WEBVTT - TechStuff Classic: How the Kepler Telescope Works 0:00:04.440 --> 0:00:12.280 Welcome to tech Stuff, a production from iHeartRadio. Hey there, 0:00:12.320 --> 0:00:15.320 and welcome to tech Stuff. I'm your host Jonathan Strickland. 0:00:15.360 --> 0:00:19.080 I'm an executive producer with iHeartRadio and how the tech 0:00:19.200 --> 0:00:23.080 are you? It is time for a classic episode of 0:00:23.400 --> 0:00:28.680 tech Stuff. This episode is titled How the Kepler Telescope Works, 0:00:28.960 --> 0:00:34.960 and it published on June eighth, twenty sixteen, Enjoy. In 0:00:35.000 --> 0:00:38.840 May twenty sixteen, researchers with the Kepler Mission at NASA 0:00:38.920 --> 0:00:41.320 held a press conference in which they announced the largest 0:00:41.440 --> 0:00:46.919 number of exoplanets verified ever at a single event, and 0:00:46.960 --> 0:00:52.440 that was one thy two hundred and eighty four verified exoplanets. Previously, 0:00:52.880 --> 0:00:55.279 from two thousand and nine, up to that point, the 0:00:55.280 --> 0:00:59.080 mission had identified and verified nine hundred eighty four planets. 0:00:59.320 --> 0:01:02.200 So this is announcement was more than doubling the number 0:01:02.320 --> 0:01:07.760 of exoplanets verified. That's incredible. So an exoplanet, just in 0:01:07.760 --> 0:01:09.560 case you don't know, is of course a planet that 0:01:09.640 --> 0:01:13.560 is orbiting another star, not the Sun. So it's planets 0:01:13.600 --> 0:01:18.520 in other star systems, solar systems that are light years 0:01:18.520 --> 0:01:22.000 away from us. And it was a really cool thing 0:01:22.120 --> 0:01:25.560 to hear about all these different exoplanets that had just 0:01:25.600 --> 0:01:30.200 been verified. What I thought was hilarious was leading up 0:01:30.240 --> 0:01:35.679 to this announcement, you had several news outlets that were 0:01:37.200 --> 0:01:39.760 guessing what was going to happen. It was just it 0:01:39.800 --> 0:01:42.960 was just complete throw stuff against the wall and see 0:01:42.959 --> 0:01:45.520 what sticks. And there were quite a few that had 0:01:45.560 --> 0:01:49.800 guessed that NASA was going to announce that the Kepler 0:01:49.840 --> 0:01:54.400 mission had somehow discovered alien life. Now, once you hear 0:01:54.440 --> 0:01:57.240 how the Kepler telescope works and what it's meant to do, 0:01:57.320 --> 0:02:01.480 you'll understand that's really not in the purview of the 0:02:01.560 --> 0:02:04.960 Kepler telescope. It is looking for planets that could potentially 0:02:05.000 --> 0:02:09.760 support life, but it doesn't have the capacity to actually 0:02:09.800 --> 0:02:14.440 detect life on those other planets unless someone sent aliens 0:02:14.440 --> 0:02:17.160 to Earth and they started messing with the Kepler telescope, 0:02:17.200 --> 0:02:19.840 in which case you could say it discovered life, but 0:02:20.040 --> 0:02:23.840 not through its primary mission. That did not happen. As 0:02:23.840 --> 0:02:26.640 far as I know, no aliens have been messing with 0:02:26.639 --> 0:02:32.480 the Kepler telescope. So let's talk about how this telescope 0:02:32.520 --> 0:02:36.760 works and this new verification method that the research team 0:02:36.840 --> 0:02:40.520 used to identify so many exoplanets. What was it that 0:02:40.840 --> 0:02:44.200 sped up the process so dramatically as to more than 0:02:44.320 --> 0:02:48.680 double the number of confirmed exoplanets. Plus i'll talk a 0:02:48.680 --> 0:02:51.519 little bit about the new candidates for Earth like planets 0:02:51.600 --> 0:02:55.720 that might be capable of supporting life. So first, let's 0:02:55.720 --> 0:03:00.720 go way back. The Kepler Telescope is named after Johann Kepler, 0:03:01.120 --> 0:03:04.880 an astronomer of the late sixteenth and early seventeenth centuries. 