Shooting Stars

Along the year, amateur observers may observe from time to time a luminous strike in the sky. This is a shooting star. Most of shooting stars are sporadic and about 6 per hour may be seen each night. Shooting stars are pieces of material, averaging in size from sand grain to pebbles, entering in Earth's atmosphere, and burning due to friction. At some periods of the year however, shooting stars become more numerous. Up to 60 e.g. may be seen per hour then. These so-called meteor showers are due to meteorids streams orbiting the Sun. These swarms are leftovers from comets. When a comet comes near the Sun, heat takes debris and gas away from it. The dusty material then is orbiting the Sun on an orbit which may even be the one of the parent comet. Or it may slightly shift due to gravitational effects or solar wind and have an orbit of its own. This steady orbit may or may not cross the orbit of the Earth. When it does, Earth ploughing into the dust stream yields a meteor shower. Dust and elements burn into the atmosphere, and shooting stars perspectively appear to come from a same point of space

Meteor streams comes repeatedly each year at the same periods hence a list of meteor showers has been established. Here is a sample of the most important

to a table of the most usual meteor showers

Exact terminology for shooting stars is the following: "meteorid" is for the pieces of material found in the streams or at the origin of an atmospheric event anyway. "Meteor" is for the shooting stars. "Fireball" is for shooting stars having an important brightness (a fireball may occur being part of a meteor shower; spectacular fireballs are yielded by 10-inch (25-cm) wide meteoroids). "Bolid" is a meteor which reaches the lower parts of Earth's atmosphere and which explodes there. "Meteorite" is for the pieces of meteors which reach Earth's surface and may be found there. Most if not all meteor stream find their origin in comets. Fast moving shooting stars like the Orionids in October or the Leonids in November may be leaving glowing incandescent bits of debris behind them due to them exploding. Such trails are called "trains". Trains may linger from several seconds to minutes as upper atmospheric winds may twist and shape them. On the other hand, "Earthgrazers" are shooting stars coming from just over the horizon, skimming over Earth's atmosphere nearly horizontally. This is seen when shooting stars' radiant is just below or near the horizon. Earthgrazers are bright, long, and colorful, and they are a fine view

Observing shooting stars is an enjoyable and easy activity. All is needed is a reclining lawn-chair, a reasonably dark sky, your eyes (no instrument is needed), and a way to record your observations. Moreover, some organisations collect data about meteors, and may help you to efficiently conduct your observations. See, e.g. at IMO, The International Meteor Organization or at Sky & Telescope. Shooting stars observers may practice all year long as activity is enjoyable even outside periods of meteor showers. For more details and updated data (dates, radiant, etc) about meteor showers, see at the same addresses than above and to these too: The American Meteor Society; Comets & Meteor Showers. A recent trend in shooting stars -as far as the advanced observers are concerned- states that they are best observed in pre-dawn hours when Earth's terminator is aligning with Earth motion on its orbit. The observer is somehow ploughing with Earth into the stream. It seems best anyway to observe meteors after midnight as your location on Earth will begin turning towards where Earth is heading on its orbit and as this side of the Earth is catching more meteors than the trailing one

Peculiar case of Leonids illustrates well how a parent comet's passage replenishes associated meteors main stream. Parent comet 55P/Tempel-Tuttle last came back into the inner solar system in 1998. Along its path already exist a main meteors stream which is the leftovers of previous comet's passages. 55P/Tempel-Tuttle orbits the Sun each 33 years. During its late passage, the comet ejected new material. These, along few centuries, are going to melt into the general comet stream. During this time, these new so-called trails may yield more important meteors rates. Stream direction is opposed to comet's orbiting one