1 00:00:10,280 --> 00:00:08,630 so when Mike and I are doing the warm up 2 00:00:12,049 --> 00:00:10,290 top for today anyone who do hear my name 3 00:00:17,000 --> 00:00:12,059 is Alissa I'm also one of the organizers 4 00:00:18,980 --> 00:00:17,010 for this conference I am slightly under 5 00:00:20,540 --> 00:00:18,990 prepared and I feel highly under 6 00:00:23,630 --> 00:00:20,550 qualified to be giving this warm-up talk 7 00:00:26,930 --> 00:00:23,640 but apparently I'm doing it anyway it is 8 00:00:29,240 --> 00:00:26,940 a very general and also a very 9 00:00:30,860 --> 00:00:29,250 abbreviated introduction into astronomy 10 00:00:32,799 --> 00:00:30,870 and planetary science just because we 11 00:00:36,170 --> 00:00:32,809 don't have enough time to do everything 12 00:00:38,090 --> 00:00:36,180 so I'm trying to cover on touch on some 13 00:00:39,410 --> 00:00:38,100 of the topics that will be discussed for 14 00:00:42,619 --> 00:00:39,420 this morning's talks so anything 15 00:00:46,099 --> 00:00:42,629 astronomy in planetary science based so 16 00:00:48,939 --> 00:00:46,109 I guess we'll just get started so 17 00:00:50,599 --> 00:00:48,949 introduction to planetary habitability 18 00:00:52,579 --> 00:00:50,609 habitability is one of the biggest 19 00:00:55,279 --> 00:00:52,589 things in my opinion in astrobiology 20 00:00:56,689 --> 00:00:55,289 right now because we're you know we have 21 00:00:58,219 --> 00:00:56,699 Kepler space telescope and lots of other 22 00:00:59,989 --> 00:00:58,229 things that are helping us to find these 23 00:01:02,000 --> 00:00:59,999 exoplanets so a big thing is how would 24 00:01:03,649 --> 00:01:02,010 we be able to tell whether or not these 25 00:01:06,289 --> 00:01:03,659 exoplanets that we're discovering if 26 00:01:08,120 --> 00:01:06,299 they're habitable or not there are a 27 00:01:10,400 --> 00:01:08,130 variety of characteristics that affect 28 00:01:12,410 --> 00:01:10,410 planetary habitability including 29 00:01:14,870 --> 00:01:12,420 composition of the exoplanet any 30 00:01:16,730 --> 00:01:14,880 atmosphere stellar radiation title 31 00:01:18,680 --> 00:01:16,740 evolution I'm not going to get to all of 32 00:01:20,600 --> 00:01:18,690 those but just so you know that they do 33 00:01:22,820 --> 00:01:20,610 exist and they are a factor in planetary 34 00:01:24,650 --> 00:01:22,830 habitability but so the first thing in 35 00:01:26,000 --> 00:01:24,660 exoplanets that I wanted to introduce is 36 00:01:28,190 --> 00:01:26,010 how we detect them how do we actually 37 00:01:29,420 --> 00:01:28,200 find these exoplanets and now that I'm 38 00:01:30,800 --> 00:01:29,430 involved in my talk I'd like to point 39 00:01:32,120 --> 00:01:30,810 out that you guys are welcome to get up 40 00:01:33,260 --> 00:01:32,130 and wander around during the time if you 41 00:01:34,580 --> 00:01:33,270 want to go get more coffee or more food 42 00:01:37,540 --> 00:01:34,590 it's supposed to be informal so you 43 00:01:41,090 --> 00:01:37,550 don't have to stay put sorry moving on 44 00:01:43,670 --> 00:01:41,100 okay two primary ways to detect 45 00:01:45,680 --> 00:01:43,680 exoplanets first way is called the 46 00:01:49,610 --> 00:01:45,690 radial velocity method or alternatively 47 00:01:53,630 --> 00:01:49,620 Doppler wobble how this works I need my 48 00:01:55,820 --> 00:01:53,640 hands that's okay when you have ok if 49 00:01:57,950 --> 00:01:55,830 this hand is the Sun and this is you 50 00:01:59,660 --> 00:01:57,960 know a planet or something when two 51 00:02:02,000 --> 00:01:59,670 objects are orbiting around each other 52 00:02:03,410 --> 00:02:02,010 you know the smaller body stays in orbit 53 00:02:06,440 --> 00:02:03,420 due to the gravitational tug of the 54 00:02:08,270 --> 00:02:06,450 larger body but in that same vein the 55 00:02:10,040 --> 00:02:08,280 smaller body will also exert a 56 00:02:11,690 --> 00:02:10,050 gravitational pull on the larger body it 57 00:02:14,230 --> 00:02:11,700 happens you know so the two things or 58 00:02:18,500 --> 00:02:14,240 orbit their common center of mass so 59 00:02:19,820 --> 00:02:18,510 it's an imperfect image because it's 60 00:02:22,160 --> 00:02:19,830 it's exaggerating 61 00:02:24,050 --> 00:02:22,170 evett ational poll all right people keep 62 00:02:27,050 --> 00:02:24,060 crossing in front that's right so in 63 00:02:28,490 --> 00:02:27,060 this case we have one son that's in the 64 00:02:30,620 --> 00:02:28,500 center and then an exoplanet orbiting 65 00:02:32,540 --> 00:02:30,630 the outside the point to take away from 66 00:02:35,630 --> 00:02:32,550 this image is that as the exoplanet 67 00:02:37,610 --> 00:02:35,640 orbits around the star there's a slight 68 00:02:44,810 --> 00:02:37,620 wobble a slight shift in the radial 69 00:02:48,080 --> 00:02:44,820 velocity of the Sun and you can you can 70 00:02:51,380 --> 00:02:48,090 measure the slight velocity wobble based 71 00:02:53,330 --> 00:02:51,390 on the red shifting of the color that we 72 00:02:55,340 --> 00:02:53,340 receive from the star so when a star is 73 00:02:57,470 --> 00:02:55,350 moving away from us the color will be 74 00:02:58,850 --> 00:02:57,480 slightly red shifted and when a star is 75 00:03:01,490 --> 00:02:58,860 moving towards us it will be slightly 76 00:03:03,380 --> 00:03:01,500 blue shifted so in this you know in this 77 00:03:05,150 --> 00:03:03,390 way we can look at a star and we watch 78 00:03:06,590 --> 00:03:05,160 over time and we see the light become 79 00:03:07,850 --> 00:03:06,600 red shifted