0:03:05.360 --> 0:03:07.520 That's not the original name of the telescope, by the way, 0:03:07.560 --> 0:03:10.000 but more on that in a little bit. So Johann 0:03:10.080 --> 0:03:13.440 Kepler is most famous for discovering the three major laws 0:03:13.440 --> 0:03:16.440 of planetary motion, although at the time no one called 0:03:16.480 --> 0:03:20.800 them laws. It would take Newton and Newton's observations before 0:03:20.840 --> 0:03:25.200 that really started to become a thing. But law number 0:03:25.280 --> 0:03:29.079 one is that the planets move in elliptical orbits around 0:03:29.120 --> 0:03:31.720 the Sun. Law number two, the time it takes to 0:03:31.800 --> 0:03:36.040 traverse any arc of a planetary orbit is proportional to 0:03:36.080 --> 0:03:39.800 the area of the sector between the central body, for example, 0:03:40.000 --> 0:03:42.920 the Sun and the arc. So you can think of 0:03:42.960 --> 0:03:45.360 the two points along the ark, the starting point and 0:03:45.360 --> 0:03:49.320 the endpoint of the arc as your barriers on one side, 0:03:49.720 --> 0:03:53.720 the Sun being the third point in what's not exactly 0:03:53.760 --> 0:03:56.160 a triangle because you have a curve line a straight 0:03:56.200 --> 0:03:59.880 line on the arc side the area within that that 0:04:00.200 --> 0:04:05.680 is proportional to the time it takes to traverse that arc. Essentially, 0:04:05.760 --> 0:04:08.320 what that tells you is that the further out you 0:04:08.360 --> 0:04:11.480 are from a star, the slower your orbit is going 0:04:11.560 --> 0:04:15.040 to be, and the closer en you are to a star, 0:04:15.120 --> 0:04:18.839 the faster your orbit is going to be. Also, there's 0:04:18.839 --> 0:04:22.400 a relationship between the square of a planet's periodic time 0:04:22.600 --> 0:04:25.400 and the cube of the radius of its orbit, which 0:04:25.440 --> 0:04:29.840 is also known as the harmonic law. That's law number three. Now, 0:04:29.880 --> 0:04:33.120 the Kepler mission all started out with a question, which 0:04:33.200 --> 0:04:36.880 was how frequent are other Earth sized planets in our 0:04:36.960 --> 0:04:41.480 galaxy the Milky Way? How common is that? Is the 0:04:41.520 --> 0:04:46.520 Earth a strange outlier that is one in a billion 0:04:46.760 --> 0:04:50.480 or one in ten billion, or even more rare than 0:04:50.520 --> 0:04:53.719 that We had no way of knowing. Now, that particular 0:04:53.800 --> 0:04:57.479 space based telescope, the Kepler telescope, tries to answer this 0:04:57.600 --> 0:05:03.280 question by looking for planets what is called the transit method. Now, 0:05:03.360 --> 0:05:07.520 this method was proposed a few times leading up to 0:05:07.760 --> 0:05:13.279 nineteen seventy one, when Frank Rosenblatt really went strong with 0:05:13.360 --> 0:05:16.599 the idea. He suggested the transit method for detecting satellites 0:05:16.720 --> 0:05:20.960 orbiting other stars. And technically, the way this works is 0:05:20.960 --> 0:05:23.479 that you look at a star and you measure the 0:05:23.520 --> 0:05:26.640 amount of light coming to Earth from that star, and 0:05:26.680 --> 0:05:30.720 you look for any variations and that any dimming of 0:05:30.720 --> 0:05:34.960 that light. Now, if a planet were to pass between 0:05:35.120 --> 0:05:38.159 that star and the Earth, you would expect the light 0:05:38.200 --> 0:05:42.640 from that star to dim a tiny amount, and that 0:05:42.680 --> 0:05:45.479 if you were able to detect that difference, and you 0:05:45.520 --> 0:05:49.600 were able to observe that this happens regularly over the 0:05:49.600 --> 0:05:52.400 course of a given amount of time, you could come 0:05:52.440 --> 0:05:55.400 to the conclusion that what you have seen is in 0:05:55.440 --> 0:05:59.880 fact a planet passing between its host star and the Earth. 0:06:00.800 --> 0:06:03.920 This is what we call transit when we see from 0:06:03.960 --> 0:06:10.240 our perspective a planet crossing its star. Now we're looking 0:06:10.279 --> 0:06:13.800 at the planet making its progress across its star in 0:06:13.880 --> 0:06:17.560 the course of that planet's year. So if it's close 0:06:17.640 --> 0:06:20.200 to the same distance from its host star as the 0:06:20.240 --> 0:06:23.279 Earth is from the Sun, you have to wait a 0:06:23.279 --> 0:06:27.320 long time to verify that that in fact is what 0:06:27.360 --> 0:06:30.840 you saw, especially if you want to truly verify it 0:06:30.920 --> 0:06:37.920 and get a few periodic instances of that dimming, and 