... Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. ... Planetary Nebula Project . ... The North America Nebula in Infrared . ... Red stars are cool, with surface temperatures of around 3,000 kelvins (K), while blue stars are hotter and can have temperatures over 30,000 K. Our own lovely "yellow" Sun's temperature is a comforting 6,000 K. [ First page ] Prev. ...