and then blue shifted and 80 00:03:11,449 --> 00:03:07,860 then red shifted and then blue shifted 81 00:03:13,790 --> 00:03:11,459 and you can infer the presence of an 82 00:03:16,400 --> 00:03:13,800 exoplanet because there has to be some 83 00:03:20,360 --> 00:03:16,410 body that's orbiting that Sun that is 84 00:03:22,900 --> 00:03:20,370 causing the the shifting of the light so 85 00:03:25,699 --> 00:03:22,910 this is one way to detect exoplanets 86 00:03:29,020 --> 00:03:25,709 second way is using transit using 87 00:03:32,000 --> 00:03:29,030 transits sorry I keep combining hands 88 00:03:34,310 --> 00:03:32,010 transits are not quite as complicated as 89 00:03:36,410 --> 00:03:34,320 Doppler shift the whole point the big 90 00:03:39,470 --> 00:03:36,420 circle have a pointer the big circle in 91 00:03:41,000 --> 00:03:39,480 the background this is a star right when 92 00:03:42,830 --> 00:03:41,010 you are just looking at a star you 93 00:03:45,140 --> 00:03:42,840 measure some amount of light coming from 94 00:03:47,300 --> 00:03:45,150 the star which is what we see is this 95 00:03:49,340 --> 00:03:47,310 solid line right here but periodically 96 00:03:50,420 --> 00:03:49,350 you're going to have a plant or well you 97 00:03:52,490 --> 00:03:50,430 wouldn't know it's a planet there's 98 00:03:55,130 --> 00:03:52,500 something that passes in front of the 99 00:03:56,330 --> 00:03:55,140 star and causes you know it blocks some 100 00:03:58,250 --> 00:03:56,340 of the light that we receive from the 101 00:03:59,300 --> 00:03:58,260 star so this is this is just a dip in 102 00:04:01,009 --> 00:03:59,310 the light levels that we're observing 103 00:04:03,500 --> 00:04:01,019 because there's something obscuring the 104 00:04:05,090 --> 00:04:03,510 view of the star so we can actually we 105 00:04:08,479 --> 00:04:05,100 can't see this this is the part that we 106 00:04:10,820 --> 00:04:08,489 can't see very rough analogy if that 107 00:04:12,530 --> 00:04:10,830 doesn't make a lot of sense if you 108 00:04:14,240 --> 00:04:12,540 imagine the car at night if you're 109 00:04:16,219 --> 00:04:14,250 standing right up close next to the car 110 00:04:18,110 --> 00:04:16,229 you can see both the car headlight and 111 00:04:20,030 --> 00:04:18,120 any insects that are flying around the 112 00:04:21,229 --> 00:04:20,040 car headlight but if you turn around and 113 00:04:23,270 --> 00:04:21,239 walk away from the car and then look 114 00:04:25,520 --> 00:04:23,280 back you can still see the car headlight 115 00:04:27,830 --> 00:04:25,530 the Sun but you can no longer make out 116 00:04:29,270 --> 00:04:27,840 the individual insects it's just it's 117 00:04:30,590 --> 00:04:29,280 just because you're too far away and you 118 00:04:32,090 --> 00:04:30,600 can't see the size of the insects so 119 00:04:33,050 --> 00:04:32,100 it's the same thing with exoplanets and 120 00:04:35,360 --> 00:04:33,060 sons we 121 00:04:37,040 --> 00:04:35,370 can't actually see this but we can 122 00:04:39,200 --> 00:04:37,050 detect the change in the light levels 123 00:04:43,280 --> 00:04:39,210 when it when a planet transits in front 124 00:04:45,500 --> 00:04:43,290 in front of a star and just in terms of 125 00:04:48,140 --> 00:04:45,510 vocabulary you'll hear transit and 126 00:04:50,840 --> 00:04:48,150 occultation a transit is what happens 127 00:04:53,270 --> 00:04:50,850 when a planet passes in front of a star 128 00:04:54,980 --> 00:04:53,280 and the occultation is the same thing 129 00:04:57,740 --> 00:04:54,990 but when the planet passes behind the 130 00:04:58,970 --> 00:04:57,750 star so it's it means the same thing it 131 00:05:00,290 --> 00:04:58,980 means you're blocking out light it's 132 00:05:04,190 --> 00:05:00,300 just whether it's in front of or behind 133 00:05:06,560 --> 00:05:04,200 the star I had someone asked me 134 00:05:08,719 --> 00:05:06,570 yesterday about uncertainties so I just 135 00:05:12,020 --> 00:05:08,729 wanted to throw up a set of example data 136 00:05:14,180 --> 00:05:12,030 so you know what real data looks like so 137 00:05:15,350 --> 00:05:14,190 all of these these dots with their with 138 00:05:17,420 --> 00:05:15,360 their error bars on them this is an 139 00:05:18,890 --> 00:05:17,430 example set of data here you know our 140 00:05:20,719 --> 00:05:18,900 average amount of light that we're 141 00:05:22,670 --> 00:05:20,729 receiving from a star is here and then 142 00:05:24,950 --> 00:05:22,680 periodically you'll have this dip in the 143 00:05:27,290 --> 00:05:24,960 light level and just to see this dip 144 00:05:29,150 --> 00:05:27,300 once is not enough but if you observe 145 00:05:31,490 --> 00:05:29,160 this over time and you see that dip 146 00:05:34,550 --> 00:05:31,500 repeated numerous times again the 147 00:05:35,600 --> 00:05:34,560 implication is that there has to be a 148 00:05:37,490 --> 00:05:35,610 planet there there has to be something 149 00:05:41,779 --> 00:05:37,500 orbiting the star that is causing this 150 00:05:44,450 --> 00:05:41,789 dip in light levels which is Kepler 151 00:05:46,490 --> 00:05:44,460 everyone hope has heard of Kepler and 152 00:05:48,200 --> 00:05:46,500 you one who does planetary science is 153 00:05:51,380 --> 00:05:48,210 really really excited about Kepler space 154 00:05:52,880 --> 00:05:51,390 telescope this is a Space Telescope and 155 00:05:54,740 --> 00:05:52,890 not a ground telescope that means that 156 00:05:57,469 --> 00:05:54,750 it's in space and not on the ground it's 157 00:05:59,810 --> 00:05:57,479 