0:06:37.960 --> 0:06:39.920 if it has if it's a start that has multiple 0:06:40.640 --> 0:06:44.479 planets alone that same orbital plane, then that's going to 0:06:44.520 --> 0:06:49.080 cause some confusion too. But by seeing the amount of 0:06:49.200 --> 0:06:52.760 light that has been dimmed, and by detecting how long 0:06:52.800 --> 0:06:57.800 it takes this dimming to change back to normal, you 0:06:57.839 --> 0:07:01.800 can start to make some conclusion like how big the 0:07:01.839 --> 0:07:05.200 planet must be, how quickly it travels tells you a 0:07:05.200 --> 0:07:08.520 bit about its orbit. It tells you also by that orbit, 0:07:08.640 --> 0:07:11.680 how close it is to its home star. As long 0:07:11.680 --> 0:07:13.840 as you know information about the home star, then you 0:07:13.880 --> 0:07:16.840 can start to make guesses as to how hot the 0:07:16.880 --> 0:07:20.840 planet is or how cold it might be, And this 0:07:20.880 --> 0:07:24.240 is how you start to draw some conclusions about the 0:07:24.320 --> 0:07:28.800 nature of that planet. Ultimately looking for planets that are 0:07:28.920 --> 0:07:34.000 similar to size, similar to Earth size, i should say, 0:07:34.600 --> 0:07:37.160 and similar to distance from its host star as the 0:07:37.200 --> 0:07:39.960 Earth is to the Sun. The reason for that is 0:07:40.000 --> 0:07:45.040 we know that if the planet is about two times 0:07:45.040 --> 0:07:48.240 the size of Earth or smaller, it's probably going to 0:07:48.280 --> 0:07:54.440 have gravity that is amenable to life as we know it. 0:07:54.440 --> 0:07:57.320 It's going to probably be a rocky planet as opposed 0:07:57.360 --> 0:08:00.760 to a gas giant. That's also important. It's probably going 0:08:00.840 --> 0:08:03.800 to be at a temperature that will allow liquid water 0:08:04.440 --> 0:08:06.880 to be on the planet, and since life as we 0:08:07.000 --> 0:08:10.760 know it depends upon the presence of liquid water, that's 0:08:10.760 --> 0:08:12.840 what we're looking for. Keeping in mind that there is 0:08:12.840 --> 0:08:15.240 the possibility there could be life out there in the 0:08:15.280 --> 0:08:19.720 galaxy that doesn't depend upon liquid water. But we have 0:08:19.760 --> 0:08:23.560 a sample size of one planet with life on it, 0:08:23.960 --> 0:08:26.120 so we have to draw our conclusions based upon the 0:08:26.280 --> 0:08:30.880 limited information we have. So assuming that water is in 0:08:30.920 --> 0:08:34.479 fact necessary for life, we need to find other planets 0:08:34.559 --> 0:08:39.240 that could potentially have water on them. So that's kind 0:08:39.240 --> 0:08:45.440 of guiding the principles behind looking for planets through the 0:08:45.480 --> 0:08:51.080 transit method. But it's really really hard to do. Now, 0:08:51.400 --> 0:08:53.920 let's get back to Frank Rosenblatt for a second. He 0:08:54.040 --> 0:08:58.160 wasn't just famous for suggesting this astronomical approach. He wasn't 0:08:58.679 --> 0:09:02.080 known as a great dronomer. He was actually better known 0:09:02.559 --> 0:09:05.640 as a leading expert in the field of artificial intelligence, 0:09:05.720 --> 0:09:12.160 particularly in the areas of recognizing visual patterns and speech recognition. 0:09:12.720 --> 0:09:16.880 So that was his specific forte. He was really working 0:09:16.880 --> 0:09:20.400 with computers so that they could recognize visual patterns, they 0:09:20.400 --> 0:09:23.080 could recognize when what you are saying when you talk 0:09:23.160 --> 0:09:27.439 to them, and these are fields that today are really 0:09:27.440 --> 0:09:30.240 coming into their own with stuff like Google's Deep Dream, 0:09:30.400 --> 0:09:33.600 where it starts to recognize patterns even if patterns aren't 0:09:33.880 --> 0:09:37.400 really in the picture. It really enhances that and looks 0:09:37.440 --> 0:09:40.559 for patterns in the in ways that are really interesting 0:09:40.920 --> 0:09:44.760 and trippy. And speech recognition, which we're all using to 0:09:44.840 --> 0:09:49.280 some degree these days, often with the personal digital assistants 0:09:49.320 --> 0:09:52.079 that are popping up all over the place. Now here's 