WEBVTT - Goodbye, Kepler Telescope 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:13.800 stuff works dot com. Hey there, and welcome to tech Stuff. 0:00:13.840 --> 0:00:16.439 I'm your host, Jonathan Strickland. I'm an executive producer and 0:00:16.480 --> 0:00:20.840 I love all things tech. And as I record this, 0:00:21.040 --> 0:00:24.840 it is the week of well Halloween in the United States. 0:00:25.360 --> 0:00:32.360 But on October Tuesday of this week eighteen, NASA chose 0:00:32.440 --> 0:00:36.680 to retire the space telescope Kepler, which had been in 0:00:36.760 --> 0:00:41.320 operation not continuously, but had been an operation since two 0:00:41.360 --> 0:00:44.239 thousand nine. I say they retired it. They didn't have 0:00:44.320 --> 0:00:46.279 much choice in the matter. The telescope had run out 0:00:46.280 --> 0:00:50.639 of fuel and could no longer hold its orientation, which 0:00:50.720 --> 0:00:53.480 is pretty important if you are using a telescope, any 0:00:53.520 --> 0:00:55.600 kind of telescope. If you've ever used any sort of 0:00:55.640 --> 0:00:58.720 magnification and you couldn't hold it's steady, you know that 0:00:58.800 --> 0:01:02.760 it's not much use. But this mission was no failure. 0:01:03.000 --> 0:01:07.200 It was actually the conclusion of a monumentally successful scientific mission. 0:01:07.720 --> 0:01:11.640 The Kepler team projected a nominal mission lifetime of three years, 0:01:12.200 --> 0:01:15.039 or maybe three and a half. The actual telescope was 0:01:15.080 --> 0:01:18.880 able to continue its original mission objectives for an additional 0:01:19.040 --> 0:01:22.000 year when it was first launched, and then Stuff started 0:01:22.040 --> 0:01:24.600 breaking down. But I'm getting ahead of myself. So let's 0:01:24.600 --> 0:01:28.040 start with the question what was Kepler's purpose? What was 0:01:28.080 --> 0:01:31.399 it built to do? The simple answer is that it 0:01:31.480 --> 0:01:35.039 was built to search the galaxy for the presence of 0:01:35.200 --> 0:01:39.560 exo planets, in other words, planets outside of our own 0:01:39.680 --> 0:01:43.400 Solar system, and that included looking for Earth like planets. 0:01:43.920 --> 0:01:46.640 Scientists had very little information to go on to make 0:01:47.000 --> 0:01:51.120 conclusions about how many stars out there might have planets. 0:01:51.240 --> 0:01:55.600 Is it common, is it infrequent? You can't really draw 0:01:55.640 --> 0:01:58.800 any other, you know, theories or or make any more 0:01:58.880 --> 0:02:03.000 hypotheses until you get more information about how frequently planets 0:02:03.080 --> 0:02:06.760 are a thing out there. And that's before you get 0:02:06.800 --> 0:02:09.680 to the question of how many planets might be similar 0:02:09.720 --> 0:02:14.400 to Earth, or, even more importantly, in our our grand 0:02:14.440 --> 0:02:17.160 scheme of things, how many of those planets might be 0:02:17.240 --> 0:02:20.120 in an orbit around their respective stars in what we 0:02:20.120 --> 0:02:23.800 would call the h Z or habitable zone. So the 0:02:23.840 --> 0:02:28.160 habitable zone, it's pretty self explanatory. It's the region surrounding 0:02:28.160 --> 0:02:32.400 a star in which water could exist in its liquid 0:02:32.440 --> 0:02:35.280 state if it were on a planet. So there's not 0:02:35.320 --> 0:02:38.840 a single range we can give to describe the habitable zone. Right, 0:02:39.000 --> 0:02:43.240 I can't just tell you it's x many millions of 0:02:43.280 --> 0:02:46.760 miles away, And the reason for that is because there 0:02:46.800 --> 0:02:50.520 are different kinds of stars. So to determine the habitable 0:02:50.639 --> 0:02:53.800 zone of a star, first you have to ask yourself 0:02:53.800 --> 0:02:58.239 the question, is this star old enough that any planets 0:02:58.240 --> 0:03:01.000 that might be orbiting it would have been around long 0:03:01.120 --> 0:03:04.880 enough to have time necessary for life to develop, because 0:03:04.919 --> 0:03:07.320 it would probably take billions of years, So you want 0:03:07.320 --> 0:03:10.480 to make sure that the solar system you're looking at 0:03:10.560 --> 0:03:13.440 is actually old enough for that to have been a possibility. 