the only distinction the benefit there 158 00:06:01,250 --> 00:05:59,820 are a variety of benefits for that an 159 00:06:02,420 --> 00:06:01,260 example being that if you're in space 160 00:06:04,790 --> 00:06:02,430 rather than on the ground you don't have 161 00:06:06,620 --> 00:06:04,800 to deal with them you know light like 162 00:06:08,840 --> 00:06:06,630 light to light pollution coming in and 163 00:06:12,310 --> 00:06:08,850 affecting the mirrors and stuff so this 164 00:06:15,860 --> 00:06:12,320 is just a artistic rendering of Kepler 165 00:06:17,570 --> 00:06:15,870 what do we have yeah Kepler the sole 166 00:06:19,640 --> 00:06:17,580 point of the kepler space telescope is 167 00:06:22,219 --> 00:06:19,650 to find exoplanets that's kind of its 168 00:06:24,469 --> 00:06:22,229 whole job which is why it's exciting at 169 00:06:26,900 --> 00:06:24,479 any one time it simultaneously looks at 170 00:06:28,550 --> 00:06:26,910 over 150,000 stars so it's not just 171 00:06:30,320 --> 00:06:28,560 looking at one little spot of light in 172 00:06:33,500 --> 00:06:30,330 finding planets it can do it for a wide 173 00:06:35,240 --> 00:06:33,510 variety of stars all at the same time it 174 00:06:36,620 --> 00:06:35,250 has that photometers the the thing that 175 00:06:39,050 --> 00:06:36,630 measures the light level and you see the 176 00:06:41,810 --> 00:06:39,060 dip in it that's the photometer Kepler 177 00:06:44,330 --> 00:06:41,820 was launched in 2009 anyone who's heard 178 00:06:45,620 --> 00:06:44,340 the news we sadly just lost a second 179 00:06:46,760 --> 00:06:45,630 wheel on Kepler which means we can't 180 00:06:48,710 --> 00:06:46,770 really steer it 181 00:06:49,999 --> 00:06:48,720 anymore so we can't actually aim it at 182 00:06:51,110 --> 00:06:50,009 one point in the sky we're not sure 183 00:06:54,680 --> 00:06:51,120 what's going to happen with Kepler but 184 00:06:56,540 --> 00:06:54,690 it's very sad um last numbers I was 185 00:07:00,200 --> 00:06:56,550 aware of that Kepler has discovered 186 00:07:02,659 --> 00:07:00,210 almost 3,000 candidate exoplanets and as 187 00:07:04,369 --> 00:07:02,669 of right now there's only 114 that have 188 00:07:06,409 --> 00:07:04,379 been confirmed as exoplanets but that's 189 00:07:08,600 --> 00:07:06,419 still a pretty impressive number now 190 00:07:12,110 --> 00:07:08,610 that we do know that there are real 191 00:07:13,760 --> 00:07:12,120 exoplanets orbiting distant stars and if 192 00:07:16,430 --> 00:07:13,770 you extrapolate the data from the part 193 00:07:19,070 --> 00:07:16,440 of the sky that we've looked at you know 194 00:07:20,779 --> 00:07:19,080 scientists other other scientists 195 00:07:22,969 --> 00:07:20,789 estimate that at about 17 billion 196 00:07:27,649 --> 00:07:22,979 earth-sized exoplanet in the Milky Way 197 00:07:29,809 --> 00:07:27,659 alone so impressive this is just an 198 00:07:32,270 --> 00:07:29,819 example set of data so these are the 114 199 00:07:34,010 --> 00:07:32,280 confirmed exoplanets that we have from 200 00:07:36,860 --> 00:07:34,020 Kepler we're looking at here this is 201 00:07:39,680 --> 00:07:36,870 planet mass on the y axis and semi major 202 00:07:41,839 --> 00:07:39,690 axis on the x axis semi-major axis is 203 00:07:45,409 --> 00:07:41,849 just orbital radius that's how far a 204 00:07:47,719 --> 00:07:45,419 planet orbits from its star also note 205 00:07:50,149 --> 00:07:47,729 this is on log scale so we are right 206 00:07:52,309 --> 00:07:50,159 here where it 1-1 where it's you know 207 00:07:55,850 --> 00:07:52,319 one earth mass and one astronomical unit 208 00:07:57,080 --> 00:07:55,860 from the Sun you can see two so they're 209 00:07:58,730 --> 00:07:57,090 rough groupings and I'm not going to get 210 00:08:00,050 --> 00:07:58,740 into the groupings what I am 211 00:08:01,100 --> 00:08:00,060 particularly interested in and I'm going 212 00:08:03,170 --> 00:08:01,110 to talk about in just a second are the 213 00:08:05,420 --> 00:08:03,180 super Earths which are in this range 214 00:08:09,469 --> 00:08:05,430 right here they're kind of this oval 215 00:08:10,879 --> 00:08:09,479 collection of planets and just to 216 00:08:13,610 --> 00:08:10,889 illustrate a point these are the hundred 217 00:08:16,100 --> 00:08:13,620 and fifty confirmed exoplanets these are 218 00:08:17,420 --> 00:08:16,110 the almost 3000 candidate exoplanets so 219 00:08:19,519 --> 00:08:17,430 they have not been confirmed yet but you 220 00:08:20,779 --> 00:08:19,529 can see they do follow the same trend so 221 00:08:22,390 --> 00:08:20,789 hopefully you know when we get enough 222 00:08:24,709 --> 00:08:22,400 data we can confirm more of those 223 00:08:28,820 --> 00:08:24,719 candidate planets as confirmed 224 00:08:30,529 --> 00:08:28,830 exoplanets so that was an introduction 225 00:08:31,969 --> 00:08:30,539 to detection and how we do that stuff I 226 00:08:34,399 --> 00:08:31,979 want to take just a minute and go into 227 00:08:37,870 --> 00:08:34,409 some theory behind super Earths because 228 00:08:40,639 --> 00:08:37,880 that's kind of my thing super Earths 229 00:08:42,469 --> 00:08:40,649 what is the super earth a super earth is 230 00:08:46,550 --> 00:08:42,479 a class of exoplanet with a mass between 231 00:08:48,110 --> 00:08:46,560 one and ten earth masses so we're at one 232 00:08:50,900 --> 00:08:48,120 astronomical unit the distance from the 233 00:08:53,660 --> 00:08:50,910 earth to the Sun is one AU super Earths 234 00:08:55,400 --> 00:08:53,670 are less than