space objects
space objects
what else is floating around in space?
let me tell you.
Meteors, meteoroids & METEORites
A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects. Objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.
A meteor, known colloquially as a "shooting star" or "falling star", is the visible passage of a glowing meteoroid, micrometeoroid, comet or asteroid through the Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere. This phenomenon is called a meteor or "shooting star". A series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the sky is called a meteor shower.
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A meteorite is a portion of a meteoroid or asteroid that survives its passage through the atmosphere and hits the ground without being destroyed. Meteorites are sometimes, but not always, found in association with hypervelocity impact craters; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites. Geologists use the term, "bolide", in a different sense from astronomers to indicate a very large impactor. For example, the USGS uses the term to mean a generic large crater-forming projectile in a manner "to imply that we do not know the precise nature of the impacting body ... whether it is a rocky or metallic asteroid, or an icy comet for example".
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Meteoroids also hit other bodies in the solar system. On such stony bodies as the Moon or Mars that have little or no atmosphere, they leave enduring craters.
INTERESTING FACTS
INTERESTING FACTS
- A meteoroid is a chunk of space rock. If it burns up while entering the Earth’s atmosphere it’s called a meteor and if a piece lands, it’s called a meteorite.
- Millions of meteoroids travel through the Earth’s atmosphere every day, but most are small and burned up quickly. Very few reach the ground.
- When a meteoroid hits the atmosphere of the Earth, they can be travelling as fast as 130,000 mph (209,215 km).
- The buying and selling of meteorite pieces in South Africa is illegal.
- A meteorite that is seen or detected as it lands are called “falls”, with those that are discovered later being referred to as “finds”.
- Meteoroids more than 10 metres in diameter are classified as asteroids.
- Of the 500 estimated meteorites that reach the ground every year, only five or six are recovered for scientists to study.
- A meteorite will hit a human being once every 180 years according to a study by Nature done in 1985. With Ann Hodges the only confirmed person to be hit by a meteorite in 1954, that means the next time somebody will be hit by a meteorite is 2134 – an average of .0055 per year.
comets
Comets, like asteroids, are small celestial bodies that orbit the Sun. However, unlike asteroids, comets are composed primarily of frozen ammonia, methane or water, and contain only small amounts of rocky material. As a result of this composition comets have been given the nickname of "dirty snowballs."
A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of loose collections of ice, dust, and small rocky particles. The coma and tail are much larger and, if sufficiently bright, may be seen from the Earth without the aid of a telescope. Comets have been observed and recorded since ancient times by many cultures.
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Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma (the central part immediately surrounding the nucleus) and the tail (a typically linear section consisting of dust or gas blown out from the coma by the Sun's light pressure. However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. The discovery of main-belt comets and active centaurs has blurred the distinction between asteroids and comets.
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Some comets have highly elliptical orbits that bring them relatively close to the Sun. As these comets near the Sun the ices found within them melt and brilliant features are formed. Below is a list of these features.
- Nucleus: the nucleus of a comet is composed of ice and rocky material. The nucleus of most comets ranges from about 10 to 100 km in diameter, though they can be as large as 100 km in diameter.
- Coma: the cloud of gases that forms around the nucleus as the coma is heated is know as the coma. These gases are usually a mixture of water vapor, ammonia, carbon dioxide.
- Dust Tail: the dust tail of a comet is composed of gases and tiny dust particles blown away from the nucleus as the comet is heated. The dust tail is the most visible part of a comet.
- Ion Tail: the ion tail is a stream of ionized gases that are blown directly away from the Sun as a result of the comet’s contact with the solar wind.
There are several famous comets, with some being known to ancient humans and some only recently appearing. Below are the most well known comets.
- Halley’s Comet.
In 1705, while studying the orbits of several known comets, Edmond Halley found that the comet observed in 1531, 1607 and 1682 was one in the same. As a result of Halley’s discovery, the comet was named after him. Halley’s Comet is visible every 75 to 76 years. - Comet Hale-Bopp.
Comet Hale-Bopp is best known to most people for the much publicized Californian cult who believed the comet to be a spacecraft. Comet Hale-Bopp was last visible in 1997 and will not be visible again for approximately 2,300 years. It is named after its co-discoverers, Alan Hale and Thomas Bopp. - Comet Shoemaker-Levy 9.
Shoemaker-Levy 9, also known as SL 9, was a string of comets that was captured by the gravity of Jupiter and subsequently began an orbit about the planet. The orbit of SL 9 assumed about Jupiter was, however, highly irregular and as a result of this irregularity SL 9 crashed into Jupiter in a brilliant display during the week of July 16, 1994. Shoemake-Levy 9 is named after its discoverers, Gene Shoemaker, Carolyon Shoemaker and David Levy.
