1 00:00:02,635 --> 00:00:03,770 UV light. 2 00:00:04,571 --> 00:00:07,073 You might know it as the stuff that causes sunburns, 3 00:00:07,073 --> 00:00:10,210 but in fact it plays a key role in making life possible. 4 00:00:10,477 --> 00:00:13,747 UV light is the range of light just beyond human vision. 5 00:00:14,114 --> 00:00:15,482 Even though we can't see it, 6 00:00:15,482 --> 00:00:19,052 UV light from the sun has fundamentally shaped the planet we live on. 7 00:00:19,452 --> 00:00:22,689 Could it be a key to finding other planets capable of supporting life? 8 00:00:23,089 --> 00:00:24,924 I know some rocket scientists who think so. 9 00:00:25,992 --> 00:00:27,427 We're here in Australia! 10 00:00:27,427 --> 00:00:28,862 And we're gonna launch some rockets. 11 00:00:30,497 --> 00:00:33,600 We're following two NASA rocket missions as they try to understand 12 00:00:33,600 --> 00:00:36,669 how stars make the planets around them suitable for life. 13 00:00:37,570 --> 00:00:41,241 I'm Miles Hatfield, and in this episode we’re exploring how ultraviolet light 14 00:00:41,241 --> 00:00:44,277 can make or break a planet's ability to support life. 15 00:00:52,118 --> 00:00:54,921 When we look for planets around other stars and try to assess 16 00:00:54,921 --> 00:00:59,059 is that a place where life exists, we're almost always talking about 17 00:00:59,059 --> 00:01:02,395 does that atmosphere have the signs of life in it? 18 00:01:02,562 --> 00:01:07,067 And so that means things on earth like do we have molecular oxygen? 19 00:01:07,067 --> 00:01:09,936 Does it have ozone? Does it have methane in the atmosphere? 20 00:01:10,236 --> 00:01:13,840 These special gases are what scientists call biomarkers - 21 00:01:13,840 --> 00:01:16,643 the traces of life we leave behind on our planet. 22 00:01:17,277 --> 00:01:21,314 But, Kevin told me, what counts as a biomarker on Earth might not 23 00:01:21,314 --> 00:01:23,817 for a planet orbiting a different kind of star. 24 00:01:23,817 --> 00:01:26,986 A lot of it depends on how much UV light the star emits, 25 00:01:26,986 --> 00:01:29,856 or what scientists call its UV flux. 26 00:01:30,190 --> 00:01:32,792 There's kind of two big things that UV light does to 27 00:01:32,792 --> 00:01:36,863 a planet’s atmosphere. One, it drives photochemistry in the atmosphere. 28 00:01:36,863 --> 00:01:41,101 So, Earth's atmosphere is a combination of things that happen photochemically 29 00:01:41,101 --> 00:01:44,237 and things that happen biologically and then float up. 30 00:01:44,671 --> 00:01:46,673 Our ozone layer is a great example. 31 00:01:46,973 --> 00:01:51,211 About two and a half billion years ago, bacteria in Earth's ancient oceans had 32 00:01:51,211 --> 00:01:54,180 just become the first photosynthesizers. 33 00:01:54,180 --> 00:01:57,817 In other words, as those little guys broke wind, Earth’s atmosphere started 34 00:01:57,817 --> 00:02:00,720 filling up with oxygen. Don’t think too hard about that. 35 00:02:00,720 --> 00:02:04,390 UV light split those oxygen molecules apart, allowing some of them 36 00:02:04,390 --> 00:02:06,226 to recombine into ozone. 37 00:02:06,493 --> 00:02:10,196 The other one is that ultraviolet light drives what we call atmospheric escape. 38 00:02:10,196 --> 00:02:15,001 And that's kind of as simple as it sounds, if a star has enough ultraviolet flux 39 00:02:15,001 --> 00:02:18,404 it heats up the atmosphere. And if the atmosphere gets hot enough, 40 00:02:18,404 --> 00:02:21,541 that atmosphere will become gravitationally unbound to the 41 00:02:21,541 --> 00:02:23,076 planet and escape. 42 00:02:23,443 --> 00:02:25,945 Believe it or not, this happened on Earth too. 43 00:02:25,945 --> 00:02:29,983 About four and a half billion years ago, when Earth was just a wee baby planet, 44 00:02:29,983 --> 00:02:33,887 its original atmosphere was mostly made of hydrogen and helium. 45 00:02:33,887 --> 00:02:36,356 That atmosphere was blown off into space, 46 00:02:36,356 --> 00:02:39,859 paving the way for the livable, breathable atmosphere we know today. 