0:03:13.639 --> 0:03:17.000 On a similar note, the size of the star matters. 0:03:17.240 --> 0:03:21.680 Larger stars have shorter lifespans than smaller stars. Generally speaking, 0:03:21.840 --> 0:03:25.239 that's because stars with greater mass will burn through their 0:03:25.280 --> 0:03:29.840 fuel more quickly than smaller stars. The process of fusion 0:03:30.200 --> 0:03:32.720 will be at a much greater rate for a larger 0:03:32.760 --> 0:03:35.120 star than it is for a smaller star. So if 0:03:35.160 --> 0:03:37.640 you have a really big star, it may only live 0:03:37.680 --> 0:03:40.600 to be a few million years old before it collapses 0:03:40.680 --> 0:03:43.200 and explodes in a supernova. Now I know, a few 0:03:43.240 --> 0:03:45.640 million years it's a long time for humans, but for 0:03:45.720 --> 0:03:49.560 stars most stars, like the smaller ones, that's not long 0:03:49.600 --> 0:03:51.880 at all. A star of the size of our sun 0:03:52.360 --> 0:03:56.840 could stick around for maybe ten billion years the sun. 0:03:57.000 --> 0:04:01.480 Our sun is currently around four point six billion years old, 0:04:01.520 --> 0:04:04.240 so we got a bit. We got a minute or 0:04:04.280 --> 0:04:08.560 two before it burns out, and honestly, before it would 0:04:08.560 --> 0:04:10.920 burn out, there would be other things going on that 0:04:11.000 --> 0:04:14.040 would be of immediate concern to us. But yeah, we 0:04:14.160 --> 0:04:17.679 got billions of years before that happens. So really, big 0:04:17.720 --> 0:04:21.120 stars are not good candidates for finding planets that might 0:04:21.160 --> 0:04:23.960 have life on them, just because they probably haven't been 0:04:23.960 --> 0:04:27.960 around long enough for life to develop. So small stars, well, 0:04:28.000 --> 0:04:30.560 that gets tricky too if the star is too small. 0:04:30.720 --> 0:04:34.919 The habitable zone overlaps a region wherein an orbiting planet 0:04:35.000 --> 0:04:40.120 would be entitled lock with its star. So title lock 0:04:40.240 --> 0:04:43.919 means the same side of the planet would always face 0:04:44.000 --> 0:04:47.560 the star, and the opposite side would always face away 0:04:47.720 --> 0:04:49.800 from the star, So one side of the planet would 0:04:49.839 --> 0:04:52.680 always be bathed in starlight. The other side of the 0:04:52.720 --> 0:04:57.480 planet would always be dark. So the side facing the 0:04:57.520 --> 0:05:00.600 star would be too warm for liquid water or to exist. 0:05:00.680 --> 0:05:02.440 Most likely it would be it would just be too hot, 0:05:02.600 --> 0:05:07.320 it would evaporate out and boil off. There's nothing out 0:05:07.320 --> 0:05:10.360 there to say that water is absolutely necessary for all 0:05:10.480 --> 0:05:13.800 kinds of life. We're going from a sample size of 0:05:13.920 --> 0:05:16.520 one planet that we know of that has life on it, 0:05:16.920 --> 0:05:20.839 So we're having to make a lot of assumptions here 0:05:20.920 --> 0:05:25.560 that could ultimately be wrong. But assuming water is necessary, 0:05:26.440 --> 0:05:29.000 very small stars and very big stars are not really 0:05:29.040 --> 0:05:33.680 good candidates for planets that may support life. Now, there 0:05:33.680 --> 0:05:35.760 are a lot of different ways to classify stars, but 0:05:35.839 --> 0:05:40.159 the modern classification system is called the Morgan Keenan system 0:05:40.360 --> 0:05:44.839 and that divides stars into spectral classes, which sources stars 0:05:44.839 --> 0:05:48.680 into categories based on the spectrum of electromagnetic radiation that 0:05:48.720 --> 0:05:52.520 the star emits. Using something like a prism, you can 0:05:52.560 --> 0:05:56.039 look at this spectrum of visible light. So prisms break 0:05:56.120 --> 0:06:00.240 up visible light into the different colors that you would see. 0:06:00.279 --> 0:06:02.840 You know, you get the visible light coming at you 0:06:02.920 --> 0:06:05.440 use a prism, and then you can actually see uh 0:06:05.480 --> 0:06:10.080 the spectrum, the full