comet
DESCRIPTION
A comet is an icy small Solar System body (SSSB) that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust and small rocky particles. Comets have been observed since ancient times. Comets have a wide range of orbital periods, ranging from a few years to hundreds of thousands of years. Short-period comets originate in the Kuiper belt, or its associated scattered disc,[1] which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort cloud, a hypothesized spherical cloud of icy bodies in the outer Solar System. Long-period comets plunge towards the Sun from the Oort cloud because of gravitational perturbations caused by either the massive outer planets of the Solar System (Jupiter, Saturn, Uranus, and Neptune), or passing stars. Rare hyperbolic comets pass once through the inner Solar System before being thrown out into interstellar space along hyperbolic trajectories. Exocomets, comets beyond our solar system, have also been detected and may be common in the Milky Way Galaxy.[2] Comets are distinguished from asteroids by the presence of a coma or a tail. 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.[3] Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System.[4][5] The discovery of main-belt comets and active centaurs has blurred the distinction between asteroids and comets (see asteroid terminology). As of January 2011 there are a reported 4,185 known comets[6] of which about 1,500 are Kreutz Sungrazers and about 484 are short-period.[7] This number is steadily increasing. However, this represents only a tiny fraction of the total potential comet population: the reservoir of comet-like bodies in the outer Solar System may number one trillion.[8] The number visible to the naked eye averages roughly one per year, though many of these are faint and unspectacular.[9] Particularly bright or notable examples are called "Great Comets".TRANSCRIPT
COMETSPrepared By:- Kishan V
WHAT ARE COMETS?
F
ar From Pluto There is a group of about millions of
celestials objects. It is know as cloud of Oort or
Kuiper-belt . These objects due to some reasons
start moving towards the sun. They are known as
comets. Comet are made up of dust and icy rocks.
COMET TAIL
W
hen the comet starts moving towards the sun the
ice which is frozen around the nucleus of the
comet starts melting. When the comet is near to
the sun the tail of it is longest and when it starts
moving far from the sun the tail becomes shorter
And last it vanishes.
TWO TYPES OF TAILS
Ion tail: Ionized gas pushed away from the comet by the solar wind. Pointing straight away from the sun.
Dust tail: Dust set free from vaporizing ice in the comet; carried away from the comet by the sun’s radiation pressure. Lagging behind the comet along its trajectory
TAILED-STAR
I
f we see from the earth we see the tail is seen
with the comet so it is know as a Tailed-star.
I
n fact it is not a star and its tail is not
permanent.
HALLEY’S COMETF
ar from orbits of more than750 comets are know.
T
he most famous comet is Halley’s comet.
I
t visits our solar family every 76 years.
I
t was last seen in 1996.
A
nd it will be again seen in 2062
EDMOND HALLEY In 1704 Sir Edmond Halley found that
that comet and it was named after Halley.
In 1704 Sir Edmond Halley hypothesized that the comets of 1456, 1532, 1607, 1682 were the same object.
He calculated a 75.7 year orbit and predicted that it would return in 1758.
Halley died; but comet returned.
HALLEY’S COMET ROTATION
COMPOSITION OF COMETI
ces• H2O, Carbon Monoxide (CO), Methanol(CH3OH), and other frozen materials
Minerals• Silicate minerals
C
omplex organic molecules and dust particles• C=Carbon• H=Hydrogen• O=Oxygen• N=Nitrogen
COMET AS BAD LUCK IN OLD AGE
In ancient days arrival of the comet was considered to
be responsiblefor war, epidemic or a natural calamity
like flood.
But mordern science has proved that arrival and
departure of a comet is just a normal event and there is
no need to panic about it.
THANK YOU