Astrum Space - These Exoplanet Discoveries Could Change Everything

Episode Date: October 5, 2026

In this compilation, we’re journeying to distant alien worlds. We’ll dig into the latest exoplanet discoveries, explore the weirdest planets ever detected, and find out whether alien life could exist in the TRAPPIST-1 system - the most Earth-like planets we’ve ever found.▀▀▀▀▀▀A huge thanks to our Patreons who help make these videos possible. Sign-up here: ⁠https://bit.ly/4aiJZNFThe Astrum book is still available in the US! Get your hands on one here: ⁠https://astrumspace.co/⁠

All right everyone, here is one of your most asked for videos, everything you could want to know about the Trappist system. And I can see why there is so much interest. It is such a unique system compared to anything else that we know of. An entire solar system contained well within the distance of Mercury and the Sun. It is one of the closest places to us that could harbor alien life outside the solar system, it being only 40 light years away from us. That means we won't be visiting it anytime soon.

But with improved technology from the James Webb Space Telescope, we will be able to gain an insight into another solar system like never before. I'm Alex McColligan and you're watching Astrum, and together we will go through the Trappist system and see why it is so special. Let's begin at the heart of the Trappist system, Trappist One itself. The ultra-cool red dwarf star, a star which is just a little bit bigger than Jupiter, but a lot more massive. Red dwarf stars are the most common type of star in the galaxy.

Even our closest neighbor, Proxima Centauri, is a red dwarf, as is 50 of the closest 60 stars to us. Being so cool means they are very long-lived. Stellar models suggest they could exist for trillions of years, which is far more than the current age of the universe. Although there are many known red dwarfs with Xer, exoplanets around them, typically red dwarfs are dubious candidates to have life. This is because the Goldilocks zone, or the distance from the star, where water could theoretically

pool on the planet's surface, is extremely close to the parent star. Meaning any exoplanets orbiting in this zone are likely tidily locked. This means one side of the planet would always be facing the star, and the other side would be in perpetual night. The nightside would be cold enough for gases in the atmosphere to freeze. Also, red dwarf stars are often flare stars, or stars that can have their brightness increase very rapidly to magnitudes brighter than they are normally. This is similar in a way to a solar flare on our sun, but on a much grander scale. This variation in temperatures and radiation is not good for life to develop on any planets

nearby, or for planets retaining their atmospheres during a huge flare. Trappist 1, however, while being a red dwarf, does not flare up as much as its other red dwarf cousins, 30 times less than a typical red dwarf star, great for the chances that atmospheres exist on the exoplanets around the star. All the exoplanets are likely to be tidily locked to the parent star, though, something they'll come on to later. Which leads us nicely to the planets of Trappist 1. Trappist 1 has astounded scientists, in that it has seven known Earth-sized planets orbit in it.

Optimistically speaking, six out of the seven planets orbit within the system's Goldilog zone. This was quite the revelation, given how key liquid water is to life, and one that I imagine came with a huge sense of satisfaction for the scientists who discovered it. If you two are keen to accomplish something yourself, and you never know what future scientific discoveries await you, you should check out the sponsor of today's video, Coddy. Coddy is all about leveling up and learning to code in a super fun and accessible way. With challenges, quizzes, and real-world projects to help you build up your coding skills

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It should be noted, though, that our current observations aren't going to be perfect and will only improve as time goes on, but this is what we think at this point in time. Trappist 1B, the closest planet to the star. It is slightly larger than Earth, but with the same mass, meaning surface gravity would be about 80% of Earth's, quite similar to Venus. It is also similar to Venus in that it has extremely thick atmosphere, potentially full of CO2, meaning that because this planet only orbits 1.7 million kilometres from the star, it's going to be really hot. A year on Trappist 1B lasts only 36 hours. This atmosphere could also be rich in water, and surface pressure is likely to be 10,000 times

greater than Earth. With such close proximity to the star and significant greenhouse gases, surface temperature is thought to be between 500 and 1,700 Celsius, not the ideal place for our type of life then. Trappist 1C is the next planet, orbiting at 2.4 million kilometres away from the star. Its year lasts 58 hours. At this distance out, it is getting about two times the starlight Earth gets from our sun. Its size and mass are about 10% more than the Earth, which means it has a very similar gravity to Earth. It is very similar to Trappist 1B, in that scientists believe it to also have a thick water vapor atmosphere, although Trappist 1C is probably less thick. This means its surface temperature is likely to be hot,

but not as high as Trappist 1B. Next is Trappist 1B. Next is Trappes 1C. Trappist 1D, only an extra 1 million kilometres further out than Trappist 1C. One year lasts only 97 hours. Trappist 1D is kind of like a mix between Earth and Mars, as it's 30% smaller than Earth and only 30% as massive, meaning the surface gravity is little under half of Earth's. It is found on the inner part of the Goldilog zone, meaning at this point in the solar system, The surface temperature is now cool enough for water to pool on the surface. It only receives 4.3% more starlight than Earth, and combine this with solar flares from the

star, it is likely to still be pretty toasty for our standards. Trappist 1D has been found to have a volatile layer on the surface, perhaps an ocean or a thick atmosphere. And this is where oceans and atmospheres become very important, because as I mentioned, All these planets are likely tidily locked, meaning a thin atmosphere or no atmosphere means that one side of the planet would be scorched and the other side would be freezing, much like what happens with Mercury. Venus, on the other hand, has a thick atmosphere which circulates the heat around the planet, meaning night or day, the temperature is the same. So if these trappist exoplanets,

like Trappist 1D has only a thin atmosphere or small ocean, the chances are that one side of the planet would be devoid of anything but rock, the other side might be covered in icees. There might be a small band of habitability along the twilight zone, but that would be it. With a large ocean or atmosphere, the planet might be able to distribute the heat much better, meaning it would be habitable all over,

as much as we understand habitability anyway. This planet may well be an ocean world, with over 250 times the amount of water more than Earth's oceans. Although other studies have suggested the atmosphere could also be similar to Venus's, we will get a better understanding from the James Webb Telescope. Travis 1E orbits another 1 million kilometres out again, at 4.4 million kilometres from the star. its year takes 146 hours, and at this distance it only gets 60% of the starlight Earth does.

Size, mass and gravity are all very Earth-like, and it is probably the only planet in the Trappist system to have a rock-iron composition like Earth. It also has a compact, hydrogen-poor atmosphere, which is good as hydrogen is a strong greenhouse gas, and will make the planet inhospitable from this distance. With this compact atmosphere, water could pool on the surface, and the temperature would be very Earth-like if a little cooler depending on the albedo of the planet and how much heat the atmosphere retains.

