Hundreds of millions of miles away from planet Earth, the spacecraft Juno is in orbit around Jupiter. For two years, it has been sending mind-boggling images of the planet back to NASA, where experts publish the incredible findings online. But now, eagle-eyed observers have spotted something sinister lurking in outer space.
Big enough to fit more than 1,300 Earths inside it, Jupiter towers over the rest of our solar system. In fact, its mass is some two-and-a-half times bigger than all the other planets combined. But despite its size, this great giant is mostly composed of hydrogen. This means that it has no solid surface to speak of.
Visible to the naked eye as a bright dot in the sky, Jupiter has fascinated stargazers since ancient times. And in 1610, the Italian astronomer Galileo Galilei observed the planet through a telescope for the first time. Looking closely, he spotted its four orbiting moons. This is believed to have been the telescopic observation of the moons of other planets.