# The things we DON'T KNOW about EXOPLANETS ## Метаданные - **Канал:** Dr. Becky - **YouTube:** https://www.youtube.com/watch?v=Q5o8b_ODjOY - **Дата:** 28.08.2025 - **Длительность:** 13:33 - **Просмотры:** 72,246 - **Источник:** https://ekstraktznaniy.ru/video/15140 ## Описание The things we don’t know are what drives science forward. A lack of knowledge, of not knowing the answer to a question is what pushes scientists to get more data, or design a new experiment. And in the case of astrophysics, those new experiments are often entirely new observatories, either on the ground or up in space, the design of which is driven by the gaps in our knowledge. So I love it when a paper is published summarising all the things we don’t yet know about a topic, and this month we saw that for exoplanet research. Exoplanets are planets orbiting other stars in our galaxy the Milky Way, we currently know of just under 6000 of them, some being the only planet around a star known, and some being in multiple planet systems just like the solar system. We’ve found everything from hot Jupiters close into their stars, to super-Earths that might be habitable since the first exoplanet was discovered in 1995. In this video I thought it would be fun to go quick fire through the 17 diffe ## Транскрипт ### Introduction [] The things that we don't know are what drives science forward. A lack of knowledge of not knowing the answer to a question is what drives scientists to get new data or design a new experiment. And in the case of astrophysics, those new experiments are often entirely new observatories either on the ground or up in space, the design of which is driven by the gaps in our knowledge. So, I love it when research papers like this from Staplefelt and Mammag are published online summarizing all the things that we don't yet know. In this case, for exoplanet research. Exoplanets are planets orbiting other stars in our galaxy, the Milky Way. And we currently know of just under 6,000 of them. Some being the only planet around a star that's known of and others being in multiple planet systems just like the solar system. We found everything from hot Jupiters close into their stars to super Earths that might be habitable all since the first exoplanet was discovered in 1995. I've made a deep dive video on the history of expplanet research if you want to check that out. But in this video, I thought it'd be fun to go quickfire through the 17 different knowledge gaps, the things that we still don't know that were summarized in this paper by Staplefeld and Mamec to figure out what's next for exoplanet science. So, let's dive in and start with knowledge gap number one, spectroscopic ### Spectroscopic observations of the atmospheres of small exoplanets. [1:30] observations of the atmospheres of small exoplanets. So spectroscopic observations means getting a spectrum where you take the light from an object and split it into its rainbow of colors to get a trace of how much light of each color or wavelength of light that you detect. Different molecules and atoms like to absorb unique colors of light. So if you get a gap at a specific color, you know that a molecule is there. So for exoplanets, what people do is wait for the exoplanet to pass in front of its star from our perspective here on Earth and try and isolate the tiny bit of starlight that passes through the exoplanet's atmosphere and record what happens to the light as it does. So that way you can work out what the atmosphere is made of. This is really hard to do though for smaller exoplanets, things like super Earths and mini Neptunes, especially for our current observatories like for example the James Web Space Telescope. as we've seen with the debate around the exoplanet K218b and whether we've actually detected a sign of life or not. So, we're going to need a new observatory that can actually detect those faint signals so we can work out if exoplanets are habitable and search for signs of life. Knowledge gap number two is modeling exoplanet atmospheres. ### Modelling exoplanet atmospheres [2:40] Exoplanets are incredibly diverse. There are quite literally millions of molecules that can make up an exoplanet's atmosphere. Add to that some exoplanets have days as long as their years. So only one side of the planet ever faces their star. You end up with incredibly complex atmospheres to model. Now what we do now is usually start with something we know like a solar system planet and extrapolate from there like modeling an exoplanet as like having a Jupiter atmosphere but just adding a few extra ingredients to see what happens and see if it matches the data. Extrapolation is no good though. So we need to start working on more complex atmospheric models so we can interpret future data better. Knowledge ### Spectral signature retrieval [3:20] gap number three, spectral signature retrieval. So, remember how I described how we work out what an exoplanet's atmosphere is made of and how different molecules have these unique signatures? Well, it's not quite so simple because again, there are quite literally millions of molecules that could make up an exoplanet's atmosphere. And all of the signatures they leave on light tend to overlap. This is only going to get more difficult as we get more sensitive telescopes in the future. So, we're going to need better algorithms for extracting this information from data. So that means better statistical methods, better machine learning methods, especially for doing this for noisy data like we get from rocky exoplanets. Knowledge gap number four ### Planetary system architectures: occurrence rates for exoplanets of all sizes [3:55] planetary system architectures, occurrence rates for exoplanets of all sizes. 