All in all, it is considered one of, if not the, most Earth-like exoplanet that we know of, and it's going to be one of the first targets of the James Webb Telescope to try and detect signs of life. How amazing would it be if it really was a cousin to Earth only 40 light years away? From Trappist 1F and beyond, we're still in the Goldilocks zone, but it's starting to get much cooler at this distance. Trappist 1F orbits a distance of 5.8 million kilometres from the star, and a year takes 220 hours, or roughly 9 days. Its size is very Earth-like, although it is less dense, meaning surface gravity would be about 80% of Earths. The most recent studies on this planet have suggested that its low density means it is likely to be 20% water,

which at this distance from the star would cause a massive greenhouse effect, meaning the water would be in gaseous form. This is known as a steam world, and it would probably be no more habitable than the ice or gas giants in our solar system due to the high pressure and temperature on the surface, likely in the hundreds of degrees Celsius. Trappist 1G is slightly bigger than Earth and orbits at 7 million kilometres, taking 12 days to do so. There hasn't been too much information discovered about this planet, other than water has again

been found on it. This planet is still found in the Goldilocks zone, although right on the far edge, so it is still a candidate for habitability. And lastly, Trappist 1H. It orbits at 9.3 million kilometres and takes 19 days to do so. It's the smallest of the known exoplanets in this system, and also the least dense, meaning its gravity is comparable to our moons. Due to the cool nature of the host star, being this far out means the planet is likely icy,

as it does have water. Theoretically, it could also have liquid water on the surface if it had a hydrogen-rich atmosphere to act as a greenhouse gas, but again, little is known about this planet. So that's all the planets. Could this system really be habitable? Well, it depends on a number of factors, but what we've seen so far is promising. Water has been detected on most, if not all, the planets. The host star is a red dwarf, but not a very active one.

If these exoplanets have strong enough magnetic fields, they could deflect a lot of the solar wind. If any of them do have magnetic fields, I can't imagine how glorious some of the aurora on those planets would look like. They are also all roughly Earth-sized, with similar gravities and densities. Not a huge factor for life, but we know it worked here. And lastly, although these planets are tidily locked, they may still have mechanisms for evenly distributing the heat across the planet. All in all, Trappist One is such an interesting system, and I can't wait to see what we find out about it in the future. My fingers are crossed, my thumbs are pressed, I'm praying that James Webb Telescope

launches successfully in 2021, what it is going to see in the universe will be astounding, I guarantee it. In a universe of seemingly infinite scale and countless wonders, it's curious that the one thing we're desperate to find is something as ordinary as ourselves. To discover, that we are not alone. Just 40 light years away in the constellation of Aquarius lies a tiny dim star. Trappist 1. It's cold, ancient and barely visible.

And yet it hosts something extraordinary. Not one, but seven Earth-sized planets. It's as if nature itself set up an experiment. Can life exist around a star like this? One by one, scientists have ruled out most of these worlds as being habitable. Too hot, too cold, no atmosphere, no chance. But one world still holds promise. Trappist 1E.

And now, thanks to data from the James Webb Space Telescope, we may finally have a glimpse of its atmosphere. What we found is astonishing. Could this be the first true Earth-like planet beyond our solar system? Could Trappist 1E host life? I'm Alex McColgan and you're watching Astrum. Join me today as we travel to the Trappist 1 star system to explore the potential for life on its most promising planet. We'll look at new data from the James Webb Space Telescope

that has pushed it to its limit. limits, revealing the likely composition of Trappist 1E's atmosphere and whether it could support life. That is, if the very star that offers the chance of life hasn't also issued a death sentence. Trappist 1 is an M8-class red dwarf. Only a little larger than Jupiter, it's 1,800 times less luminous than our sun, a difference that's like comparing a candle to a college running track floodlight. Although the star was first discovered in 1999, its full planetary lineup wasn't revealed until 2017

when it became the first and only planetary system to be discovered by the Trappist optical robotic telescope. This telescope is made up of two parts, Trappist South in the Chilean Mountains and Trappist North in Morocco's Atlas Mountains. They use transit photometry, a technique that measures periodic changes in the brightness of a star to find orbiting planets. In other words, if a planet passes between us and the star, then some of its light is blocked, and so we detect a dip in the star's apparent output. By taking multiple observations, the telescopes were able to isolate the individual orbits of multiple planets around Trappist 1. Initially, their data analysis only found the three innermost planets,

but further data from both of the Trappist telescopes, as well as the Spitzer Infrared Space Telescope, took this total to 7. And not only that, but they are all rocky, and all, at least roughly, earth-sized, making this the most Earth-like planets found around any star. If you'd like to know more about all the individual planets around Trappist 1, I made a video about them. You can check it out with the link on screen. But with such a small, dim star at the center, is there really any hope that they could be habitable? For any of these planets to receive enough light to support life, the orbits need to be much

closer than we are to our Sun. In the Trappist 1 system, the planets certainly are. In fact, all seven are incredibly close. Trappist 1E orbits only one-th of Mercury's orbit, which means it could be tidily locked to its host star, the same side of the planet facing the star at all times, just like we only ever see one side of our own moon. This has significant implications for the habitability of the planet, and we'll dive into those later in the video.

But more interestingly, its orbital distance also means that it is right in the the middle of the predicted habitable zone, where it receives about two-thirds of the energy that we do from our sun. And that is why scientists are so curious about this planet. But it takes more than light for life to thrive. Trappist 1E would almost certainly need an atmosphere, so that's exactly what scientists have been looking for using our most powerful space-based telescope, James Webb. The teams who were involved with developing James Webb were rewarded with guaranteed observation

time. One group, the deep reconnaissance of exoplanet atmospheres through multi-instrument spectroscopy, that's right, the Dreams team immediately wanted to set James Webb's sights on the Trappist One system. The James Webb Space Telescope is uniquely sensitive and precise, so much so that it can detect spectral signatures from the thin band of gas that makes up the atmospheres of these planets, a whole 40 light years from our own. It does this thanks to a technique called transmission spectroscopy. As an exoplanet passes its mother star, James Webb not only measures the drop in brightness,

but also how the spectrum of light changes. The telescope's near-infrared spectrometer, or NERSPEC for short, measures the wavelengths of infrared radio, the radiation closest to the visible spectrum. Molecular bonds absorb energy in this range, and different bonds like this carbon-hydrogen bond in methane, or this carbon-oxygen-double bond in carbon dioxide, absorb different wavelengths. It means that by measuring which wavelengths are absorbed as a planet transits its star, we can first of all work out if there is an atmosphere, and then, if so, determine which gases

are present. And it's been particularly easy to get a read at Trappist 1. In fact, the data we have is 10 times more sensitive than what we have on any other system. Why? Counterintuitively, it's because the star is relatively dim. The light a planet obscures causes a bigger relative drop in apparent brightness of this star than the same planet passing in front of a large bright star. A bigger difference is easier to measure.

Using these measurements, the team have already discounted Trappist 1C and D from having atmospheres, but results from observations of Trappist 1E, a rocky planet around 0.9 times the size of Earth, were so intriguing that scientists couldn't ignore them. It looked like this planet may, in fact, have an atmosphere. And that was more than enough evidence for the Dreams team to decide to use up all their guaranteed James Webb time trying to find more. So far, they've seen four Trappist 1e transits with James Webb. But what did they find? Well, we can start by discounting a few possibilities. We now know that

Trappist 1E does not have a primordial atmosphere, one a planet is born with. These are usually dominated by light gases like helium and hydrogen, which haven't been detected. They were likely stripped away by the star's radiation, early on on in its life, nor does it seem to have a carbon dioxide dominant atmosphere like Venus, which is thick and dense. An atmosphere like that of Mars, which is thin and sparse, is also unlikely given the recent measurements. Believe it or not, all of this is good news, as it's unlikely that any of these atmospheres

could support life, well, not as we know it anyway. So what atmosphere does it have? Here's the big one. There could be an Earth-like atmosphere, one dominated by a heavier gas such as nitrogen, with a strong greenhouse effect from water, carbon dioxide, or methane. Such an atmosphere with a surface pressure of around one bar, equivalent to Earth's, may be able to sustain enough heat transfer to the dark side of the planet to allow a global surface ocean, despite it being tidily locked.

