1 00:00:09,209 --> 00:00:06,680 [Music] 2 00:00:10,500 --> 00:00:09,219 thank you very much thank you very much 3 00:00:13,260 --> 00:00:10,510 for the organizers for putting together 4 00:00:14,640 --> 00:00:13,270 this very interesting program and for 5 00:00:15,990 --> 00:00:14,650 giving me the opportunity to tell you a 6 00:00:19,109 --> 00:00:16,000 little bit about some of the research 7 00:00:21,599 --> 00:00:19,119 we've been doing in my group I had 8 00:00:25,290 --> 00:00:21,609 submitted a much longer title more 9 00:00:27,150 --> 00:00:25,300 detailed maybe more complicated and when 10 00:00:28,679 --> 00:00:27,160 I looked at the program I found it 11 00:00:30,599 --> 00:00:28,689 shortened to this and I thought just 12 00:00:31,679 --> 00:00:30,609 like you don't argue with an editor of 13 00:00:33,330 --> 00:00:31,689 nature when they're willing to accept 14 00:00:35,700 --> 00:00:33,340 your paper and want to change your title 15 00:00:39,090 --> 00:00:35,710 I thought I'm not gonna argue with the 16 00:00:41,310 --> 00:00:39,100 organizers and basically this is my talk 17 00:00:46,020 --> 00:00:41,320 summarized and in a smaller number of 18 00:00:48,420 --> 00:00:46,030 words yes I will tell you about some 19 00:00:50,700 --> 00:00:48,430 work in which we discovered that you can 20 00:00:52,920 --> 00:00:50,710 sort of reproduce the observed radius 21 00:00:55,320 --> 00:00:52,930 valley that separates the super earth 22 00:01:00,800 --> 00:00:55,330 and the subducting population just from 23 00:01:04,079 --> 00:01:00,810 a plan information point of view so 24 00:01:05,310 --> 00:01:04,089 thanks to the - very nice previous talks 25 00:01:07,560 --> 00:01:05,320 I don't really have to do much 26 00:01:09,060 --> 00:01:07,570 introduction so the population that I'll 27 00:01:11,310 --> 00:01:09,070 be talking about are these super Earths 28 00:01:13,140 --> 00:01:11,320 and sub Neptune's these planets that as 29 00:01:15,240 --> 00:01:13,150 up to date are the most common planets 30 00:01:16,860 --> 00:01:15,250 that we have been discovered and they're 31 00:01:20,100 --> 00:01:16,870 almost everywhere as I'm sure you know 32 00:01:22,260 --> 00:01:20,110 and they're intriguing they were 33 00:01:24,000 --> 00:01:22,270 entering for me for a long time somebody 34 00:01:27,210 --> 00:01:24,010 who's been studying transformation for 35 00:01:28,590 --> 00:01:27,220 many years because these planets are so 36 00:01:30,930 --> 00:01:28,600 different for what we have in our solar 37 00:01:34,520 --> 00:01:30,940 system right typically they are in 38 00:01:37,020 --> 00:01:34,530 between the size of Earth and Neptune on 39 00:01:39,540 --> 00:01:37,030 orbital periods that are built in the 40 00:01:41,550 --> 00:01:39,550 orbit of mercury um in addition we know 41 00:01:42,870 --> 00:01:41,560 for several of those planets that the 42 00:01:44,820 --> 00:01:42,880 radii are so large 43 00:01:47,100 --> 00:01:44,830 given their masses that they must have 44 00:01:49,440 --> 00:01:47,110 about a few percent of the total mass 45 00:01:52,050 --> 00:01:49,450 budget is sort of a hydrogen helium 46 00:01:53,520 --> 00:01:52,060 envelope and so we were just curious to 47 00:01:56,280 --> 00:01:53,530 see whether we can understand the 48 00:01:58,560 --> 00:01:56,290 formation of these planets by sort of 49 00:02:01,080 --> 00:01:58,570 self consistently treating the gas 50 00:02:05,580 --> 00:02:01,090 accretion and the subsequent evolution 51 00:02:05,910 --> 00:02:05,590 and laughs from those planets so here we 52 00:02:08,190 --> 00:02:05,920 go 53 00:02:11,550 --> 00:02:08,200 so when you form a planet you start 54 00:02:13,019 --> 00:02:11,560 accreting a core in the disk one of the 55 00:02:15,059 --> 00:02:13,029 key things you need to do is right you 56 00:02:17,980 --> 00:02:15,069 need to basically you're converting 57 00:02:21,070 --> 00:02:17,990 loads of gravitational binding energy 58 00:02:24,850 --> 00:02:21,080 into heat as you're accusing your rocky 59 00:02:27,190 --> 00:02:24,860 core and the seat can very effectively 60 00:02:28,780 --> 00:02:27,200 be transported away if you're doing this 61 00:02:31,570 --> 00:02:28,790 in a disc when you initially have a very 62 00:02:34,450 --> 00:02:31,580 small body if that body is smaller then 63 00:02:36,730 --> 00:02:34,460 basically the Bondi radius or the radius 64 00:02:39,130 --> 00:02:36,740 where the thermal speed equally escape 65 00:02:40,450 --> 00:02:39,140 speed of your planet if that's inside 66 00:02:42,760 --> 00:02:40,460 the physical rays of the planet your gas 67 00:02:45,070 --> 00:02:42,770 will just flow by carry away the heat 68 00:02:48,580 --> 00:02:45,080 and you can affect very efficiently cool 69 00:02:50,920 --> 00:02:48,590 you're growing embryo however once you 70 00:02:52,800 --> 00:02:50,930 grow a core we're basically the physical 71 00:02:58,480 --> 00:02:52,810 size of your planet becomes comparable 72 00:03:01,060 --> 00:02:58,490 or smaller than the spondee radius then 73 00:03:02,890 --> 00:03:01,070 you start holding on to the gas because 74 00:03:05,950 --> 00:03:02,900 now there is a region outside the 75 00:03:07,840 --> 00:03:05,960 physical core radius of your planet up 76 00:03:11,890 --> 00:03:07,850 to which the gas will be gravitationally 77 00:03:14,920 --> 00:03:11,900 bound to you and once this happened any 78 00:03:17,620 --> 00:03:14,930 in you know you're still accreting your 79 00:03:19,480 --> 00:03:17,630 core so you're still heating your core 80 00:03:21,190 --> 00:03:19,490 but any of that heat can no longer 81 00:03:23,950 --> 00:03:21,200 easily be carried away by the gas 82 00:03:26,260 --> 00:03:23,960 flowing by but no the gas that you're 83 00:03:27,910 --> 00:03:26,270 creating and holding on to starts to act 84 00:03:30,430 --> 00:03:27,920 like a thermal blanket and now you have 85 00:03:33,430 --> 00:03:30,440 to think of your planet as a couple 86 00:03:36,760 --> 00:03:33,440 system your atmosphere in your core and 87 00:03:38,080 --> 00:03:36,770 so as a consequence the course that are 88 00:03:40,150 --> 00:03:38,090 underlying these hydrogen helium 89 00:03:43,240 --> 00:03:40,160 envelopes sort of have the maximum 90 00:03:44,710 --> 00:03:43,250 temperature that can have and still hold 91 00:03:46,630 --> 00:03:44,720 on to hydrogen Amandla because there 92 00:03:49,000 --> 00:03:46,640 would be any hotter the envelope will be 93 00:03:51,850 --> 00:03:49,010 unbound and then you could