A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma a fuzzy outline or atmosphere due to solar radiation and sometimes a tail.The coma is created as the comet gets closer to the Sun, causing water, carbon dioxide and other compounds to sublime quickly changing from solid to gas from its surface.Comets are made of ice, dust and small rocky particles.The name comet comes from the Greek word meaning ‘hair of the head it came from the Greek philosopher Aristotle who observed comets as ‘stars with hair .Short term comets also known as periodic comet) have orbital periods of less than 200 years while long term comets have orbital periods of over 200 years.
Halley's Comet
Halley’s Comet or Comet Halley as it is also known is the most well known comet.It is known as a periodic comet(or short term comet because the time it takes to orbit the Sun is less than 200 years.Records of humans observing Halley’s Comet go back thousands of years, with appearances noted by Babylonian, Chinese and European star gazers.It can be seen with the naked eye from Earth every 75 to 76 years although the time period has between 74 and 79 years in the past.It last appeared in the inner Solar System in 1986 and will return again sometime in 2061 start charging your camera battery.Halley’s Comet is named after English astronomer Edmond Halley who first determined its period of orbit. It was the first comet to be recognized as having a periodic orbit.Halley’s Comet appearance in 1986 allowed researchers to investigate its make up more closely using spacecraft. While some previous theories were proven correct, other models were altered with the new information. For example, while earlier models predicted the comet to feature many volatile ices, the actual amount was less than first expected.The tail and fuzzy glow you see around Halley’s Comet is known as a coma. It occurs when the comet gets close to the Sun and compounds such as frozen water and carbon dioxide sublime rapidly change from solid to gas from its surface.While the coma over Halley’s Comet can stretch up to 100,000 km across, the nucleus is actually small, only around 15km 9.3 miles long, 8km 5 miles wide and 8km 5 miles thick.
Comet Shoemaker-Levy 9
In July 1994, the Shoemaker-Levy 9 comet broke apart and collided with Jupiter. This event gave astronomers a unique opportunity to observe what happens when such a collision occurs.The largest fragments were 2 km 1.2 mi in diameter and struck Jupiter at a speed of around 60 km/s (37 mi/s). The impact scars were clearly visible for months after the impact.Shoemaker-Levy 9 was originally located by astronomers Eugene M. and Carolyn Shoemaker and David Levy in March 1993.
Meteorids
A meteoroid is a small rock or particle of debris in our solar system. They range in size from dust to around 10 metres in diameter larger objects are usually referred to as asteroids. A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor. If you’ve ever looked up at the sky at night and seen a streak of light or shooting star’ what you are actually seeing is a meteor. A meteoroid that survives falling through the Earth’s atmosphere and colliding with the Earth’s surface is known as a meteorite.The fastest meteoroids travel through the solar system at a speed of around 42 kilometres per second 26 miles per second.The Earth’s atmosphere experiences millions of meteors every day.Meteors are easier to see during the lower light conditions of night.A small percentage of meteoroids fly on a path that goes into the Earth’s atmosphere and then back out again, they are known as Earth grazing fireballs.When many meteors occur in a close time frame in the same part of the sky it is called a meteor shower.Around 500 meteorites reach the Earth’s surface every year but of those only around 5 ever make it to scientists for study.Meteorites that are observed as they fall through the Earth’s atmosphere and later recovered are called falls all others are called ‘finds. To this date there have been around 1000 collected falls and 40000 finds.
Asteroid
Asteroids are small Solar System bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds some scientists suggest that asteroids could have brought they necessary chemicals to start life on Earth.Asteroids are similar to comets but do not have a visible coma fuzzy outline and tail like comets do.Asteroids are also known as planetoids or minor planets.Asteroids vary greatly in size, some feature diameters as small as ten metres while others stretch out over hundreds of kilometres. Note that objects under ten metres in diameter are generally regarded as meteoroids.The first asteroid was discovered in 1801 by Italian astronomer Giuseppe Piazzi. Named Ceres, it features a diameter of around 950 kilometres and is now regarded as a dwarf planet. Ceres was given dwarf planet status in 2006, along with Pluto, Eris, Makemake and Haumea.The asteroid belt lies roughly between the orbits of Mars and Jupiter in the Solar System. It is home to a large amount of irregular shaped asteroids that range in size from dust through to the dwarf planet Ceres.The technology used for discovering asteroids has improved dramatically since original discoveries and astronomers now have access to a range of powerful telescopes to aid in their research and discoveries it is believed by many scientists and researchers that an asteroid impact was the cause behind the extinction of the dinosaurs around 65 million years ago. these movies sometimes featured dubious science they certainly increased public awareness of the topic.There are now many groups and organizations that use automated systems to discover near Earth asteroids. While many are discovered, they rarely have the potential to cross paths with Earth. There have been many ideas suggested as ways to avoid the unlikely but potentially devastating impact of an asteroid collision with Earth, these include using nuclear explosions to break the asteroid into smaller pieces or other weapons to deflect it off course.
