Astronomy Picture of the Day

Explanation: What causes sprite lightning? Even though they have been recorded for over 30 years, their root cause remains unknown. Some thunderstorms have them, but most don't. These mysterious bursts of light in the upper atmosphere momentarily resemble gigantic jellyfish. A few years ago high speed videos were taken detailing how red sprites actually develop. The featured image was captured last month in high definition from Italy is one of the highest resolution images of sprites yet taken. One unusual feature of sprites is that they are relatively cold -- they operate more like long fluorescent light tubes than hot compact light bulbs. In general, red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side.