REID REIMERS:
Sci-Fi writers and filmmakers love to take us to bizarre and outlandish planets: ones with two suns or forbidding worm-filled deserts. But the more we learn about the real planets out there in the universe, the more it seems like the most extreme Sci-Fi planets from the most creative imaginations aren't really that extreme.

Because the real world has everything from planets where it rains hot glass to ones with no star at all. So, here's a compilation of the weirdest, most extreme planets we've ever heard of. And if you're a writer: I hope you're taking notes.

First, most of those Sci-fi planets have weather that humans can at least sort of learn to tolerate. I can't think of any stories with self-heating helium rain, but that's a real thing. And it's surprisingly close to home. Let me explain.

Even though the Sun is 150 million kilometers away, the heat that reaches Earth drives all the weather and climate on our planet. But way out in the solar system, the amount of heat from the Sun drops off dramatically, so the gas giants get just a tiny percent of the solar radiation that reaches Earth.

And yet, some of these planets' most noticeable features are bright spots and dramatic stripes, which are telltale signs of intense weather. And it's not an illusion: There is raging weather on these planets, and it's not driven by the weak energy they get from the Sun. Instead, their weather is fueled from the inside out.

This so-called internal heating is not a rare phenomenon at all, so the better we get to know these internal heat sources, the better we can understand how they drive weather within our solar system and on much more distant worlds. Unfortunately, there's no simple, one-size-fits-all explanation for internal heating. It has different origins on different planets, and the effects vary too.

In our solar system, Jupiter creates more internal heat than any other planet. It's radiating out 70% more heat than it gets from the Sun.

Scientists think that's because it's still contracting: It's so massive that the outer layers are constantly squeezing the material at the core, putting it under huge amounts of pressure. 

Inside, things work kind of like a pressure cooker. As the pressure rises, particles move faster, which means the temperature goes up. Then, massive convection currents transport this heat from the core through thousands of kilometers of liquid hydrogen to a layer just beneath the clouds. There, it acts like a warm tropical ocean fueling a hurricane. It powers the spiraling storms you can see all over the surface of Jupiter, and because the internal heat never changes, hurricane season on Jupiter lasts all year long.

It also produces another interesting feature:. Since this internal heat radiates out evenly, Jupiter's temperature doesn't vary between the poles and the equator; even its poles are as warm as the rest of the planet! 

As unusual as it sounds, Jupiter's not an oddball. Something similar seems to be happening on Neptune, which gives off more than twice as much heat as it gets from the Sun. That makes it about the same temperature as Uranus, even though it's roughly one-and-a-half billion kilometers farther from the Sun. 

Scientists believe that, like Jupiter, Neptune is also still contracting, creating that pressure cooker in its core. And that seems to fuel an atmosphere full of turbulent storms and supersonic winds that can reach more than 2,400 kilometers per hour. 

That internal heat also seems to be what sets it apart from Uranus. The two planets are known as twins because their size and composition is so similar, but Uranus has no internal heat source, so its surface is mostly smooth and calm.

Uranus is actually the only gas giant in our solar system that doesn't produce its own heat, though. Saturn, the one remaining gas giant, also radiates more heat than it receives from the Sun. But Saturn isn't contracting like Jupiter and Neptune. Instead, scientists believe most of its heat comes from helium condensing in clouds and raining down toward the core.

As helium droplets fall, friction with the atmosphere creates a tiny amount of heat. Since helium rain is constantly falling across Saturn, those tiny bits of heat combine to warm up the entire planet.

All that heat has a pretty significant effect on Saturn's climate. It doesn't just drive the types of storms we see on Jupiter and Neptune, either. It also shapes Saturn's seasons. The giant planet is on an axis that's a lot like Earth's, so we'd expect it to experience seasons a lot like ours.

And there are some seasonal changes in Saturn's atmosphere, but they're way less pronounced than what you'd expect. That's because the main source of heat is internal, so the tilt of its axis doesn't matter much. Temperatures stay pretty even all year long.

If we didn't know about internal heating, the weather on these giant planets would be pretty baffling. So figuring out the causes and effects of internal heating is important for understanding the weather of many planets.

