1Comets

=Comets = media type="custom" key="3494874" A comet is basically an icy body that releases gas or dust as it moves through space. Comets consists of a solid nucleus surrounded by a cloudy atmosphere called the coma. They have one or two tails made up of either gas or dust.Most comets are too small or too faint to be seen without a telescope. Some comets, however, become visible to the unaided eye for several weeks as they pass close to the sun. We can see comets because the gas and dust in their comas and tails reflect sunlight. Also, the gases release energy absorbed from the sun, causing them to glow.

Comets are classified according to how long they take to make one orbit. Short-period comets need less than 200 years to complete one orbit, while long-period comets take 200 years or longer.

Astronomers believe that comets are leftover debris from a collection of gas, ice, rocks, and dust that formed the outer planets about 4.6 billion years ago. Some scientists believe that comets originally brought to Earth some of the water and the carbon-based molecules that make up living things.

Parts of a Comet
The nucleus of a comet is a ball of ice and rocky dust particles that resembles a dirty snowball. The ice consists mainly of frozen water but may include other frozen substances, such as ammonia, carbon dioxide, carbon monoxide, and methane. Scientists believe the nucleus of some comets may be fragile because several comets have split apart for no apparent reason. As a comet nears the inner solar system, heat from the sun vaporizes some of the ice on the surface of the nucleus, spewing gas and dust particles into space. The comet's coma is formed from this gas and dust. Radiation from the sun pushes dust particles away from the coma. These particles form a tail called the dust tail. At the same time, the solar wind -- that is, the flow of high-speed electrically charged particles from the sun-converts some of the comet's gases into ions (charged particles). These ions also stream away from the coma, forming an ion tail. Comet tails always face away from the sun because of solar wind and solar radiation. Most comets are thought to have a nucleus that measures about 10 miles (16 kilometers) or less across. Some comas can reach diameters of nearly 1 million miles (1.6 million kilometers). Some tails extend to distances of 100 million miles (160 million kilometers).

=Hale-Bopp=

On July 23, 1995, an unusually bright comet 7.15 AU outside of Jupiter's orbit was discovered independently by Alan Hale, New Mexico and Thomas Bopp, Arizona. The new comet, designated C/1995 O1, is the farthest comet ever discovered by amateurs and appeared 1000 times brighter than Comet Halley did at the same distance. The comet is the brightest comet since Comet West in 1976. From Hubble Space Telescope images, the comet's diameter has been determined to be about 40 km. The Pic du Midi Observatory has ascertained from their observations that the comet's rotation rate is 11.4 hours.

The comet Hale-Bopp made its fly-by past the Earth in 1997. Hale-Bopp appeared bright to the unaided eye because its unusually large nucleus gave off a great deal of dust and gas. The nucleus was estimated to be about 18 to 25 miles (30 to 40 kilometers) across. Hale-Bopp, like other comets, had 2 tails; one of dust, and the other of ion (this one is distinguished by its blue-ish colours in photographs). This ion tail acts a bit like a sort of "wind sock" that gets deflected in the direction of the outflowing solar wind.



**Chart of Hale-Bopp's Perihelion**

 * Perihelion distance:** 0.9141 AU
 * Perihelion date:** 01 April 1997 UT 03:19 (31 March 22:19 EST)
 * Closest approach to Earth:** 1.3 AU
 * Date of closest approach to Earth:** 22 March 1997
 * Next Perihelion:** ~2380 years
 * Previous Perihelion:** ~4200 years ago
 * Orbital inclination:** 89.43 deg.
 * Orbital eccentricity:** 0.9951
 * Argument of perihelion:** 130.59 deg.
 * Longitude of ascending node:** 282.47 deg



media type="custom" key="3473096"

=Quick Facts=


 * On March 9, 1997, there was a total solar eclipse in central Asia.
 * Mid-day of March 22 is when Hale-Bopp reached its closest distance to Earth, 1.315 AU (112 million miles, or 197 million km)

Links for more info
[] []