0:09:52.080 --> 0:09:57.200 the problem. Rosenblatz suggested approach was not practical at the 0:09:57.240 --> 0:10:03.120 time in the early seventies, the technological sophistication necessary to 0:10:03.200 --> 0:10:06.240 detect and analyze such a very tiny change in a 0:10:06.280 --> 0:10:10.760 star's brightness. If we were looking for an Earth sized 0:10:10.880 --> 0:10:15.559 planet at a distance similar to what Earth is from 0:10:15.720 --> 0:10:20.200 our sun, we're talking about a reduction of one ten 0:10:20.360 --> 0:10:23.800 thousandth the brightness of a star, and that dimming lasts 0:10:23.800 --> 0:10:27.960 between two and sixteen hours, So that's not a lot 0:10:27.960 --> 0:10:31.800 of time, and it's certainly not a big difference in brightness. 0:10:31.840 --> 0:10:33.920 You have to have a very sensitive instrument in order 0:10:33.960 --> 0:10:35.760 to be able to pick that up, and that just 0:10:35.800 --> 0:10:39.600 didn't exist in nineteen seventy one. Now, we also have 0:10:39.600 --> 0:10:41.320 to keep in mind that stars tend to be much 0:10:41.440 --> 0:10:44.760 much bigger than planets. For example, the Sun's diameter is 0:10:44.760 --> 0:10:47.320 one hundred and nine times greater than the Earth's diameter, 0:10:47.920 --> 0:10:50.960 and because of that, that's why with the distance is 0:10:51.000 --> 0:10:54.080 involved and the size is involved, it's such a tiny 0:10:54.240 --> 0:10:58.000 change in the brightness of the star. However, NASA began 0:10:58.080 --> 0:11:00.400 to explore how they might be able to use the 0:11:00.440 --> 0:11:05.040 transit method to detect exoplanets in a practical way. Back 0:11:05.080 --> 0:11:07.960 in nineteen eighty four, they were essentially laying out the 0:11:08.000 --> 0:11:12.120 requirements necessary to detect planets with a reasonable amount of confidence. 0:11:12.920 --> 0:11:16.480 A conference that they held on High precision photometry acted 0:11:16.520 --> 0:11:20.960 as the launching ground figuratively speaking, for discussions about a 0:11:21.080 --> 0:11:25.800 space based telescope designed to detect a transiting planet. The 0:11:25.840 --> 0:11:30.640 idea being that in space there would be less noise 0:11:31.080 --> 0:11:34.480 in the signal to noise ratio, you could get it 0:11:34.520 --> 0:11:37.840 outside the atmosphere. The effects of the atmosphere would not 0:11:38.120 --> 0:11:42.440 be an impediment to a space telescope, and it'd be 0:11:42.440 --> 0:11:46.439 more likely to pick up something as tiny as this 0:11:46.600 --> 0:11:50.160 change in brightness. I'll be back in just a moment 0:11:50.200 --> 0:11:53.280 to talk more about how the Kepler telescope works after 0:11:53.320 --> 0:12:06.360 this quick break, So in nineteen ninety two, NASA proposed 0:12:06.400 --> 0:12:08.960 new missions to look into the possibility of life in 0:12:09.000 --> 0:12:11.960 our galaxy, and the first concept that came up with 0:12:12.400 --> 0:12:16.040 was called the Frequency of Earth Sized Inner Planets or 0:12:16.200 --> 0:12:23.600 FREZIP FRSIP, but that proposal was rejected largely because there 0:12:23.679 --> 0:12:26.480 was doubt at the time that our technological sophistication had 0:12:26.520 --> 0:12:30.120 actually reached a level sufficient to detect any transiting planets 0:12:30.120 --> 0:12:33.160 of Earth like size. So, in other words, if we 0:12:33.280 --> 0:12:35.560 had gone forward with it, we would have built a 0:12:35.600 --> 0:12:38.920 tool that was not up to the task of actually 0:12:38.920 --> 0:12:40.760 doing what was supposed to do, and we would have 0:12:40.800 --> 0:12:45.120 wasted millions of dollars in the process, not something NASA 0:12:45.120 --> 0:12:49.000 could easily afford to do now. Two years later, in 0:12:49.080 --> 0:12:53.880 nineteen ninety four, a team proposed FREZIP again with a 0:12:53.960 --> 0:12:58.439 space based telescope in lagrange orbit, but again a committee 0:12:58.440 --> 0:13:00.880 determined the price would be similar to that of the Hubble, 0:13:01.000 --> 0:13:05.200 which was incredibly expensive and also had been a black 0:13:05.320 --> 0:13:09.520 eye on NASA because when the Hubble launched, it launched 0:13:09.520 --> 0:13:13.880 with a defect that later had to be corrected in space. 