point to a you so they 235 00:08:58,189 --> 00:08:55,410 orbit very very closely to their parent 236 00:08:59,569 --> 00:08:58,199 stars they do have some a centricity and 237 00:09:00,260 --> 00:08:59,579 I'll talk about that in just a second 238 00:09:03,980 --> 00:09:00,270 that just means 239 00:09:05,480 --> 00:09:03,990 how how oval your orbit is if you're not 240 00:09:08,680 --> 00:09:05,490 traveling in a perfect circle around 241 00:09:11,240 --> 00:09:08,690 your star you're in an eccentric orbit 242 00:09:13,130 --> 00:09:11,250 super-earths are primarily terrestrial 243 00:09:14,540 --> 00:09:13,140 which is exciting when we come back to 244 00:09:18,410 --> 00:09:14,550 astrobiology because the assumption 245 00:09:20,750 --> 00:09:18,420 right now is that to find sorry to find 246 00:09:26,060 --> 00:09:20,760 a habitable planet it would have to be 247 00:09:29,360 --> 00:09:26,070 terrestrial like the earth all right 248 00:09:31,280 --> 00:09:29,370 it's too early to talk this much so 249 00:09:34,220 --> 00:09:31,290 primarily their terrestrial secondarily 250 00:09:35,600 --> 00:09:34,230 they are ocean worlds they have no solar 251 00:09:37,040 --> 00:09:35,610 system counterpart like I said you know 252 00:09:39,860 --> 00:09:37,050 they're up to ten times the size of the 253 00:09:41,870 --> 00:09:39,870 earth and they orbit even closer to our 254 00:09:44,300 --> 00:09:41,880 son then like we're mercury orbits 255 00:09:45,680 --> 00:09:44,310 roughly there's a variety of 256 00:09:46,820 --> 00:09:45,690 characteristics about these again I'm 257 00:09:47,990 --> 00:09:46,830 not going to have time to go into all of 258 00:09:49,820 --> 00:09:48,000 them but just so you know that they 259 00:09:52,070 --> 00:09:49,830 exist I'm going to talk briefly about 260 00:09:54,050 --> 00:09:52,080 the composition the interior of the 261 00:09:55,460 --> 00:09:54,060 super Earths any tectonic activity that 262 00:09:58,010 --> 00:09:55,470 goes on because that's a pretty key 263 00:10:00,290 --> 00:09:58,020 thing and also how atmosphere and how 264 00:10:04,070 --> 00:10:00,300 all those things affect out ability how 265 00:10:06,140 --> 00:10:04,080 are we on time okay we're okay so this 266 00:10:07,370 --> 00:10:06,150 just in case I lost anyone with a little 267 00:10:09,530 --> 00:10:07,380 bit more terminology for anyone who 268 00:10:11,150 --> 00:10:09,540 doesn't do planets in this case the 269 00:10:14,060 --> 00:10:11,160 yellow blob in the middle that's a son 270 00:10:16,370 --> 00:10:14,070 and the blue planet here is on a perfect 271 00:10:18,560 --> 00:10:16,380 circular orbit and in that case the 272 00:10:20,570 --> 00:10:18,570 eccentricity we say is zero it's just 273 00:10:22,160 --> 00:10:20,580 it's a perfect circle in the case with 274 00:10:24,230 --> 00:10:22,170 the red planet you kind of have this 275 00:10:26,570 --> 00:10:24,240 fried egg picture right here the fried 276 00:10:28,850 --> 00:10:26,580 egg image with with an oval orbit means 277 00:10:30,800 --> 00:10:28,860 that you have a centricity it the Easton 278 00:10:32,900 --> 00:10:30,810 tricity is not zero and again semi-major 279 00:10:37,090 --> 00:10:32,910 axis is just the orbital radius the 280 00:10:41,330 --> 00:10:40,370 so composition I'm trying to try it 281 00:10:43,760 --> 00:10:41,340 going to try to not make it too 282 00:10:45,710 --> 00:10:43,770 scientific when you model soup the 283 00:10:47,810 --> 00:10:45,720 interior of super Earths you have three 284 00:10:50,300 --> 00:10:47,820 different things you have an ice mass 285 00:10:53,180 --> 00:10:50,310 fraction a mantle mass fraction and 286 00:10:55,040 --> 00:10:53,190 decor mass fraction and you just model 287 00:10:58,580 --> 00:10:55,050 those three different homogeneous 288 00:11:00,350 --> 00:10:58,590 concentric shells the outer layer is all 289 00:11:02,720 --> 00:11:00,360 water it can be either liquid or frozen 290 00:11:04,910 --> 00:11:02,730 but it's a water outer shell you have a 291 00:11:06,770 --> 00:11:04,920 silikal in the middle and you have an 292 00:11:10,250 --> 00:11:06,780 inner core of either solid or liquid 293 00:11:12,470 --> 00:11:10,260 iron so these are these three basic 294 00:11:13,820 --> 00:11:12,480 assumptions about bulk composition for 295 00:11:14,150 --> 00:11:13,830 super Earths but given what i was 296 00:11:16,550 --> 00:11:14,160 talking 297 00:11:18,410 --> 00:11:16,560 with detection when you have radial 298 00:11:20,540 --> 00:11:18,420 velocity data when you can feel that 299 00:11:23,480 --> 00:11:20,550 Doppler wobble the Doppler wobble tells 300 00:11:25,519 --> 00:11:23,490 you the mass of an exoplanet and with 301 00:11:27,619 --> 00:11:25,529 the transit transit data that gives you 302 00:11:28,819 --> 00:11:27,629 the radius so if you have basic 303 00:11:30,619 --> 00:11:28,829 information about the mass and the 304 00:11:31,850 --> 00:11:30,629 radius of a planet you can infer 305 00:11:33,559 --> 00:11:31,860 something about its bulk composition 306 00:11:38,179 --> 00:11:33,569 which is what leads us to this theory 307 00:11:39,410 --> 00:11:38,189 for super earth interiors this is the 308 00:11:42,110 --> 00:11:39,420 most scientific slide I'm going to show 309 00:11:43,819 --> 00:11:42,120 but don't be too frightened again it's 310 00:11:45,710 --> 00:11:43,829 just those three mass fractions so we 311 00:11:47,470 --> 00:11:45,720 have ice mantle and core mass fractions 312 00:11:51,050 --> 00:11:47,480 eat this is called a ternary diagram 