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Fireball, generic name of the shooting stars or meteors, that appear in the sky with garish light or sound phenomena: bright wake, large and persistent, explosions and detonations. They are in fact blocks and fragments of metallic or stony matter, which give off the light when crossing the densest part of Earth’s atmosphere; They say those meteorites that reach the Earth’s surface. At amateur astronomers the fireball word designates all meteorite they reach during their appearance at least the magnitude corresponding to the maximum magnitude reached by the planet Venus: thus a magnitude greater than that of any star and planet and second only to the brightness of the Sun, moon and of a part of the galactic supernovas and novas.
There is no upper limit of brightness, meteors of magnitude were observed higher than that of the sun. The fireballs, unlike almost all the common meteorites, may have, in addition to white, other well perceptible colors: the main ones are emerald green, red, electric blue and orange; They can present clearly perceptible diameters, with nuclei in addition to 1st diameter. During their appearance, which can last up to more than 10 s, with documented cases up to 101 s, may have explosions, fragmentation and have no straight lines. The change in brightness during the apparition is related to the composition and structure of the cosmic body, called meteoroids, which gives rise to fireball. The meteors can give rise to noise, generally similar to distant thunder, salutes of artillery, explosions of quarry mines. Typically, these sounds are perceived from 1 to 3 minutes after the appearance of the visual fireball, since, being of the sounds, require a certain time to reach the witnesses. In addition, the sounds are perceptible only when they are generated at a height of not more than 50 km, because to greater heights are reflected upward going to fade in the upper atmosphere: these sounds are due to disintegration, often explosive, the meteoroid.
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