0:13:14.040 --> 0:13:17.120 A team had to be sent up to make some 0:13:17.280 --> 0:13:20.640 tweaks to the Hubble space telescope, so that it would 0:13:20.960 --> 0:13:24.000 perform more closely to what it was supposed to do 0:13:25.280 --> 0:13:29.160 because one of its mirrors was not right at any rate, 0:13:29.760 --> 0:13:33.160 they didn't want to involve a you know, or didn't 0:13:33.200 --> 0:13:36.760 want to invest in a big time project that was unproven, 0:13:37.920 --> 0:13:42.520 especially after the Hubble issue, so they rejected the proposal. 0:13:43.240 --> 0:13:45.199 By the way, in case you're wondering what a lagrange 0:13:45.360 --> 0:13:49.439 orbit is, that refers to five specific orbits around the Sun. 0:13:50.480 --> 0:13:52.520 In two of the orbits L one and L two, 0:13:52.880 --> 0:13:56.160 a spacecraft would orbit the Sun either just inside the 0:13:56.200 --> 0:13:59.000 Earth's orbit or just outside the Earth's orbit. So, in 0:13:59.000 --> 0:14:02.199 other words, if you were look top down, you would 0:14:02.280 --> 0:14:06.120 have a spacecraft that would be just inside of the 0:14:06.280 --> 0:14:09.880 Earth orbit moving at the same speed, or one just 0:14:09.960 --> 0:14:12.160 outside the Earth orbit moving at the same speed as 0:14:12.200 --> 0:14:14.920 the Earth around the Sun. And you might think, well, 0:14:14.920 --> 0:14:17.320 how is that possible? Because earlier you mentioned if you're 0:14:17.320 --> 0:14:21.120 closer in to the star, you move faster, and if 0:14:21.160 --> 0:14:23.120 you're further out from the star, you move slower. So 0:14:23.120 --> 0:14:26.280 how would a spacecraft keep up with the Earth. The 0:14:26.320 --> 0:14:30.640 answer is gravity. Earth's gravitational pull would be enough to 0:14:30.800 --> 0:14:35.240 hold the spacecraft in that orbit, that lagrange orbit, and 0:14:35.640 --> 0:14:38.120 you could do this. You might want to do this 0:14:38.160 --> 0:14:40.000 for lots of reasons. If it's on the inside of 0:14:40.000 --> 0:14:43.440 the Earth's orbit, you could do it to study the 0:14:44.640 --> 0:14:48.120 Sun as it faces Earth. If you did it outside 0:14:48.400 --> 0:14:50.920 the Earth's orbit, you could look away from the Earth 0:14:51.040 --> 0:14:53.600 out into the outer Solar System and not have the 0:14:53.600 --> 0:14:57.520 Earth in the way when you're studying those planets. There's 0:14:57.560 --> 0:15:00.520 also another one. L three Lagrange orbit is on the 0:15:00.560 --> 0:15:05.800 opposite side of the Sun from the Earth, essentially following 0:15:06.040 --> 0:15:09.080 more or less the same orbital path as the Earth. 0:15:09.440 --> 0:15:11.720 This is a great way to see the far side 0:15:11.880 --> 0:15:16.360 of the Sun while the Earth is in its normal location, 0:15:17.400 --> 0:15:20.560 So if you wanted to study the far side of 0:15:20.320 --> 0:15:23.960 the Sun you could do that and look for solar activity. 0:15:24.560 --> 0:15:27.120 Then there's L four and L five, which are sixty 0:15:27.160 --> 0:15:31.360 degrees separated either before or after the Earth's orbit. But 0:15:31.560 --> 0:15:34.040 enough about that. Those are the Lagrange orbits. The idea 0:15:34.120 --> 0:15:35.880 being that when you place something in there, it tends 0:15:35.880 --> 0:15:38.800 to be pretty stable. But NASA had determined that putting 0:15:38.800 --> 0:15:41.360 something into one of those orbits would be really expensive, 0:15:43.160 --> 0:15:46.680 so eventually they came to the conclusion that perhaps they 0:15:46.680 --> 0:15:49.840 would want to just put the Kepler telescope in an 0:15:49.960 --> 0:15:52.760 orbit around the Sun in its own orbit, not a 0:15:52.840 --> 0:15:57.480 lagrange orbit. Meanwhile, engineers started to experiment with charge coupled 0:15:57.600 --> 0:16:00.040 device sensors to see if they could be made to 0:16:00.000 --> 0:16:04.600 detect tiny changes in light, and lab experiments with CCDs 0:16:04.720 --> 0:16:06.840 proved that they were a pretty good candidate for this. 0:16:07.560 --> 0:16:10.960 So let's talk