spectrum of light. And this kind 0:06:10.120 --> 0:06:14.560 of approach, you would have spectral lines interspersed through a 0:06:14.680 --> 0:06:17.200 range of colors. It would be like little black bars 0:06:17.960 --> 0:06:21.760 that would be throughout the spectrum. In eruptions in the spectrum, 0:06:21.760 --> 0:06:24.800 if you if you will, those lines indicate the abundance 0:06:25.120 --> 0:06:29.920 of certain elements and the type of element will UH 0:06:30.160 --> 0:06:32.400 you can determine what type of element is by where 0:06:32.400 --> 0:06:36.839 on the spectrum. Those spectral lines are mostly However, the 0:06:36.880 --> 0:06:41.039 spectral lines correspond with the stars surface temperature, and the 0:06:41.040 --> 0:06:45.520 classification of stars from hottest to coolest goes like this, 0:06:46.040 --> 0:06:51.880 oh B A, F G K, M. Some people use 0:06:51.920 --> 0:06:55.280 a handy mnemonic device to remember that, like, oh be 0:06:55.440 --> 0:07:00.599 a fine guy, kiss me kind of sweet. If you 0:07:00.640 --> 0:07:03.599 think about it, oh BI and A stars typically burn 0:07:03.680 --> 0:07:05.920 out before the time we would expect it would take 0:07:05.960 --> 0:07:08.880 for life to develop on orbiting planets, So those are 0:07:09.320 --> 0:07:13.360 your larger, hotter stars. That leaves us with F, G, K, 0:07:13.800 --> 0:07:18.640 and M stars as candidates for stars that might host 0:07:18.720 --> 0:07:23.600 planets that could potentially support life. For low mass cooler stars, 0:07:23.880 --> 0:07:27.200 the habitable zone will be closer in than if the 0:07:27.240 --> 0:07:30.120 star were larger and hotter. So, in other words, you 0:07:30.160 --> 0:07:35.600 have to have that perfect temperature or range of temperatures 0:07:35.720 --> 0:07:38.640 for water to exist in liquid form on the surface 0:07:38.640 --> 0:07:41.200 of the planet. So if a planet is too close 0:07:41.240 --> 0:07:43.800 to its star, it's possibly going to be tidally locked, 0:07:43.800 --> 0:07:45.960 and it's also gonna be too hot. If it's too 0:07:45.960 --> 0:07:48.640 far away, it's going to be too cold. So a 0:07:48.720 --> 0:07:51.600 planet must be in orbit around its respective star in 0:07:51.680 --> 0:07:54.560 such a way that it is not in title lock. 0:07:54.960 --> 0:07:58.120 It's not too close, it's not too far, it's not 0:07:58.240 --> 0:08:00.760 too hot, it's not too cold. And for that reason 0:08:00.800 --> 0:08:03.400 a lot of people have also started calling the habitable 0:08:03.480 --> 0:08:09.760 zone the Goldilocks zone because it's just right. Okay, So 0:08:09.800 --> 0:08:13.360 we have some ideas about planets that could in theory 0:08:13.400 --> 0:08:16.720 support life if they fell into the habitable zone. It 0:08:16.800 --> 0:08:18.880 doesn't mean that they definitely have life on them. We 0:08:18.960 --> 0:08:22.320 cannot make that determination. All we could say is, well, 0:08:22.600 --> 0:08:25.480 in theory, water could exist on that planet, and that's 0:08:25.520 --> 0:08:27.880 the best we can say. So that's one thing, But 0:08:27.960 --> 0:08:31.000 detecting planets in the first place is actually something else. 0:08:31.040 --> 0:08:33.440 Just because we could say, in theory, if a planet 0:08:33.440 --> 0:08:36.440 were to exist within this band of ranges around its star, 0:08:36.840 --> 0:08:39.000 it might be able to support life, doesn't mean we've 0:08:39.000 --> 0:08:42.760 actually found any planets, right. We have to figure out 0:08:42.800 --> 0:08:45.720 how to do that. So we have really powerful telescopes 0:08:45.760 --> 0:08:48.959 here on Earth, but that's not really gonna cut it. 0:08:49.559 --> 0:08:53.240 Even with a telescope that has an enormous aperture several 0:08:53.280 --> 0:08:56.760 meters across, the conditions are such that we're not going 0:08:56.800 --> 0:08:59.680 to be able to directly image planets. They're just the 0:08:59.679 --> 0:09:03.040 star are too far away. The distance between us and 0:09:03.120 --> 0:09:09.040 nearby stars is enormous light years, and comparatively speaking, the 0:09:09.120 --> 0:09:12.800 distance