20 years ago, the question was, do all stars have exoplanets orbiting them? Whereas now the question seems to be, do all stars have multiple exoplanets orbiting them? And if so, how are the planets spaced differently in different systems? And where do you find the heaviest versus the lightest planets? Right now, it seems like the solar system with its distribution of planets might be a bit of a weirdo. But that could be because our current detection methods for finding exoplanets are a little bit biased towards finding heavier planets and planets closer in. So, if we're going to figure this out, we're going to need either better detection methods that aren't biased or better instruments that allow us to get to those smaller planets. Knowledge gap number five, occurrence rates and uncertainties for temperate rocky ### Occurrence rates and uncertainties for temperate rocky planets [4:40] planets. Basically, is Earth a weirdo or not? How common are rocky Earth-sized planets in the habitable zone around their star where it's not too hot and not too cold for life to exist? We found a few such planets, but our current detection methods and instruments means it's harder to find these. So again, less biased techniques and better instruments will help us get a better count on how many Earthlike planets there are out there. Knowledge gap ### Yield estimation for exoplanet direct imaging missions [5:05] number six, yield estimation for exoplanet direct imaging missions. Basically, how many exoplanets in the habitable zone can we actually take a direct image of? NASA's next big observatory is the Habitable Worlds Observatory, HWO, and it's set to launch in the 2040s. It aims to take a direct image of around 100 planets in the habitable zone around their star. To do this, we'll use what's called a coronagraph that blocks the light from the star, revealing the much fainter light that's reflected off the planet. To do this for Earthlike planets, you need an incredibly high contrast. You need to be able to detect things that are 10 billion times fainter than the brightest thing in your image. That kind of technology does not exist yet. Our current observatories can only hit around the 10 to 100 million times fainter mark. So, we're going to need a huge amount of investment in these technologies to get ready for the Habitable Worlds Observatory. Knowledge gap number seven is intrinsic properties ### Intrinsic properties of known exoplanet host stars [5:55] of known exoplanet host stars. One of the biggest things that limits our understanding of exoplanets is the stars that they orbit. The blindingly bright things that are flickering and varying all the time and mess up our measurements of the exoplanets. The next discovery of the most Earthlike planet could well come around a star that we haven't spent decades observing and recording its properties. So, we're going to need more extensive catalogs of star properties over a long period of time. Gaia has given us the start of that and the Reuben Observatory when it comes online soon will give us that over the next 10 years. Knowledge gap number eight, mitigating stellar jitter as a ### Mitigating stellar jitter [6:30] limitation to sensitivity of dynamical methods to detect small temperate exoplanets and measure their masses and orbits. Or in other words, we can't find the low mass exoplanets amongst all of the noise of a star varying in brightness. Again, monitoring stars with the Reuben Observatory over a long period of time will help here, but also pushing the next missions and observatories to have a lower noise floor so that we can detect more of those faint Earthlike planets. Knowledge ### Dynamical confirmation of exoplanet candidates [6:55] gap number nine, dynamical confirmation of exoplanet candidates and determination of their masses and orbits. While we have just under 6,000 confirmed exoplanets, we also have 15,000 candidate exoplanets that have been spotted through the transit method, where a planet passes in front of its star and causes a dip in the stars light that we know it's there. But if we only spot that dip once rather than on a regular cycle as the planet continues to orbit its star, then we can't be sure we've actually detected an exoplanet. To confirm that it's there, we'd like to spot the wobble of its star as the planet pulls on its orbit. But for that, we need a spectrum. So, while Reubin is set to find a deluge of candidate exoplanets, we need to organize the follow-up spectroscopic work to confirm ### Observations and analyses of direct imaging targets [7:40] that they're there. Knowledge gap number 10, observations and analyses of direct imaging targets. Before the habitable world observatory launches, we need to choose the star planet systems that we intend to target and take the direct images of. And we'll need to know everything there is to know about those stars before we do that. From how much dust is around those stars from are they interacting with their neighbor stars, what's the velocity of those stars, what are those stars made of so we can fully understand the light that they give out. All those things are needed to ensure that missions like the habitable world's observatory are efficient and successful. Knowledge gap number 11 ### Understanding the abundance and distribution of exozodiacal dust [8:15] understanding the abundance and distribution of exozodiacal dust. Zodiacal dust is the dust that we find in the plane of our own solar system that lines up with the zodiac constellations in the sky, hence the name. Other star systems will