Every day, it seems as though a new exoplanet—the term for planets located outside our solar system—is discovered. And some of these planets have features so unbelievable, they seem like something straight out of science fiction.
We can’t see exoplanets with our own eyes, even through strong telescopes. They’re just too small. So how can we tell what they’re made of or what they look like? The answer is light. By analyzing the light an object emits (or in the case of a planet, reflects), we can get an idea of what their surfaces might be like. When the light of a host star passes through the atmosphere of a planet, it emits certain types of light (including light invisible to us, such as infrared and x-rays) based on what is on the planet’s surface and within the atmosphere. We can analyze this light to learn more about the planet. Through this method, we’ve discovered many interesting alien worlds.
I’ve rounded up 15 of the coolest sounding planets for you, so take a look around and pick your favorite!
A Planet Made of Diamonds
55 Cancri e is very close to its host star, and therefore very hot. Scientists also think that this planet is mainly composed of carbon. Put heat, pressure, and carbon together, and what do you get? That’s right—scientists think that 55 Cancri e may actually be an entire gas-giant sized planet that’s covered in diamonds.
The Black Planet
A planet that’s pitch black in surface color? Scientists think that could be the case for HD 149026b, because its atmosphere contains a high concentration of heavy metallic elements. It’s also possible the planet glows red because of its surface temperature (3,700 degrees F).
A Planet that Shouldn’t Exist
Kepler-78b is a planet that is only 20% larger than Earth, but 69% more massive. The strangest thing about it, though, is how close it is to its host star: only 550,000 miles (Mercury is about 28.5 million miles from our Sun, for comparison). There’s no way it could have evolved that close to a star because when the star system was forming, the star was larger than it is presently. The planet is so close to its star that it would have had to form inside the star itself to be in its present position. That’s impossible—so how did it get there?
A Comet-Like Planet
Exoplanet Osiris ( HD 209458 b) is so close to its star that the planet’s temperature is estimated to be around 18,000 degrees F. This extreme temperature means that the planet is shedding 10,000 tons of hydrogen from its atmosphere every second. The result is that it has a comet-like tail behind it in space.
The Oldest Known Planet
PSR B1620-26 b, also called the Genesis planet, is the oldest exoplanet we’ve ever found. The Earth is around 4.5 billion years old, but PSR B1620-26 b clocks in at 13 billion years old, which means it evolved just 1 billion years after the Big Bang. Oh, the stories it could tell.
A Planet Where It Rains Rubies and Sapphires
Scientists have discovered a planet where it appears to rain rubies and sapphires. The clouds on the Jupiter-like planet HAT-P-7b, located about 1,000 light years from Earth, are infused with the same mineral that composes these precious gems. The planet also suffers from violent storms, so it’s likely that these rubies and sapphires are scattered planet-wide.
A Planet Made of Burning Ice
The Neptune-sized planet Gliese 436 b has a very strange feature: it has burning ice under its surface. The planet is closer to its sun than Mercury is to ours, so it’s blisteringly hot. Between its solid, rocky core and its crust, pressure has packed water in so tightly that it’s actually turned to solid ice, despite the high temperatures due to its proximity to its star.
A Planet That’s Being Devoured
Around 300 light years away, scientists have discovered HIP68468, a Sun-like star that’s actually eating its own planets. Scientists found a concentration of lithium (which stars burn through over the course of their life) within the star that can only be explained by the sun actually having consumed the planets that orbit it.
A Water World?
Kepler-62e, close in size to Earth, is exciting to scientists for many reasons, but the most prominent one is that its surface seems to be completely covered in water. It’s likely a warm and humid planet, which means it might be hospitable to life. After all, where there’s water, there’s a good chance that some sort of alien microbe (at the least) may have developed.
A Planet That’s Gone Rogue
A planet without a host star? That's what scientists thought was the case for 2MASS J2126, which appeared to be a world making it way through space, a “rogue planet.” Since then, scientists have discovered that this planet does indeed have a star—but it’s 600 billion miles away from it, making this the largest star system we’ve found.
A Planet Made of Cork
TrEs-4 might not actually be made of cork, but from what we know about its density, it might as well be. It’s the largest exoplanet we’ve ever discovered (70% larger than Jupiter), but only has 3/4 of that planet’s mass. That means whatever it’s made of, it’s incredibly light and has a density approximating cork.
A Tatooine-Like Planet
While binary star systems are common (more common even than our single-star system!), we rarely find one planet orbiting multiple suns, like Tatooine from Star Wars. It’s not the first time we’ve discovered one, though Kepler-1647b is the largest. What’s even more interesting about this planet is that it’s within the habitable zone—it’s close enough to its host star to have liquid water on the surface, but far enough away to not be scorched by extremely hot surface temperatures.
A Magenta Planet
Forget yellow or red or blue—we’ve got a pink planet to talk about! GJ 504b is almost 60 light years from Earth and is Jupiter-sized, with one interesting characteristic—it’s a newly formed planet, and is still glowing with heat, which makes the surface appear a shade of magenta.
A Lava Planet
UCF1.01 isn’t the only lava-covered planet we’ve discovered, but it is the smallest. At just 33 light years away from Earth, it’s practically our celestial neighbor, and it appears that the entire planet’s surface might just be covered in magma.
An Earth-like planet
We’ve discovered some crazy planets, but the wackiest of all might be the most normal—a rocky, Earth-sized planet within the habitable zone of its star in our nearest star system, just 4 light years away. Does Proxima b have liquid water on its surface? Can it support life? Scientists are studying the planet closely, hoping to find answers to our many questions.