47 00:02:40,793 --> 00:02:44,097 One of the things we’ve learned in the last couple of years is the Sun is 48 00:02:44,097 --> 00:02:48,501 atypical in that it’s about five times less magnetically active than 49 00:02:48,501 --> 00:02:51,004 typical stars of its age. 50 00:02:51,004 --> 00:02:54,174 And magnetic activity is what drives the ultraviolet flux, 51 00:02:54,174 --> 00:02:59,012 so just because we have great data on the Sun it doesn’t mean that we can take that 52 00:02:59,012 --> 00:03:03,249 data and apply it broadly to any type of star like the Sun out and beyond. 53 00:03:03,816 --> 00:03:05,385 That's why Kevin and his team 54 00:03:05,385 --> 00:03:08,821 are looking at Alpha Centauri, our closest stellar neighbors. 55 00:03:09,222 --> 00:03:12,525 This three star system is a little more than four light-years away. 56 00:03:12,926 --> 00:03:16,796 Kevin and his team are focusing on the larger Sun-like stars, 57 00:03:16,796 --> 00:03:18,698 Alpha Centauri A and B. 58 00:03:19,132 --> 00:03:22,802 They’re our best chance to measure UV light from Sun-like stars that aren’t, 59 00:03:22,802 --> 00:03:24,404 well, our Sun. 60 00:03:25,705 --> 00:03:27,540 But SISTINE can’t do it alone. 61 00:03:27,540 --> 00:03:31,211 Another rocket mission is set to launch right after SISTINE and would capture 62 00:03:31,211 --> 00:03:35,248 wavelengths of UV light too hot for SISTINE to handle. So to speak. 63 00:03:35,481 --> 00:03:39,786 And members of team number two, fittingly named DEUCE, had just arrived. 64 00:03:39,786 --> 00:03:43,890 I'd heard they could be found somewhere around here - probably hiding away 65 00:03:43,890 --> 00:03:47,193 hoping to get some work done before we started shoving cameras in their faces. 66 00:03:47,460 --> 00:03:48,127 Nice try. 67 00:03:48,695 --> 00:03:49,529 Hey Emily. 68 00:03:49,829 --> 00:03:50,563 Hey. 69 00:03:50,730 --> 00:03:55,201 Your team DEUCE and SISTINE are both measuring ultraviolet light. 70 00:03:55,201 --> 00:03:58,371 So what's the difference between the things you're measuring? 71 00:03:58,371 --> 00:03:59,372 What are you studying differently? 72 00:03:59,372 --> 00:04:02,875 So DEUCE measures the extreme ultraviolet, which is a very 73 00:04:02,875 --> 00:04:07,313 energetic form of light, and SISTINE is measuring far ultraviolet light, 74 00:04:07,313 --> 00:04:10,049 so a little bit less energetic, longer wavelengths. 75 00:04:10,049 --> 00:04:13,987 And we have a little overlap in our spectrum so that we can actually have 76 00:04:13,987 --> 00:04:18,424 a much broader spectrum than either of us would get alone. 77 00:04:18,424 --> 00:04:19,492 I see. Okay. 78 00:04:19,492 --> 00:04:21,261 So like overlap to just check that 79 00:04:21,261 --> 00:04:24,964 like, okay, I'm seeing the same thing in that region of overlap as you are. 80 00:04:24,964 --> 00:04:26,099 And then we can calibrate together. 81 00:04:26,099 --> 00:04:26,866 Exactly. 82 00:04:26,866 --> 00:04:27,967 Got it. I see. 83 00:04:28,201 --> 00:04:29,602 Launching a few days apart, 84 00:04:29,602 --> 00:04:33,273 DEUCE and SISTINE will work together like one super mission. 85 00:04:33,673 --> 00:04:37,644 The end goal goes beyond Alpha Centauri and even Sun-like stars 86 00:04:37,944 --> 00:04:40,880 to an understanding of star-planet systems in general. 87 00:04:41,180 --> 00:04:44,484 Alpha Centauri is the closest star system to Earth, 88 00:04:44,817 --> 00:04:50,089 other than the Sun, and has in its triple stars one that’s a sun-like star. 89 00:04:50,089 --> 00:04:53,860 So we can use that star to see what other stars 90 00:04:53,860 --> 00:04:56,896 that might have planets around it look like. 91 00:04:56,896 --> 00:04:59,432 What is your role during launch? What are you going to be doing? 92 00:04:59,766 --> 00:05:02,001 So, I will be steering the payload. 93 00:05:02,001 --> 00:05:05,305 You are pointing the telescope and making sure it's aligned on the star? 94 00:05:05,305 --> 00:05:06,005 Yeah. 95 00:05:06,005 --> 00:05:08,041 Wow. Yeah, that's a big job. 96 00:05:08,041 --> 00:05:08,875 Yeah. 97 00:05:09,575 --> 00:05:10,343 Next time, 98 00:05:10,343 --> 00:05:13,846 as we prepare for launch, a look behind the scenes at the space vehicles 99 00:05:13,846 --> 00:05:14,714 that will get us there. 100 00:05:15,515 --> 00:05:16,349 Vroom. Vroom.