about CCDs for a second. They're designed 0:16:10.960 --> 0:16:14.480 to move an electrical charge, typically in a way that 0:16:14.560 --> 0:16:17.680 allows a device to convert the electrical charge into something else, 0:16:17.720 --> 0:16:22.640 like a digital value. And CCD image sensors are important 0:16:22.680 --> 0:16:26.880 in digital imaging, particularly for highly sensitive imaging, such as 0:16:26.920 --> 0:16:29.480 with very low levels of light. Now you can find 0:16:29.520 --> 0:16:33.840 digital cameras with CCDs, but many also use or rather 0:16:34.000 --> 0:16:38.280 instead they'll use active pixel sensors or the SMOs se 0:16:38.400 --> 0:16:43.000 moss CMOS sensors. And it used to be that there 0:16:43.080 --> 0:16:47.920 was a noticeable gap in quality that CCDs were demonstrably 0:16:48.240 --> 0:16:52.200 much higher quality than sea moss sensors. These days, that 0:16:52.280 --> 0:16:57.440 gap is much more narrow, it's not as blatant as 0:16:57.440 --> 0:17:00.800 it used to be, so we've seen the technology of 0:17:00.800 --> 0:17:02.920 one start to catch up to the technology of the other. 0:17:03.720 --> 0:17:07.400 Within the CCD you have millions of tiny light sensitive 0:17:07.480 --> 0:17:12.119 squares called photo sites, and each photo site corresponds to 0:17:12.160 --> 0:17:16.159 an individual pixel in the final image. It uses the 0:17:16.200 --> 0:17:21.560 photoelectric effect to turn photons into electrons. That's actually an oversimplification. 0:17:21.960 --> 0:17:25.640 It really uses photons to energize electrons push them into 0:17:25.760 --> 0:17:29.920 higher energy bands, and that is the key to how 0:17:30.040 --> 0:17:33.920 CCDs work. Essentially, photons raise the energy level of electrons 0:17:33.920 --> 0:17:37.440 from low energy valence bands to high energy conduction bands. 0:17:37.720 --> 0:17:41.320 And each photo site has a positively charged capacitor when 0:17:41.320 --> 0:17:45.320 the photon converts that electron when it adds that energy 0:17:45.359 --> 0:17:48.040 to an electron, the electron is then attracted to the 0:17:48.080 --> 0:17:52.080 positively charged capacitor and the number of photons that penetrated 0:17:52.119 --> 0:17:56.479 the CCD affects the voltage that this creates, and that 0:17:56.560 --> 0:18:00.360 voltage is then converted into a digital signal. The whole 0:18:00.440 --> 0:18:03.959 array is actually cooled through a series of heat pipes 0:18:04.160 --> 0:18:08.119 that run through an external radiator, so they're actually ratiing 0:18:08.200 --> 0:18:12.080 the heat directly out into space. So as this generates heat, 0:18:12.119 --> 0:18:14.600 they just vent that off into space and it keeps 0:18:14.720 --> 0:18:17.560 the whole thing cool enough for it to operate without 0:18:17.600 --> 0:18:22.359 overheating and causing any problems. Now, in nineteen ninety six, 0:18:22.880 --> 0:18:25.560 two years later. So remember this was first proposed in 0:18:25.640 --> 0:18:30.080 ninety two and rejected, ninety four, rejected, ninety six, proposed again, 0:18:30.840 --> 0:18:33.159 and at this point they started to make some changes. 0:18:33.200 --> 0:18:35.760 One of those was decided to put the telescope into 0:18:35.760 --> 0:18:38.840 a solar orbit rather than a lagrange orbit. It was 0:18:38.880 --> 0:18:42.320 also the point where they renamed the project Kepler, after 0:18:42.400 --> 0:18:46.760 the astronomer we talked about earlier. But this proposal was 0:18:46.840 --> 0:18:49.760 also rejected. This time is because no one at that 0:18:49.840 --> 0:18:54.000 point had proven that a telescope could simultaneously observe thousands 0:18:54.080 --> 0:18:56.920 of stars. One of the big selling points of the 0:18:56.960 --> 0:18:59.879 Kepler telescope is that has a very wide field of 0:19:00.200 --> 0:19:04.080 view and can keep an eye on one hundred thousand 0:19:04.160 --> 0:19:11.920 stars simultaneously. But NASA budget overseers were saying, no one's 0:19:11.960 --> 0:19:14.400 proved that you could do this yet, so researchers went 0:19:14.400 --> 0:19:17.120 to work on a prototype photometer to prove it could 0:19:17.200 --> 0:19:21.680 be