313 00:11:52,819 --> 00:11:51,060 each of these different sides is just 314 00:11:56,420 --> 00:11:52,829 measures a different fractional amount 315 00:11:57,980 --> 00:11:56,430 of the ice the mantle and the core so 316 00:12:00,439 --> 00:11:57,990 the best example because we were just 317 00:12:01,970 --> 00:12:00,449 saying you know to to be habitable we're 318 00:12:03,350 --> 00:12:01,980 assuming that an exoplanet is going to 319 00:12:05,300 --> 00:12:03,360 have to be terrestrial there has to be 320 00:12:06,710 --> 00:12:05,310 you know something to stand on like we 321 00:12:10,040 --> 00:12:06,720 can't stand on a Jupiter so that would 322 00:12:13,220 --> 00:12:10,050 be pointless so in this case water is 323 00:12:15,110 --> 00:12:13,230 measured here it's this anyway hold on 324 00:12:17,389 --> 00:12:15,120 so right here this is when water is 100 325 00:12:19,160 --> 00:12:17,399 and this side is when water is zero so 326 00:12:21,110 --> 00:12:19,170 we call this side the terrestrial side 327 00:12:24,319 --> 00:12:21,120 there's no significant water presence on 328 00:12:26,329 --> 00:12:24,329 a planet and the whole point of a 329 00:12:28,129 --> 00:12:26,339 ternary diagram is because it's a grid 330 00:12:30,530 --> 00:12:28,139 representation of the relationship 331 00:12:32,090 --> 00:12:30,540 between the water the mantle in the core 332 00:12:34,370 --> 00:12:32,100 mass fractions so we can actually throw 333 00:12:36,110 --> 00:12:34,380 some some science and some theory and 334 00:12:38,569 --> 00:12:36,120 some other stuff in here and get a 335 00:12:40,340 --> 00:12:38,579 working equation for the relationship 336 00:12:42,889 --> 00:12:40,350 between these three mass fractions when 337 00:12:45,079 --> 00:12:42,899 you model super Earths so to be 338 00:12:46,970 --> 00:12:45,089 habitable right now we're looking at 339 00:12:57,660 --> 00:12:46,980 anything that falls on the terrestrial 340 00:13:03,150 --> 00:13:01,230 um very briefly plate tectonics for 341 00:13:04,530 --> 00:13:03,160 anyone who is unfamiliar I know jess is 342 00:13:05,490 --> 00:13:04,540 doing the Geo talk tomorrow so I'm not 343 00:13:07,770 --> 00:13:05,500 going to spend a lot of time on this 344 00:13:09,180 --> 00:13:07,780 there are two main ways to transport 345 00:13:10,590 --> 00:13:09,190 heat and we have to transport heat in an 346 00:13:13,050 --> 00:13:10,600 exoplanet you have conduction and 347 00:13:14,580 --> 00:13:13,060 convection rock is a really sucky 348 00:13:16,530 --> 00:13:14,590 conductor so we're not going to work 349 00:13:19,170 --> 00:13:16,540 with conduction there are two main ways 350 00:13:22,710 --> 00:13:19,180 of having convective cycles in a planet 351 00:13:26,910 --> 00:13:22,720 we have either stagnant tectonics or I'm 352 00:13:29,130 --> 00:13:26,920 sorry stagnant lid stuff or actual plate 353 00:13:31,440 --> 00:13:29,140 tectonics like on earth so stagnant lid 354 00:13:33,720 --> 00:13:31,450 is when you have no plate tectonic 355 00:13:35,670 --> 00:13:33,730 activity it's just an outer crust of a 356 00:13:38,100 --> 00:13:35,680 planet that has cooled off more than the 357 00:13:40,140 --> 00:13:38,110 interior so the heat burst its way 358 00:13:41,640 --> 00:13:40,150 through the crust like these little like 359 00:13:44,640 --> 00:13:41,650 all the volcanoes that are on Io that's 360 00:13:46,380 --> 00:13:44,650 an example of stagnant lid as opposed to 361 00:13:48,960 --> 00:13:46,390 something like earth which does have 362 00:13:50,040 --> 00:13:48,970 plate tectonics and in that case this is 363 00:13:51,690 --> 00:13:50,050 this image here so you have these 364 00:13:53,700 --> 00:13:51,700 convection cells that are carrying the 365 00:13:55,350 --> 00:13:53,710 heat material is created if the 366 00:13:56,940 --> 00:13:55,360 mid-ocean ridges here and then the 367 00:13:59,940 --> 00:13:56,950 plates slide apart and then they're 368 00:14:02,280 --> 00:13:59,950 recycled down in subduction zones so 369 00:14:04,140 --> 00:14:02,290 there these are the two big arguments 370 00:14:06,890 --> 00:14:04,150 and theories for for which super-earth 371 00:14:10,400 --> 00:14:06,900 do the arguments being that super Earths 372 00:14:12,930 --> 00:14:10,410 because there's so much more massive 373 00:14:13,860 --> 00:14:12,940 their their gravity has increased which 374 00:14:16,140 --> 00:14:13,870 is going to cause an increase in 375 00:14:17,400 --> 00:14:16,150 pressure and this these people say that 376 00:14:19,170 --> 00:14:17,410 the pressure is going to be so great 377 00:14:21,030 --> 00:14:19,180 that it's going to actually cause fault 378 00:14:22,500 --> 00:14:21,040 blocking and the plates are not going to 379 00:14:24,750 --> 00:14:22,510 be able to deform at all so you're going 380 00:14:26,130 --> 00:14:24,760 to have a stagnant lid system the other 381 00:14:28,410 --> 00:14:26,140 side of the argument say that the 382 00:14:29,790 --> 00:14:28,420 greater the increased mass of the super 383 00:14:31,650 --> 00:14:29,800 Earths is going to cause an increase in 384 00:14:33,420 --> 00:14:31,660 stress and when you have an increase in 385 00:14:35,760 --> 00:14:33,430 stress the plates will be more easily 386 00:14:37,470 --> 00:14:35,770 deformed so we you know we haven't 387 00:14:38,400 --> 00:14:37,480 actually confirmed this one way or the 388 00:14:42,720 --> 00:14:38,410 other but just so you know there are 389 00:14:44,190 --> 00:14:42,730 arguments out there basic introduction 390 00:14:46,380 --> 