:03,415 --> 00:49:04,949 you hit the atmosphere, and then you 1067 00:49:04,949 --> 00:49:07,618 rapidly crash into the ocean. 1068 00:49:07,618 --> 00:49:10,621 So that's probably how the mission ends. 1069 00:49:10,621 --> 00:49:12,356 We could stop getting funding. 1070 00:49:12,356 --> 00:49:14,359 But hopefully we keep writing good proposals, 1071 00:49:14,359 --> 00:49:18,863 and are able to motivate NASA to keep funding us. 1072 00:49:18,863 --> 00:49:20,465 Yeah. 1073 00:49:20,465 --> 00:49:21,733 - Hi, I just had a question. 1074 00:49:21,733 --> 00:49:24,068 Has NuSTAR, at all, gathered evidence 1075 00:49:24,068 --> 00:49:29,007 to kind of support answers for the missing baryon problem? 1076 00:49:29,007 --> 00:49:30,441 - [Daniel] The missing baryon problem? 1077 00:49:30,441 --> 00:49:31,376 - Yeah. 1078 00:49:31,376 --> 00:49:33,311 - Interesting question. 1079 00:49:34,512 --> 00:49:37,214 I do not think we have done any work on that. 1080 00:49:37,214 --> 00:49:40,318 That's, ah, a lot of the work to try to address 1081 00:49:40,318 --> 00:49:42,220 that tends to be in the lower-energy X-rays, 1082 00:49:42,220 --> 00:49:46,124 or in the higher-energy ultraviolet light. 1083 00:49:46,124 --> 00:49:47,992 - Right, yeah, I saw your range was down 1084 00:49:47,992 --> 00:49:50,628 to about three KeV, so I wasn't sure. 1085 00:49:50,628 --> 00:49:53,665 - [Daniel] Oh, missing baryon or dark matter? 1086 00:49:53,665 --> 00:49:56,201 - Actually, well, you could go with dark matter, too. 1087 00:49:56,201 --> 00:49:59,070 If you've seen any interesting spikes around three KeV. 1088 00:49:59,070 --> 00:50:02,173 - So dark matter, again, could be a whole lecture, 1089 00:50:02,173 --> 00:50:05,210 but a good fraction of the Universe is not made 1090 00:50:05,210 --> 00:50:08,479 out of protons, electrons, neutrons; things we're used to. 1091 00:50:08,479 --> 00:50:10,581 There's a weird thing called dark matter, 1092 00:50:10,581 --> 00:50:12,617 and then there's an even weirder thing called dark energy 1093 00:50:12,617 --> 00:50:14,786 that is actually most of the Universe. 1094 00:50:14,786 --> 00:50:16,154 The stuff we're used to is 1095 00:50:16,154 --> 00:50:19,223 about four percent of the Universe. 1096 00:50:19,223 --> 00:50:20,892 NuSTAR has done some studies, 1097 00:50:20,892 --> 00:50:24,429 has two papers now, out, looking for evidence 1098 00:50:24,429 --> 00:50:28,033 of dark matter decay in the NuSTAR band. 1099 00:50:28,033 --> 00:50:31,302 We've set stricter limits than anyone has set before, 1100 00:50:31,302 --> 00:50:32,770 but haven't detected it. 1101 00:50:32,770 --> 00:50:34,171 That would have been the whole talk 1102 00:50:34,171 --> 00:50:36,775 if we had found anything, yeah. 1103 00:50:43,782 --> 00:50:45,550 Questions, or? 1104 00:50:45,550 --> 00:50:47,485 If, I think we'll call it. 1105 00:50:47,485 --> 00:50:49,520 I will be here if anybody wants to come up 1106 00:50:49,520 --> 00:50:51,589 and ask other questions, but thank you for coming. 1107 00:50:51,589 --> 00:50:53,391 Thank you for braving the rain. 1108 00:50:53,391 --> 00:50:54,859 And thank you.