done. In nineteen ninety seven, they had finished building 0:19:21.800 --> 0:19:25.040 that prototype photometer, and in nineteen ninety eight they demonstrated 0:19:25.240 --> 0:19:27.720 that it could observe six thousand stars in a single 0:19:27.760 --> 0:19:30.000 field of view and generate data that could then be 0:19:30.119 --> 0:19:33.080 analyzed the results of this project were published in a 0:19:33.080 --> 0:19:38.400 paper in nineteen ninety nine. So nineteen ninety nine, seven 0:19:38.480 --> 0:19:44.960 years after the initial proposal, it's proposed yet again, and 0:19:45.000 --> 0:19:49.920 it got rejected yet again. So why was it rejected 0:19:49.960 --> 0:19:53.520 this time, Well, it was rejected on the grounds that 0:19:53.520 --> 0:19:56.560 there was no evidence the photometer would be precise enough 0:19:56.600 --> 0:19:59.840 to find Earth sized planets that could also operate in 0:20:00.119 --> 0:20:04.600 orbit in the presence of noise. So now the argument was, 0:20:04.920 --> 0:20:08.280 all right, you've shown that it's precise enough to detect 0:20:08.680 --> 0:20:11.480 a planet, but maybe not an Earth sized one because 0:20:11.480 --> 0:20:14.159 those are particularly small. They're not the size of a 0:20:14.160 --> 0:20:18.639 gas giant, so we need to prove that, and we 0:20:18.720 --> 0:20:21.000 aren't sure that if you're in space, you will be 0:20:21.040 --> 0:20:25.400 able to differentiate a planet passing between Earth and its 0:20:25.560 --> 0:20:30.800 host star or just some random piece of space debris 0:20:30.880 --> 0:20:35.600 that happens to pass between a star and Earth. Until 0:20:35.600 --> 0:20:38.440 you can prove that, we're not giving you any monies. 0:20:39.280 --> 0:20:42.840 So the engineers built another test bed and they prove 0:20:42.920 --> 0:20:48.600 that the Kepler telescope could operate satisfactorily even within noise, 0:20:48.680 --> 0:20:53.639 that their analysis would be able to differentiate between false 0:20:53.720 --> 0:20:57.399 positives and the real thing. So two thousand rolls around 0:20:57.480 --> 0:21:00.280 and the Kepler gets proposed one more time, and this 0:21:00.400 --> 0:21:03.080 time it's selected as one of three proposals out of 0:21:03.119 --> 0:21:07.080 a total of twenty six to compete for NASA approval. 0:21:08.080 --> 0:21:10.480 So it then goes on to compete with these other 0:21:10.520 --> 0:21:13.679 two projects. And essentially this is the way NASA works. 0:21:13.840 --> 0:21:20.400 They have teams proposed different potential missions, and then they 0:21:20.440 --> 0:21:23.480 whittle that down to a group of finalists and then 0:21:23.560 --> 0:21:28.960 they say fight it out, convince us to fund your project. 0:21:29.800 --> 0:21:34.200 And sometimes only one project gets funded. And that was 0:21:34.240 --> 0:21:37.119 the case for Kepler, and in two thousand and one 0:21:37.160 --> 0:21:41.439 it won the right to be funded. It became Discovery 0:21:41.560 --> 0:21:46.080 Mission number ten. So the Kepler Telescope is a discovery 0:21:46.200 --> 0:21:50.000 spacecraft by that definition. The actual work on the mission 0:21:50.080 --> 0:21:52.840 began in two thousand and two, and that started with 0:21:53.040 --> 0:21:57.600 orders placed for the detectors for those CCDs, and the 0:21:57.600 --> 0:22:01.919 telescope was completed and lawnlaunched, and it was launched on 0:22:01.960 --> 0:22:05.919 March six, two thousand and nine, and went into space 0:22:06.000 --> 0:22:09.480 around its solar orbit. So here's some stats about the 0:22:09.560 --> 0:22:13.560 Kepler Telescope and the Kepler spacecraft. The diameter of the 0:22:13.560 --> 0:22:17.600 photometer is just shy of a meter. It's point ninety 0:22:17.680 --> 0:22:22.000 five meters in diameter, which is about three feet. The 0:22:22.000 --> 0:22:27.359 camera has a ninety five megapixel array. So your typical 0:22:27.400 --> 0:22:31.600 smartphone has an eight to maybe thirteen megapixel camera on it. 0:22:31.640 --> 0:22:35.399 This one is a ninety five megapixel camera, and it 0:22:35.440 --> 0:22:38.199 can continuously monitor the brightness of more than one hundred 0:22:38.200 --> 0:22:43.439 thousand stars simultaneously. The field of view is thirty three 0:22:43.480 --> 0:22:47.600 thousand times greater than that of the Hubble Space telescope, 0:22:47.640 --> 0:22:51.720 so it's looking at a pretty wide range of space. 