The universe

hariram 8th std ‘b’ sec

The universe

The Universe is all of spacetime and

everything that exists therein, including

all planets, stars, galaxies, the contents

of intergalactic space, the

smallest subatomic particles, and

all matter and energy.

The distances among heavenly or celestial

bodies in the space themselves and from the

earth are so large that they are measured in

the units of light year and parsec .

LIGHT YEAR

The light year is defined as the distance

travelled by light in one year . The speed of

light is 3,00,000 km/s .

The parsec [“ parallax of one arcsecond’’

symbol pc] is a unit of length, equal to just

over 30 trillion kilometres, or about light

3.26 years.The parsec is used in

astronomy.The distance of the closest star

Proxima centauri which is the companion of

Alpha Centauri is 1.3 pc.

The cluster of stars is called GALAXY .A

galaxy contains billions of stars ,dust and

gases which are held together by the

gravitational attraction between the

components . Galaxies are classified based

on their shapes like spiral , elliptical or

irregular .

A star is a huge ball of glowing luminous

gases held together by gravity . It has its own

light . Most of the stars comprise of two

common gases hydrogen and helium . Due to

the chemical reactions of hydrogen and

helium , a large amount of heat and light is

generated . It is because of this light that the

stars glow in the night . The total number of

stars in the universe is approximately 10^22.

In modern astronomy, a constellation is a specific area of the celestial sphere as defined by the International Astronomical Union (IAU). These areas had their origins in star patterns from which the constellations take their names. There are 88 officially recognized constellations, covering the entire sky. When astronomers say an object is "in" a given constellation, they mean it is within the boundaries of one of these defined areas of sky.

Other cultures also have, or had, their own constellations, such as Chinese, Hindu and Australian Aboriginal. The names of these constellations are not recognized by the IAU.

It is the imagination of the poets , farmers, astronomers and it is made about 6000 years ago.

The constellation Ursa Major contains the

group of stars commonly called the Big

Dipper. The handle of the Dipper is the Great

Bear's tail and the Dipper's cup is the Bear's

flank. The Big Dipper is not a constellation

itself, but an asterism, which is a distinctive

group of stars. Another famous asterism is

the Little Dipper in the constellation Ursa

Minor.

The most famous star in Ursa Minor is Polaris, the North Star. This is the star that is nearest to the North Celestial Pole. If you stood at the north pole, Polaris would be almost directly overhead. If you can spot Polaris in the sky, you can always tell which way is north. In addition, the angle of Polaris above the horizon tells you your latitude on the Earth. Because of this, Polaris was the most important star for navigating at sea.

To find Polaris, first find the Big Dipper. If you follow the two stars at the end of the cup upwards (out of the cup of the Big Dipper), the next bright star you will run into is Polaris. The distance to Polaris on the sky is about five times the angle between the two stars at the end of the cup of the Big Dipper. Because they are so useful for finding the all-important North Star, these two stars are known as the Pointer Stars. They are also calledDubhe and Merak (Merak is the one at the bottom of the cup).

the constellation of Orion is one of the most recognizable patterns of stars in the northern sky. Orion, the hunter, stands by the river Eridanus and is accompanied by his faithful dogs, CanisMajor and Canis Minor. Together they hunt various celestial animals, including Lepus, the rabbit, and Taurus, the bull. According to Greek mythology, Orion was in love with Merope, one of the Seven Sisters who form the Pleiades, but Merope would have nothing to do with him. Orion's tragic life ended when he stepped on Scorpius, the scorpion. The gods felt sorry for him, so they put him and his dogs in the sky as constellations. They also put all of the animals he hunted up there near him. Scorpius, however, was placed on the opposite side of the sky so Orion would never be hurt by it again.

Scorpius is the beast which finally killed the

Great Hunter, Orion.

This is one of the 13 constellations of

the Zodiac.

Scorpius, sometimes known as Scorpio, is

one of the constellations of the zodiac. Its

name is Latin for scorpion, and its symbol

is (Unicode ♏). It lies between Libra to the

west and Sagittarius to the east. It is a large

constellation located in the southern

hemisphere near the center of the Milky Way.

Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is easily recognizable due to its distinctive 'M' shape when in upper culmination but in higher northern locations when near lower culminations in spring and summer it has a 'W' shape, formed by five bright stars. It is bordered by Andromeda to the south, Perseus to the southeast, and Cepheus to the north. It is opposite the Big Dipper.

A solar system refers to a star and all the

objects that travel in orbit around it.

Our solar system consists of the sun - our

star - eight planets and their natural

satellites (such as our moon); dwarf planets;

asteroids and comets. Our solar system is

located in an outward spiral of the Milky Way

galaxy.

The Sun is the star at the center of the Solar System. It is almost spherical and consists of hot plasma interwoven with magnetic fields.[12][13] It has a diameter of about 1,392,684 km (865,374 mi),[5] around 109 times that of Earth, and its mass (1.989×1030kilograms, approximately 330,000 times the mass of Earth, M⊕) accounts for about 99.86% of the total mass of the Solar System.[14] Chemically, about three quarters of the Sun's mass consists of hydrogen, whereas the rest is mostly helium. The remaining 1.69% (equal to 5,600 M⊕) consists of heavier elements, including oxygen, carbon, neon and iron, among others.[15]

The term planet is ancient, with ties to history, science, mythology, and religion. The planets were originally seen by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union (IAU) officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects ofplanetary mass based on where or what they orbit. Although eight of the planetary bodies discovered before 1950 remain "planets" under the modern definition, some celestial bodies, such as Ceres, Pallas, Juno, Vesta (each an object in the Solar asteroid belt), and Pluto (the first-discovered trans-Neptunian object), that were once considered planets by the scientific community are no longer viewed as such.