Gas giants are the ones that are most likely to produce lots of heat internally, because their fluid layers can contract and move around more easily, but rocky planets like Earth are no strangers to internal heating either. Our planet still has a lot of heat left over from its formation, but scientists estimate that nearly half of Earth's internal heat is being constantly generated by the radioactive decay of elements in the core.

The heat that releases helps churn up metals in the core, which powers our magnetic field, and drives the movement of magma, which gives us plate tectonics.

So, internal heat is at work in a lot of places, including our own planet. And the better we understand how internal and external heating work together in our own solar system, the better we can predict what conditions will be like on other, far-off worlds.

So, let's take what we've learned and consider the weather on planets that are much farther away and much harder to observe.

Given the reliability of forecasts here on Earth, it probably shouldn't surprise you to learn that it's tough to work out the weather on planets that orbit other stars.

But not impossible. I promised you glass rain, and here's Hank to deliver.

HANK GREEN:
We got a lot of wacky weather here on Earth giving us crazy things like thundersnow and firenados, but it turns out we are very lucky because things get way weirder and wilder on other planets. So let's take a look at some exoplanets, including some where it rains molten glass and ice is hot.

62 light years away, on the exoplanet HD 189733B, winds are strong enough to make the rain fall sideways. Researchers from the University of Warwick learned about this weird world by studying it with the La Silla Telescope in Chile.

They waited for the planet to pass in front of a star, and then analyzed the starlight that passed through its atmosphere. This allowed astronomers to determine the composition of the planet's atmosphere, and also tell which way the wind was blowing and how strong it was.

And it turns out the winds on this planet are more than 15 times faster than the speed of sound. And when it rains there, it doesn't rain water. It rains hot glass. Astronomers found that the planet's atmosphere was full of particles of magnesium silicate. Here on Earth, silicates are the main components of rocks and sand.

And this world orbits its star in a mere 53 hours, with temperatures that can range from 1000 to 3300 degrees Celsius. So when the silicate hits its melting point about 1900 degrees, it effectively turns into liquid glass that can rain down through the clouds. And when it reaches the cooler layers of the atmosphere, it solidified into shards of glass that then get whipped around by its supersonic winds. So if you would like to go on vacation there, I would like a postcard, but I'm not coming with you.

Now, this next planet doesn't have wicked winds. In fact, it doesn't even look like your average planet, thanks to a cloud of hydrogen gas that follows it around like a comet's tail. But astronomers didn't know this when they first discovered the planet Gliese 436b. It wasn't until they looked at the planet in ultraviolet light that they were able to figure out what was going on.

Gliese 436b orbits a red dwarf, and it's so close to the star that it orbits every 2.6 days. Because the two are so close to each other, the star heats the planet's atmosphere to the point where the hydrogen gets all excited and starts to escape. But once the hydrogen gets into space, it starts to cool off and condense into a cloud.

Now, you might think that radiation from the star would push that hydrogen cloud away, but this red dwarf is too weak to do that. So the cloud just gets pulled along by the planet, stretching the cloud into a tail as it circles the star. Plus, with all the hydrogen escaping the atmosphere, Gliese 436b is left with heavier molecules, which start to bond in extreme ways because of the hot temperatures and powerful gravity.

Scientists think the conditions might be just about right to make a special kind of water called Ice X. Water, as you and I know, is just hydrogen and oxygen, right? And when those molecules of H2O get cold enough, we end up with the average everyday kind of ice.

But Ice X is different. To make it, intense pressures have to force those molecules into an extremely tight configuration, which lets the ice stay solid at temperatures over 400 degrees Celsius. So basically, astronomers believe that Gliese 436b may be covered in hot ice.

Now if you think that sounds like a rough place to call home, stay away from this last planet. HD 80606b is about four times as massive as Jupiter and it has an incredibly elliptical orbit. It takes about 111 days to complete one trip around its star, and for the vast majority of that time, it's pretty far away from it.

But for a span of less than 24 hours, it's so close to its star that it creates a dramatic temperature change, so dramatic that it essentially causes the atmosphere to explode. Astrophysicists at the University of California, Santa Cruz realized this while studying the planet using the Spitzer Space Telescope. Over the course of six hours, they measured a temperature rise of about 700 degrees Celsius.