cool until 94 00:03:54,040 --> 00:03:51,860 you find that envelope to you again and 95 00:03:57,190 --> 00:03:54,050 so you know that the temperature of 96 00:03:58,840 --> 00:03:57,200 these course it's between 10 to the 4 97 00:04:01,270 --> 00:03:58,850 and 10 to the 5 Kelvin not depends on 98 00:04:04,060 --> 00:04:01,280 whether you are in earth or 10 times the 99 00:04:09,190 --> 00:04:04,070 earth mass and then on top you have 100 00:04:10,810 --> 00:04:09,200 sitting this hydrogen helium envelope so 101 00:04:12,160 --> 00:04:10,820 what's the structure of this envelope 102 00:04:14,320 --> 00:04:12,170 and how do you create this envelope so 103 00:04:17,500 --> 00:04:14,330 initially you just have whatever is 104 00:04:19,180 --> 00:04:17,510 found within your Bondi radius and you 105 00:04:20,979 --> 00:04:19,190 can do some simple math and count up how 106 00:04:23,560 --> 00:04:20,989 much mass that is and you find but 107 00:04:26,050 --> 00:04:23,570 typically less than point one percent of 108 00:04:27,640 --> 00:04:26,060 the total planet mass so it's cute if 109 00:04:30,820 --> 00:04:27,650 you just want some envelope but it's not 110 00:04:31,750 --> 00:04:30,830 enough right to form these sub Neptune's 111 00:04:33,190 --> 00:04:31,760 which have like 112 00:04:35,770 --> 00:04:33,200 few percent of the total mass in 113 00:04:36,160 --> 00:04:35,780 hydrogen helium you have to do something 114 00:04:38,350 --> 00:04:36,170 else 115 00:04:39,760 --> 00:04:38,360 to accrete more gas so what is the 116 00:04:40,930 --> 00:04:39,770 something else but something else is 117 00:04:43,750 --> 00:04:40,940 that you just have to wait a little bit 118 00:04:46,000 --> 00:04:43,760 for your envelope to cool and contract 119 00:04:48,760 --> 00:04:46,010 as your envelopes that's the cookin 120 00:04:51,400 --> 00:04:48,770 contract you can pile on more gas on the 121 00:04:54,340 --> 00:04:51,410 outside and see your planet keep Kim 122 00:04:56,680 --> 00:04:54,350 keep growing its envelope mass so in 123 00:04:58,570 --> 00:04:56,690 detail what you have is your envelope 124 00:05:00,880 --> 00:04:58,580 structure is mostly at about eight 125 00:05:02,530 --> 00:05:00,890 because the energy is being transported 126 00:05:04,480 --> 00:05:02,540 by convection but then you start 127 00:05:06,580 --> 00:05:04,490 developing a small outer range of layer 128 00:05:09,220 --> 00:05:06,590 that basically is where your envelope 129 00:05:12,580 --> 00:05:09,230 shrinks and contracts such that you can 130 00:05:15,600 --> 00:05:12,590 accrete more material and so interesting 131 00:05:17,860 --> 00:05:15,610 enough in this face of graphic creations 132 00:05:19,180 --> 00:05:17,870 you're a creationist basically just 133 00:05:21,190 --> 00:05:19,190 limited by cooling because if you can 134 00:05:24,940 --> 00:05:21,200 cool faster you just can create more gas 135 00:05:26,170 --> 00:05:24,950 faster and so what is nice it is was 136 00:05:27,940 --> 00:05:26,180 this understanding you can write down 137 00:05:31,150 --> 00:05:27,950 what the typical envelope mass that you 138 00:05:32,710 --> 00:05:31,160 can it create is given other parameters 139 00:05:35,110 --> 00:05:32,720 of your system so that's what I've shown 140 00:05:37,210 --> 00:05:35,120 here F is just a fraction of the total 141 00:05:39,610 --> 00:05:37,220 atmospheric mass to the core math and 142 00:05:41,440 --> 00:05:39,620 you can see not surprisingly it skills 143 00:05:43,210 --> 00:05:41,450 as the mouth of a planet because of you 144 00:05:45,370 --> 00:05:43,220 xx radius right if you're bigger your 145 00:05:47,460 --> 00:05:45,380 body radius is figure and so you have 146 00:05:50,110 --> 00:05:47,470 more region to hold on to an atmosphere 147 00:05:51,550 --> 00:05:50,120 it scale to the disk lifetime because it 148 00:05:55,510 --> 00:05:51,560 sets the timescale you have for a 149 00:05:57,880 --> 00:05:55,520 creation rate and the opacity because 150 00:05:59,440 --> 00:05:57,890 and specifically the opacity at the rate 151 00:06:01,690 --> 00:05:59,450 of convective boundary where you connect 152 00:06:07,840 --> 00:06:01,700 the rate of region of your envelope to 153 00:06:09,400 --> 00:06:07,850 the isothermal radiative region because 154 00:06:11,590 --> 00:06:09,410 that's the bottleneck for cooling right 155 00:06:13,630 --> 00:06:11,600 any heat that wants to escape from the 156 00:06:16,270 --> 00:06:13,640 envelope and your core needs to 157 00:06:17,830 --> 00:06:16,280 basically go from the optic thick to the 158 00:06:20,260 --> 00:06:17,840 thin part at this rate of convective 159 00:06:22,570 --> 00:06:20,270 battery so those two 0 order you can 160 00:06:24,640 --> 00:06:22,580 understand this and the good news is 161 00:06:27,130 --> 00:06:24,650 typical this lifetimes on our planet 162 00:06:29,200 --> 00:06:27,140 masses you can indeed create several 163 00:06:34,000 --> 00:06:29,210 percents of the planets total mass as 164 00:06:36,280 --> 00:06:34,010 hydrogen so that's great one cute site 165 00:06:38,350 --> 00:06:36,290 note because the outer layer of your 166 00:06:40,660 --> 00:06:38,360 planet and these they are almost 167 00:06:43,210 --> 00:06:40,670 isothermal and therefore they have an 168 00:06:44,290 --> 00:06:43,220 close to exponential density profile so 169 00:06:46,300 --> 00:06:44,300 the 170 00:06:48,700 --> 00:06:46,310 atmospheric reed is actually only 171 00:06:51,700 --> 00:06:48,710 logarithmically dependent on the gas 172 00:06:55,059 --> 00:06:51,710 disc density that you have because 173 00:06:57,279 --> 00:06:55,069 that's only how it enters basically into 174 00:07:01,480 --> 00:06:57,289 the equation so it's not super sensitive 175 00:07:04,240 --> 00:07:01,490 to to those details so that's sort of a 176 00:07:06,180 --> 00:07:04,250 nice thing but okay so we should be 177 00:07:09,189 --> 00:07:06,190 happy we can accrete our atmospheres 178 00:07:11,499 --> 00:07:09,199 turns out we don't get to keep all of 179 00:07:13,360 --> 00:07:11,509 the stuff we have accreted the first 180 00:07:16,869 --> 00:07:13,370 thing that's going to happen to us is 181 00:07:19,899 --> 00:07:16,879 the falling the gaskets will go away 182 00:07:22,510 --> 00:07:19,909 eventually and if that happens basically 183 00:07:24,279 --> 00:07:22,520 you lose the pressure support in the 184 00:07:26,830 --> 00:07:24,289 disk and so basically if you know look 185 00:07:29,350 --> 00:07:26,840 at your planet the outer