between a planet and its host star is nothing 0:09:12.840 --> 0:09:16.000 at all. Right, a few million miles is nothing compared 0:09:16.040 --> 0:09:19.200 to light years. So the light reflecting off a planet 0:09:19.559 --> 0:09:23.920 would also be much much, much much less bright than 0:09:23.960 --> 0:09:26.520 the light coming off of a star, like maybe a 0:09:26.559 --> 0:09:30.600 billion times less bright. So if we're looking at a 0:09:30.640 --> 0:09:34.680 star of comparable size and brightness to our Sun, then 0:09:34.720 --> 0:09:38.120 the planet that orbits it it will end up reflecting 0:09:38.160 --> 0:09:40.400 some light off of it, but it will be a 0:09:40.480 --> 0:09:43.000 tiny fraction of the light that's coming from the Sun. 0:09:43.080 --> 0:09:46.800 So our earth based telescopes would blur this light together 0:09:46.880 --> 0:09:49.320 due to diffraction, and we wouldn't really be able to 0:09:49.320 --> 0:09:52.280 tell the difference. We wouldn't be able to distinguish the 0:09:52.360 --> 0:09:56.280 planet from the star, so direct observation with Earth based 0:09:56.280 --> 0:10:01.520 telescopes is a non starter. However, we could look at 0:10:01.559 --> 0:10:04.560 indirect ways to observe the presence of a planet or 0:10:04.600 --> 0:10:09.520 to uh too, guess whether or not a planet is there. 0:10:10.600 --> 0:10:13.560 So stars have a gravitational poll on their planets, but 0:10:13.640 --> 0:10:17.720 planets also exert a gravitational poll on their host stars, 0:10:18.040 --> 0:10:20.800 and as planets move through their orbits around the star, 0:10:21.080 --> 0:10:24.960 they caused the star to wobble a little bit. The 0:10:25.000 --> 0:10:30.680 center of this gravitational poll is likely within the the 0:10:31.080 --> 0:10:34.320 diameter of the star itself, but it's not right at 0:10:34.320 --> 0:10:36.160 the center of the star. So the star kind of 0:10:36.200 --> 0:10:39.600 wiggles a little bit as the planets orbit around it. 0:10:40.440 --> 0:10:44.320 So if you are able to detect this wobble, if 0:10:44.320 --> 0:10:48.400 you're able to see it, then you could uh then 0:10:48.480 --> 0:10:52.120 deduce that there's something in orbit around that star. We've 0:10:52.200 --> 0:10:56.440 used this methodology to detect binary stars that were too 0:10:56.440 --> 0:10:59.679 close together for our Earth based telescopes to differentiate between 0:10:59.720 --> 0:11:03.760 the too. We call this the astrometric method of detecting 0:11:04.040 --> 0:11:08.880 binary stars. But planets are much smaller than stars, so 0:11:09.120 --> 0:11:12.800 the wobbles that are produced by planets are much smaller 0:11:12.840 --> 0:11:17.200 than would be produced by binary star systems AUH. It 0:11:17.320 --> 0:11:20.880 is the oldest methodology for searching for exoplanets, but for 0:11:20.960 --> 0:11:24.160 many years no one could confirm that any wobbles they 0:11:24.160 --> 0:11:26.800 were seeing actually meant there were planets in orbit around 0:11:26.800 --> 0:11:30.200 those stars. That changed in the era of space telescopes. 0:11:30.280 --> 0:11:32.480 That changed in the era of more advanced telescopes in 0:11:32.520 --> 0:11:36.000 the nineties, but let's set that aside for now. The 0:11:36.080 --> 0:11:40.200 Kepler telescope would be powerful enough to use an alternative 0:11:40.240 --> 0:11:43.760 method to detect exo planets. This is the so called 0:11:44.120 --> 0:11:48.199 transit method, and the transit method looks for indications that 0:11:48.280 --> 0:11:53.000 a planet is moving between a star and Earth. That is, 0:11:53.080 --> 0:11:56.880 it is transitting across the face of the star from 0:11:57.000 --> 0:12:00.240 our perspective. Now, we would detect this by measure ring 0:12:00.400 --> 0:12:04.040 the amount of light coming from the star. The planet 0:12:04.040 --> 0:12:06.200 would still be too far away and too small for 0:12:06.280 --> 0:12:08.240 us to see. It's not like we would see a 0:12:08.320 --> 0:12:11.920 tiny black dot moving across the star. But what we 0:12:11.960 --> 0:12:14.880 could do is measure exactly how much light are we 0:12:15.000 --> 0:12:18.000 receiving from that star. And if we noticed that there 0:12:18.080 --> 0:12:21.040 was a dip in the intensity of that light, it 0:12:21.040 --> 0:12:25.400 would indicate that something had passed between the star and us, 0:12:25.880 --> 0:12:29.040 that something had blocked some of that light from getting 0:12:29.120 --> 0:12:32.760 at us. A dip that happens with regularity would indicate 0:12:32.800 --> 0:12:35.520 that there is a planet in orbit around that star. 0:12:35.880 --> 0:12:40.280 That if we're seeing every so often that little dip happened, 0:12:40.720 --> 0:12:42.720 it would tell us, all right, there's something that's orbiting 0:12:42.720 --> 0:12:45.079 the star. And every time it comes across, that's when 0:12:45.120 --> 0:12:48.240 we see the dip, and that's why there's this gap 0:12:48.600 --> 0:12:52.959 between dips. If it's regular, that is, if it were irregular, 0:12:53.120 --> 0:12:55.400 we wouldn't necessarily know what the heck is going on, 0:12:55.600 --> 0:12:59.200 unless maybe it was multiple planets that were in orbit 0:12:59.280 --> 0:13:04.040 around the star. It would, however, require a very powerful 0:13:04.200 --> 0:13:07.000 and very precise telescope, and not only that, it would 0:13:07.000 --> 0:13:10.400 also require the planet's orbit around its star to be 0:13:10.440 --> 0:13:12.600 in an alignment so it would actually pass between the 0:13:12.600 --> 0:13:14.480 star and us. In other words, it would need to 0:13:14.480 --> 0:13:17.880 be at the right angle. So if the orbit was 0:13:17.920 --> 0:13:21.520 at a tilt from our perspective, if it were orbiting 0:13:21.520 --> 0:13:24.600 its star, but in such a way that its pathway 0:13:24.640 --> 0:13:27.560 did not cross between us and the star, we wouldn't 0:13:27.600 --> 0:13:31.840 see any indication of it because the light woulden't dim, 0:13:31.880 --> 0:13:34.599 you know, the light would still be coming straight at us. 0:13:34.600 --> 0:13:37.600 So it requires a couple of different things for for 0:13:37.720 --> 0:13:40.360 us to even pick it up. NASA started looking into 0:13:40.400 --> 0:13:43.240 the possibility of using the transit method to detect planets 0:13:43.280 --> 0:13:45.840 in the nineteen eighties, and one early step was a 0:13:45.840 --> 0:13:50.520 workshop at the NASA Aims Research Center in high precision photometry. 0:13:50.880 --> 0:13:55.319 Photometry is the science of the measurement of intensity of light. 0:13:55.679 --> 0:13:57.520 That's what I was talking about earlier, about measuring how 0:13:57.600 --> 0:14:01.040 much light is coming to you. That's using photometry. That 0:14:01.120 --> 0:14:04.440 science has been around for a bit. And you know, 0:14:04.480 --> 0:14:06.760 it's obvious that not everything that emits light does so 0:14:06.880 --> 0:14:10.360 at the same intensity. Right, Some things are brighter than others, 0:14:10.400 --> 0:14:13.600 some things are dimmer than others. Light isn't just on 0:14:13.960 --> 0:14:19.000 or off. There's a magnitude associated with it. Quantifying magnitude 0:14:19.840 --> 0:14:23.440 was really tricky. I have more to say about photometry 0:14:23.560 --> 0:14:25.880 and its history in just a second, but first let's 0:14:25.880 --> 0:14:36.120 take a quick break to thank our sponsor. Okay, we're 0:14:36.200 --> 0:14:38.080 back now. One day I'm going to have to do 0:14:38.240 --> 0:14:42.520 a full episode about photometry. The history of photometry is fascinating. 0:14:42.560 --> 0:14:44.400 It actually it dates all the way back to the 0:14:44.400 --> 0:14:48.200 ancient Greeks and Romans. But obviously, by the time we're 0:14:48.200 --> 0:14:51.960 talking about the the events that would lead into the 0:14:51.960 --> 0:14:54.760 development of the Kepler telescope, NASA was looking into something 0:14:54.760 --> 0:14:57.440 a little more sophisticated than what the ancients were capable 0:14:57.440 --> 0:15:02.640 of doing. Now, during the workshop on photometry, the group 0:15:02.760 --> 0:15:06.960 had several goals they wanted to achieve. One was determine 0:15:07.040 --> 0:15:12.440 which astronomical problems