Using a computer simulation, they discovered that the temperature difference between the front side of the planet facing the star and the back side of the planet facing away from the star created a shockwave. This shockwave could ripple around the planet and produce wind speeds of over 17,700 kilometers per hour.

These enormous wind storms keep raging until the planet moves away from the star, and its atmosphere has a chance to settle down again. Then, the cycle repeats.

So when you hear people talking about the next big blizzard or polar vortex or hurricane headed our way, just know that we still got things pretty good here on Earth. At least the next apocalypse isn't only 111 days away.

REID REIMERS:
Yeah, I don't think that'd be a terribly nice place for a summer home. Maybe that's why sci-fi writers don't dream up these weird planets.

But sometimes it's not so much the planet that's weird, as the whole star system. In fact, the very first exoplanets ever discovered were found around the most extreme objects in the universe that actually made the discovery possible. Let me, sans burly beard, fill you in on the details. 

If you're a fan of astronomy, you probably think you know the story of the first time we discovered a planet outside our solar system. it goes something like this, once upon a time, long ago, it was 1995... (fast forward)...and by observing changes in the star's motion, Swiss astronomers found our very first exoplanet orbiting the star 51 Pegasi. It's an amazing story, but it has just one problem. 

The planet that became known as 51 Pegasi B wasn't the first planet discovered around another star, or the second, or ever the third, it just happened to be the first planet we found around a star like our sun. People often forget about the first true exoplanets because they orbit something very different, a pulsar. That's right, between 1992 and '94, astronomers discovered a whole star system around one of the weirdest objects in the universe. The pulsar in question is PSR B1257+12 which thankfully some astronomers nicknamed Lich. It's about 23 hundred light-years from Earth. Like all pulsars, lich is a special version of a neutron star, an object with a kind of misleading name.

They aren't stars in the normal sense because they don't convert hydrogen into helium in their cores. Instead, these objects are actually the leftover cores of other stars.

They form when stars more massive than our sun end their lives with powerful supernova explosions which are some of the most violent events in the universe. The star explodes outward, its core compressed under unimaginable pressure. So much pressure in the fact that the electrons and protons inside its atom are literally crushed together into neutrons. What's left is basically a ball of solid neutrons about 20 kilometers across, and because that ball is a lot smaller than what the core started as, it also spends a lot faster just like how a dancer does when they pull in their arms. Lich, for example, makes an entire rotation every 6.22 milliseconds.

Most neutrons stars have a powerful magnetic field which can blast out beams of radiation like radio waves. Depending on the star's orientation, that beam can sweep across eath like a lighthouse as the star rotates, sending a pulse of radio waves our way. If it does, we call it a pulsar.  Timing this beam is how astronomers figure out a pulsar's rotation rate and they're some of the most accurate clocks in existence.

I'm not kidding, lich's period isn't exactly the 6.22 milliseconds I mentioned earlier, it's actually -well... this and that incredible precision is how the very first exoplanets were found. In 1992, astronomers studying this recently discovered pulsar noticed something unusual: the timing of this supposedly super-accurate clock seemed to be drifting, It was a tiny change, but it was enough to alter the exact distance between lich and earth, meaning its pulses sometimes arrived a little early or a little late. And since we can normally rely on a pulsar's timing to be very steady, these changes must have corresponded to stuff around it, tugging on the star and affecting its orbit.

Looking for a pattern in timing variations, astronomers were able to figure out not only that there were planets, three of them, but also how massive they are. They started out some pretty technical names, but they've since been nicknamed Poltergeist, Phobetor, and Dragur.  and their massive were one of the real surprises. Not only do two of the planet have masses only a few times as much as earth, but one has a mass similar to our moon. this makes them some of the smallest exoplanets ever detected.

But you probably wouldn't want to visit there. All three orbit their pulsar at least twice as close as the earth orbits the sun which is probably a bad place to be with all those powerful magnetic fields. Actually, if you think about it, it seems like these planets really shouldn't exist at all. They shouldn't have been able to survive the supernova that destroyed their original star.

So how'd they do it? Easy, they probably didn't. It's much more likely that they formed after their host star blew up from another start that was also destroyed. seriously, if you see a star about to blow up, just back away very very quickly.
 