Were this confirmed, that would make headlines the world over. However, that might be too much to ask. The data instead slightly favours the idea that Trappist 1e is a cold planet without a global ocean. High levels of methane instead create a reverse greenhouse effect. Trappist 1 has a surface temperature of about 2,400 Kelvin, much cooler than our sun's 5,670 And more of the energy it outputs is shifted to the near-infrared wavelengths. Atmospheric methane can absorb that energy before it even reaches the surface of the planet,

then re-emitted into space, resulting in a cooler atmosphere. For the tidily locked trappist 1E, this would mean that liquid water may only exist on the surface of the planet that permanently faces the star. No global ocean here. that's not necessarily bad news for life either. Such conditions could satisfy Darwin's warm little pond hypothesis of the origin of life. And atmospheric modeling has backed this up. Simulations suggest that even if Trappist 1E has limited water, or if what water there is is locked on the dark side of the planet, it could still have a stable atmosphere. Although this may lead to

what's known as Terminator habitability, where life could only find a home across a dynamic band in perpetual twilight that separates day from night. But water on the surface isn't the only option. We know Trappist 1e is rocky, but not much more than that. It may be an icy volcanic planet with a subsurface ocean like we find on Europa and Enceladus in our own solar system. Life on Earth is believed by some to have formed near deep sea. events and the same process could happen on 1E.

No matter where on Trappist 1E water may be, life is possible. There's an energy source and potentially an atmosphere that provides the building blocks for life. But there is one issue. Although all these things are possible, scientists can't completely rule out the possibility that Trappist 1E is a cold, barren, and airless marble with no atmosphere at all. So, we need to talk about what could prevent a stable atmosphere from ever forming, and in this case, it's the red dwarf star, Trappist 1 itself. Imagine standing with me on Trappist 1E just for a second.

Look up. The star above us would appear more than four times as large as our sun in the sky. The star would be a deep red, orange colour, illuminating the sky as if it were in perpetual sunset. What a sight that would be. Now, Red Dwarfs are extremely active, and they produce more powerful flares than our sun, and more often too. The worst recorded geomagnetic storm to ever hit Earth was the Carrington event in 1859, a greater than one in 100-year event.

Trappist 1 is believed to release a flare this powerful more than once every two days. You'd likely be able to watch solar flares arcing out into space in real time. And they carry huge amounts of energy towards a planet, enough that over time any atmosphere could be stripped away, making life as we know it all but impossible. That's assuming that the atmosphere was ever allowed to form at all. Red dwarfs are stupendously long-lived. Trappist 1 is expected to exist for 10 trillion more years, that is, 700 times the current age of the universe. By comparison, our son likely only has 5 billion

years left before it becomes a red giant. You might think given the stability and lifespan of a red dwarf, there would be plenty of time for life to find a way, but because of their long lives, their chaotic and energetic teenage years before red dwarf stars settled down are correspondingly longer. It's during these formative years that some planets begin to produce their own atmosphere, slowly replacing their primordial hydrogen- helium atmosphere with one comprised of heavier molecular gases such as carbon dioxide, nitrogen and methane. These chemicals are released from inside the planet through volcanic activity. The problem is, if the aggressive atmosphere-stripping phase of a star lasts too long,

then an Earth-sized planet might not have enough resources within its interior to fully generate a stable, life-supporting secondary atmosphere. The unfortunate reality is that if a planet's atmosphere isn't established before 5 billion years, it may never generate one, condemning the planet to a death sentence before it was ever allowed to live. With Export Development Canada, Canadian businesses are competing, leading and winning in more international. markets, like how agri-food businesses are strengthening global food supply, and critical minerals are powering industries of the future. Their ambition can't be contained. And with EDC behind them, neither can their growth. Export Development Canada is the financial partner for Canadian businesses

going global. Visit EDC.ca for more. I know it's actually sounding rather hopeless for Trappist 1E, And I bet you're wondering, how is this one of the most promising planets? But we don't yet know one way or the other whether an atmosphere has survived or not. We've already seen there are hints of its existence, and although the star's violent outbursts may be one eased downfall, they may also be completely necessary for life to begin. UV radiation from flares may be essential to create RNA building blocks, molecules that are central to the metabolism of every life form ever found.

And now that Trappist 1 is in its karma main sequence phase, with lower UV and X-ray irradiation than in its juvenile past, there is a chance of a stable, habitable atmosphere existing on Trappist 1E. And that atmosphere could have protection from the continuing flares with its own magnetic field, just like the Earth does. The Earth's magnetic field exists because its outer core is a moving mass of molten iron and nickel. There is a good chance that Trappist 1E has a similar system.

In fact, Trappist 1E's close orbit to the Red Dwarf could actually help maintain its magnetic field. If Trappist 1E's orbit is eccentric, this would cause repeated compression and relaxation of the planet's shape. This process creates internal friction that could heat the interior as much as zero 0.18 watts per meter squared. That's roughly 24 times the tidal heating flux generated in the Earth. We see a similar process in Jupiter's moon, Io.

IOT is tidily locked with an eccentric orbit and gets stretched and squashed by the gravitational interactions with the other Jovian moons, pumping it full of energy and making it the most volcanically active body in the solar system. So, where does this leave us? Well, we may have an Earth-sized, volcanically active, rocky planet with the building blocks for life, its own atmosphere and magnetic field, orbiting in the habitable zone of a relatively calm red dwarf, or it could be a cold dead world. So let us know in the comments which you think will eventually be confirmed.

We might not get an answer until the proposed Habitably World's Observatory, a telescope designed to look for life around stars like our own, which launches in 2041. But until then, James Webb's observations are our best bet. The fact we are able to measure the light absorbed by a thin, gaseous layer around a rocky planet orbiting a dim red dwarf star 40 light years away is pretty incredible. And scientists haven't given up hope. They've learned from the first sets of James Webb data, and modified their technique to achieve more precise measurements. With another 15 transit observations planned before December, they expect to be able to confirm

the presence or absence of carbon dioxide and a secondary atmosphere, a key step in the search for life on 1E. Perhaps Trappist 1E and its neighbours will turn out to have a unique inhospitable atmosphere, or perhaps one that could theoretically support life. Or maybe, just maybe, we'll find one just like home. It's exciting to find so much potential for life relatively nearby, even in the midst of an extreme environment. But whatever the atmosphere turns out to be on Trappist 1E, with the recent discovery of formations

on Mars that are thought to have been impossible to form without life, I find it hard to shake the feeling that the discovery of extraterrestrial life feels inevitable. The only question is, when? You have probably heard of the Kepler Space Observatory, a spacecraft that hunted for exoplanets in our galaxy. It carefully examined a patch of space which contained roughly 150,000 visible stars, and with its combined camera resolution of 94 megapixels, it searched for stars that dip in brightness periodically.

