Artist rendering of an “eyeball world,” where one side of a tidally locked planet is always hot on the sun-facing side and the back side is frozen cold. Definitely a tough environment, but might some of the the planets be habitable at the edges? Or might winds carry sufficient heat from the front to the back? (NASA/JPL-Caltech)
The very first planet detected outside our solar system powerfully made clear that our prior understanding of what planets and solar systems could be like was sorely mistaken.
51 Pegasi was a Jupiter-like massive gas planet, but it was burning hot rather than freezing cold because it orbited close to its host star — circling in 4.23 days. Given the understandings of the time, its existence was essentially impossible.
Yet there it was, introducing us to what would become a large and growing menagerie of weird planets.
Hot Jupiters, water worlds, Tatooine planets orbiting binary stars, diamond worlds (later downgraded to carbon worlds), seven-planet solar systems with planets that all orbit closer than Mercury orbits our sun. And this is really only a brief peak at what’s out there — almost 4,000 exoplanets confirmed but billions upon billions more to find and ...