When astronomers first started looking for planets orbiting other stars (called exoplanets), nobody knew if other solar systems were rare or common. As recently as 1995, we had never confirmed a single planet outside our own system.
Since then, the picture has flipped completely. Astronomers have now confirmed more than 5,000 exoplanets, and statistical estimates suggest that essentially every star has at least one planet orbiting it. Many have several. Some “rogue planets” don’t orbit any star at all - they drift through interstellar space alone.
The current best guess is that the Milky Way galaxy contains a few hundred billion stars and well over a trillion planets. Quite a few of those planets are in their star’s “habitable zone” - the orbital range where liquid water could potentially exist. Whether any of them have life is still completely unknown. But there’s far, far more “real estate” out there than anyone suspected just a few decades ago.
