1. They can melt solid silver. These massive exoplanets orbit very close to their parents stars and can hit temperatures in excess of 1,000 degrees Celsius (1,832 Fahrenheit) at their daytime surfaces. That’s hot enough to melt many elements and some metals, including lead and silver.
2. How Jupiters were never predicted. Despite making up an estimated fifth of all known exoplanets and being the first such worlds to be confirmed, hot Jupiters were a complete surprise to scientists. Their planet-formation models never predicted planets of this type – a sort of bonus in the search for Earth-like planets.
3. They’re slowly boiling away. Hot Jupiters are gas giants, so their proximity to a nearby star heats the gas at the surface, causing it to expand and boil off the planet, leaving a trail in its orbit. It’s thought that the hot Jupiter HD 189733b, found 63 light years from Earth, is losing 100 million to 600 million kilograms (220 million to 1,323 million pounds) of mass every second.
4. Scientists can easily locate them. Hot Jupiters block out a lot of light when they pass in front of their parent star, and their close orbits mean they travel in front of the star more often over any given period. Their huge gravity also causes their star to wobble, making them easier to detect.
5. Deadly rain falls on their surfaces. Some hot Jupiters don’t appear red to the naked eye. Scientists think that silicate particles in their atmosphere make them look blue and that these particles are melting in the oppressive heat of the atmospheres, to form a lethal rain of molten glass.