regions of your 186 00:07:31,540 --> 00:07:29,360 atmosphere and because you remove the 187 00:07:35,320 --> 00:07:31,550 gases from the outside will want to 188 00:07:38,680 --> 00:07:35,330 expand into vacuum just because they can 189 00:07:40,450 --> 00:07:38,690 and because of that and because there's 190 00:07:43,800 --> 00:07:40,460 plenty of energy in the inner parts of 191 00:07:47,170 --> 00:07:43,810 the envelope the planet will shed 192 00:07:49,659 --> 00:07:47,180 several tons to up to 70% of all the gas 193 00:07:53,589 --> 00:07:49,669 it just has retreated during the discus 194 00:07:57,430 --> 00:07:53,599 virzal phase as the gases goes away and 195 00:07:58,839 --> 00:07:57,440 so as a result you not only lose several 196 00:08:01,570 --> 00:07:58,849 times of percent of the envelope math 197 00:08:04,779 --> 00:08:01,580 you just accreted but your planet also 198 00:08:06,820 --> 00:08:04,789 fairly rapidly can shrink in size to 199 00:08:09,689 --> 00:08:06,830 size us that are just a few times the 200 00:08:12,040 --> 00:08:09,699 core radius rather than these very large 201 00:08:13,990 --> 00:08:12,050 radio that are comparable to the Baniya 202 00:08:16,930 --> 00:08:14,000 radius and that's because right mass 203 00:08:18,969 --> 00:08:16,940 loss takes away energy and therefore the 204 00:08:24,790 --> 00:08:18,979 remaining material can cool and shrink 205 00:08:26,920 --> 00:08:24,800 more quickly but it's okay right 206 00:08:28,809 --> 00:08:26,930 we still again this is the what you're 207 00:08:30,820 --> 00:08:28,819 left with after this dispersal face 208 00:08:33,490 --> 00:08:30,830 you're still fine because you still get 209 00:08:36,850 --> 00:08:33,500 a percent or a few percent for your 210 00:08:38,800 --> 00:08:36,860 typical planet cases so just remember if 211 00:08:40,300 --> 00:08:38,810 you ever want to form these planets just 212 00:08:42,279 --> 00:08:40,310 make sure that you can create about a 213 00:08:44,860 --> 00:08:42,289 factor of two or more in your initial 214 00:08:47,230 --> 00:08:44,870 envelope mass then you need so that you 215 00:08:51,670 --> 00:08:47,240 okay with losing about half of it during 216 00:08:54,069 --> 00:08:51,680 the gas this parental phase what happens 217 00:08:56,319 --> 00:08:54,079 next was sort of interesting and that we 218 00:08:58,000 --> 00:08:56,329 didn't really expect it until we thought 219 00:09:01,780 --> 00:08:58,010 about it in detail well 220 00:09:03,340 --> 00:09:01,790 now we thought both probably be good now 221 00:09:06,250 --> 00:09:03,350 we get to keep the rest of the envelope 222 00:09:08,230 --> 00:09:06,260 and we're done and in some cases who's 223 00:09:10,660 --> 00:09:08,240 actually true so what we discovered is 224 00:09:12,400 --> 00:09:10,670 from then on they're two different 225 00:09:13,930 --> 00:09:12,410 pathways for your planets they're two 226 00:09:16,150 --> 00:09:13,940 different regimes in which your planet 227 00:09:17,830 --> 00:09:16,160 can cool and contract so tell me about 228 00:09:19,510 --> 00:09:17,840 the more obvious one and the one that 229 00:09:23,680 --> 00:09:19,520 has been studied and love more detail 230 00:09:25,750 --> 00:09:23,690 first so and the first regime when you 231 00:09:29,230 --> 00:09:25,760 look at the total energy budget of the 232 00:09:31,270 --> 00:09:29,240 planet that's available for cooling if 233 00:09:32,800 --> 00:09:31,280 that's dominated by basically the 234 00:09:36,130 --> 00:09:32,810 thermal and variational energy in your 235 00:09:38,200 --> 00:09:36,140 envelope in those cases your planet will 236 00:09:39,640 --> 00:09:38,210 indeed from then onwards just cool and 237 00:09:41,680 --> 00:09:39,650 contract 238 00:09:46,120 --> 00:09:41,690 and you get to keep the atmosphere you 239 00:09:47,410 --> 00:09:46,130 have accreted and this is many of our 240 00:09:50,050 --> 00:09:47,420 solar system planets are still at the 241 00:09:53,110 --> 00:09:50,060 face and the cooling time right can take 242 00:09:54,760 --> 00:09:53,120 Giga years and your planet just cools 243 00:09:56,380 --> 00:09:54,770 and contracts if you look at the profile 244 00:09:58,750 --> 00:09:56,390 right what happens is the radius 245 00:10:01,480 --> 00:09:58,760 collector foundry we'll just move inward 246 00:10:04,720 --> 00:10:01,490 in time and the isothermal region will 247 00:10:08,290 --> 00:10:04,730 expand and it's all good when are you in 248 00:10:10,120 --> 00:10:08,300 this room you're in this regime when the 249 00:10:11,200 --> 00:10:10,130 heat capacity for cooling is dominated 250 00:10:14,020 --> 00:10:11,210 by the envelope wouldn't that 251 00:10:16,090 --> 00:10:14,030 corresponds to typical course that our 252 00:10:18,100 --> 00:10:16,100 model on the earth and a hydrant helium 253 00:10:20,560 --> 00:10:18,110 envelope when you have about five 254 00:10:24,310 --> 00:10:20,570 percent or more of the total mass in 255 00:10:26,560 --> 00:10:24,320 these envelopes more interesting is the 256 00:10:28,360 --> 00:10:26,570 second regime where this is reversed so 257 00:10:29,620 --> 00:10:28,370 if you have only a few percent of the 258 00:10:32,620 --> 00:10:29,630 total mass in the envelope 259 00:10:35,020 --> 00:10:32,630 then you actually have more thermal 260 00:10:37,720 --> 00:10:35,030 energy stored in your core that's 261 00:10:39,610 --> 00:10:37,730 available for cooling then binding 262 00:10:41,920 --> 00:10:39,620 energy of your envelope so what this 263 00:10:44,950 --> 00:10:41,930 means is the fine the envelope will want 264 00:10:47,680 --> 00:10:44,960 to cool and contract of course but as 265 00:10:50,140 --> 00:10:47,690 its am giving away energy and once the 266 00:10:51,640 --> 00:10:50,150 current are basically the same amount of 267 00:10:54,250 --> 00:10:51,650 energy is being resupplied by the 268 00:10:55,930 --> 00:10:54,260 underlying core and instead of 269 00:10:59,590 --> 00:10:55,940 contracting your envelope basically 270 00:11:03,370 --> 00:10:59,600 stalls at this radius and it keeps 271 00:11:05,290 --> 00:11:03,380 losing mass so until you can drain 272 00:11:07,510 --> 00:11:05,300 basically enough energy from the core 273 00:11:10,000 --> 00:11:07,520 that both the envelope and core can cool 274 00:11:11,210 --> 00:11:10,010 significantly you continue this mass 275 00:11:13,610 --> 00:11:11,220 loss and so 276 00:11:16,189 --> 00:11:13,620 this case you can strip the entire 277 00:11:19,249 --> 00:11:16,199 envelope