INTERESTING FACTS
- Sometimes comets are referred to as “dirty snowballs” or “cosmic snowballs”. This is because they are composed mostly of ice, rock, gas and dust.
- Comets orbit the Sun in elliptical paths – just like the planets. The path of a comet though is far more elliptical than that of any planet.
- A comet has four components: a nucleus, a coma, a dust tail and an ion tail.
- The nucleus of a comet contains the vast majority of its total mass.
- Comets have a halo when they move close to the Sun. What happens is the solar radiation vaporizes the ice and gas gas in the comet into a halo around it. The halo is known as the comets coma.
- The ion tail of a comet is the result of solar winds that blow the gas particles directly away from the Sun.
- A comet’s dust tail is a trail of dust and rocky material that is left behind as it moves along its orbit path.
- Comets are believed to originate in one of two regions – the theorized Oort Cloud, or the Kuiper Belt found beyond the orbit of Neptune and the dwarf planet Pluto.
- The Oort cloud is an outer region of the Solar System 50,000-150,00 times the distance from the Sun to Earth that is believed to contain dormant comets. Some of the comets that originate here have orbits lasting millions of years.
- The Kuiper Belt is ring of dormant comets located just beyond the orbit of Neptune. The comets originating here have orbits lasting hundreds of years or fewer.
- The most famous comet is Halley’s Comet. It has been observed since at least 240 B.C. Its orbit makes it visible from Earth every 76 years. It was named after the British astronomer Edmond Halley.
- Notable comets include Comet Hale-Bopp, which was discovered in 1995 and Comet Hyakutake, discovered in 1996.
- There are over 3,000 currently known comets. Scientists believe that there be up to one billion comets in our solar system.
- A great comet is one which is bright enough to be visible from Earth without the need for a telescope. Approximately one great comet happens every ten years.
ASTEROIDS and their belts
Asteroids are small, airless rocky worlds revolving around the sun that are too small to be called planets. They are also known as planetoids or minor planets. In total, the mass of all the asteroids is less than that of Earth's moon. But despite their size, asteroids can be dangerous. Many have hit Earth in the past, and more will crash into our planet in the future. That's one reason scientists study asteroids and are eager to learn more about their numbers, orbits and physical characteristics. If an asteroid is headed our way, we want to know that.
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There are millions of asteroids, many thought to be the shattered remnants of planets within the young Sun's solar nebula that never grew large enough to become planets. The large majority of known asteroids orbit in the asteroid belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects. Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups: C-type, M-type, and S-type. These were named after and are generally identified with carbon-rich, metallic, and silicate (stony) compositions, respectively. The size of asteroids varies greatly, some reaching as much as 1000 km across.
Asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition: while asteroids are mainly composed of mineral and rock, comets are composed of dust and ice. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice. The difference between asteroids and meteoroids is mainly one of size: meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials.
Most asteroids lie in a vast ring between the orbits of Mars and Jupiter. This main asteroid belt holds more than 200 asteroids larger than 60 miles (100 kilometers) in diameter. Scientists estimate the asteroid belt also contains more than 750,000 asteroids larger than three-fifths of a mile (1 km) in diameter and millions of smaller ones. Not everything in the main belt is an asteroid — for instance, comets have recently been discovered there, and Ceres, once thought of only as an asteroid, is now also considered a dwarf planet.
Asteroids can reach as large as Ceres, which is 940 km (about 583 miles) across. On the other hand, one of the smallest, discovered in 1991 and named 1991 BA, is only about 20 feet (6 meters) across. |
Many asteroids lie outside the main belt. For instance, a number of asteroids called Trojans lie along Jupiter's orbital path. Three groups — Atens, Amors, and Apollos — known as near-Earth asteroids orbit in the inner solar system and sometimes cross the path of Mars and Earth.
Ever since Earth formed about 4.5 billion years ago, asteroids and comets have routinely slammed into the planet. The most dangerous asteroids are extremely rare, according to NASA.
An asteroid capable of global disaster would have to be more than a quarter-mile wide. Researchers have estimated that such an impact would raise enough dust into the atmosphere to effectively create a "nuclear winter," severely disrupting agriculture around the world. Asteroids that large strike Earth only once every 1,000 centuries on average, NASA officials say. Smaller asteroids that are believed to strike Earth every 1,000 to 10,000 years could destroy a city or cause devastating tsunamis.
An asteroid capable of global disaster would have to be more than a quarter-mile wide. Researchers have estimated that such an impact would raise enough dust into the atmosphere to effectively create a "nuclear winter," severely disrupting agriculture around the world. Asteroids that large strike Earth only once every 1,000 centuries on average, NASA officials say. Smaller asteroids that are believed to strike Earth every 1,000 to 10,000 years could destroy a city or cause devastating tsunamis.