00:14:44,200 to atmosphere I do not work in 391 00:14:47,550 --> 00:14:46,390 atmospheres so again under qualified to 392 00:14:52,080 --> 00:14:47,560 give this talk we have a couple people 393 00:14:53,430 --> 00:14:52,090 doing atmospheric things the point I 394 00:14:56,460 --> 00:14:53,440 want just wanted to make without being 395 00:14:59,220 --> 00:14:56,470 too scientific is that we can measure 396 00:15:01,890 --> 00:14:59,230 the we can detect the atmospheres of 397 00:15:03,690 --> 00:15:01,900 some of these exoplanets and if we find 398 00:15:05,910 --> 00:15:03,700 things in the atmosphere like carbon 399 00:15:07,320 --> 00:15:05,920 dioxide or water vapor you know some 400 00:15:08,760 --> 00:15:07,330 other things those are what we call bio 401 00:15:10,710 --> 00:15:08,770 signatures and they indicate the 402 00:15:11,519 --> 00:15:10,720 presence of life on a planet so for 403 00:15:14,610 --> 00:15:11,529 example something like 404 00:15:16,739 --> 00:15:14,620 oxygen oxygen is unstable on its own so 405 00:15:18,300 --> 00:15:16,749 when we have oxygen in the atmosphere on 406 00:15:20,300 --> 00:15:18,310 earth we know oxygen is only there 407 00:15:22,619 --> 00:15:20,310 because there's life on this planet so 408 00:15:24,869 --> 00:15:22,629 kind of a rough assumption but we'll go 409 00:15:27,540 --> 00:15:24,879 with it if we found something like that 410 00:15:29,460 --> 00:15:27,550 on a you know in an exoplanet atmosphere 411 00:15:30,780 --> 00:15:29,470 it would not necessarily guarantee the 412 00:15:32,910 --> 00:15:30,790 presence of life but it would be like 413 00:15:36,269 --> 00:15:32,920 hey that's something to look at because 414 00:15:38,249 --> 00:15:36,279 there's some bio signature there and how 415 00:15:40,160 --> 00:15:38,259 that happens is something like this so 416 00:15:43,139 --> 00:15:40,170 this is again so here you have oh god 417 00:15:45,119 --> 00:15:43,149 you have sorry here you have the transit 418 00:15:47,790 --> 00:15:45,129 in front in the occupation in back and 419 00:15:50,460 --> 00:15:47,800 when the planet passes in front you take 420 00:15:52,470 --> 00:15:50,470 an image of the star by itself and you 421 00:15:54,900 --> 00:15:52,480 take an image of the star with the 422 00:15:56,069 --> 00:15:54,910 planet in front and you do I don't know 423 00:15:57,420 --> 00:15:56,079 what's called it's like a negative you 424 00:15:59,489 --> 00:15:57,430 take the difference of the two images 425 00:16:01,679 --> 00:15:59,499 and what you're left with like if you 426 00:16:03,360 --> 00:16:01,689 you know if you subtract I don't know 427 00:16:04,949 --> 00:16:03,370 how to explain this cuz I don't do it if 428 00:16:06,329 --> 00:16:04,959 you take an image of just the star and 429 00:16:08,100 --> 00:16:06,339 then an image of the star and the planet 430 00:16:09,210 --> 00:16:08,110 if you subtract them you're left with 431 00:16:12,780 --> 00:16:09,220 the image of the planet or something 432 00:16:14,670 --> 00:16:12,790 like that and you can magically you know 433 00:16:16,079 --> 00:16:14,680 you can see this little blue shell you 434 00:16:17,699 --> 00:16:16,089 see the atmosphere and you can get a 435 00:16:20,069 --> 00:16:17,709 spectrum and when you have a spectrum 436 00:16:22,139 --> 00:16:20,079 you can infer based on where the peaks 437 00:16:24,150 --> 00:16:22,149 are what the the chemical makeup is of 438 00:16:30,689 --> 00:16:24,160 that atmosphere so it's possible was my 439 00:16:32,910 --> 00:16:30,699 point you can do that habitability short 440 00:16:35,579 --> 00:16:32,920 thing for habitability again earth is 441 00:16:37,889 --> 00:16:35,589 currently the only planet that we know 442 00:16:39,780 --> 00:16:37,899 to be inhabited and because of that fact 443 00:16:41,429 --> 00:16:39,790 it's kind of the only thing that we're 444 00:16:43,230 --> 00:16:41,439 left with when we talk about habitable 445 00:16:44,460 --> 00:16:43,240 zones and what it means to be a 446 00:16:46,590 --> 00:16:44,470 habitable planet just because it's the 447 00:16:49,189 --> 00:16:46,600 only thing we know so we define 448 00:16:51,420 --> 00:16:49,199 something called a habitable zone a 449 00:16:54,540 --> 00:16:51,430 habitable zone is the distance from a 450 00:16:57,389 --> 00:16:54,550 star for which a planet can support 451 00:16:58,499 --> 00:16:57,399 liquid water on its surface so you're 452 00:17:00,360 --> 00:16:58,509 going to have an inner edge in an outer 453 00:17:02,369 --> 00:17:00,370 edge of the habitable zone if you're in 454 00:17:04,380 --> 00:17:02,379 this nice band going around your star if 455 00:17:05,880 --> 00:17:04,390 you're on the inner edge of the 456 00:17:07,439 --> 00:17:05,890 habitable zone if you're too close to 457 00:17:08,730 --> 00:17:07,449 the star you're going to get a runaway 458 00:17:09,960 --> 00:17:08,740 greenhouse effect because everything's 459 00:17:11,789 --> 00:17:09,970 going to be evaporated which is kind of 460 00:17:13,439 --> 00:17:11,799 what we see on Venus if you're on the 461 00:17:15,090 --> 00:17:13,449 outer edge of the habitable zone you're 462 00:17:16,710 --> 00:17:15,100 too far away from the star and 463 00:17:17,429 --> 00:17:16,720 everything's going to get too cold and 464 00:17:19,260 --> 00:17:17,439 you're going to have a runaway 465 00:17:21,779 --> 00:17:19,270 glaciation effect everything's going to 466 00:17:24,569 --> 00:17:21,789 freeze which is not really what we see 467 00:17:27,189 --> 00:17:24,579 on Mars but work with