Observation 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 at altitude of about between 80 to 100 miles (130-160 km) or sometimes 56 miles (90 km). Orionids, for example, are lighting up at a altitude of 68 miles (109 km) as they have burned completely when reaching 60 miles (97 km). Some 10 to 40 tons of meteor dust enter our atmosphere every day. Meteorids are interplanetary dust, either remnants from the solar system's formation, or they are produced by collisions between asteroids or comets from long ago. Meteorids provide Earth's atmosphere with particles of minerals or metals. 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 mostly leftovers from comets or sometimes a asteroid. When a comet comes near the Sun, heat takes debris and gas away from it as larger chunks of dust, rock and ice shed get deposited like a trail along the orbit, a field of tiny meteoroids in the making. 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. A subtle interaction between dust grains and sunlight called Poynting-Robertson drag creates an extra, though tiny, force on the grains which, over long periods of time, can amount to a significant change in the orbit. 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. It is a phenomenon called 'atmospheric ram pressure' and not friction strictly, which heats the impacting body to a very high temperature, and as the hot object streaks through the atmosphere, it leaves behind a glowing trail of superheated atmospheric gases and vaporized meteor material that rapidly cools and fades in just a few seconds. Each day, generally, 40 tons of meteoritic materials fall upon Earth. The density of cosmic dust between planets generally is much lower than it is near Earth. Even to collect some water which have ran upon your home's roof, letting the bucket dry and using a magnet in there will yield small amount of such material! Meteor streams comes repeatedly each year at the same periods hence a list of meteor showers has been established. Here is following a sample of the most important. Most meteorites, generally, have their origin like fragments of asteroids while others are cosmic dust shed by comets. Rarer are meteorites which are impact debris from the surfaces of the moon and Mars. Most meteorites are of the type chondrites, which are remnants from the early solar system planetesimals which eventually formed planets. Some iron meteorides originated at planetesimals that formed larger planets when our solar system was young, about 4.5 billion years ago and making up only 5 percent of meteorites falling to Earth each year. As such they provide valuable insights into the materials of those times, which could withstand high temperatures and extreme environments of the forming solar system! They even provide for materials unknwon at Earth, like, for example, panguite, a refractory material discovered recently. The solar system is full of small, speeding objects indeed. These objects frequently pummel planetary bodies. With the Earth the Moon and Jupiter, Saturn's rings are the only location where scientists and amateur astronomers have been able to observe impacts as they occur. Current-day impact rates for small particles at Saturn are about the same as those at Earth,, for example, hinting to that such a meteoroidic population has a constant structure throughout the solar system

