Stars and the solar system

Stars and the solar system

Milky way galaxyMilky way galaxy

The milky way galaxy which is our own galaxy . It contains

about two hundred billion stars and other countless objects . The stars of this

galaxy spread from its centre like a spiral . It is therefore known as a spiral galaxy .

The StarsThe StarsStars are very hot and huge heavenly objects made up of very hot gases . They appear

like dots only because they are very very far

away from us . The nearest star to the

earth is the Sun itself . The next nearest star

is the alpha centuari or proxima centuari .

After the sun it is the star Sirius which is the

brightest star in the sky .

Pole StarPole StarThe pole star known as dhruv tara in hindi is a

special star present in the northern hemisphere . This star unlike the other stars, appears to be fixed at one

place . Because of this special feature, the star has

been very useful to travellers. The pole star

defines the north direction . The other directions can

then be defined with respect to this direction .

ConstellationsConstellationsA close and careful

observation of the stars on a clear night reveals that some of these stars

appear to form some kind of patterns that appear to resemble some familiar shapes. Such a group of

stars is known as a constellation . Some

prominent constellations are Orion, Ursa major,

Ursa minor and Cassiopeia .

The MoonThe MoonThe moon, our nearest

neighbour in space, is a natural satellite of the earth . It does not

have any light of its own . Its observed silvery glow is only due

to the light of the sun reflected by its surface . We all observe that the shape and size of the front or bright part of the moon appears to change gradually

everyday . It takes nearly 29.5 solar days for the moon to make one complete revolution around

the earth .

Phases of the MoonPhases of the MoonAlthough half of the moon is

always illuminated by the sun’s light, the lighted up portion of the moon appears to change

shape . This is due to change in relative position of the earth , sun and the moon . On a full moon day, the earth lies in

between the moon and the sun . On this day the full face of the

moon is visible . On a new moon day the moon is on the

other side of the earth hence we cannot see it . On the days

following the new moon day the illuminated part of the moon appears in crescent shape .

Moon’s surfaceMoon’s surface

On July 20, 1969 the American astronaut Neil Armstrong landed

on moon for the first time, followed by Edwin Aldrin . They

found moon’s surface to be dusty and barren . Crates, upto

hundreds of kilometers wide, cover its surface . It also has large no. of mountain ranges, valleys and lava plains . The moon does not possess any atmosphere and there is no

whether . The temperature on moon is ranging from 100’C to

173’C at night .

The Solar System The Solar System Our solar system consists of the sun and the eight

planets . The eight planets are mercury, Venus, earth,

mars, Jupiter, Saturn, Uranus, and Neptune . The solar system also

consists of minor planets or asteroids a hosts of

comets and meteors . The gravitational pull between the sun and these bodies

keeps them revolving them around it .

sunsunThe solar system is dominated by the sun, which accounts for almost 99.9% of the matter of the whole system . The sun is

also the source of almost energy in the solar system .

The sun is essentially a sphere of hot gases . The temperature of the bright disc is about 6000

K . The radius of the sun is almost 100 times of the earth and its mass is about a million times the mass of the earth .

MercuryMercuryMercury lies closer to the sun than

any other planet . It is a dry, hot and virtually airless planet . It has craters like the moon . Mercury is

much smaller in size than the earth . It is occasionally visible just before sunrise or immediately after sunset . Hence, it is often known as the morning or evening star . Being close to the sun, it takes only 88 earth days to go around

the sun once .

VenusVenusVenus is the brightest object in our after the sun and the moon . Its bright appearance is due to its cloudy atmosphere which reflects almost three-fourth of

the sunlight falling on it . Venus is almost the same size as the

earth but rotates relatively slowly around its axis . It rotates

from east to west . Venus is even hotter than mercury

because of CO2 in its atmosphere . This gas traps

most of the sun’s heat . Venus is also called evening or morning star because it is only visible

these times .

EarthEarthThe earth is a very unique and

special planet of our solar system . It has life on its surface

because of the presence of water, suitable atmosphere and

a blanket of ozone layer and right size and right distance

from the sun so that it has right temperature range and gravity .

The earth also has an ozone layer which absorbs the

ultraviolet radiation from the sun and protects us from its harmful

biological effects .

Mars Mars Mars usually appears reddish in colour hence, it is also often known as the red planet . Its

surface resembles a cold, high altitude desert . Its surface temperature and surface

pressure both are very low . The diameter of mars is only a little more than half of that of earth . Mars has two natural satellites or moons named Phobos and Deimos . Mars

has a low average density as compared to the earth .

Jupiter Jupiter

Jupiter is the largest of all planets . Its volume is 1300

times more than that of earth . Jupiter consists mainly of

hydrogen and helium in gaseous form . Its cloud cover

is made up of methane, in gaseous form, with some

ammonia in crystalline form . Jupiter has at least 63 known

moons. The largest four are called Io, Europa, Ganymede, and

Callisto.

SaturnSaturnSaturn is quite similar to Jupiter in size, mass and

composition . It is the second largest planet of the solar

family . It is distinguished by its very unique and special

system of rings . These rings give it a beautiful appearance .

These can only seen clearly with the help of a telescope . As of April 2014, there are 62 known satellites of Saturn .

URANUSURANUS

Uranus is also a very large planet . It in fact is the third largest planet of the solar

system . Hydrogen and methane have been detected in the atmosphere of this planet .

This planet is observed to have blue-green colours .

Uranus has 27 moons that we know of. Five of the moons are

large and the rest are much smaller. The five large moons

are called Miranda, Ariel, Umbriel, Titania, and Oberon.

NeptuneNeptune

Neptune is very far away f rom the sun and is

v is ib le only through a te lescope . I t has been named af ter the roman

sea god Neptune . Neptune has th i r teen

moons that we know of . The largest moon is

Tr i ton .  

Minor bodies in the solar system

Minor bodies in the solar system

Apart from the sun and the planets there are some minor bodies in solar sys tem . They

are asteroids, meteors and comets .

ASTEROIDSASTEROIDS

Asteroids are very small planets or planetoids that are found mainly in a belt between the orbit of mars and Jupiter . Astronomers

have discovered more than 500 asteroids which are larger than 48 km in diameter . Ceres is the largest of the asteroids

discovered till now .

CometsCometsThe name comet means a

ha i ry s tar . Comets are re la t ive ly smal l and icy

ce lest ia l bodies revolv ing around the sun . Comets

are only v is ib le when they are near the sun, th is is

because the in tense so lar heat vapor izes par ts o f

the i r icy mat ter and creates the i r i l luminated

ta i l . The best known per iod ic comet is Hal ley 's

comet . I t appears a f ter every 76 years .

Meteors and meteoritesMeteors and meteoritesMeteors are re la t ive ly smal l bodies that a lso revolve round the sun.

some of them may enter in to the ear th ’s

a tmosphere f rom outer space . Th is makes them

shine br i l l i ant ly l ike f i rebal ls . We ca l l them

fa l l ing s tars . Some meteors that are so large

that a par t o f them is ab le to reach the sur face of ear th , they are ca l led

meteor i tes .

Artificial satellitesArtificial satellitesArtificial satellites are man-made

objects which can be made to revolve around the earth . Artificial satellites perform

various tasks, such as transmitting radio, telephone and television signals, sending back

information for weather forecasting, military surveillance

and for locating mineral resources . Satellites that are being put to the maximum use

are the geostationary satellites . A geostationary satellite appears to remain fixed with respect to a

particular point .

Group members Group members

RISHABH CHAUHAN

ISHANT CHAUHAN

VINAY KADYAN

MD. ARSH

HARSHIT CAHUAHAN

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