2. Topics to be covered in this chapter are:
1. Celestial objects 9.Statellites
2. Astronomy 10.Astronomyin ancient india
3. Moon 11.Mangalyan
4. Stars 12.Asteroids
5. Constellation 13.Comets
6. Earth 14.Meteors and meteorites
7. Sun 15.Meteor shower
8. Planets 16.Artificial satellites
3. 1.Celestial objects:
The stars, the planets, the moon and
many others objects in the sky are know
as the celestial objects. So, whatever
heavenly bodies we see in the sky are
known as celestial objects.
*The science which deals with the study
of the celestial objects is known
astronomy. The one who study this
science is knows as astronaut.
4. 2. Astronomy:
The study of celestial objects and associated
phenomenon is called as astronomy. The
astronauts use telescope for studying the
celestial objects.
*As our sky is far away from away from us
and so are the celestial objects. So, in order to
study these distant objects we use telescope.
*Moon is known as satellites as it revolves around the earth.
5. 3. Moon
Phases of the moon
The various shapes of the bright part of the moon as seen during the
month. They are known as the phases of moon. Moon is a non-
luminous body.
*the moon does not their own light.
6. Q. Why phases of the moon occur?
Ans- The moon does not produce its own light, where as the sun and
other stars do, whereas the sun and other stars do. We see the moon
because the sunlight falling on it gets reflected towards us. We,
therefore, see only that part of the moon, from which the light of the
sun is reflected towards us.
Position of the moon in its orbit and its corresponding phases.
7. The Full Moon Day:
when the whole disc of moon facing
towards the earth is visiable to us. It is know
as the full moon day. It is generally occurs on
the 14th day.
8. New Moon Day
Its occurs on the 15th day and the moon is
not visible because it receives no light from
the sun.
9. Crescent moon
The next day of the new moon day,
when only a small portion of the
moon is visiable in the sky. This is
known as the crescent moon.
10. An American astronauts named Neil Armstrong and Aldrin who landed
on moon with the help of a vehicle named Apollo11 in July 1969. the two
scientists noted down that the surface of the moon is a rocky desert.
There was no water or vegetation present on the surface of moon. It was
rocky land. That is why life is not possible on moon and only 1/6th of
gravitational pull that we have on earth is present on moon. If we talk
about the temperature of moon during day time it is 100 degree Celsius
and in night it is 168 degree celsius because of such inhabitable
conditions. Life is not present on moon.
11. *In the night when we see in the sky there are some objects which twinkle . So those
twinkling bodies are stars.
*Star is a luminous body because It can emit its own light.
*We see them in night only because during day, the light of sun is so intense that it
becomes difficult to see them.
*likewise we have some stars like objects present in our sky which do not twinkle but
they keep on shining. They are known as planets.
*Distance between the sun and the is about 150,000,000 kilometers (150 million km).
4.Stars
12. *The next nearest star is Alpha Centauri. It is at a distance of about 40,000,000,000,000 km
from the Earth.
• As it is not easy to such a long distance in kilometers, so the units used to express the distance
between the objects of universe is ‘light year’.
• There is a star named as pole star. It is also called a stationary star because it does not move
and it is the brightest star. It is situated on the axis of earth that is why it appears immovable.
13. Q.How we define light year?
Ans- It is the distance travelled by light in one year.
Q.Why does the sun appear to rise in the east and set in the
west?
Ans- As the earth rotates from west to east on its axis, so, the
sun appears to rise in the east and set in the west.
14. 5.Constellations
the stars forming a group that has a recognizable shape is called a
constellation. The shapes of constellations resemble objects familiar to
those people.
Ex:(a)Ursa Major( it is also knows as the Big dipper)
(b)Orion
(c)Cassiopeia
15. Ursa Major: one of the most famous constellation which you can
see during summer time, in the early part of the night is Ursa major.
It is also know as the big dipper, the great bear or the Saptarshi.
Orion: orion can be seen during winter season in the late evenings. It
ha sseven or eight bright stars. Orion is also called the hunter.
The star Sirius is the brightest star in the sky, is located close to orion.
Cassiopeia: it is another prominent constellation in the northen sky.
It is visiable during winters in the early part of the night. It looks like a
distorted letters W and M.
16. 6. The Earth
• It resolves around the sun. there are
seven other planets that revolve
around the sun. the tilting of the earth
on its axis and its revolving around the
sun causes seasonal changes on earth.
The eight planets in their order
distance from the sun:
• Mercury *Jupiter
• Venus *Saturn
• Earth *Uranus and
• Mars *Neptune.
17. 7. Sun
The sun is the nearest star from us. It is continuously emitting huge
amount of heat and light. The sun is source of almost all energy on the
earth. In fact, the sun is the main source of heat and light for all the
planets.