It gets nasty in there. Many neutron stars also have companion stars in orbit around them and lich may have been no exception. Sometimes in systems like this, material from that companion star gets pulled onto the neutron star. It might even be an especially common process for pulsars.

Eventually, if enough material gets stolen, the companion star basically disintegrates, forming a disk of debris around the pulsar.  Now, around regular, young, stars, planets form from disks like this, so it's reasonable to say that would happen around dying stars too. As far as we can tell, that's likely how Poltergeist and its friends ended up in the universe. Of course, if that all sounds like a pretty unlikely scenario to you, the data would agree.

While planets seem to be incredibly common around normal stars, we found them orbiting less than 1% of known pulsars, and that's probably a good thing because pulsar planets have to be among the universe's most tortured objects.

 
I mean, how many planets are born from a dying star while in orbit around anything dying star, it's not exactly a field of daisies. The first exoplanets that we ever found might often get overlooked, but studying them can remind us that studying the universe is rarely what we think it's supposed to be like.

From the very beginning, we knew exoplanets are going to be weird, and since the 1990s, we've been proven right over and over again.   

If anything, it really expands our sense of what constitutes a normal exoplanet. But where some planets have extreme stars, others have no star at all. It must be lonely and cold. Here's Caitlyn to tell us how that works. 

CAITLYN HOFMEISTER:
Earth just wouldn't be earth without the light of our star beaming down on us every day. But even though it's hard to imagine that's what life is like for rouge planets. Young large planets that aren't tethered to any star. These free agents may sound unusual, but astronomers believe there may actually be 50% more of them than so-called normal star-bound planets. 

Since we've only just observed them in the past decade or so, there's still a lot we don't know about these planets. Some of the first sightings of them came in 2006 and 2007 when a team of astronomers from Japan and New Zealand was surveying the center of the milky way looking for brown dwarfs.

Small, cool failed stars that weren't big enough to ignite fission reactions in their core. Since brown dwarfs are so small and dim, scientists were scoping them out in the same way they look for exoplanets, waiting for them to transit or pass in front of a distant star in the background. 

Over the course of their study, the team monitored 50 million stars in the center of the milky way, and in the end, they observed 474 objects transiting those stars. But a handful of those objects were especially puzzling. Ten of the transits lasted less than two days, indicating the objects were much smaller than brown dwarfs. So the astronomers thought they were observing regular exoplanets, but then they couldn't find any evidence of nearby stars. 

They started to suspect they were looking at rogue planets, but since the objects were ten to twenty thousand light-years from us, they weren't able to get a very close look. 

But in 2012, another team found something a little closer to home. Only 80 light-years from earth astronomers found what they affectionately called PSO J318.5-22 it too turned up in search for brown dwarfs, this time using a telescope called Pan-Starrs which thanks to its super-sensitive camera is really good at detecting the hard to spot infrared heat signatures of brown dwarfs.

And while difficult to sport, brown dwarfs are much larger than planets, and at just six times Jupiter's mass, PSOJ was clearly a planet and not a brown dwarf, and its infrared signature showed that it was much younger than a brown dwarf probably only 12 million years old. And again, this weird world appeared to be all on its own. It's rare for such a large planet to orbit more than 10 astronomical units from its star, and PSOJ had no stellar neighbor in that range. Instead, it seemed to be happily orbiting the center of the milky way like any other star.

So now that we're pretty sure we've observed rouge planets directly, what do we really know about them? Honestly, not much. At this point we can only guess about how they could have formed. Right now, a form of sibling rivalry seems most likely. The leading theory is called Planet-Planet Scattering, where one gas giant kicks another out of the vicinity during the gravitation jostling that takes place as a star system is forming. 

Another theory is that the rogue planet may have once orbited a star, but the star itself pushed it out of the way. When stars reach the end of their hydrogen-burning lives, they begin expanding into red giants and this process could eject planets from its system. 

So rogue planets were predicted to exist back in the 1990s, but we've only recently started observing them now that we might have actually found a few. And scientists have calculated by extrapolating from the small samples they've explored so far, that there might actually be billions of these orphan planets out there. But don't feel bad for them, rogue planets are young and independent, wandering around on their own wild and free. 

