Weather can get pretty rough here on Earth, but there’s a rocky exoplanet located about 40 light-years away that features some of the most extreme temperature fluctuations ever seen by astronomers—reaching temperatures so high that lava flows directly on the surface.
Remember 55 Cancri e? Sure you do — and if you don't, you should. After all, it may be the first diamond planet ever discovered that orbits a Sun-like star. At least we think it is; if there's one thing 55 Cancri e is good at, it's fooling astronomers into thinking it's something that it's not.
When you combine a compound like water with intense heat, said water evaporates. No mystery there. But when you throw extreme pressure into the mix, something funny happens. The compound can actually achieve what is called a "supercritical" fluid state, taking on properties of liquid and gas alike.
At first, the exoplanet 55 Cancri e didn't look all that impressive: just another large rocky planet circling its star every couple of days. But a recalculation of its orbit has revealed that it's the galaxy's densest known planet.