The theory is that if a star dims regularly in constant intervals, it's because one of its planets has passed in front of it from Kepler's perspective, which causes that star to dim. The Kepler mission has been wildly successful, beyond the expectations of most. Discovering a total of 2,662 planets since 2009. But sadly, Kepler hasn't been in full operation since 2013, as two out of its four reaction wheels have failed. These reaction wheels keep the viewing angle of the spacecraft stable, otherwise it loses sight of its fixed field of view. The reaction wheels that were still working couldn't keep Kepler steady enough to continue its mission.

So instead of abandoning the spacecraft altogether, NASA came up with a new mission. Instead of fighting against the rotation as it orbits, it would see what it could find in different fields of view. The way it did this was quite ingenious. In solar wind pressure, they could keep the spacecraft aligned for about three months looking at one patch of sky, all the while preventing rotation of the spacecraft. So very much a balancing act. During the second mission, or K2 as they called it, it found even more exoplanets, which brought

it to the 2,662 total, with about twice that still considered exoplanet candidates. But on the 30th of October, just two weeks ago from writing this script, Kepler finally ran out of fuel, and the mission has been retired. Kepler will be left roughly 100 million kilometers away from us, forever orbiting the sun now that it can finally rest after its almost 10-year mission. Because of this mission, 2,946 scientific papers have been published. found worlds similar in size to our own, and has confirmed that there are more planets than stars in our galaxy. But what now? Is that the end for exoplanet hunting? Fortunately, it's not.

Earlier this year, NASA launched the Tess spacecraft, an ambitious upgrade to Kepler. But what sets Tess, or the transited exoplanet survey satellite, apart from Kepler? Well, and like Kepler, tests will be in orbit of the Earth and not the Sun. Its orbit is quite interesting, in that it approaches the orbital distance of the Moon, except its orbital plane is about 40 degrees compared to the Moon. This highly elliptical orbit maximizes the time it can spend observing the stars. During its orbit, it approaches close to the Earth, during which time it will transmit the data it has collected, before set on its camera. cameras back to the sky. It orbits the Earth roughly twice a month, meaning it avoids the

gravitational tugs of the moon that would otherwise affect its orbit. Tess began testing its cameras as it approached its orbital plane in July 2018. It fixed its view on a region of space, and this is what it saw over the course of 17 hours. The first thing that comes into view is this big white blob that moves across the image. This This is actually a comet, and you can even see the direction of its tail shift as it moves around the sun. These two stars here are variable stars, or stars that change in brightness very quickly for astronomical standards.

Most of the other dots in the image are fixed stars, although if we speed up the footage, you can even see a few asteroids moving across the image. Here are a few of them moving by here. In August of 2018, Tess reached its intended orbit and began its own mission in earnest. Although still using the transit photometry method to find exoplanets like Kepler did, it is different in that it has 4 16 megapixel cameras, which each covers a square 24 degrees across. That's wide enough to easily fit in an entire constellation. These four cameras are arranged so tests can view a whole strip of the sky at once.

It will lock onto this section of the sky for 27 days before moving on to the next, eventually covering the whole southern sky over the course of its first year. After that, it will move on to the northern sky, eventually observing 85% of the total sky, an area 350 times bigger than the Kepler telescope. Here, you can see the Kepler and the K2 fields of view for comparison. Through this method of observation, the poles will be under constant surveillance, meaning it will be able to detect exoplanets even if their orbital periods are greater than 27 days in these sectors.

TESC won't be the only exoplanet hunting mission either. The ESA will be launching their own version of this mission in 2026, called PEOPLEC. Plato. And once the James Webb Space Telescope is finally in operation, it will look at trying to image these exoplanets to see what kind of atmosphere they have. One last exciting proposal, which hasn't been approved yet, is the New World's mission. It would be a large occultor that would block the intense light of a distant star in order to see the planets around it.

It would work with missions like the James Webb Telescope, or have its own dead Our galaxy is filled with strange planets. Now, this should not surprise anyone. You just need to look at our own solar system to get a sense of the variety that exists. Rocky planets, gas giants, boiling surfaces, icy worlds. Some planets with rings, others with moons, some with storms the size of entire smaller planets. But those pale in comparison to the minds. in comparison to the marvels that exist once you start to look further afield.

To date, NASA has confirmed the existence of more than 6,000 exoplanets in the Milky Way, and while many of them seem to follow the mould of what we would see in our solar system, others, to say the least, seem truly bizarre. Worlds with multiple suns in their skies. Worlds with rain made of molten iron. with rings the size of Venus's orbit, worlds larger or hotter than stars. But out of all this, what are the strangest planets we've discovered? What are the marvels our galaxy has in store for us?

And what further wonders may still be out there. I'm Alex McColgan and you're watching Astrum. Join me today in this supercut as we take a look at the military Heways' strangest exoplanets. When it comes to planets, many things can make them strange. For instance, sometimes strangeness is not found in the planet itself, but how it moves around its star. While we are used to some large or small orbits in our solar system, how long or short can

a year actually get? Let's start off close to home. Mercury has a pretty short year. 88 Earth days, which is the shortest orbit that we know of in our solar system, and very interestingly, due to the way Mercury rotates, one Mercurian day is twice as long as its year. Yes, there's exactly two years in its solar day. So should anyone ever live on Mercury, you would have to switch around your way of thinking when it comes to describing a shorter reference of time. But it's kind of cheating to say a year

on Mercury takes half a day, when it still takes 88 Earth days. So let's keep to Earth time scales, as the point of reference. Outside of the solar system, most exoplanets that we know of have really short years, and that's because of the way we detect the majority of exoplanets. There are observatories that look closely at thousands of stars at the same time, looking to see if an orbiting exoplanet passes in front of its parent star, causing the star to dim ever so slightly from our perspective. In order for us to confirm that the dip in brightness is caused by an exoplanet,

we need to see a pattern of dips in regular intervals. So if an exoplanet does transit a star, but it takes two Earth years before it transits again, then we would need to be constantly monitoring the star for many years before we can confirm that the dips in the star's brightness are caused by an exoplanet. On the other hand, exoplanets with really short years, like a few days or weeks long, can be confirmed as exoplanets very quickly. This means that most exoplanets that we know of only take a few days to orbit.

The famous trappist system exoplanets all orbit their parent star within one month. The closest planet to the star only takes 1.5 days. So, out of all these thousands of exoplanets that we have discovered so far, which is the planet Which one has the shortest year? Incredibly, there's a pulsar out there which has a planet, although it could also potentially be the core of another collapsed star, which orbits around the pulsar in only 48 minutes and 58.5 seconds. How can this happen?

Well, not only is the orbiting object extremely close to the pulsar, but it is moving very fast. A neutron star is also very small, at most only around 30 kilometers across. yet it is incredibly massive, so much so that its gravity even bends a light around it. A fast-moving object can stay in orbit because the neutron star's gravity is strong enough to keep it there. Although, you may say this is cheating again, a pulsar isn't really a star, more like a star remnant. So what about a main sequence star? In this case, the shortest year that we know of goes to K2-137B.

B, a planet that's year lasts only 4.31 hours. Because it is orbiting a main sequence star, the Earth-size exoplanet is surely orbiting within the star's atmosphere, and will eventually either be ripped apart by tidal forces, or fall into the star completely as atmospheric drag slows it down. On the other end of the scale, the longest year that we know of, belonging to a planetary mass object, is this beautifully named. planet. This Jupiter-type objects year lasts roughly 1 million years.

