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* DARK AS COAL: TrES-2b is an orb so dark, it is said to be less reflective than coal. The reason: at an estimated 1200 degrees Celsius, it is too hot to support clouds. In addition, its atmosphere is heavy with chemicals that absorb light, such as vapourised potassium and sodium. Where Earth reflects about 37% of the light it receives from the Sun, and Jupiter reflects about 52%, TrES-2b reflects less than 1%. Spotted in 2006, it has been nicknamed the planet of eternal night.
* AN ORB OF HOT ICE: Surface temperatures hover around 500 degrees Celsius on Gliese 436b, 32 light years from Earth. And yet its surface is made up of a kind of ice, formed under atmospheric pressure levels so high, it cannot melt. Because it is pressure rather than temperature that keeps the ice solid, the material has been nicknamed Ice X. The planet was discovered in 2004.
* DIAMOND CORE: Discovered in 2004 and sitting 41 light years away, the rocky planet 55 Cancri e is so hot (temperatures are at about 2400 degrees Celsius; hot enough to melt iron) that its surface is believed to be a “lava ocean”. Atmospheric pressure is so high, meanwhile, that some of the carbon it contains has likely been compressed into a core of diamond.
* COTTON-CANDY WORLD: The gas giant WASP-193 b, discovered in 2023 and situated 1,181 light years from Earth, has a density so low, it has been nicknamed the “cotton-candy planet”. It is about 50% bigger than Jupiter, for context, and has only 13% of that planet’s mass; and Jupiter is a gas giant to begin with.
* A RAIN OF GLASS: The blue planet HD 189733 b sits 64 light years away and looks quite Earth-like. Discovered in 2005, it is anything but. The planet’s cobalt hue comes from an atmosphere so hot, it has turned the silica in its air into glass. The clouds here are laced with shards, so is the rain. Howling winds send this rain flying sideways, or whips it into tornadoes.
Some of the planets we have found hint at our own distant future, in evocative ways.
* THE ANCIENT GIANT: PSR B1620−26 b has been nicknamed Methuselah because it is one of the oldest planets ever discovered. Formed about 12 billion years ago (Earth is just over 4.5 billion years old), it orbits two burnt-out stars. It was discovered in 2003.
* THE LITTLE SNACK: WASP-12 b is currently being consumed by its star, WASP-12. Discovered in 2008, the planet orbits so close to it sun that it is being dragged apart. The pressure on it is so great, it has developed a comet-like tail, and a somewhat egg-like shape.
* STRIPPED BARE: TOI-849 b has had its atmosphere so blasted out of existence by the radiation from its sun that all that remains is the naked core of this gas giant. The planet was discovered in 2020 and is 730 light years away.
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ABOUT THE IMAGES ABOVE…
Most of the images NASA releases, of planets, stars and galaxies, are not of course photographs (captured in real time by a lens, as the term “photography” is understood here on Earth).
What they are is a translation of light signatures — because most of what our instruments capture, when it comes to the cosmos, consists of readings relayed as light. How far is a planet, how dense is its star, what colours would it exhibit to the human eye… all these questions are answered by studying the light that makes its way from that body to the various lenses we have now deployed on Earth and off it.
In order to use this data to render scientifically accurate images, NASA works with the Infrared Processing and Analysis Center (IPAC) set up and run jointly with the California Institute of Technology (CalTech).