REID: So maybe it's not so bad after all, I mean, they know they're in good company. And at least we have some idea of how rogue planets got that way because there are planets out there that are so strange that our models of how planets even work can't explain them. According to the known laws of astrophysics, these planets shouldn't exist.

And here's a baby-faced Reid to tell you why. 

Pretty much as long as humans have looked up at the night sky, we've been studying astronomy. In all this time, we've learned so much about the universe beyond our solar system, and have found lots of exoplanets orbiting other stars. But there's a lot that scientists still don't know. In fact, three relatively recent exoplanet discoveries are completely baffling researches because according to what we know about astronomy, they shouldn't exist. 

The first of these planets is called Kepler-78b, which was discovered using data from NASA's Kepler space telescope, and orbits a star about 400 light-years away from earth, based on changes in its star's light, astronomers calculated that Kepler-78b's radius is about 1.2 times the radius of Earth, and it's about 1.7 times as massive as the earth. 

This means it also has a similar density to the earth. So the researchers think its composition is similar too. With lots of rock and iron. But that's where the similarities stop. Kepler-78b is about 100 times closer to its star than Earth is to the sun, and its surface temperatures might even get up to 3,100 kelvin. Basically, it's kinda like earth if death was a blazing inferno. This planet's super close orbit to its host star means its year only lasts eight and a half hours. 

And scientists don't understand how Kepler-78b even exists because it doesn't fit any of the current theories about planetary formation it's just too close to its star. See, when Kepler-78b was first forming from the gas and dust-filled protoplanetary disk, its host star was even larger so if the planet was orbiting where it is now, it would have been inside its star, which is impossible. 

Another option is that it formed farther away and migrated closer, but scientists think that's pretty unlikely since it probably would have kept going and plummeted into the star. As of now, it's a mystery. The main thing we do know about Kepler-78b is that it'll probably only be around for another three billion years or so it'll move closer and closer to its host star until the gravity eventually tears it apart. 

 
Our next mysterious planet is called Kepler-10c which was also detected using data from the Kepler space telescope and is about 560 light-years away from us. Its radius isn't all that special, it's only about 2.3 times the radius of Earth, and initially, because of its size, scientists predicted that Kepler-10c would have a thick gaseous atmosphere making it like a mini Neptune. 

Instead, they found a planet with a mass that might be between 14 and 17 times the earth's which suggests it's a really dense rocky planet without much of an atmosphere. A mass that large is basically unheard of in a planet of that size, which is why astronomers dubbed it a mega-Earth. Which you know, sounds pretty cool.

Based on our current understanding of planets, one this massive without an atmosphere shouldn't even exist. Theoretically, it would have grabbed a bunch of nearby lighter elements with its huge gravitational force as the star system was forming and turned into a gas giant like Jupiter. But it probably never even had an atmosphere because it if did at some point, it would have held onto it. 

So right now, scientists are just left with another giant rock in space that they can't really explain. Last but not least, we have a gas giant named HD-106906b which is 11 times as massive as Jupiter and discovered using data from the Hubble space telescope and the Magellan telescope in Chile. 

This planet orbits a really young star 300 light-years away from earth. The system is only 13 million years old, but that's not what makes it weird, see HD-106906b orbits its star at a distance of 650 astronomical units. That's more than 20 times the average distance between the sun and Neptune. 

A planet that far away from its host star shouldn't have had enough gaseous and rocky materials to grow that huge, especially in such a relatively short period of time. Somehow, it exists.

Some researchers think it might have formed inside the dust-filled debris disk surrounding its host star, and got kicked out later, but they're still not sure. A recent study seems to support this idea, suggesting that the planet might have even captured some of that dusty material, and might be surrounded by a ring or shroud

But that's just one hypothesis, and until astronomers get more data, the planet is still an enigma. These three planets are just a drop in the bucket that is our universe, and we still have so much to learn. Really, it's the strangest discoveries that make astronomy so cool. 

Every time we start to think we understand how certain things work, like planetary formation, amazing surprises get thrown our way. 

Okay, writers, you have your assignment, now show me what you got. Thanks for watching this Sci Show Space compilation. If you'd like to keep watching, we've got a compilation on unusual places to look for life that you might enjoy. And if you'd like to help us make more videos, you can check out patreon.com/scishowspace.