Still, for some planets, talking about how long it takes for them to orbit their star, doesn't make sense at all. After all, some orbit more than one. In our solar system, we like to keep things simple. Just the one star found in the center, with everything else orbiting around it, as is the case for most planetary systems found in the universe. However, there are some planetary systems out there where things get a bit more complicated, specifically multi-star systems, where there are two or more stars that orbit each other.

In such configurations, what happens to any planets orbiting them? In fact, can planets orbit them at all with the gravitational tugs from different directions? To answer the latter question, the simple answer is yes. Planets can orbit in such situations, although to answer the former question, there is no one-answer-fits-all rule about how a planetary system in a multistar system might look. What we can do, however, is explore some of the possibilities out there. But before we look at planets, it would be good to understand how multistar systems work. For the most part, stable star systems have organized themselves in the world.

to hierarchical systems. This is due to the proximity in which they formed with each other, which we will touch on a little later. Binary star systems are generally simple enough. Binary stars orbit around a barricenter, or in other words, their center of mass. If the masses of these two stars are similar, then nearly symmetrical elliptical orbits are often seen. Although there can be occasions where they orbit in circles in a similar fashion to Pluto

and Sharon. In the case that one object is more massive than the other, then the more massive objects orbit doesn't take it as far out compared to the less massive object. Beyond binary systems, you can have 3, 4, 5, 6, 7, or more stars in the same system, and as you will see, there is a structure within these systems to keep them stable. In the case of 3 stars, you'll have 2 stars orbiting each other in a by binary configuration, with the third orbiting around a barrier center with the other two. This keeps the system stable, because if three stars had their orbits cross, one would

certainly get ejected from the system at some point. In a three star system, two of the stars are contained in their own enclosed little system, acting as one star in the grand scheme of the whole system itself. We group this binary configuration into a tier, with that tier acting together in its association with the single star. In a way, once you have grouped the binary configuration in the system, this upper tier now acts like a two star system again, with the two stars and the one star orbiting each other. In the case of four stars, you'll either have two binary configurations orbiting around a barry centre, or one binary system orbiting a barry centre with a third star, and all three

of those stars orbiting around a barry centre with a fourth star. From here on is where the hierarchical system really comes in handy. With a chart like this, you can easily see how the system works. In the two binary configuration case, you have the two binaries orbiting the system's center of mass. In the single binary and two single stars configuration, you'll add another lower tier in the configuration. You have the binary here, which orbits this third star, and all three of these stars are orbiting together with the fourth star. If there are more stars in the system, say five, you can have an array of configurations,

with various binaries or single stars on a variety of tiers. Yet with this chart you can easily see where the mass lies. You can do the same for systems with six, seven, or more stars, but anything above seven is exceptionally rare and probably won't remain stable, although maybe maybe even if you can't be Maybe there are examples somewhere in the universe where it exists. So let's add planets into the mix. Could there be a planet out there with seven suns in its sky? Well, yes.

Let's have a look at this hypothetical seven star system again. By here, there are three stars in a configuration, two in a binary configuration and a single star. We see that the single star has planets that specifically only orbit that star. have one sun. Beyond that, there are planets that orbit both that star and its binary companions. These planets could be said to have three suns as they are orbiting three stars. Going to the top tier, there is a planet here that orbits the entire system. This planet could be said to have seven suns. Let's see what that looks like outside this graph. Interestingly, in a seven star system, from this

This distance, it only looks like the orbit of a binary. That's because each set of stars is found in one of these two points. Here is the planet with seven suns. Its orbit takes it so far out that these stars aren't very bright in the sky, so even though it has seven suns, they don't really provide much in the way of warmth or light. Zooming in on the set containing three stars, we see the planets which orbit all three of these stars. These stars would appear much larger in this planet sky compared to the planet sky that was orbiting all seven.

In this example, the two in the binary configuration appear almost too close together to distinguish, with the single star clearly separate. The other four stars that are part of the other set in the system are dim in the sky, they are very far away, and again don't provide much in the way of light or warmth, meaning there is a clear day and night on these planets. Interestingly though, this other set of stars would get marginally brighter and dimmer during their orbits, and the distance between their system's orbits would get more noticeable as they get closer.

Lastly, let's look at a planet orbiting just the one star in this system. It orbits closely to the star and is tidily locked, although the night side would be disrupted by the binary configuration this star orbits with, as the planet's orbit can take. take it between the single star and the binary stars. The binaries orbit together closely, and so wouldn't easily be distinguished in the sky without a filter. Again, the other set of stars in the system would be dim and appear far away. This may make you wonder how many systems out there have more than one star.

Are we unusual? Or is it the trend that there is only one star per system? Well, if you look up into a clear night sky, it may surprise you to know that most of these stars are binaries. The brightest star in the sky, Sirius, is a binary. Alpha Centauri, the closest star to us, is a binary, or maybe even a trinary if you include Proxima. Polaris, the North Star, is also a binary.

So for the longest time, astronomers thought that we were the unusual ones. However, it's coming to light with the improvements in technology that this is not the case, and that most star systems only contain one star. Perhaps the reason why the brightest stars in our sky are binaries is because they are giving off twice the light. Single stars are just generally dimmer and harder to see in comparison. It doesn't help either that 85% of all stars in existence are red dwarfs, and it seems that only about 25% of them have companions.

In fact, it's interesting that binaries occur much more frequently with the really massive stars, the blue and white giants. This could be because of how these stars formed. Red dwarfs weren't pumped with as much material as they were forming, hence why they never attained the mass of a blue giant. In an environment where forming a blue giant is possible, however, models suggest that several stars could form at the same time. At first, these systems would be chaotic, the stars would be ejected until order could be found.

The ones that remained and survived were the ones that ended up absorbing the most interstellar medium, thus becoming the most massive of stars. The interstellar medium that ended up caught in protoplanetary disks around these stars later form planets. The first planet we ever discovered with more than one sun in its sky was Kepler 16,000. B, spotted by NASA's Kepler Space Telescope in 2011. At the time, it became known as the Tatouine planet. However, Kepler 16B is no desert world, but is actually a gas giant around 0.3 times

the mass of Jupiter. Tracing its orbit around its star has fascinated scientists who are trying to unravel the three-body problem, the complicated mathematics that traces how three-body re-orbiting bodies interact with each other. Since then, a handful of other Tatouine planets with their multiple stars in their sky have been discovered, indicating that they are not uncommon in our universe. After all, more than half of all stars in our galaxy have at least one partner. But what would it be like to live on a planet with two suns in the sky? Or to help us visualize the point, how much would having a second star impact us here on Earth? How hot would Earth get? What would

the day and night cycle be like? Would it be possible for life as we know it to survive in a multi-star system? Well, it depends. Let's keep our sun as it is, and only make the second star the variable in this thought experiment. As we know, stars come in all sizes from small, cool, cool and dim red dwarfs, all the way up to large, hot, and bright blue super giants. In a binary star system, the stars orbit around the system's barric center, or the center of mass. Depending on the mass of the stars and the distances between them, you'll have differences in how these orbits look. For similarly sized stars, the orbit could look circular in nature, or in an ellipse. On the other hand, the bigger discrepancy there is between