also have dust that hangs out in the plane that the exoplanets orbit in, hence exodiacal dust. And dust plays havoc with our observations. It absorbs light at different wavelengths and interferes with our measurements of say exoplanet atmospheres. It can make direct imaging more difficult because it can add a background glow that blurs out a fake planet. So we need to understand how bright that dust can be, what it can do to light, how many stars have the dust, and how much dust. Also, we can inform how much contrast we'll need on those future missions like HWO. Knowledge gap number 12. Measurements of accurate ### Measurements of accurate transiting planet radii [9:05] transiting planet radi. To work out what a planet is made of, you start by calculating its density. So its mass divided by its volume, which you work out from its diameter. And we get diameter from the transit from how much light is blocked. But for that you need to know the size of the star first. But that can be very difficult if there are many other stars nearby and the light all smears together. So we need better accuracy on how big stars are coming from all of these star surveys that are going to be done so that we can better understand how big planets are. Knowledge gap number 13, properties of ### Properties of atoms, molecules and aerosols in exoplanet atmospheres [9:40] atoms, molecules, and aerosols in exoplanet atmosphere. As I said before, there are a plethora of different molecules that could be in an exoplanet's atmosphere. And we don't always have the lab data to know what wavelengths of light does a specific molecule absorb and how do these different molecules behave as an atmosphere's pressure and temperature changes. So again, more chemistry lab work is going to be needed to have a bigger, better database of all of these different molecules so we can better work out what is an exoplanet's atmosphere made of. Knowledge gap number ### Exoplanet interior structure and material properties [10:05] 14. Exoplanet interior structure and material properties. The habitability of a planet is not just about the temperature and what an atmosphere is made of. The inside of a planet also plays a big role as well. To understand this, we need better modeling of the inside of planets and how different materials react at different temperatures and pressures. So, this is going to be a lot of work alongside geoysicists and material scientists as ### Quantify and mitigate the impacts of stellar contamination [10:30] well. Knowledge gap number 15, quantify and mitigate the impacts of stellar contamination on transmission spectroscopy for measuring the composition of exoplanet atmospheres. As we've heard, stars are always interfering with our ability to detect and characterize exoplanets. For example, star spots, like sunspots on our own sun, can lead to gaps in the amount of light detected at a given color that can mimic the presence of molecules in an exoplanet's atmosphere that aren't really there. So, again, we're going to need better monitoring of stars, but also better modeling of stars and correction techniques for when a star spot does get in the way. The last thing we want to do is claim that we found an exoplanet that's, you know, capable of supporting life, but in reality, it's just a star spot. Speaking of signs of life, knowledge gap number ### Complete the inventory of remotely observable exoplanet biosignatures [11:15] 16 is to complete the inventory of remotely observable exoplanet bio signatures and their false positives. A bio signature is exactly what it sounds like, a sign of life. And usually that comes in the form of a molecule found in an exoplanet's atmosphere that as far as we know on Earth is only produced by life. But we don't want any false positives. So again, a lot of chemistry lab work and modeling is needed to identify new bio signatures and work out what they'd look like in an exoplanet atmosphere. So we know what to look for. And finally, knowledge gap number 17. ### Understanding planet formation and disk properties [11:45] Understanding planet formation and disc properties. We can't understand exoplanets without understanding how they form from the dusty disc of gas and debris that's left behind around newly formed stars. How does disc structure lead to different masses of planets forming and what kind of chemistry goes on in those discs? and how much of the chemistry that's needed to make the building blocks for life occurs in that protolanetary disc rather than on individual planets after they formed. Lots of work with the James Ob Space Telescope and radio observatories like ALMA will be needed to understand these protolanetary discs in more detail again to help decide on the best targets for future missions. So there you have it. All 17 of the knowledge gaps for exoplanet research identified by Staplefelt and Mame Egg. Each of these goals brings us closer to finding more Earthlike planets, uncovering any possible signs of life out there in the universe, and ultimately figuring out where we all came from. Cuz let's face it, we're not just doing research on exoplanets here. We're also figuring out humanity's place in the universe with ### Bloopers [12:56] the whole debate around the exo. Shut up. Lower noise floors. Noah lower noise floors. No lower noise floors. Say that 20 times faster. Rocky like explanatory. Ow. Jesus. Oh, good god. I'm just malfunctioning everywhere today. Oh, when did the upgrade to Mac OS sequoia pop up in the background? That's rude. I'll just be in the corner just like that'll be all I can look at during the edit. That thing just being like upgrade, upgrade.