energetically you have enough 278 00:11:20,929 --> 00:11:19,259 energy and it gets easier and easier 279 00:11:24,949 --> 00:11:20,939 from an energy point of view right once 280 00:11:27,079 --> 00:11:24,959 you lose half your envelope mass it's 281 00:11:29,480 --> 00:11:27,089 even easier energetic little second half 282 00:11:32,210 --> 00:11:29,490 because you're not shrinking your rate 283 00:11:33,860 --> 00:11:32,220 of convective boundary so that was 284 00:11:35,960 --> 00:11:33,870 really intriguing so basically what plan 285 00:11:37,100 --> 00:11:35,970 four major will tell you by default you 286 00:11:39,199 --> 00:11:37,110 should expect a bimodal distribution 287 00:11:40,579 --> 00:11:39,209 planet sizes the ones that got to keep 288 00:11:47,629 --> 00:11:40,589 the hydrogen helium envelopes and the 289 00:11:50,629 --> 00:11:47,639 ones that get to lose it there's one 290 00:11:52,579 --> 00:11:50,639 other thing to keep in mind it's not 291 00:11:54,860 --> 00:11:52,589 only an energy argument there are 292 00:11:57,410 --> 00:11:54,870 planets for which they have enough 293 00:11:59,389 --> 00:11:57,420 energy to unbound the envelopes and lose 294 00:12:01,369 --> 00:11:59,399 them however that there's not enough 295 00:12:03,170 --> 00:12:01,379 plane so they could be not enough time 296 00:12:06,619 --> 00:12:03,180 because this mass loss center can take 297 00:12:08,119 --> 00:12:06,629 actually get gears but in many cases it 298 00:12:10,309 --> 00:12:08,129 actually turns out that the cooling time 299 00:12:10,759 --> 00:12:10,319 scale can catch up with a mass lost time 300 00:12:15,769 --> 00:12:10,769 scale 301 00:12:18,429 --> 00:12:15,779 so basically when your mass loss becomes 302 00:12:21,889 --> 00:12:18,439 long compared to your cooling time scale 303 00:12:23,900 --> 00:12:21,899 then your envelope can cool and contract 304 00:12:26,299 --> 00:12:23,910 and you can shut off any subsequent mass 305 00:12:28,369 --> 00:12:26,309 loss and the reason for this is again 306 00:12:31,069 --> 00:12:28,379 because of the isothermal structure on 307 00:12:33,170 --> 00:12:31,079 the outside because you have an 308 00:12:35,360 --> 00:12:33,180 exponential tail in there and so as soon 309 00:12:37,280 --> 00:12:35,370 as you increase the region over which 310 00:12:39,290 --> 00:12:37,290 this exponent is expanding just a little 311 00:12:41,689 --> 00:12:39,300 bit the mass lot rate drops 312 00:12:43,129 --> 00:12:41,699 significantly any concern of the mass 313 00:12:46,309 --> 00:12:43,139 loss and you can cool it a little bit 314 00:12:47,540 --> 00:12:46,319 more and save your atmosphere so what 315 00:12:49,100 --> 00:12:47,550 I'll show you is the criterion for 316 00:12:51,170 --> 00:12:49,110 keeping most of the envelopes is that 317 00:12:52,790 --> 00:12:51,180 basically your cooling time scale has to 318 00:12:54,259 --> 00:12:52,800 become faster than your math last time 319 00:12:56,900 --> 00:12:54,269 scale okay 320 00:12:58,309 --> 00:12:56,910 so much for a theory let's try to put 321 00:12:59,660 --> 00:12:58,319 this all together so with what I told 322 00:13:01,819 --> 00:12:59,670 you you know kind of make it our model 323 00:13:04,689 --> 00:13:01,829 making your own planet you can take the 324 00:13:08,210 --> 00:13:04,699 sort of observed mass distribution of 325 00:13:09,769 --> 00:13:08,220 planetary cores which are good proxy for 326 00:13:11,480 --> 00:13:09,779 the total mass of the planet because 327 00:13:13,910 --> 00:13:11,490 these envelopes are only a small 328 00:13:15,920 --> 00:13:13,920 fraction of the total mass then I told 329 00:13:17,900 --> 00:13:15,930 you you can calculate how much hydrogen 330 00:13:19,669 --> 00:13:17,910 helium they should accrete 331 00:13:21,919 --> 00:13:19,679 how much they should lose during the 332 00:13:24,259 --> 00:13:21,929 distance brizl phase and then we can 333 00:13:25,300 --> 00:13:24,269 just involve them under the what we call 334 00:13:29,510 --> 00:13:25,310 core apart masks 335 00:13:31,520 --> 00:13:29,520 scenario and indeed what we found is you 336 00:13:33,890 --> 00:13:31,530 do get this portal distribution to the 337 00:13:36,590 --> 00:13:33,900 thread histogram is basically the 338 00:13:38,600 --> 00:13:36,600 outcome of this very simple model in 339 00:13:42,530 --> 00:13:38,610 this gray is a comparison with the 340 00:13:44,810 --> 00:13:42,540 actual observation so what the drinking 341 00:13:46,970 --> 00:13:44,820 is just from a pure planet formation 342 00:13:49,940 --> 00:13:46,980 point of view you seem to be able to 343 00:13:54,020 --> 00:13:49,950 reproduce this by mortal distribution 344 00:13:55,760 --> 00:13:54,030 that's observed in the exoplanet size 345 00:13:57,800 --> 00:13:55,770 distribution of these super earth and 346 00:14:00,740 --> 00:13:57,810 subnet tune and we heard from James 347 00:14:05,090 --> 00:14:00,750 already so this is by no way to say that 348 00:14:08,810 --> 00:14:05,100 this is the only thing going on and we 349 00:14:11,450 --> 00:14:08,820 heard that food preparation can give you 350 00:14:14,660 --> 00:14:11,460 this bimodal distribution also and I 351 00:14:17,300 --> 00:14:14,670 think we need to actually combine those 352 00:14:20,090 --> 00:14:17,310 two to really come up with a model that 353 00:14:22,280 --> 00:14:20,100 can do it all but it's very intriguing 354 00:14:24,620 --> 00:14:22,290 to me that just for information would 355 00:14:27,470 --> 00:14:24,630 give you this and this was just a first 356 00:14:29,990 --> 00:14:27,480 cut my current grad student has done a 357 00:14:33,410 --> 00:14:30,000 more detailed comparison so we not only 358 00:14:36,350 --> 00:14:33,420 have histograms right we now also have a 359 00:14:39,020 --> 00:14:36,360 two-dimensional distribution of oval 360 00:14:42,950 --> 00:14:39,030 period and size distribution these are 361 00:14:45,740 --> 00:14:42,960 the observations you see up here he 362 00:14:49,850 --> 00:14:45,750 repeated the same model but just plotted 363 00:14:51,950 --> 00:14:49,860 this now in 2d to do a comparison and 364 00:14:55,760 --> 00:14:51,960 again I think he finds a very good 365 00:14:59,210 --> 00:14:55,770 agreement with observations specifically 366 00:15:01,910 --> 00:14:59,220 we get a similar slope in this radius 367 00:15:03,710 --> 00:15:01,920 valley as the observation is very easy 368 00:15:05,930 --> 00:15:03,720 to understand where the slope comes from 369 00:15:07,700 --> 