A comet is a small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma (atmosphere) or a tail — both primarily from the effects of solar radiation upon the comet's nucleus. Comet nuclei are themselves loose collections of ice, dust and small rocky particles, measuring a few kilometres or tens of kilometres across

Parts of a Comet A comet is made up of the following parts: 1)nucleus 2)coma 3)hydrogen envelope 4)dust tail 5)ion tail

The nucleus is the main, solid part of the comet. The nucleus is usually 1 to 10 kilometers in diameter, but can be as big as 100 kilometers. It is composed of rock.

. The coma is a halo of evaporated gas (water vapor, ammonia, carbon dioxide) and dust that surrounds the nucleus. The coma is made as the comet warms up and is often 1,000 times larger than the nucleus. It can even become as big as Jupiter or Saturn (100,000 kilometers). The coma and nucleus together form the head of the comet.

una The comet's dust tail always faces away from the sun. The tail is made of small (one micron) dust particles that have evaporated from the nucleus and are pushed away from the comet by the pressure of sunlight. The dust tail is the easiest part of the comet to see because it reflects sunlight and because it is long, several million kilometers (several degrees of the sky). The dust tail is often curved because the comet is moving in its orbit at the same speed that the dust is moving away, much as water curves away from the nozzle of a moving hose. Comets often have a second tail called an ion tail (also called the plasma or gas tail). The ion tail is made of electrically charged gas molecules (carbon dioxide, nitrogen, water) that are pushed away from the nucleus by the solar wind. Sometimes, the gas tail disappears and later reappears when the comet crosses a boundary where direction of the sun's magnetic field is reversed. pressure of sunlightreflects

HALE BOPPHALLEY

Hale-Bopp was discovered on July 23, 1995 at a great distance from the Sun, raising expectations that the comet would brighten considerably by the time Earth. Although predicting the brightness of comets with any degree of accuracy it passed close to is very difficult, Hale-Bopp met or exceeded most predictions when it passed perihelion on April 1,Sunperihelion The passage of Hale-Bopp was notable also for inciting a degree of comet-related panic not seen for decades. Rumours that an alien remarkable currency, and spacecraft was following the comet gained inspired a mass suicide among followers of a cult named Heaven's Gate.panicalienspacecraftmass suicidecultHeaven's Gate Hale-Bopp's orbital position was calculated as 7.2 astronomical units (AU) from the Sun, placing it between Jupiter and Saturn and by far the greatest distance from Earth at which a comet had been discovered.Most comets at this distance are extremely faint, and show no discernible activity, but Hale-Bopp already had an observable coma.An image taken at the Anglo-Australian Telescope in 1993 was found to show the then-undiscovered comet some 13 AU from the sun a distance at which most comets are essentially unobservable.astronomical unitsJupiterSaturncoma Anglo-Australian Telescope

Halley's Comet or Comet Halley (officially designated 1P/Halley) is the most famous of the periodic comets and can currently be seen every 75–76 years. Although many comets with long orbital periods may appear brighter and more spectacular, Halley is the only short-period comet that is clearly visible to the naked eye, and thus, the only naked-eye comet certain to return within a human lifetime. During its returns to the inner solar system it has been observed by astronomers since at least, but it was not recognized as a periodic comet until the eighteenth century when its orbit was computed by Edmond Halley, after whom the comet is now named. Halley's Comet last appeared in the inner Solar System in 1986, and will next appear in mid Halley's orbit is highly elliptical, and focused on the Sun. Its perihelion, its closest distance to the Sun, is just 0.6 AU (between the orbits of Mercury and Venus), while its aphelion, or farthest distance from the Sun, is 35 AU, or roughly the distance of Pluto.

Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. They are known as minor planets. 1)Are also known as the Minor Planets. 2)Orbit the Sun mainly between the orbits of Mars and Jupiter. 3)Usually range in size from 1 kilometer to 1000 kilometers across. 4)Are difficult to observe because of their small size. 5)Gaspra (above) and Ida (right) are two known Asteroids. Ceres, Pallas, Juno and Vesta are some other of the larger Asteroids. 6)Sometimes have moons that orbit them. Notice the small moon that orbits Ida (right).