check 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; those are beginning to burn at a altitude of 45.2 miles; fireballs brighter than Venus may be seen about a rate of one a night. When a fireball glows blue or green that indicates it contained nickel or magnesium, while orange mean the object is traveling relatively slowly. "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. "Bolid" and "fireball" are sometimes used one for each other, as the bolids usually are about 3 ft-wide (1 meter) and of an important density; about 8 to 10 are occurring each year and they can allow for meteorites to reach ground. 556 bolides occurred at Earth in a 20-year period (1994-2013) as the Chelyabinsk event was the largest asteroid to hit Earth in this period. Bolids explosions in the atmosphere do not come random, occurring within one calendar day of each other, or with three or fewer calendar days’ difference, which could hint to that bolids might result streams of debris associated with small asteroids or comets. Bolids usually burn with a green light. Larger bolids may descent down to 31 miles in altitude; bolids generally may be observed from a distance up to 500 miles as weather conditions at mid-latitudes may lower that to about 185 miles; when a bolid enteres the atmosphere it yields a intense white light as when he reaches the denser layers of it, it heats and turns red. At last, due to repeated vibrations, it eventually explodes as it creates shock waves similar to those of a supersonic airplane. Bolids and fireballs too may be leaving luminous trains behind them, lasting from a few seconds to a few minutes. Green fireballs are typically explained as meteors whose shockwaves lead to electrically charged oxygen similar to that seen in auroras not to be confused with ball lightning, orbs of light usually seen during thunderstorms connecting ground to the ionosphere (albeit meteors may help to such links). Like a example of meteorites reaching the surface, last to hit down in Virginia, USA, occurred in 1878, 1924, and 2010. Such space rocks are coming at a speed of 200 mph (320 km/h) and crash with the sound of a bookshelf falling over. The number of fireballs peaks by the weeks around the vernal equinox, for reasons not fully understood as are too meteorite which manage to make their way down to the ground. About 10 fireballs may be spotted per night in average, as 10 to 30 percent more are seen in spring. The number of ordinary meteors, at the contrary, peaks (in the Northern Hemisphere) by fall. Most, if not all, meteor streams find their origin in comets when such parent-bodies are coming, at regular intervals, to orbit close to the Sun and then back to the confines of the solar system. Those comets, then, are leaving behind trails of debris. When such trails are meeting the orbit of the Earth, that give a meteor shower. With time, the smaller bits of material left in a debris trail tend to be pressured away by the solar wind as the larger particles -between a marble and a peeble-size- remain in it, leading to that those oldest trails might produce lesser, but brighter meteors and even fireballs or bolides. 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. Some showers are known for producing 'fireball' meteors that appear at least as bright as the planet Venus. The larger the particle hitting the Earth's atmosphere, the brighter the meteor trail which is a ionization trail as the speeding particle causes electrons to be ripped away from atoms in the atmosphere. The meteor trails from a Perseid meteor, for example, can be many miles long and remain visible for several seconds

check a a view of the frequency of bolids at Earth 1994-2013

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. Maximize your observing session go as far away from urban light pollution as possible, albeit caring for safety (dark locations are not necessarily the best ones for safety!) A bright moon can be just as detrimental to good meteor viewing as bright lights downtown. Be sure to dress appropriately function of the weather which might include mittens or gloves, and blankets, for example. Some advice to prepare to look for meteors in the darkest patch of sky you can find, as meteors can appear anywhere overhead and related it to the shower's radiant, the apparent point of origin of them. Let your eyes hang loose and don't look in any one specific spot. Relaxed eyes will quickly zone in on any movement up above. Be patient and watch for at least half an hour. If you have to look at some documentation, use a red light as any light will destroy the night vision to which your eyes will have accustomed. Some flashlights have handy interchangeable filters or you can always made some kind of red filter of your own. 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. The branch of the NASA which has the question of the meteorids in charge is the 'Meteoroid Environment Office' (MEO). Meteorites which manage to make their way to the Earth's surface are often looked for by some amateurs for aesthetic and trade purposes as astronomers may also be on the hunt as far as science is concerned. Very rare carbonaceous chrondrite meteorites, for example, are among the most chemically primitive meteorites and of interest in terms of the origins of the solar system or the beginnings of life at Earth. Fireballs and bolides can be observed by sensors of the U.S. military satellites. The Air Force Space Command's Air, Space and Cyberspace Operations directorate signed in September 2014 a agreement with NASA to provide data for the Fireball and Bolide Reports NASA website

It is customary, during a shooting stars observation session to watch the point halfway between the radiant and the zenith, albeit you can also let your gaze wander. Counts also can be made on several nights before and after the forecasted peak to have some data about the shower behavior away from the peak. For the case of the Perseids, for example, usually good numbers of meteors should be seen on the preceding and following nights as well as the shower is generally at one-quarter strength one or two nights before and after the maximum. Between the Perseids shower limits, which are Jul. 17-Aug. 24, a few Perseids can be seen only. Professional astronomers are interesting themselves into how shooting stars showers are impacting the Moon too. During several hours, for example, the Geminids may cause 11 impact flashes as meteor grains reach the surface at speeds of 80,000 mph and the flash lasting only one tenth of a second

The 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