Astronomy Picture Of The Day Explore the cosmos Every day, a new image or photograph of the fascinating universe is presented along with a short explanation by an astronomer. 2021 August 19
Explanation: This bright perseid meteor streaks through the Earth's atmosphere at 60 km per second. It is seen in the starry Milky Way. It was captured in dark Portugal skies on August 12 and moves left to right through the frame. Its bright trail begins near Deneb (alpha Cygni), and ends near Altair, stars of the northern Summer Triangle. These two brightest stars on planet Earth's night, the perseid meteor, briefly eclipses them both. The bright meteors of the Perseid Shower are evident in the trail's greenish glow. The cosmic sand grains, which have been swept up from periodic comet Swift Tuttle, are moving at a speed that is fast enough to produce the characteristic green emission atomic oxygen at altitudes around 100 km before vaporizing in an illuminating flash.