the star's masses, the closer the barricenter will be to the more massive star. Let's say we plonk a red dwarf, which is the smallest star type, in a close orbit around our sun. Even though a red dwarf can be as little as 7.5% the mass of our sun, it's already going to have a big impact on us. From our perspective, the star would look like it orbits the sun, meaning there would be times when it transits in front of the sun and other times where it eclipsed by the sun. Our year would be shorter if we stay one astronomical unit from the star's barricenter. Because of the increase in mass and gravity of the system from the extra star, Earth's velocity would have to be faster in order to not be pulled into the stars. Either that

or its orbit would have to be slightly further out if we want to maintain our current velocity. The increase in temperature from the star would be noticeable too, definitely making it unbearable for humans, but exactly how hot would depend on a variety of factors, like a runaway greenhouse effect, the heat of the star, and more. But let's say we place Earth's orbit in such a location that we can survive. Seasons would still be massively impacted, as the tilt of the planet would be secondary to the distance to the second star. When the second star is as far away as possible and a hemisphere on Earth was also experiencing winter, it would get extremely cold. On the other hand, combine a summer with the second style passing as closely as possible,

and it will be incredibly hot. Additionally, a curious phenomenon with red dwarfs is that they also produce huge flares, much larger than the ones our sun produces. They would easily knock satellites offline on a regular basis, and Earth would have spectacular aurora. Our power grid as it stands would also be under serious threat from these stellar flares, as they would act like hemisphere-wide EMP bombs. The interactions with the second star could well make our sun more active too, meaning it too may produce more flares. So even with the smallest type of star, our habitability on Earth would be under serious threat. Increase the mass of the

second star, and you'll start to get additional stars. problems, like increased UV radiation, making going outside more and more dangerous. You'll also have two shadows a lot of the time. Once you turn the second star into something like a blue super giant, there really won't be a place in the solar system where there is even a hope of habitability. Blue super giants can be many times the mass of our sun, the theoretical limit being 150 solar masses, although some argue this should be higher. Their volume is also big. They make the sun look absolutely puny in comparison. They can be millions of times more luminous than our sun too,

with devastating stellar winds, enough to rip our atmosphere off over a relatively short time frame. Larger again are yellow super giants, and then red super giants. While not as massive or as luminous as blue super giants, red super giants are the largest stars in existence. If you plop the largest known of these stars directly into the center of our solar system, not only would they easily encompass Earth, but everything up until Saturn. That's 10 billion times the volume of our sun. However, there is a scenario where we could be in a binary star system with a super giant and still be on a habitable planet.

You see, binary stars can orbit very far apart, taking thousands of years to complete one orbit. The most extreme cases can see a binary star system with a separation of over a light year, and what can happen is that planetary systems will form around each of these stars separately, Meaning that if Earth was in one of these planetary systems, it would only have the one parent star, even if that star was part of a binary. The second star would be easily visible in the night sky, but may not make much of an impact during the day, depending on its luminosity. Stellar winds from the other star would have very little impact on Earth, as our sun's powerful

magnetic field would redirect most of it away. The big problem with a super giant on your doorstep is that it is a ticking time bomb. Supergiants tend to be on the verge of erupting in a supernova. A supernova going off only one light year away would be catastrophic, probably sterilizing the entire planet as radiation from the shockwave passes over. And that's not to mention the gamma ray burst from the resulting neutron star. In fact, a recent study has suggested that being within 50 light years, that being within 50 light of a supernova going off would be close enough to be catastrophic in nature.

However, the good news is that we don't know of a star capable of erupting in a supernova within 100 light years. Going back to the single parent-style binary star configuration, on Earth with a single sun, we have a set day and night cycle. However, should we have a second sun outside of our orbit, but still pretty close to us, it's going to mess with our day and night cycle pretty badly. There would only be tiny parts of the year where you would get a proper day and night cycle, and as the year progresses, you'd get less and less of a night, until at one point you'd have no night at all. So, living on a planet with more than one sun is no walk in the park. No wonder

Luke wanted to leave Tatween. Still, they are likely more hospitable than conditions on our next category of strange planets. Rogue planets. Rogue planets are one of the great mysteries left in the universe. They are planetary-sized objects that are not gravitationally bound to a star. We don't fully understand how they formed. Perhaps they were born in a planetary system but got ejected during the system's turbulent beginnings.

Following that thought, perhaps our own solar system also had additional planets at the beginning, before they were cast away to forever roam the galaxy alone. Rogue planets could also be proto-stars that simply fail to absorb the mass needed to become a star or even a brown dwarf. We expect there to be billions to trillions of them out there in just our galaxy alone. Although because they are hard to detect, this really is an educated guess at best. However, since the turn of the century, we have started to detect a few of these mysterious objects.

How can that be when there are no stars lighting them up, and since they don't emit their own light? If they are pitch black, how do we have any hope of detecting them at all? Well, this is where a very interesting detection technique comes in, called gravitational microlensing. On this channel, we have explored various exoplanet hunting techniques in the park. past, mainly the radial velocity method, and the earlier mentioned transit method. The radial velocity method measures the wobble of a star caused by the gravity of orbiting

exoplanets. As we talked about earlier, the transit method measures the brightness of a star over a long period of time and looks for the dips in the star's brightness when an exoplanet passes in front of it. However, these methods are only useful for detecting exoplanets around stars, and generally these exoplanets tend to be large and have very close orbits. The gravitational microlensing method is an exciting method, because not only can it find exoplanets much further away from their host stars, but these planets can also be as small as Mars, or possibly even smaller than that, and still be detected. Additionally, rogue planets with no star at all can be detected with this method.

almost too good to be true, but there is one catch. So how does it work? Gravitational lensing is a well-known phenomenon in astronomy and has been used for years to detect some of the most distant galaxies that we know of. Einstein predicted this phenomenon back in 1936, and with the development of telescope technology, it has been confirmed by observation. Basically, the further away a light source is from us, the dimmer it becomes thanks to the The reason objects get dimmer with distance is that photons spread out as they travel,

meaning the further away you are from the object, the fewer photons that reach your eyes. However, when there is a body with a large amount of mass, like a galaxy or galaxy cluster, the mass of the object warps the curvature of space-time, depending on how massive it is. Light follows the curvature of space-time, meaning that if light emitted by a distant object travels past a massive object, the light photons that would have otherwise gone off in these directions, bend back around thanks to the object's gravity, making the background object appear brighter to an observer here than it otherwise would have done, as more light photons are reaching them now.

Gravitational lensing is very obvious when we look at the biggest types of objects, galaxy clusters, because these objects warp space-time the most. This means that if we are aligned just right with a galaxy cluster and a distant galaxy, the distant galaxy would appear much brighter. The light from the distant galaxy bending around the nearer galaxy would also actually make the galaxy appear stretched, sometimes into the form of a ring. You may have seen these Hubble images before, where distant galaxies appear totally distorted thanks to this gravitational lensing effect.

And here is a CGI example of what you are saying. seeing, which may help you understand why this happens. Now, as I mentioned, more recently, the use of gravitational lensing has also been used to help astronomers detect exoplanets. Stars and planets are much less massive than galaxy clusters, but gravitational lensing still happens to a small degree. When a star transits in front of a distant star, the distant star will become brighter as its This light follows the curvature in space-time around the foreground star.