00:15:05,940 in the coop at Mastro's mechanism I told 370 00:15:09,290 --> 00:15:07,710 you what separates the planets that keep 371 00:15:11,780 --> 00:15:09,300 the envelope where's the ones that lose 372 00:15:13,700 --> 00:15:11,790 is just whether the cooling timescale is 373 00:15:15,860 --> 00:15:13,710 faster or smaller than the mass less 374 00:15:18,560 --> 00:15:15,870 time scale so setting those two equal we 375 00:15:19,940 --> 00:15:18,570 can solve for the slope and these are 376 00:15:22,490 --> 00:15:19,950 complicated things because they depend 377 00:15:23,990 --> 00:15:22,500 on many things of your planet but the 378 00:15:26,870 --> 00:15:24,000 nice thing is because one of them has 379 00:15:28,970 --> 00:15:26,880 this exponential in it so to first order 380 00:15:30,230 --> 00:15:28,980 all that really matters is the things in 381 00:15:32,390 --> 00:15:30,240 the exponent and the things in the 382 00:15:33,800 --> 00:15:32,400 exponent is only is it just the mass of 383 00:15:35,870 --> 00:15:33,810 the planet the speed of sound and 384 00:15:38,600 --> 00:15:35,880 basically the size of your planet the 385 00:15:42,350 --> 00:15:38,610 race vector boundary so we know those 386 00:15:44,030 --> 00:15:42,360 and so you can you can rewrite them as a 387 00:15:45,650 --> 00:15:44,040 function of period and science because 388 00:15:48,980 --> 00:15:45,660 that's what the would-be observations 389 00:15:50,630 --> 00:15:48,990 are plotted in and derive what the slope 390 00:15:53,990 --> 00:15:50,640 should be it's just straight out of here 391 00:15:57,019 --> 00:15:54,000 and what you get is this minus 0.1 we're 392 00:15:58,819 --> 00:15:57,029 just in very good observations that 393 00:16:02,449 --> 00:15:58,829 actually James also showed from the fun 394 00:16:04,699 --> 00:16:02,459 alien paper similar to the foot 395 00:16:06,560 --> 00:16:04,709 evaporation results very exactly the 396 00:16:08,240 --> 00:16:06,570 slope will fall depends on the density 397 00:16:10,910 --> 00:16:08,250 you can see this again just from the 398 00:16:13,850 --> 00:16:10,920 things that are in the exponent so the 399 00:16:16,340 --> 00:16:13,860 location of the slope we to find it's 400 00:16:18,860 --> 00:16:16,350 consistent with rocky compositions and 401 00:16:21,470 --> 00:16:18,870 that we found that at most you can have 402 00:16:27,949 --> 00:16:21,480 about 20% water fraction in those 403 00:16:30,319 --> 00:16:27,959 planets then of course you can do better 404 00:16:32,480 --> 00:16:30,329 so so far we had assumed that all stars 405 00:16:34,130 --> 00:16:32,490 exactly like the Sun so the first thing 406 00:16:39,560 --> 00:16:34,140 was to actually model the true stellar 407 00:16:43,100 --> 00:16:39,570 population of the Kepler data set and by 408 00:16:44,750 --> 00:16:43,110 doing so much surprisingly but it's good 409 00:16:46,759 --> 00:16:44,760 to confirm we've got an even better 410 00:16:48,380 --> 00:16:46,769 agreement with observations you can see 411 00:16:50,000 --> 00:16:48,390 this the spreads out a little bit 412 00:16:54,439 --> 00:16:50,010 because the spread and stellar 413 00:16:56,269 --> 00:16:54,449 properties but nothing revolutionary new 414 00:17:00,560 --> 00:16:56,279 here we knew that it should be similar 415 00:17:02,060 --> 00:17:00,570 so that's good but what is nice is now 416 00:17:03,769 --> 00:17:02,070 we can ask questions and make 417 00:17:05,900 --> 00:17:03,779 predictions of how the corporate 418 00:17:07,880 --> 00:17:05,910 massless mechanism should depend on 419 00:17:09,319 --> 00:17:07,890 various stellar properties and where it 420 00:17:12,650 --> 00:17:09,329 gives different results from what you 421 00:17:15,319 --> 00:17:12,660 would expect if this radius valley is 422 00:17:18,949 --> 00:17:15,329 shaped predominately by foot evaporation 423 00:17:22,309 --> 00:17:18,959 so I want to give you two examples one 424 00:17:24,860 --> 00:17:22,319 is how it depends on the bulla metric 425 00:17:27,020 --> 00:17:24,870 luminosity of the star here it's plotted 426 00:17:30,190 --> 00:17:27,030 as stellar mass again just because this 427 00:17:32,930 --> 00:17:30,200 is what's been done by the observers so 428 00:17:35,750 --> 00:17:32,940 in the core part mattress mechanism 429 00:17:37,820 --> 00:17:35,760 why does a star matter at all um the 430 00:17:41,720 --> 00:17:37,830 star matters through the metric 431 00:17:43,340 --> 00:17:41,730 luminosity because the insulation or the 432 00:17:46,100 --> 00:17:43,350 effective temperature that your planet 433 00:17:48,560 --> 00:17:46,110 has sets the outer boundary condition 434 00:17:51,740 --> 00:17:48,570 for massless so this is where the star 435 00:17:53,120 --> 00:17:51,750 comes in so um 436 00:17:54,980 --> 00:17:53,130 what this means is if you have a higher 437 00:17:57,410 --> 00:17:54,990 luminosity star or a planet that has a 438 00:18:00,260 --> 00:17:57,420 higher insulation you have a faster of 439 00:18:02,540 --> 00:18:00,270 mass loss rate and so in the end you can 440 00:18:04,580 --> 00:18:02,550 strip a more mass of core if you have a 441 00:18:07,730 --> 00:18:04,590 higher bottom entry manasa T so this 442 00:18:09,380 --> 00:18:07,740 means if you have because of the mass 443 00:18:11,330 --> 00:18:09,390 from another relationship of stars which 444 00:18:15,170 --> 00:18:11,340 is well measured and studies more 445 00:18:18,080 --> 00:18:15,180 massive stars of higher luminosities we 446 00:18:21,290 --> 00:18:18,090 find in the core pod Matloff scenario 447 00:18:24,500 --> 00:18:21,300 that this this radius valley moves the 448 00:18:26,450 --> 00:18:24,510 larger stellar masses to larger planet 449 00:18:28,250 --> 00:18:26,460 sizes as a function of stellar mass and 450 00:18:31,070 --> 00:18:28,260 we can even measure the slope this 451 00:18:34,250 --> 00:18:31,080 actually isn't quite as agreement with 452 00:18:36,110 --> 00:18:34,260 observation you can again derive this 453 00:18:38,660 --> 00:18:36,120 analytically very simply again from 454 00:18:41,000 --> 00:18:38,670 exactly the same argument same exponent 455 00:18:43,550 --> 00:18:41,010 again you're just rewriting this because 456 00:18:46,100 --> 00:18:43,560 now you're writing this explicitly in 457 00:18:47,720 --> 00:18:46,110 terms of the insulation received and you 458 00:18:49,010 --> 00:18:47,730 can analytically even derive the slope 459 00:18:51,560 --> 00:18:49,020 but you can of course do this 460 00:18:52,940 --> 00:18:51,570 numerically also this is one thing where 461 00:18:54,980 --> 00:18:52,950 we predict something quite different 462 00:18:57,140 --> 00:18:54,990 from fort evaporation right for 463 00:19:01,130 --> 00:18:57,150 preparation as we prayed from James is 464 00:19:04,160 --> 00:19:01,140 driven by the x-ray and UV radiation 465 00:19:06,110 --> 00:19:04,170 from the star this is more strong 466 00:19:09,500 --> 00:19:06,120 relative to the below metric luminosity 467 00:19:12,230 --> 00:19:09,510 for lower mass stars so a lower mass 468 00:19:15,040 --> 00:19:12,240 stars for given bolometric luminosity 469 00:19:17,540 --> 00:19:15,050 should be more efficient as stripping 470 00:19:20,660 --> 00:19:17,550 planetary course should be able to strip 471 00:19:22,640 --> 00:19:20,670 a larger core than then higher math 472 00:19:26,780 --> 00:19:22,650 stars for the same volumetric luminosity 473 00:19:29,600 --> 00:19:26,790 and so when this data was interpreted by 474 00:19:32,780 --> 00:19:29,610 jung chanwoo using for reparation models 475 00:19:35,180 --> 00:19:32,790 she's to basically get the strength she 476 00:19:37,940 --> 00:19:35,190 suggested that the underlying planet's 477 00:19:40,820 --> 00:19:37,950 mass distribution needs to be have a 478 00:19:42,890 --> 00:19:40,830 coral positive linear correlation with a 479 00:19:46,940 --> 00:19:42,900 stellar host master to get this positive 480 00:19:48,620 --> 00:19:46,950 trend so for us we have the same 481 00:19:50,360 --> 00:19:48,630 underlying time mass distribution would 482 00:19:52,580 --> 00:19:50,370 say it's independent of stella host mass 483 00:19:54,590 --> 00:19:52,590 because we get this trend if you wish by 484 00:19:56,900 --> 00:19:54,600 default just from their bolometric 485 00:19:58,900 --> 00:19:56,910 luminosity that's one way where there's 486 00:20:03,300 --> 00:19:58,910 quite different predictions 487 00:20:05,040 --> 00:20:03,310 between these two mechanisms there is a 488 00:20:06,360 --> 00:20:05,050 there are several others but this is 489 00:20:11,730 --> 00:20:06,370 another one which I think it's quite 490 00:20:14,250 --> 00:20:11,740 clean this is dependent on Stella age so 491 00:20:15,990 --> 00:20:14,260 we heard from James that it's the 492 00:20:19,410 --> 00:20:16,000 youngsters that are really active right 493 00:20:21,270 --> 00:20:19,420 its youngsters that drive most of the 494 00:20:23,520 --> 00:20:21,280 math laws and most of the food of 495 00:20:24,840 --> 00:20:23,530 operation is happening in the core part 496 00:20:27,000 --> 00:20:24,850 math class 497 00:20:29,270 --> 00:20:27,010 this happens over Giga time skill is 498 00:20:31,710 --> 00:20:29,280 basically continuously happened from 499 00:20:33,840 --> 00:20:31,720 basically the birth of your planet until 500 00:20:37,080 --> 00:20:33,850 today so their plan is even today that 501 00:20:39,690 --> 00:20:37,090 are still being converted from super sub 502 00:20:42,480 --> 00:20:39,700 Neptune into supers and so if you plot 503 00:20:45,960 --> 00:20:42,490 basically this is now a relative 504 00:20:48,180 --> 00:20:45,970 occurrence of sub Neptune's to super 505 00:20:50,780 --> 00:20:48,190 earth as a function of age you can see 506 00:20:53,070 --> 00:20:50,790 if you go from 1 to say 10 Giga here's 507 00:20:54,900 --> 00:20:53,080 your plan is still shrink you can see 508 00:20:57,000 --> 00:20:54,910 this 2 here but you also see that you 509 00:20:58,350 --> 00:20:57,010 get more and larger super Earths because 510 00:21:00,120 --> 00:20:58,360 you know the Neptune's that are still 511 00:21:03,380 --> 00:21:00,130 stripped sub Neptune's that are so 512 00:21:06,030 --> 00:21:03,390 stripped and converted into super so 513 00:21:07,950 --> 00:21:06,040 what this means is that if you can study 514 00:21:10,890 --> 00:21:07,960 these populations as a function of age 515 00:21:12,990 --> 00:21:10,900 that we predict that the occurrence rate 516 00:21:14,430 --> 00:21:13,000 of super Earths should still increase if 517 00:21:17,040 --> 00:21:14,440 you go from half a giggle year to a 518 00:21:22,380 --> 00:21:17,050 giggle year to several giga years with 519 00:21:30,210 --> 00:21:27,530 [Music] 520 00:21:32,610 --> 00:21:30,220 and that there will be a few planets 521 00:21:35,490 --> 00:21:32,620 today that you can catch in the valley 522 00:21:37,770 --> 00:21:35,500 losing mass right now just because some 523 00:21:42,080 --> 00:21:37,780 of them have just the right time scales 524 00:21:47,400 --> 00:21:42,090 for that so let me conclude 525 00:21:49,470 --> 00:21:47,410 so planet formation itself seems to give 526 00:21:52,110 --> 00:21:49,480 you a bimodal distribution and planet 527 00:21:54,060 --> 00:21:52,120 sizes so core cooling just by itself 528 00:21:55,710 --> 00:21:54,070 wants to either let you have these 529 00:22:00,240 --> 00:21:55,720 hydrogen helium envelopes or strip you 530 00:22:03,540 --> 00:22:00,250 entirely light atmospheres that contain 531 00:22:06,600 --> 00:22:03,550 less than about 5% of the total mass of 532 00:22:09,090 --> 00:22:06,610 the planet and can be stripped entirely 533 00:22:11,400 --> 00:22:09,100 because there's enough energy and to do 534 00:22:14,460 --> 00:22:11,410 so whereas heavy atmosphere is more than 535 00:22:16,870 --> 00:22:14,470 roughly 5% of the total planet's mass 536 00:22:20,470 --> 00:22:16,880 and will just cool and contract 537 00:22:23,140 --> 00:22:20,480 Virgilia time feels the majority of the 538 00:22:24,910 --> 00:22:23,150 rocky and exoplanets are basically fully 539 00:22:27,790 --> 00:22:24,920 consistent with having formed with the 540 00:22:30,580 --> 00:22:27,800 hydrogen helium envelope and that 541 00:22:33,850 --> 00:22:30,590 basically being stripped course of what 542 00:22:35,680 --> 00:22:33,860 we see today we find that these cores on 543 00:22:38,080 --> 00:22:35,690 average have densities quite similar to 544 00:22:41,830 --> 00:22:38,090 the earth so suggest that they are not 545 00:22:43,540 --> 00:22:41,840 true Waterworld may be pointing 546 00:22:46,420 --> 00:22:43,550 deformation inside the ice line but 547 00:22:50,080 --> 00:22:46,430 we'll see as we have better models and 548 00:22:51,610 --> 00:22:50,090 better data the curse the coop at 549 00:22:54,520 --> 00:22:51,620 massless proceeds over 550 00:22:56,140 --> 00:22:54,530 Agia timescales the occurrence rate or 551 00:23:01,540 --> 00:22:56,150 super earth respect to sub Neptune's 552 