me here 468 00:17:29,289 --> 00:17:27,199 call this the Goldilocks zone Goldilocks 469 00:17:32,799 --> 00:17:29,299 principle too hot too cold right in the 470 00:17:35,140 --> 00:17:32,809 middle I like this one just because it 471 00:17:36,669 --> 00:17:35,150 this image just because it kind of shows 472 00:17:39,549 --> 00:17:36,679 you what I mean with the whole habitable 473 00:17:41,289 --> 00:17:39,559 zone thing so here we have a our Sun on 474 00:17:43,510 --> 00:17:41,299 the top and these are our planets going 475 00:17:45,909 --> 00:17:43,520 across the top line here you see mercury 476 00:17:47,710 --> 00:17:45,919 mercury is very very far within the 477 00:17:49,240 --> 00:17:47,720 habitable zone sorry the blue band is 478 00:17:51,340 --> 00:17:49,250 our habitable zone Mercury's not 479 00:17:52,600 --> 00:17:51,350 habitable all here's Venus it's kind of 480 00:17:53,919 --> 00:17:52,610 on the inner edge of the habitable zone 481 00:17:56,140 --> 00:17:53,929 it has that runaway greenhouse effect 482 00:17:59,890 --> 00:17:56,150 here's the earth right in the middle of 483 00:18:02,590 --> 00:17:59,900 this blue habitable zone we exist happy 484 00:18:04,240 --> 00:18:02,600 us and here's Mars and again it's not an 485 00:18:07,270 --> 00:18:04,250 exact science this image it's just kind 486 00:18:08,529 --> 00:18:07,280 of illustrative so we have Mars that's 487 00:18:11,169 --> 00:18:08,539 close to the outer edge of the habitable 488 00:18:14,350 --> 00:18:11,179 zone and we do have someone talking 489 00:18:17,590 --> 00:18:14,360 about em Dorf today I believe Gliese 581 490 00:18:20,440 --> 00:18:17,600 is an m-dwarf yes good Gliese 581 is an 491 00:18:21,610 --> 00:18:20,450 m-dwarf excellent and Gliese 581 has a 492 00:18:25,899 --> 00:18:21,620 whole bunch of planets which is really 493 00:18:27,549 --> 00:18:25,909 exciting G the planet Gliese 581g is 494 00:18:29,380 --> 00:18:27,559 right in the middle of its habitable 495 00:18:32,010 --> 00:18:29,390 zone too sad part about Gliese 581g s 496 00:18:35,440 --> 00:18:32,020 that we think it doesn't actually exist 497 00:18:37,779 --> 00:18:35,450 but ignoring Gliese 581g let's look at 498 00:18:39,610 --> 00:18:37,789 Gliese 581d which is still at least kind 499 00:18:41,560 --> 00:18:39,620 of sort of borderline in the habitable 500 00:18:43,480 --> 00:18:41,570 zone so that just means that look we 501 00:18:45,190 --> 00:18:43,490 found an exoplanet and it's kind of sort 502 00:18:49,360 --> 00:18:45,200 of almost in the habitable zone so maybe 503 00:18:51,549 --> 00:18:49,370 there could be life there type stuff the 504 00:18:53,649 --> 00:18:51,559 other thing to note all of this talk 505 00:18:55,090 --> 00:18:53,659 about habitable zone is based solely on 506 00:18:56,230 --> 00:18:55,100 the assumption of having liquid water 507 00:18:58,330 --> 00:18:56,240 present on the surface of the planet 508 00:19:00,190 --> 00:18:58,340 there are lots of other characteristics 509 00:19:01,750 --> 00:19:00,200 that come into play when you really want 510 00:19:06,130 --> 00:19:01,760 to consider whether or not the planet is 511 00:19:07,750 --> 00:19:06,140 habitable for example tidal locking this 512 00:19:15,220 --> 00:19:07,760 in no way takes into account tidal 513 00:19:18,190 --> 00:19:15,230 locking so tidal locking is when two 514 00:19:20,770 --> 00:19:18,200 orbiting bodies show the same face to 515 00:19:21,850 --> 00:19:20,780 each other all the time so I'm easiest 516 00:19:26,560 --> 00:19:21,860 analog again would be like the 517 00:19:28,419 --> 00:19:26,570 earth-moon system ah sorry um the moon 518 00:19:30,460 --> 00:19:28,429 is tidally locked to the earth which is 519 00:19:31,510 --> 00:19:30,470 why we we always see the same face of 520 00:19:36,580 --> 00:19:31,520 the moon the moon does not seem to 521 00:19:43,090 --> 00:19:36,590 rotate but not explaining that very well 522 00:19:45,730 --> 00:19:43,100 if we had two things like this that 523 00:19:47,200 --> 00:19:45,740 orbit like this at each other they are 524 00:19:49,690 --> 00:19:47,210 tightly locked because you always see 525 00:19:54,190 --> 00:19:49,700 the same face that's my point those were 526 00:19:55,960 --> 00:19:54,200 moons um sorry so yes tightly locked 527 00:19:58,330 --> 00:19:55,970 moon is tidally locked to the earth 528 00:20:00,810 --> 00:19:58,340 which is just another another factor I 529 00:20:03,010 --> 00:20:00,820 don't have an image of that sorry 530 00:20:04,120 --> 00:20:03,020 exomoons I just wanted to touch on 531 00:20:06,010 --> 00:20:04,130 briefly I think we have a couple talks 532 00:20:07,570 --> 00:20:06,020 about excellence as well oh and a note 533 00:20:09,430 --> 00:20:07,580 that i forgot to put a layer the 534 00:20:11,710 --> 00:20:09,440 habitable zone does shrink when you 535 00:20:15,760 --> 00:20:11,720 consider smaller stars this is on a log 536 00:20:17,320 --> 00:20:15,770 scale so back back here the habitable 537 00:20:20,260 --> 00:20:17,330 zone is actually wider than it is up 538 00:20:22,810 --> 00:20:20,270 here when you have a smaller star that 539 00:20:23,980 --> 00:20:22,820 is you know less there's less heat and 540 00:20:25,720 --> 00:20:23,990 less energy and stuff coming off of 541 00:20:28,299 --> 00:20:25,730 something like an M Dorf so the 542 00:20:30,700 --> 00:20:28,309 habitable zone both moves inward closer 543 00:20:32,529 --> 00:20:30,710 to the star and also becomes narrower so 544 00:20:36,039 --> 00:20:32,539 it's a narrower band of