Additionally, should the foreground star have an exoplanet or exoplanets, the distant star will also get slightly brighter when these transit in front of the distant star too. This is the process of gravitational microlensing. This process is so accurate that small Earth or Mars-sized exoplanets can be detected, and potentially even large exo moons. simply need to measure the little peaks in brightness to distinguish between the individual bodies orbiting the foreground star. Now, as I mentioned, there is a catch with this method.

And that is that star transits are actually quite rare, because they really need to be aligned just right from our perspective, and the galaxy is simply huge. There's so much space in between stars. This is why, up until now, the transit method has had a far better success rate and detecting exoplanets, because exoplanets orbit and transit their stars a lot quicker than stars transit other stars. So, in order to spot these events, what we need is to observe a huge swath of sky in one go.

Enter the Nancy Grace Roman Space Telescope, previously known as the W-First Observatory. This telescope, due to be launched no later than 2027, is comparable in size and will provide images with a sharpness similar to the Hubble Space Telescope, except the Roman Space Telescope will be equipped with a 228 megapixel camera and a 2.8 square degree field of view, which is 100 times larger than Hubble. With this field of view, it will be able to keep track of a much larger section of the sky, and monitor for microlensing events. How does this all fit in with rogue planets?

Well, much like stars, rogue planets that transit in front of a distant star will also make that star slightly brighter, and if the Roman Space Telescope is looking at that section of the sky, it should be able to detect it. In fact, throughout its five-year initial mission, scientists hope that the Roman Space Telescope can give us a much better indication of how many rogue planets and Earth-sized exoplanets there are out there. Now, while it is possible that rogue planets are in any section of the sky, the Roman Space Telescope will focus its time looking towards the center of our galaxy.

There are a lot more stars here, so transit should be more frequent, and this will increase the chances of spotting microlensing events. It is amazing to me that there are ways to detect these otherwise invisible objects that emit no light, and all you need to do is look at the brightness of a background star, and And as a rogue planet passes in front of it, the gravitational microlensing event will reveal key details about the rogue planet, like its mass. So have we detected any rogue planets this way at all? As it happens, yes we have.

There are a few ground-based programs on the hunt for rogue planets operating right now, like Ogle, Moa, and Super Macho. At present, they have found 22 rogue planet candidates in all, with the most excellent An exciting one being Ogle 2012 BLG 1323. If this rogue planet gets confirmed, it will be the smallest rogue planet discovered by some ways, being roughly the mass of Earth. How a body like this comes to be free floating in space, we don't really know yet. What might conditions be like on a rogue planet? The first fact to consider is that they would be incredibly dark places, no nearby.

No nearby star means that conditions there would be pitch black. You might think that this might mean that they would be extremely cold places too, but this might not actually be the case. No nearby star also means that there is no nearby source of atmosphere-stripping solar winds, which might actually help a rogue planet to retain any atmosphere it started out with. A 1999 research paper suggested that a hydrogen-rich atmosphere around a rogue planet could actually allow it to trap in enough of its heat that it could sustain Earth-like oceans. Still, any life that wanted to live on such a planet would have to be more akin to our

chemosynthetic species on Earth that survive next to deep sea vents, relying on the planet's molten core to provide heat and nutrients. Photosynthesis would obviously be a no-go on a rogue planet. Other than that, rogue planets could potentially come in all shapes and sizes. Any planet that was flung out of its home system would, by definition, be a rogue planet. They could be gas giants or rocky planets. So the context of where a planet is can make it pretty strange. But what about the planet themselves? What are some of the weirdest, strangest phenomena we might encounter on an exoplanet. Well, let's step away from dark, chilly rogue planets to something at the other extreme.

WASP 76B is an exoplanet discovered in 2013 as part of the wide-angle search for planets program. Since its first discovery, it has fascinated scientists due to its unusual properties. ESO's very large telescope recently found one special characteristic in particular. On this planet, temperatures are so hot that instead of water rain, it rains molten iron. How can this be? Exoplanets that are very close to their stars, with very small orbits, are the easiest to discover, because we can see a very clear pattern on the star's light curve over a short period of time.

Wasp 76 is one such planet. Plus, it is huge, way bigger than Jupiter, and combine this with the fact that it only takes 1.8 Earth days to make one orbit, it made it comparatively easy to detect. But detecting the presence of an exoplanet is one thing. How do astronomers know anything about its physical characteristics? Interestingly, the first thing astronomers do is find out the physical characteristics of the parent star, WASP 76. The distance to the star is determined, and then the star is classified based on its brightness

and colour. Knowing the distance helps us determine how bright it is, and we measure its colour simply by observing it, which helps us determine how hot it is. If the star is on the main sequence, then this chart also helps us know the radius and mass of the star, as they all tend to follow a pattern. Once we have that information, we can determine the characteristics of the orbiting planet itself. Knowing the mass and radius of the star means we can measure the mass of the orbiting planet using some clever equations based on the law of universal gravitation. As it happens,

WASP 76B is a super Jupiter, way bigger than our Jupiter. That means that although it is massive, this mass is spread out across a large volume, likely making it a gas giant. Orbiting this close The star means the planet is probably tidily locked. Only one side faces the star at any given time. Also, due to the proximity of the planet, it orbits within the star's atmosphere, the physics of which we really don't understand yet. However, the star facing side will be extremely hot, estimated to be around 2,400 degrees Celsius, easily hot enough to vaporize metals.

goes on to suggest the nightside is about 1,500 degrees Celsius, still blisteringly hot, but much cooler. To find out what WASP 76B is made of, though, we need to go back to the light curve of the transit. Scientists look for differences in the light when the planet passes in front of the star, as light from the star will shine through the planet's atmosphere. Certain atoms block certain wavelengths of light, so any reduced wavelengths help us know what is in the atmosphere.

This is known as spectroscopy. For WASP 76B, the biggest surprise that scientists detected was an abundance of iron in the atmosphere. Based on what we know about the planet so far, it seems like iron exposed to the day side of the planet is vaporized, where it is transported through strong wind processes to the terminator line between the day and the night side of the planet. the temperature is low enough for the iron to start to cool and condense, producing iron raindrops which fall deep into the atmosphere. By the time the wind has reached the morning side of the planet, iron can no longer

be detected. This remarkable measurement taken by the espresso instrument on ESO's very large telescope is the first time variations have been spotted like this on an ultra-hot gas giant, although it probably won't be the last time. It's hot enough that they rain molten iron are certainly hot places to be. But they are not the hottest exoplanet we've seen. So how hot can a planet get? Nestled in a tight orbit only 5 million kilometers from its parent star, roughly 10 times

closer than Mercury orbits our sun, sits a planet that is a raging inferno. Kelt 9 is a mercilessly hot star. 9,700 degrees Celsius is almost twice the temperature of our own sun. The lone planet that orbits it, known as Kelty 9b, is a gas giant almost twice Jupiter size and three times its mass. And orbiting that close to such a blaze, its daytime temperature surpasses that of some stars. Kelt 9b was recorded to have a temperature of 4,300 degrees Celsius, making it hotter than your average red dwarf star. Unsurprisingly, its hydrogen atmosphere is boiling off into space, but is then being dragged back into its star at a predicted rate of 100,000 tonnes of hydrogen

per second. In time, all of Kelt 9b's atmosphere will be drained away. leaving the planet's core exposed to that blistering heat. Kelp 9b's core will either be eaten then, or the planet as a whole, will be consumed when the star Kelp 9 expands in 300 million years. In the meantime, the surface of Kelp 9b is hot, hot enough that molecules on its surface break down, ripped apart by all that energy. All in all, it would not be a nice place to live.

