Lunar Eclipse:
The partial or complete obscuration of light of moon for an observer on the earth is called lunar eclipse. Lunar eclipse takes place when the earth comes in position between the sun and the moon. In this way, the shadow of the earth is cast on the moon and the moon does not get sunlight in this position. Lunar eclipse occurs only when there is full moon. But this does not happen on every full moon because of inclination of the axis of earth to its orbit.
Solar Eclipse:
Solar eclipse occurs when the moon comes in between the Sun and the earth and its shadow is cast across the face of the earth.
The solar eclipse occurs when the moon moves to a position between the Sun and the Earth. During this process it throws shadow on the earth. This shadow is categorized in umbral and penumbra. The people who are in the umbral region are unable to see the sun at all. This condition is known as the total eclipse of the sun. While the people in penumbra region can see the sun partly this is known as the partial eclipse of the sun.
This happens with the new moon when the moon is in conjunction with the sun. this does not happen at every new moon because of the inclination of the orbit of the moon to the orbit of earth around the sun.
Asteroids:
Asteroids are also known as planetoids. These are small, irregularly shaped rocky objects which orbit the Sun between the orbits of Mars and Jupiter. Asteroids are also known as the minor planets. Basically the word Asteroid means “Starlike”. Ceres asteroid was the first to be discovered.
Meteorites:
Meteorites are small chunks of iron and rock thought to be resulted from collisions between asteroids. They also may be formed when comets disintegrate into fragments. Meteorites enter the earth’s atmosphere and become a meteor. A meteor is a “falling star” that is usually seen in the sky at night. A meteor will burn up from frictional heating as it enters the atmosphere. Most of the meteors burn up before they reach the earth. If they do not reach the ground they become meteorites. Meteorites can be seen at a distance of 70 miles from the earth. Meteorites are heavy objects which weigh about 60 tons.
Comets:
Comets are those bodies which revolve round the sun. they are mainly composed of ice and dust. Most comets have three parts which are as under.
i) A solid centre.
ii) A head or round coma, that surrounds the centre and consists of dust particles mixed with frozen water, frozen methane and frozen water, frozen methane and frozen ammonia.
iii) A long tail of dust and gases that escape from the head. Most comets stay near the solar system.
Other characteristics of comets are as under:
• Comet is usually about 10 km or 6 miles across.
• Comets are usually made up of ice and dust.
• Millions of comets are present in the solar system.
• Halley’s comet is the famous example.
• Comets usually move around the sun in the elliptical orbits.
Light Year:
The distance travelled by light at speed of 186,000 miles per seconds in one year is known as a light year. One light year is approximately 9461,000 million kilometres or 5875000 miles. Light year is also used to measure the distance between the galaxies.
Astronomical Unit:
The distance between the Sun and the Earth is called as Astronomical Unit. This unit is also used in the measurement of distances between the heavenly bodies within the solar system. The earth is one A.U away from the Sun and the Pluto is 39 A.U away from the Earth.
Black hole:
Black Hole is a hypothetical region in space which has a big gravitational pull for which no matter or radiation can escape from it. Even it is believed that light cannot escape from it. Black Hole usually likes at the centre of galaxy.
Super Nova:
A Super Nova is an exploding star. At the end of its phase as a Red Giant, a heavy star explodes as a Supernova shining briefly as brightly as a thousand million stars. Recent Supernova was observed on the night of Feb 23, 1987. This occurred in Large Magellanic Cloud.
Nebula:
Nebula is derived from a Greek word which means “Cloud”. In the sky there are clouds like objects, which are classified as Nebulae. There are both luminous diffuse nebulae and dark obscuring nebulae over the Milky Way. They are made up of dust and gases.
Aurora:
Aurora or Kutub-i-Raushani is a luminous meteoric phenomenon of electrical character seen in Polar Regions with a tremulous motion and giving forth streams of eight Aurora. It is generally believed that the aurora is actually caused by radiation from the Sun-spots.
Solar Wind:
Solar wind is the stream of electrically charged particles especially protons and electrons, which are emitted by the Sun, predominantly during solar flares and sunspots activity. Some of these particles become trapped in the Earth’s magnetic field forming the outer Van Allen radiation belt, but some penetrate into the upper atmosphere where they congregate in narrow zones in the region of the Earth’s magnetic poles producing aurora displays.
Cosmic Rays:
Cosmic Rays are charged particles moving as fast as the speed of light. Most of the particles are protons, while some are alpha particles and electrons. They travel throughout our galaxy, including the solar system and some strike the earth’s atmosphere. They can be detected by instruments on the Earth. Nobody knows how cosmic rays are formed. Some of them are formed by exploding stars or supernova and some come from outside our Galaxy.
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