0:22:52.480 --> 0:22:54.840 Keep in mind, the Milky Way Galaxy has one hundred 0:22:55.160 --> 0:22:58.680 billion stars in it, so one hundred thousand is nothing. 0:22:58.880 --> 0:23:03.360 It's it's a tiny little drop in an enormous bucket. 0:23:04.160 --> 0:23:06.840 Let's talk about the spacecraft though. The Kepler spacecraft is 0:23:06.880 --> 0:23:10.040 two point seven meters in diameter, that's about nine feet. 0:23:10.560 --> 0:23:13.360 It's four point seven meters tall, that's about fifteen point 0:23:13.440 --> 0:23:16.879 three feet, and it weighed one thousand and fifty two 0:23:16.960 --> 0:23:20.240 point four kilograms or two three hundred and twenty point 0:23:20.280 --> 0:23:23.560 one pounds at the time of launch. Why is it 0:23:24.320 --> 0:23:26.840 just the time of launch, Well, part of that weight 0:23:27.119 --> 0:23:30.879 was taken up by fuel hydrozene propellant, which it has 0:23:31.040 --> 0:23:34.840 used some of since it was launched, there was eleven 0:23:34.880 --> 0:23:39.560 point seven kilograms of fuel at that point, so that 0:23:39.640 --> 0:23:41.679 makes a difference. Also the fact that it's in space 0:23:42.320 --> 0:23:44.960 hard to weigh things. In space. You can talk about mass, 0:23:45.240 --> 0:23:50.960 but weight not as relevant. It generates electricity with one 0:23:51.040 --> 0:23:53.840 hundred and nine point eight square feet or about ten 0:23:53.880 --> 0:23:57.879 point two square meters of solar panels. Now those solar 0:23:57.880 --> 0:24:00.960 panels can provide one thousand and one one hundred watts 0:24:01.000 --> 0:24:04.960 of electrical current. The spacecraft also has a twenty amp 0:24:05.040 --> 0:24:08.840 hour lithium ion battery that's a rechargeable battery, so when 0:24:08.880 --> 0:24:13.800 it's generating excess electricity, it charges the battery and everything 0:24:13.880 --> 0:24:18.240 can continue to be powered. Once it launched, it became 0:24:18.320 --> 0:24:21.919 part of the Exoplanet Exploration Program Office, part of the 0:24:22.040 --> 0:24:26.280 Jet Propulsion Laboratory, so it's been shifted from one group 0:24:26.280 --> 0:24:29.399 in NASA to another one to actually manage the mission. 0:24:31.040 --> 0:24:33.520 So basically, the way the Kepler works, it has more 0:24:33.600 --> 0:24:35.720 than one hundred thousand stars in its view and it 0:24:35.760 --> 0:24:38.760 can detect these very tiny fluctuations in the light from 0:24:38.800 --> 0:24:43.520 those stars, and typically, up until recently, we just had 0:24:43.560 --> 0:24:46.400 to keep those stars under observation for a really long 0:24:46.480 --> 0:24:50.639 time to see if that fluctuation would repeat at regular intervals, 0:24:50.920 --> 0:24:54.000 and it wasn't just something passing between us and the star. 0:24:55.000 --> 0:24:58.720 And that was how we would go from a signal 0:24:58.840 --> 0:25:02.240 that was a potential planet to a verified planet. It 0:25:02.280 --> 0:25:05.400 also explains why, over the course of several years we 0:25:05.400 --> 0:25:08.680 were only able to verify nine hundred eighty four exoplanets, 0:25:08.720 --> 0:25:11.959 with a whole bunch of candidates that maybe are exoplanets 0:25:11.960 --> 0:25:14.280 but were not sure, so he can't call them that. 0:25:15.000 --> 0:25:18.119 But then you had this make tenth announcement of one thousand, 0:25:18.160 --> 0:25:21.960 two hundred eighty four exoplanets. So what changed? How could 0:25:22.000 --> 0:25:26.960 we potentially do that? They actually the researchers had analyzed 0:25:27.000 --> 0:25:31.440 four thousand, three hundred two potential signals these candidate planets, 0:25:32.160 --> 0:25:34.440 and out of those four thousand, three hundred two they 0:25:34.840 --> 0:25:38.560 decided that one two hundred eighty four should be verified 0:25:38.680 --> 0:25:41.639 as actual exoplanets because they had a greater than ninety 0:25:41.760 --> 0:25:44.879