would benefit by increased photometric precision. So 0:15:13.320 --> 0:15:16.200 we've got this technology, if we make it better, what 0:15:16.360 --> 0:15:18.520 could we use it to do? What would it be 0:15:18.600 --> 0:15:21.440 good for? Another was to get a handle on what 0:15:21.600 --> 0:15:25.200 the current level of precision was with the latest equipment, 0:15:25.280 --> 0:15:27.720 So not just what would it be good for if 0:15:27.760 --> 0:15:30.080 we made it better, but how good is it right now? 0:15:31.000 --> 0:15:33.760 Another goal was to identify any of the things that 0:15:33.760 --> 0:15:37.480 would limit the precision of photometry, so what stands in 0:15:37.520 --> 0:15:40.920 our way of making this technology better? And finally, the 0:15:41.000 --> 0:15:44.200 last goal was to make recommendations to overcome or sidestep 0:15:44.400 --> 0:15:48.320 any of those limitations. The workshop was considered a success, 0:15:48.520 --> 0:15:51.400 and that led to a second workshop that was held 0:15:51.440 --> 0:15:56.000 in NASA Commission to study to determine if a multi 0:15:56.120 --> 0:16:01.520 channel photometer built on silicon photo diodes would be practical, 0:16:02.040 --> 0:16:05.480 and the researchers found that such photometers were incredibly precise, 0:16:06.040 --> 0:16:08.400 but they would also have to be super cooled down 0:16:08.400 --> 0:16:12.640 to less than negative one degrees celsius or negative three 0:16:13.360 --> 0:16:17.800 degrees fahrenheit, the temperature of liquid nitrogen. In other words, Now, 0:16:17.840 --> 0:16:20.280 since I'm gonna do an episode about photometry in the future, 0:16:20.280 --> 0:16:23.000 I'm going to skip a deep explanation of how those 0:16:23.000 --> 0:16:26.280 devices work for now. Just know that they are all 0:16:26.320 --> 0:16:33.280 about quantifying the intensity of light that is hitting them. 0:16:33.520 --> 0:16:36.440 So let's go back to our history lesson leading up 0:16:36.480 --> 0:16:41.040 to the Kepler telescope. In the early NASA officials were 0:16:41.080 --> 0:16:44.880 considering a suite of new missions for the organization to pursue. 0:16:45.240 --> 0:16:47.520 Some of them were aimed at getting a more comprehensive 0:16:47.600 --> 0:16:50.960 understanding of our own Solar system, but some were meant 0:16:50.960 --> 0:16:54.840 to search for planets outside of our immediate neighborhood. One 0:16:54.840 --> 0:16:58.600 of those proposed missions got the name free SIP or 0:16:58.840 --> 0:17:02.480 f R E s I P, which stood for Frequency 0:17:02.640 --> 0:17:07.040 of Earth size Inner Planets. Like all the proposed missions, 0:17:07.359 --> 0:17:10.760 the team had to outline the scientific and technical requirements 0:17:10.800 --> 0:17:13.520 to complete mission objectives, as well as how much they 0:17:13.640 --> 0:17:17.800 estimated it would cost, and a proposed schedule and management plan. 0:17:18.800 --> 0:17:21.520 Free SIP would land on the chopping block. It would 0:17:21.520 --> 0:17:24.760 not make it through in that initial round, and in 0:17:24.840 --> 0:17:28.360 nine two there just wasn't sufficient evidence that the technical 0:17:28.400 --> 0:17:31.400 equipment would be sensitive enough to pick up the transit 0:17:31.440 --> 0:17:34.159 of a distant planet and yet also be able to 0:17:34.200 --> 0:17:37.960 filter out noise. So what NASA HQ was saying was 0:17:38.680 --> 0:17:41.320 this is it's not that your idea doesn't have merit, 0:17:41.359 --> 0:17:43.960 it's that we cannot be certain that the equipment you 0:17:44.000 --> 0:17:46.920 would use would actually achieve the goals, and we don't 0:17:46.960 --> 0:17:49.520 want to spend millions of dollars on something that ultimately 0:17:49.560 --> 0:17:53.200 doesn't work. The scientific community still felt that the objective 0:17:53.280 --> 0:17:58.000 was worth pursuing, so in nineteen scientists organized another workshop 0:17:58.200 --> 0:18:02.119 called Astrophysical Science with a space born photometric telescope in 0:18:02.240 --> 0:18:07.040 mountain View, California. More specifically, not just mountain View, California, 0:18:07.280 --> 0:18:11.080 this event took place at SETI Headquarters cet IS the 0:18:11.160 --> 0:18:16.919 Search for Extra Terrestrial Intelligence. Also in NASA announced the 0:18:16.920 --> 0:18:21.280 initiation of Discovery class missions. Now that's a category of 0:18:21.320 --> 0:18:24.440 missions that are supposed to be complementary to the larger 0:18:24.600 --> 0:18:27.879 missions that NASA pursus. So these are supposed to be 0:18:27.920 --> 0:18:32.600 smaller and therefore also less expensive than the bigger missions. 