The list of discovered alien planets rises to over 6,000.

From planets made of diamonds to planets hotter than the Sun, from planets twice the size of Jupiter to planets raining down shards of glass: over 6,000 planets have officially been discovered outside our Solar System, a veritable zoo of cosmic objects that already includes another 8,000 candidates awaiting confirmation. NASA announced this historic milestone, almost exactly 30 years after the discovery of 51 Pegasi b, the first exoplanet discovered around a star like the Sun.

It all began in 1989 with HD 114762 b, the first exoplanet observed, but confirmed only two decades later. Since then, very slowly at first, the list of planets discovered around other stars has grown rapidly. Over 1,000 in the last three years alone, it has now reached over 6,000 objects of all masses, orbital characteristics, and sizes, from Neptune-like planets to hot Jupiters, gas giants with very high temperatures, and rocky super-Earths with a mass much larger than our planet, and a handful of planets located in the so-called habitable zone, i.e., at the right distance from the star to support liquid water.

"There's one we haven't found yet: a planet just like our own. At least, not yet," NASA states in the video it released to celebrate the 6,000th exoplanet milestone, "but we're entering the next great chapter of exploration: worlds beyond our imagination." This announcement comes almost exactly 30 years after scientists discovered the first exoplanet around a Sun-like star, 51 Pegasi b. Discovered on October 6, 1995, by astronomers Michel Mayor and Didier Queloz, 51 Pegasi b is a gas giant 0.64 times more massive than Jupiter, located about 50 light-years away. This list is set to grow rapidly, as another 8,000 planets have already been observed, the existence of which must be confirmed by new, more detailed observations.