Why does the most hostile planet ever found rain glass? HD 189733b sits 63 light-years away, a deep blue world that looks like Earth's twin — but the blue isn't oceans, it's clouds of molten silicate glass catching starlight. A year lasts two days, the day side bakes at 930°C, and winds scream around the planet at 5,400 mph, seven times the speed of sound. We've mapped its weather better than we mapped Earth's a century ago. #hd189733b #glassrain #exoplanet #spacetok #astronomy