0:18:33.320 --> 0:18:37.240 The Frecept team would resubmit their proposal as a Discovery 0:18:37.280 --> 0:18:41.280 class mission, but then NASA ultimately rejected that second attempt, 0:18:41.960 --> 0:18:44.359 and the reason they gave was that they felt that 0:18:44.400 --> 0:18:47.960 the mission as described would be too expensive to qualify 0:18:48.080 --> 0:18:52.560 as a Discovery class mission. In a team of scientists 0:18:52.600 --> 0:18:55.919 at the University of Geneva announced that they had discovered 0:18:55.960 --> 0:19:00.080 an exo planet in the constellation Pegasus. This exo and 0:19:00.119 --> 0:19:04.680 it got the designation fifty one pegasie B. The team 0:19:04.760 --> 0:19:08.960 had used the so called Wobble method radial velocity method 0:19:09.160 --> 0:19:12.840 to detect this planet, and that helped fuel interest in 0:19:12.840 --> 0:19:17.960 the search for more exoplanets in the free SIP team 0:19:17.960 --> 0:19:21.640 had yet another chance to propose a flight mission, and 0:19:21.720 --> 0:19:24.800 this time they made a really big adjustment to their proposal. 0:19:24.840 --> 0:19:28.200 Actually they made two big adjustments. It's just that one 0:19:28.240 --> 0:19:32.639 of them was perhaps more important and more key to 0:19:32.880 --> 0:19:36.560 getting approval, and that was changing the parameters of the mission. 0:19:36.840 --> 0:19:41.080 The original proposal required putting a spacecraft in a lagrange orbit. 0:19:41.320 --> 0:19:44.440 Now that's a position in space where the combined gravitational 0:19:44.480 --> 0:19:48.199 forces of two large bodies equal the centrivigal force of 0:19:48.240 --> 0:19:52.600 a body that's in that position between the two or 0:19:52.640 --> 0:19:55.320 around the two. So the two large bodies in the 0:19:55.359 --> 0:19:58.400 case that we care about are the Earth and the Sun. 0:19:59.080 --> 0:20:03.440 So there are five lagrange points that are in that 0:20:03.560 --> 0:20:08.320 vicinity around the Sun and Earth. They have designations that 0:20:08.400 --> 0:20:11.480 go from L one up to L five, So L 0:20:11.560 --> 0:20:15.879 one lagrange orbit is at a point between Earth and 0:20:15.920 --> 0:20:18.679 the Sun. It's much closer to the Earth than the 0:20:18.720 --> 0:20:22.760 Sun because gravity depends upon mass and distance, and the 0:20:22.800 --> 0:20:25.919 Earth is much less massive than the Sun, so you 0:20:25.920 --> 0:20:27.760 need to get closer if you want to have all 0:20:27.800 --> 0:20:30.680 that stuff kind of balance out. L two is actually 0:20:30.760 --> 0:20:34.520 located behind Earth with respect to the Sun, so in 0:20:34.520 --> 0:20:39.080 an orbit that's uh, that's further out from the Sun 0:20:39.200 --> 0:20:42.080 than Earth is. L three is actually on the opposite 0:20:42.160 --> 0:20:45.520 side of the Sun from where the Earth is. L 0:20:45.600 --> 0:20:48.119 four and L five are in effect at an orbit 0:20:48.200 --> 0:20:52.640 sixty degrees ahead and sixty degrees behind the Earth, respectively. 