On the note of planets hotter than stars, is it possible for planets to exist that are larger than their parent stars too? If you were to imagine a star system, you'd probably think of a giant star being orbited by smaller planets, and generally speaking, this is the standard for star systems across the universe. However, solar systems come in many shapes and sizes. Could it be that there are planets out there that are bigger than the star they are orbiting. And leading on from that, how big can planets get? What's the biggest one that we know of? First of all, let's define one point.

When we talk of big, what we are actually referring to is the volume of an object, not its mass. In order for a star to be a star, it has to be over a certain mass, namely 0.08 solar masses, or 8% of our star. Sun's mass. Below this threshold, the object is classified as a brown dwarf, because it didn't become massive enough for nuclear fusion to take place in its core. Lower masses than brown dwarfs are simply planets, asteroids, and dust.

So the minimum mass of a star is 0.08 solar masses. Is there also an upper limit? Theoretically, the most amount of mass a star can attain is about 150 solar masses. before models suggest it would lose its stability. Although, interestingly enough, there are some stars in existence that seemingly contradict that theory, with masses that are estimated to be around 300 solar masses. Regardless, just because a star is massive doesn't mean that it's big. Some of the densest stars in existence, neutron stars, are one to two solar masses and can be

only 30 kilometers across. Imagine fitting the vast mass of our star, an object so huge that it dwarves Jupiter considerably, let alone us, and squeeze up to two of these in a space the size of a large city. While these stars are tiny volume-wise, they easily have enough mass to host a grand solar system that could stretch far beyond our own. We have discovered exoplanets around neutron stars. due to the detection method used to discover them, we can only really define their mass, not their radius. It would make sense, though, that these planets are many times bigger than the tiny star, as we have asteroids in our solar system, which can be hundreds of

kilometres across, let alone planets thousands of kilometres across. White dwarfs are another example of tiny stars that likely have larger planets orbiting them. White dwarfs are the remnants of red giant stars. stars that weren't massive enough to become neutron stars in a supernova explosion when they reached the end of their lives. Instead, they shed their outer layers in a planetary nebula, leaving behind the core of the star, or what is known as a white dwarf. Nuclear fusion does not take place in a white dwarf, meaning their luminosity comes solely

from stored thermal radiation. This makes them quite dim stars, and they only get dimmer over time. that would have survived the star's evolution from main sequence to red giant to white dwarf could well be larger than the small remnant white dwarf, which is typically the radius of Earth. There came a confirmation of such a planetary system in 2020, thanks to the Tess Observatory, an exoplanet known as WD-1856B. What's remarkable about this system is that the planet orbits the white dwarf relatively

closely, meaning it survived the star going through its red giant phase. The red giant phase would have easily enveloped where the planet now resides, so this means the planet must have fallen or scattered into this orbit after the event, perhaps thanks to the gravitational influences of the star's other undiscovered planets, or even from nearby stars that the white dwarf is gravitationally bound to. In any case, it's an incredible system indeed. When it comes to main sequence stars, planets larger than them are tricky to find too. We believe that main sequence stars make up the majority of stars in the universe.

These can be very big objects, as internal pressure from the reactions in the core keeps the radius large. We'd have to look for stars right around the dividing line between brown dwarfs and red dwarfs to find a main sequence star small enough to host a larger planet. Remember, the difference between a brown dwarf and a main-sequent star is whether nuclear fusion takes place in the star's core, which we believe happens above 0.08 solar masses, and we also believe the dividing line between a planet and a brown dwarf is around 13 Jupiter masses. So, one of our best bets to find a tiny star with a large planet is looking around the red dwarf VHS-1256-1257.

Its exoplanet is one of the few exoplanets to be discovered using direct imaging. Its host star is dim enough, the exoplanet is far enough away from the star, and big enough to be seen simply by using a powerful telescope. Unfortunately, though, this means that while the mass of the exoplanet has been determined, we can't know of its radius for sure. However, this is one of the most likely candidates that we know of. Also, because of the margins of error involved, it could well be that either or both objects are brown dwarfs, meaning we can't say if this is truly a star and planet system.

So while we don't have definitive proof of a planet being bigger than its whole star, we have found some promising candidates, and there's almost certainly cases out there that we haven't found yet. Some of the smallest stars out there have a radius of roughly 70,000 kilometres. Some of the biggest planets out there can be double or triple that. Which leads on to the final question I wanted to cover here. What is the biggest exoplanet that we know of? Unfortunately, it is not clear cut.

One possible answer is GQ. Lupe B. It is another directly imaged exoplanet, which again means we don't have a good grasp on its physical characteristics. From the margins of error involved, it could be a brown dwarf, but it's probably the largest exoplanet that we know of. Scientists have estimated its radius to be three times the size of Jupiter, but again, there are margins of error involved. Other contenders to this throne would be D.H. Tori B and Rocks, 4-2bb.

We've looked at a lot of exoplanets in the course of this video today, some of the hottest, the coldest, planets with multiple stars, planets with none, the fastest orbits, and the longest. But I want to finish with an exoplanet that would be visually stunning if its existence were to be confirmed. J1407B, touted as the first exoplanet discovered with a ring system like Saturn. Sometimes, it is surprisingly tricky to spot ring systems around planets. It was only in 1977 that Uranus' rings were discovered. Jupiter's rings were only spotted in 1979 when they were imaged by the passing Voyager probe, and Neptune's rings weren't seen until the early 1980s. This is because, in the absence of nearby probes to photograph them, rings are usually discovered

via either the transit method or stellar occultation, when they pass in front of a near or distant star, causing the light reaching us to momentarily dim. Usually, you have to be looking carefully. However, not so with J-1407B. When planets like Jupiter pass in front of its neighbouring star, they can sometimes block as little as 1% of the star's light. Their rings, much less than that. When J1407B passed in front of its star, it blocked an incredible 95% of the star's light.

Why was this? In 2012, researchers who noticed this phenomenon in the super wasp data came up with the answer. J1407B had rings. Massive ones. By evaluating the dips in the light, astronomers were able to detect a a complex ring structure around the planet that covers more than 40,000 times the area of Saturn's rings. For point of reference, this represented rings as large as the orbit of Venus around our

Sun. Just like with Saturn, at least one small moon had begun to form within the rings, creating gaps and indicating that the planet's rings will not last forever. However, right now, if this interpretation of the data is correct, they would be a sight to behold. Sadly, there is a reason to look at this answer with suspicion. J1407B supposedly travels around a star once every 10 years, but since that initial eclipse, no equivalent dimming events have been cited.

Scientists are attempting to explain whether this means J1407B was actually just a one-off event, A free-floating brown dwarf with its own protoplanetary disk that just so happened to pass by the star by coincidence, or whether J-1407b could still be an orbiting planet with massive rings, albeit ones that are much thinner than first anticipated. So, there we have it, some of the strangest exoplanets out there. Are there any you feel I've missed? What were your favorites? Let me know in the comments.

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before they run out. Unfortunately, everywhere else, they're all gone already.