18. 8.Planets
The planets look like stars, but they do not
have light of their own.
The time taken by a planet to complete one
rotation is called its period of rotation. some
planets are known to have moons/satellites
revolving around them.
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19. 9. Satellites
Any celestials body revolving around
another celestials body is called its
satellites. Moon is a satellite of the
earth. There are many man-made
satellites revolving round the earth.
These are called artificial satellites.
This Photo by Unknown Author is licensed under CC BY-ND
20. 10. Astronomy in the ancient India
The work of Aryabhata on astronomy can be found in his writing
‘Aryabhatiya’.
When the shadow of the earth falls on the moon, it causes lunar
eclipse. When the shadow of the moon falls on the Earth, it causes
solar eclipse.
Aryabhata also found the distance between the Earth and the moon,
which is very close to the known value today.
21. Mecury:The planet mercury is nearest to the sun.
it is the smallest planet of our solar system. Because
mecuary is close to the sun, it is very difficult to
observe it, it has no satelites.
Venus:It is earths nearest planetary neighbour. It
is the brightest plannet in the night sky. Sometimes
venus appears in the eastern sky before sunrise.
Sometimes it appears in the western sky just after
sunset. Therefore it is often called a morning or an
evening star,although it is not a star.
This Photo by Unknown
Author is licensed under CC
BY-NC-ND
22. Earth:it is only the planet in the solar system on which life is know to
exist.it has one moon. From space, the e arth appears blue – green due to
the reflection of light from water and landmass on its surface.
• The axis of rotation of the earth is not
perpendicular to the plane of its
orbit. The tilt is responsiable for the
changes of seasons on the earth.
23. Environmental conditions responsiable for the existance of
life on the earth:-
*just the right distance from the sun so ,that it has the right
temperature range,
*the prence of water,
*suitable atmosphere
*a blanket of ozone.
This Photo by Unknown Author is licensed under CC BY-SA-NC
24. Mars:The next planet, the first outside the orbit of the earth is Mars.it appears
slightly reddish and, therefore, it is also called the red planet. It has two small
natural satellites.
Jupiter:It is the largest planet of the solar
system.it is largetest planets such that, 1300
times earth. However, the mass of the Jupiter
is about 318 times that of our earth.
This Photo by Unknown Author is licensed under CC BY-SA
25. Saturn:Beyond Jupiter is Saturn which appears yellowish in colour. What make it
unique in the solar systemis its ring. These rings are not visiable with the naked eye.
You can observe them with a small telescope.
Saturn also has a large number of satellites.
One interesting thing about Saturn is that it is
least dense amongall the planets. Its density
is less than that of water.
26. Uranus and Neptune
These are the outermost planets in the solar system. They can be seen
only with the help of large telescopes. Like Venus, Uranus also rotates
from east to west.
The most remarkable feature of Uranus is that it has highly titled
rotational axis. So, in its orbital motion it appears to roll on its side.
Uranus and Neptune
27. Inner planets:The first four planets, Mercury, Venus, Earth and Mars are
called the inner planets. They have only a few Moons.
Outer planets:The planets
outside the orbit of Mars, namely Jupiter,
Saturn, Uranus and Neptune are called the
outer planets. They have a ring system
around them. The outer planets have large
number of Moons.
29. Indian Space Reasearch Organization (ISRO) launched india’s first
Mars orbiter mission – Mangalyaan, on November 5, 2013. it
was successfully placed into an orbit of mars on September 24,
2014. with this india became the first country in the world to do
so in its first attempt.
This Photo by Unknown Author is licensed under CC BY
30. 12.Asteroid
Thereis a large gap in between the orbits of Mars and Jupiter.
This gap is occupied by a large number of small objects that
revolve around the sun. These are called asteroids. Asteroids
can be through large telescopes.
31. 13.Comets
Comets are also members of our solar system. They revolve around
the sun in highly elliptical orbits. However, their period of revolution
around the sun is usually very long. A comet appears generally as a
bright head with a long tail.
One such comet is helley’s comet, which appears after nearly every
76 years. It was last seen in 1986.
HALLEY’S COMET
32. Meteor Showers
When the earth crosses the tail of comet, swarms of meteors are seen.
These are known as meteor showers. some meteor showers occur at
regular intervals each year.
33. Artificial Satellites
Artificial satellites are man-made. They are launched from the earth. They revolve around
the earth much closer than earth’s natural satellite, the moon.
They are used for-
*forecasting weather
*transmitting
*television and radio signals
*telecommunication
*remote sensing
India has built and launched several artificial satellites.
Aryabhata was the first Indian satellite. Some other
Indian satellites are INSAT, Kalpana-1, IRS, EDUSAT, ect.
This Photo by Unknown Author is licensed under CC BY-SA
This Photo by Unknown Author is