It is first planet and closest to the sun.It is

also the smallest planet in the solar system.it

has no atmosphere because its gravitational

force is not enough to permanently hold an

atmosphere.the surface of Mercury is heavily

cratered.

It is the second planet from the sun which is closest to the

earth.It has the same size as that of the earth.it is visible

after sunset and before dawn.therefore,Venus is also know

as evening and the monrning star.

Earth is the third planet from the sun.It is

the only planet where life exists.All life

supporting factors like moderate

temperature,oxygen,water and other

essential things are present on the earth.It is

about 12,800 kms in diameter

It is the fourth planet from the Sun.It is seen

as a reddish coloured object in the sky.It is

also known as red planet.It is about ½ of the

size of the Earth.

Jupiter is the fifth planet from the sun and it

is the largest planet in the solar

system,about 1300 times of earth.Its mass is

318 times that of earth.

It is the sixth planet from the sun and the

second largest planet.Its size and mass is also

consists mainly of hydrogen.It has several

rings around it which consist of

particles.Saturn has 31 known moons.

Uranus is the seventh planet from the Sun. It has the

third-largest planetary radius and fourth-largest planetary

mass in the Solar System. Uranus is similar in composition

to Neptune, and both are of different chemical

composition to the larger gas giants Jupiterand Saturn.

Thus, astronomers sometimes place them in a separate

category called "ice giants". Uranus's atmosphere, although

similar to Jupiter's and Saturn's in its primary composition

of hydrogen and helium, contains more "ices", such as

water, ammonia, andmethane, along with traces of

other hydrocarbons

Neptune is the eighth and farthest planet from the Sun in

the Solar System. It is the fourth-largest planet by

diameter and the third-largest by mass. Among the gaseous

planets in the Solar System, Neptune is the most dense.

Neptune is 17 times the mass of Earthand is slightly more

massive than its near-twin Uranus, which is 15 times the

mass of Earth, and not as dense as Neptune.[c] Neptune

orbits the Sun at an average distance of 30.

Pluto (134340 Pluto) is the largest object in

the Kuiper belt, [i] [j]; the tenth-most-massive

known body directly orbiting the Sun; and

the second-most-massive known dwarf

planet, after Eris.

The world's first artificial satellite, the Sputnik 1, was launched by the Soviet Union in 1957. Since then, thousands of satellites have been launched into orbit around the Earth. Some satellites, notably space stations, have been launched in parts and assembled in orbit. Artificial satellites originate from more than 40 countries and have used the satellite launching capabilities of ten nations. A few hundred satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, Vesta, Eros, and the Sun. it is may be artificial or natural.

The Moon is Earth's only natural satellite. Although not the

largest natural satellite in the Solar System, it is, among

the satellites of major planets, the largest relative to the

size of the object it orbits.

COMETS Comets are very small sized and beautiful celestial

bodies that revolve around the sun in an elliptical

path.These take very long time for completing one

revolution.

Comets have a distinct head (ball) and a luminous

tail moving across the sky with very high velocity .

The tail always points away from the sun .

The most famous and known comet is HALLEY’s

comet . It appears in the sky once in 76 years .

Asteroids are minor planets, especially those of the inner

Solar System. The larger ones have also been

called planetoids. These terms have historically been

applied to any astronomical object orbiting the Sun that

did not show the disc of a planet and was not observed to

have the characteristics of an active comet, but as minor

planets in the outer Solar System were discovered,

their volatile-based surfaces were found to resemble

comets more closely and so were often distinguished from

traditional asteroids.

The man-made satellites are called artificial

satellites. the artificial satellites are placed

in the space which revolve arround the earth

Sputnik-I by USSR in 1957.

USES OF ARTIFICIAL SATELLITES 1.Weather forecasting.

2.Telephone communication.

3.Television and radio transmission.

4.Remote sensing.

The structure of the Earth is divided

into layers. These layers are both physically

and chemically different. The Earth has an

outer solid crust, a highly viscous mantle, a

liquid outer core, and a solid inner core.

The crust is the outermost layer of the Earth. It is made of solid rocks. It is mostly made of the lighter elements, silicon,oxygen, aluminium. Because of this, it is known as sial (silicon = Si; aluminium = Al) or felsic.

The mantle is the layer of the Earth right below the crust. It is made mostly of oxygen, silicon and the heavier elementmagnesium. It is known as siam (Si + am for magnesium) or mafic. The mantle itself is divided into layers. The uppermost part of the mantle is solid, and forms the base of the crust.

It is made of the heavy rockperidotite. The continental and oceanic plates include both the crust proper and this uppermost solid layer of the mantle. Together this mass makes up the lithosphere. The lithosphere plates float on the semi-liquid aesthenosphere below.

Upper aesthenosphere: magma

Lower aesthenosphere

Lower mantle

The core is made of solid iron and nickel, and is about 5000–6000oC.

Outer core is a liquid layer below the mantle,

Inner core, is the very center of the Earth. It is very hot and, due to the high pressure, it is solid.

An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earth's crustthatcreates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.

Earthquakes are measured using observations from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter magnitude scale.

The point of origin of earthquake under the

Earth is called focus or hypocentre.The point

directly above the focus on the surface is called

its epicentre.

The earth’s crust is made up massive

interlocking blocks of rocks called tectonic

plates. Tectonic plates are placed on the

semiliquid rock called mantle.

Structural damage and fire. Surface trembling from seismic waves often damages buildings. Depending on the severity of the earthquake, gas mains may break, starting numerous fires. Foreshocks, small earthquakes that sometimes precede the main earthquake, can be used as a warning system that a large shock may be on the way. Thousands of aftershocks may follow an earthquake and can be quite destructive, especially to those structures that have already been weakened and damaged.