0:20:52.840 --> 0:20:56.760 In its orbit. Now, a satellite at L one would 0:20:56.800 --> 0:20:59.880 have an unobstructed view of the Sun, and that's why 0:20:59.880 --> 0:21:03.640 we put the solar in Heliospheric Observatory there. A satellite 0:21:03.640 --> 0:21:06.400 at ALL two would have a view of deep space, 0:21:06.520 --> 0:21:08.760 and it would be shaded from the Sun because it 0:21:08.760 --> 0:21:10.879 would be in the shadow of Earth. That's where the 0:21:10.960 --> 0:21:15.520 James Webb Space Telescope will eventually be. These orbits require 0:21:15.560 --> 0:21:18.760 a lot of adjustments to keep a satellite stable, otherwise 0:21:18.760 --> 0:21:21.040 they would drift out of orbit and move into a 0:21:21.040 --> 0:21:25.280 collision course with a celestial body like the Sun, for example, 0:21:25.760 --> 0:21:28.240 Moving a telescope into one of those orbits and keeping 0:21:28.240 --> 0:21:30.800 it there would have required a lot more fuel and 0:21:30.880 --> 0:21:34.879 thus added expense to the mission. So this new proposal 0:21:35.240 --> 0:21:39.560 for what was originally called Free SIP suggested putting the 0:21:39.560 --> 0:21:42.960 telescope in a normal solar or orbit rather than on 0:21:43.040 --> 0:21:46.320 a grange orbit, and that brought the cost down significantly, 0:21:46.320 --> 0:21:48.960 and the mission also got a new name. This was 0:21:49.000 --> 0:21:52.480 the second big change, and that new name was Kepler, 0:21:52.680 --> 0:21:57.440 after Johannes Kepler, the seventeenth century German astronomer. The mission 0:21:57.600 --> 0:22:02.359 still did not get greenlit at that time, however, then 0:22:02.720 --> 0:22:05.760 they tried again and they got turned down again. The 0:22:05.800 --> 0:22:09.040 team were told they needed to demonstrate the photometry system 0:22:09.080 --> 0:22:11.680 they had in mind would actually be sufficient to pick 0:22:11.760 --> 0:22:15.080 up the transit of a planet across its star. So 0:22:15.160 --> 0:22:17.800 they built a testing facility at the Aimes Research Center 0:22:18.040 --> 0:22:21.080 and they began running more than a hundred fifty simulations 0:22:21.119 --> 0:22:24.160 to prove that their system would actually work. In two 0:22:24.200 --> 0:22:29.320 thousand one, NASA officials finally gave approval to Kepler. This 0:22:29.400 --> 0:22:32.040 was the fifth proposal for that mission, and it was 0:22:32.119 --> 0:22:37.120 designated as the tenth Discovery Class mission. For nearly a decade, 0:22:37.200 --> 0:22:40.959 engineers and scientists got to work building the actual telescope. 0:22:41.000 --> 0:22:43.399 I'll talk more about how it worked in just a moment, 0:22:43.440 --> 0:22:47.520 but the telescope launched on March sixth, two thousand nine. 0:22:47.920 --> 0:22:50.600 It was on top of a three stage Delta two 0:22:50.680 --> 0:22:53.480 rocket that's what was used as the launch vehicle, and 0:22:53.560 --> 0:22:55.879 more than a month would go by once it reached 0:22:55.880 --> 0:22:59.359 its orbit before it would take the first image of 0:22:59.400 --> 0:23:02.879 a small patch of sky. It was a small patch 0:23:02.880 --> 0:23:06.200 of sky which was occupied by part of the constellation Sicknus, 0:23:06.280 --> 0:23:09.959 the Swan and Lyra or a liar, also known as 0:23:10.000 --> 0:23:14.120 the harp. There's a term for this moment when a 0:23:14.160 --> 0:23:17.960 space telescope like this sends back its first image, and 0:23:18.040 --> 0:23:21.439 it's called first light, which I think is kind of cool. Also, 0:23:22.119 --> 0:23:25.119 it had the equivalent of a lens cap. It's a 0:23:25.119 --> 0:23:28.080 a very very large lens cap because the telescope has 0:23:28.160 --> 0:23:31.200 quite a large opening at one end, but that had 0:23:31.240 --> 0:23:34.520 to be jettisoned first before any images could be sent back. Obviously, 0:23:34.520 --> 0:23:37.600 otherwise you just get if you've ever taken a picture 0:23:37.600 --> 0:23:39.600 with a camera that still had a lens cap on, 0:23:40.080 --> 0:23:42.600 you know, what you get, you get pitch black darkness. 0:23:43.960 --> 0:23:47.159 That same little small patch of sky. By the way, 0:23:47.280 --> 0:23:50.440 while it is a tiny, tiny portion of the overall 0:23:50.560 --> 0:23:53.679 night sky, it's home to around four and a half 0:23:53.920 --> 0:23:58.600 million stars. Kepler's job was to monitor around a hundred 0:23:58.600 --> 0:24:02.879 seventy thousand of the stars simultaneously, So its job was 0:24:02.920 --> 0:24:05.800 just to monitor the brightness of those stars and look 0:24:05.840 --> 0:24:11.840 for tiny variations in their luminosity, regular ones, periodic dips 0:24:12.000 --> 0:24:15.760