habitable zone 545 00:20:38,710 --> 00:20:36,049 pneus moons I just wanted to mention 546 00:20:40,480 --> 00:20:38,720 real quick like an exoplanet so an 547 00:20:42,519 --> 00:20:40,490 exoplanet is an extrasolar planet and 548 00:20:44,580 --> 00:20:42,529 EXO moon is an extrasolar moon it's just 549 00:20:46,840 --> 00:20:44,590 a moon that orbits an extrasolar planet 550 00:20:48,340 --> 00:20:46,850 if they exist it would be really really 551 00:20:50,409 --> 00:20:48,350 nice if we could find them to be roughly 552 00:20:52,060 --> 00:20:50,419 earth-sized because there is you know 553 00:20:55,330 --> 00:20:52,070 possibility to have a habitable exomoons 554 00:20:57,549 --> 00:20:55,340 besides just a habitable exoplanet and 555 00:20:59,590 --> 00:20:57,559 the the upside of looking at exomoons 556 00:21:03,070 --> 00:20:59,600 this time is is this thing's too long 557 00:21:04,450 --> 00:21:03,080 good side of looking at exomoons this 558 00:21:06,370 --> 00:21:04,460 time is because they're gonna be 559 00:21:08,980 --> 00:21:06,380 hopefully a lot more numerous than the 560 00:21:10,510 --> 00:21:08,990 exoplanets if you consider planets that 561 00:21:14,139 --> 00:21:10,520 are the size of Jupiter and Saturn right 562 00:21:15,279 --> 00:21:14,149 now they have a whole lot of moons so 563 00:21:16,750 --> 00:21:15,289 we're hoping that if we can find these 564 00:21:18,090 --> 00:21:16,760 huge super Earths that are really really 565 00:21:21,639 --> 00:21:18,100 large maybe they would have a similar 566 00:21:24,430 --> 00:21:21,649 increase and you know what am I think if 567 00:21:27,700 --> 00:21:24,440 you have 100 exoplanets and each one has 568 00:21:29,680 --> 00:21:27,710 ten moons even you've already increased 569 00:21:31,299 --> 00:21:29,690 the number of potentially habitable 570 00:21:34,750 --> 00:21:31,309 bodies so we're looking at exomoons as 571 00:21:38,320 --> 00:21:34,760 well this is just an image from Renee 572 00:21:40,899 --> 00:21:38,330 Heller as an example XO moon system so 573 00:21:43,840 --> 00:21:40,909 here we have a hypothetical earth-sized 574 00:21:45,399 --> 00:21:43,850 moon that is orbiting this orange 575 00:21:47,980 --> 00:21:45,409 exoplanet in the background and there 576 00:21:49,920 --> 00:21:47,990 its star is it star in the background so 577 00:21:54,010 --> 00:21:49,930 just an example system 578 00:21:56,410 --> 00:21:54,020 um I also wanted to mention Triton this 579 00:21:57,940 --> 00:21:56,420 x11 stuff I'm not going to do a lot 580 00:21:59,920 --> 00:21:57,950 about the capturing but just so you know 581 00:22:02,020 --> 00:21:59,930 Triton is one of the coolest moons is 582 00:22:04,000 --> 00:22:02,030 our system it is a moon of Neptune and 583 00:22:06,190 --> 00:22:04,010 we think it might be captured because it 584 00:22:08,680 --> 00:22:06,200 actually travels I don't know what the 585 00:22:10,270 --> 00:22:08,690 word is it Rhett visit retrograde thank 586 00:22:11,800 --> 00:22:10,280 you it travels backwards like all the 587 00:22:15,070 --> 00:22:11,810 other moons are going this way Triton 588 00:22:17,230 --> 00:22:15,080 swimming upstream so trite in school and 589 00:22:19,360 --> 00:22:17,240 it has it has an atmosphere and it has 590 00:22:21,130 --> 00:22:19,370 some nitrogen sublimation stuff going on 591 00:22:25,270 --> 00:22:21,140 so it's cool someone's talking about 592 00:22:27,490 --> 00:22:25,280 Triton there it is good so that's mostly 593 00:22:29,170 --> 00:22:27,500 the end for me what was the point the 594 00:22:32,050 --> 00:22:29,180 point was that there are a lot of 595 00:22:33,280 --> 00:22:32,060 factors that that you have to consider 596 00:22:35,320 --> 00:22:33,290 when you're talking about planetary 597 00:22:38,230 --> 00:22:35,330 habitability especially with this new 598 00:22:39,250 --> 00:22:38,240 science of exoplanets super Earths are 599 00:22:41,980 --> 00:22:39,260 going to be the big thing in XO 600 00:22:45,150 --> 00:22:41,990 planetary science went with related with 601 00:22:47,710 --> 00:22:45,160 relation to habitability in astrobiology 602 00:22:49,990 --> 00:22:47,720 exomoons are really a new thing so 603 00:22:52,450 --> 00:22:50,000 exoplanets started relatively recently 604 00:22:55,360 --> 00:22:52,460 moons or even really really more 605 00:22:56,740 --> 00:22:55,370 recently good job the largest moon in 606 00:22:58,900 --> 00:22:56,750 our system is Ganymede which is still 607 00:23:01,270 --> 00:22:58,910 only a quarter of a percent Earth's size 608 00:23:02,740 --> 00:23:01,280 thanks to Kepler we have a whole lot of 609 00:23:04,780 --> 00:23:02,750 planets that we're discovering and we 610 00:23:06,400 --> 00:23:04,790 have all these great ways to detect 611 00:23:08,860 --> 00:23:06,410 exoplanets right now so we have dr. 612 00:23:11,770 --> 00:23:08,870 wobble we have transit data all this 613 00:23:13,630 --> 00:23:11,780 sort of stuff and hopefully science will 614 00:23:17,410 --> 00:23:13,640 keep going and we will eventually find a 615 00:23:18,940 --> 00:23:17,420 habitable exoplanet or eczema um and if 616 00:23:21,190 --> 00:23:18,950 we have just a couple minutes I can do 617 00:23:22,620 --> 00:23:21,200 questions otherwise we will carry on to 618 00:23:25,810 --> 00:23:22,630 Mike who is going to introduce the 619 00:23:27,490 --> 00:23:25,820 second half of today's talks but I think 620 00:23:28,990 --> 00:23:27,500 we have I have like three minutes if 621 00:23:30,400 --> 00:23:29,000 anyone has a quick question before Mike