00:23:03,310 --> 00:23:01,550 will increase with time the cursed core 553 00:23:06,970 --> 00:23:03,320 cooling does depend on the below metric 554 00:23:10,330 --> 00:23:06,980 luminosity of the star we predict that 555 00:23:13,960 --> 00:23:10,340 the radius valley should shift to larger 556 00:23:16,030 --> 00:23:13,970 planet sizes of masses and as you go to 557 00:23:20,850 --> 00:23:16,040 increasing stellar masses because of the 558 00:23:22,840 --> 00:23:20,860 stellar mass luminosity relationship we 559 00:23:24,400 --> 00:23:22,850 predicted there's no change in the 560 00:23:25,720 --> 00:23:24,410 underlying silent mass distributions 561 00:23:28,150 --> 00:23:25,730 with the typical plant masses are the 562 00:23:30,940 --> 00:23:28,160 same around a sun-like star and the star 563 00:23:32,620 --> 00:23:30,950 that's a 0.8 0.6 times the height of the 564 00:23:38,800 --> 00:23:32,630 Sun so again that's something that you 565 00:23:42,400 --> 00:23:38,810 can test observational II and I think 566 00:23:45,550 --> 00:23:42,410 most importantly I think in future work 567 00:23:48,370 --> 00:23:45,560 that basically we started but it's still 568 00:23:50,650 --> 00:23:48,380 ongoing is it's basically the effort to 569 00:23:53,520 --> 00:23:50,660 really combine the foot evaporation 570 00:23:57,550 --> 00:23:53,530 models and the crop out mass loss models 571 00:23:59,980 --> 00:23:57,560 to correctly and completely model this 572 00:24:01,570 --> 00:23:59,990 atmospheric loss because my suspicion is 573 00:24:03,820 --> 00:24:01,580 that probably this will be needed to 574 00:24:06,220 --> 00:24:03,830 correctly interpret the observations and 575 00:24:09,520 --> 00:24:06,230 make inferences for example about the 576 00:24:11,970 --> 00:24:09,530 planets densities in their evolution so 577 00:24:18,430 --> 00:24:11,980 thank you very much 578 00:24:21,470 --> 00:24:18,440 [Applause] 579 00:24:23,419 --> 00:24:21,480 and sorry about the 3d numbering I don't 580 00:24:26,330 --> 00:24:23,429 know what I don't know I can just say 581 00:24:29,049 --> 00:24:26,340 it's my dead leg somehow this this made 582 00:24:38,539 --> 00:24:29,059 sense some time ago 583 00:24:41,240 --> 00:24:38,549 thank you very much hookah Denis Oh 584 00:24:43,340 --> 00:24:41,250 Geoff University of Exeter it's probably 585 00:24:46,970 --> 00:24:43,350 a weird question but can there be a 586 00:24:51,169 --> 00:24:46,980 situation when an atmosphere of a planet 587 00:24:54,159 --> 00:24:51,179 being stripped away from from one planet 588 00:24:56,450 --> 00:24:54,169 and then being gained by another planet 589 00:24:57,769 --> 00:24:56,460 it's like it's a great question I 590 00:25:00,440 --> 00:24:57,779 thought about this a little but I think 591 00:25:02,899 --> 00:25:00,450 it's hard in reality so for starters we 592 00:25:06,110 --> 00:25:02,909 see this happening all the time or it's 593 00:25:08,720 --> 00:25:06,120 not so uncommon I think it's harder for 594 00:25:10,460 --> 00:25:08,730 planets and the reason is that unlike 595 00:25:12,289 --> 00:25:10,470 stars a binary star that's close and can 596 00:25:14,029 --> 00:25:12,299 have mass transfer the planets are not 597 00:25:15,740 --> 00:25:14,039 closed spacial for a long time because 598 00:25:17,720 --> 00:25:15,750 of the capillary and shear so they do 599 00:25:19,879 --> 00:25:17,730 come by and they're not that far apart 600 00:25:21,590 --> 00:25:19,889 but that's only a short time in their 601 00:25:23,330 --> 00:25:21,600 orbit right because then the complaing 602 00:25:25,970 --> 00:25:23,340 here most of the time is actually spent 603 00:25:28,460 --> 00:25:25,980 quite far apart so for that reason I 604 00:25:37,789 --> 00:25:28,470 think it's very unlikely to have to 605 00:25:41,269 --> 00:25:37,799 happen yeah Daniel from MIT in the plot 606 00:25:44,480 --> 00:25:41,279 of planet radius versus period the lower 607 00:25:47,480 --> 00:25:44,490 population the average size seems to go 608 00:25:49,310 --> 00:25:47,490 down with periods so if these are 609 00:25:52,310 --> 00:25:49,320 supposed to be like rocky cores why 610 00:25:53,810 --> 00:25:52,320 would they get smaller with increasing 611 00:25:55,580 --> 00:25:53,820 period is there a reason from planet 612 00:25:57,259 --> 00:25:55,590 formation to expect that okay no so I 613 00:26:00,320 --> 00:25:57,269 think so let me just make sure what we 614 00:26:02,779 --> 00:26:00,330 talk about the same plot the one where 615 00:26:05,720 --> 00:26:02,789 you have period on the x axis and radius 616 00:26:15,950 --> 00:26:07,760 it's not letting me go back it's 617 00:26:18,950 --> 00:26:15,960 hilarious it does it doesn't let me go 618 00:26:20,690 --> 00:26:18,960 back so they're okay only forward Oh 619 00:26:23,210 --> 00:26:20,700 thought this one is good right you mean 620 00:26:24,980 --> 00:26:23,220 this one right yes or the lower red blob 621 00:26:26,990 --> 00:26:24,990 right you're saying this goes down with 622 00:26:29,360 --> 00:26:27,000 period right or at least it looks like 623 00:26:31,310 --> 00:26:29,370 yeah so the reason is it gets harder 624 00:26:33,260 --> 00:26:31,320 because the lower because when you're 625 00:26:35,540 --> 00:26:33,270 further away from the star you receive a 626 00:26:37,640 --> 00:26:35,550 lower bolometric luminosity so it gets 627 00:26:40,460 --> 00:26:37,650 harder to strip the core so it means you 628 00:26:41,840 --> 00:26:40,470 can only strip lower mass planets and so 629 00:26:44,390 --> 00:26:41,850 that's why they look smaller so the 630 00:26:47,630 --> 00:26:44,400 equivalent planets that are that would 631 00:26:51,380 --> 00:26:47,640 be here I still stuck in this model in 632 00:26:53,090 --> 00:26:51,390 the sub Neptune population because the 633 00:26:55,730 --> 00:26:53,100 outer boundary condition that's given by 634 00:26:57,920 --> 00:26:55,740 the volumetric luminosity of the star is 635 00:27:01,970 --> 00:26:57,930 such that the mass loss rate is slower 636 00:27:04,600 --> 00:27:01,980 and so you get stuck being a sub Neptune 637 00:27:07,340 --> 00:27:04,610 rather than being converted into a super 638 00:27:09,860 --> 00:27:07,350 this is where that dependence on period 639 00:27:17,870 --> 00:27:09,870 comes from as you go to larger orbital 640 00:27:19,640 --> 00:27:17,880 periods does it make sense yeah maybe 641 00:27:22,400 --> 00:27:19,650 I'll have to think hard about it but if 642 00:27:24,110 --> 00:27:22,410 I interpret the lower red blob it's just 643 00:27:26,690 --> 00:27:24,120 a core that's like stripped of 644 00:27:28,340 --> 00:27:26,700 everything mmm I would assume that like 645 00:27:29,960 --> 00:27:28,350 everything that falls into that 646 00:27:33,230 --> 00:27:29,970 population is roughly gonna have the 647 00:27:34,850 --> 00:27:33,240 same size now so Ike not like you're 648 00:27:36,620 --> 00:27:34,860 right and saying like some of them might 649 00:27:39,200 --> 00:27:36,630 not make it to that population at longer 650 00:27:41,180 --> 00:27:39,210 periods but if you do make it to that 651 00:27:44,180 --> 00:27:41,190 population shouldn't you have the same 652 00:27:45,830 --> 00:27:44,190 size regardless of period no because 653 00:27:49,340 --> 00:27:45,840 there's this mass dependence right but 654 00:27:51,920 --> 00:27:49,350 because because you receive you have a 655 00:27:53,540 --> 00:27:51,930 you have a colder outer boundary 656 00:27:56,060 --> 00:27:53,550 condition your mass loss rate is lower 657 00:27:58,820 --> 00:27:56,070 if you go further away so a large a 658 00:28:01,040 --> 00:27:58,830 larger masses can still hold on to their 659 00:28:03,170 --> 00:28:01,050 envelope and that's why these guys get 660 00:28:05,210 --> 00:28:03,180 stuck up there so if you would plot this 661 00:28:07,070 --> 00:28:05,220 on planet Mars you'll see that in each 662 00:28:09,230 --> 00:28:07,080 period you have the same planet mass 663 00:28:11,480 --> 00:28:09,240 distributions but the ones that become 664 00:28:14,110 --> 00:28:11,490 super Earth are different depending on 665 00:28:17,629 --> 00:28:14,120 how far away you are from the star 666 00:28:25,849 --> 00:28:24,229 I was wondering we think that in the 667 00:28:28,999 --> 00:28:25,859 process of planet formation there are 668 00:28:31,789 --> 00:28:29,009 also a lot of giant in yes so I was 669 00:28:33,979 --> 00:28:31,799 wondering how that like having impact my 670 00:28:35,239 --> 00:28:33,989 effect these populations thank you for 671 00:28:41,799 --> 00:28:35,249 asking that question because those 672 00:28:45,909 --> 00:28:41,809 impacts are my other big passion so 673 00:28:49,249 --> 00:28:45,919 indeed so rightful giant impact actually 674 00:28:51,469 --> 00:28:49,259 one of my PhD students are just finished 675 00:28:53,509 --> 00:28:51,479 there's quite a lot of work on the 676 00:28:56,449 --> 00:28:53,519 atmospheric loss in giant impacts and 677 00:28:58,999 --> 00:28:56,459 what he showed is that for hydrogen 678 00:29:00,709 --> 00:28:59,009 helium envelopes they're amazingly good 679 00:29:04,399 --> 00:29:00,719 at stripping the atmosphere which is 680 00:29:06,109 --> 00:29:04,409 quite different actually from sort of 681 00:29:08,779 --> 00:29:06,119 secondary atmospheres but you only get 682 00:29:09,979 --> 00:29:08,789 loss of 10 or 20% and typical 10 impact 683 00:29:11,509 --> 00:29:09,989 so that's again actually because of the 684 00:29:13,190 --> 00:29:11,519 heating you have so much energy 685 00:29:15,229 --> 00:29:13,200 deposited in the core that you 686 00:29:17,299 --> 00:29:15,239 significantly heat the core and the 687 00:29:20,209 --> 00:29:17,309 envelope that you tend to lose it all 688 00:29:21,889 --> 00:29:20,219 for those sort of systems so I would 689 00:29:23,269 --> 00:29:21,899 used to say that oh they can't be too 690 00:29:25,039 --> 00:29:23,279 many giant impacts because that will 691 00:29:27,529 --> 00:29:25,049 mess up our plot too much but it's not 692 00:29:29,629 --> 00:29:27,539 quite so clear anymore because if you 693 00:29:31,909 --> 00:29:29,639 really strip everything you could hide 694 00:29:35,209 --> 00:29:31,919 many giant impacts in here and just be 695 00:29:40,180 --> 00:29:35,219 either a neptune or a super-earth and 696 00:29:42,799 --> 00:29:40,190 not that much in between I I do think 697 00:29:44,569 --> 00:29:42,809 they happen at some level maybe not 698 00:29:46,489 --> 00:29:44,579 quite as prominent as I believe they 699 00:29:48,229 --> 00:29:46,499 used to be but I think the fact that he 700 00:29:51,499 --> 00:29:48,239 found that you tend to strip everything 701 00:30:01,959 --> 00:29:51,509 and makes it more easily reconcilable 702 00:30:06,589 --> 00:30:04,909 Rowan worth Harvard's um I was wondering 703 00:30:08,209 --> 00:30:06,599 do you take rays of cooling mechanisms 704 00:30:09,409 --> 00:30:08,219 into account in your outflows do you 705 00:30:11,930 --> 00:30:09,419 think that's going to be important 706 00:30:13,369 --> 00:30:11,940 that's all that's a great question uh we 707 00:30:15,889 --> 00:30:13,379 think we thought about this a little bit 708 00:30:19,699 --> 00:30:15,899 but I think it does need and deserves 709 00:30:21,949 --> 00:30:19,709 more attention so the reason why you 710 00:30:23,810 --> 00:30:21,959 need both the star so as James said so 711 00:30:26,209 --> 00:30:23,820 nicely right in the score pot math laws 712 00:30:28,309 --> 00:30:26,219 the energy basically comes from the 713 00:30:30,199 --> 00:30:28,319 interior of the planet both the what's 714 00:30:30,770 --> 00:30:30,209 left in the envelope and the core and 715 00:30:32,300 --> 00:30:30,780 that's 716 00:30:34,250 --> 00:30:32,310 basically providing the energy to lift 717 00:30:36,350 --> 00:30:34,260 the material sort of out of the 718 00:30:38,270 --> 00:30:36,360 potential well however its cooling it 719 00:30:41,360 --> 00:30:38,280 erratically so it's not enough to just 720 00:30:45,680 --> 00:30:41,370 escape and so this is why the star comes 721 00:30:48,470 --> 00:30:45,690 in again so because you do need the the 722 00:30:50,900 --> 00:30:48,480 photons the volumetric luminosity is not 723 00:30:53,720 --> 00:30:50,910 the hard photons just the normal photons 724 00:30:56,240 --> 00:30:53,730 to keep your gas at sort of the typical 725 00:30:58,310 --> 00:30:56,250 temperature you would expect so as long 726 00:31:00,410 --> 00:30:58,320 as you can satisfy this that you will 727 00:31:02,390 --> 00:31:00,420 roughly be in the naive equilibrium you 728 00:31:04,130 --> 00:31:02,400 expect you're okay but there can be 729 00:31:06,410 --> 00:31:04,140 cases especially if you go far enough 730 00:31:08,120 --> 00:31:06,420 away from the star where this will this 731 00:31:10,430 --> 00:31:08,130 assumption will break down and that's 732 00:31:14,770 --> 00:31:10,440 definitely something that we started 733 00:31:17,720 --> 00:31:14,780 thinking about it in more detail yes