1. Astronomers
Aristotle-Earth is Spherical
Eratosthenes-size of the Earth
Aristarchus-Heliocentric universe
Hipparchus-star catalogue
Claudius Ptolemy- Ptolemic System
Nicolaus Copernicus- Copernican Theory
Tyco Brahe- location of heavenly bodies
Johannes Kepler- 3 basic Laws of Planetary
Motion
Galileo Galilei- telescope
Isaac Newton- Laws of motion

2. Solar System
Galaxy
Universe

3. Solar System- FACTS
Our Solar System consists of a
1. Central Star (the Sun)
2. Eight planets orbiting the sun
3. Moons,
4. Asteroids
5. Comets
6. Meteors
7. Interplanetary gas,
8. Dust, and all the “space” in between them.

4. Solar System- FACTS
 4.6 billion years ago/14 billion years ago
Everything in the solar system orbits or revolves
around the sun
Sun contains around 98% of all the material in
the solar system
Powerful gravity attracts all the other objects in
the solar system towards the sun.
They spend eternity orbiting around their parent
star(Sun)

5. Solar System- ORIGIN
Nebular Theory
The Solar System formed from a cloud of dust
and gas (Nebula) about 4.6 billion years ago.
Nebula- produced by the explosion of a
previous star

6. Solar System- ORIGIN
Big Bang Theory
 It proposes that the universe exploded out of
a hot dense point about 13.7 billion years ago
 The universe started with a cataclysm that
created space and time and all the matter and
energy that has ever existed in the universe.

7. Solar System- COMPOSITION
 Center Star of our Solar System. Its part include Corona,
Photosphere and Chromospheres. It derives its heat from nuclear
fusion of Hydrogen nuclei becoming Helium nuclei.
It is the source of all energy for life on Earth.
332,900 Earth masses
About three quarters of the Sun's mass consists of hydrogen, while
the rest is mostly helium.
On the Sun’s surface ,there are dark patches known as sunspots.
These are patches of gas that looks dark since they are cooler than
their surroundings.
The light from the Sun takes approximately 8 minutes to reach
Earth
Stars produce light. Planets reflect light
A star’s temperature determines its color. The coldest stars are red.
The hottest stars are blue.
Solar System- SUN

9. Solar System- PLANETS
Planet word comes from Greek ,which means wandering star.
Planets are heavenly bodies ,which revolve around the Sun in elliptical orbits.
Earlier it was considered there were 9 planets in Solar system but lately one planet called Pluto
was de-classified from being a planet.
Between Inner & Outer Planets ,there is a ring of small bodies , which are made of rock & metal,
these are called Asteroids. They also keep moving around the Sun .This ring is also called Asteroids
Belt.
Planets are categorized according to composition and size. There are two main categories of
planets:
1.Terrestial Planets (Earth-like/ Inner Planets) – Mercury, Venus, Earth and Mars.
2.Jovian Planets (Jupiter-like/Outer Planets and Giants) – Jupiter, Saturn, Uranus, Neptune.
Differences:
Size-Terrestial are smaller than Jovian Planets.
Density- Terrestial have average densities about 5 times that of water while Jovians have
about 1.5 times that of water.
Composition-terrestial are mostly rocks and metallic materials while Jovians have gases like
Hydrogen and Helium.

10. Mercury –The Innermost Planet
 It is named after messenger of the Roman Gods
88 days-Revolution
Mercury has extreme temperature fluctuations, ranging from 800F
(daytime) to -270F (nighttime).
It is the closest planet to the Sun
Even though it is the closest planet to the sun, Scientists believe there
is ICE on Mercury! The ice is protected from the sun’s heat by crater
shadows.
It is also the smallest, and its orbit is the most not fully circular.
It does not have any satellite.
There is no water or atmosphere
It can be seen with naked eyes.
There are no seasons on its surface

11. Venus –The Veiled Planet
 It is named after Roman goddess of love & beauty .
Venus is surrounded by thick cloud cover that is why it is called “Veiled
Planet”.
 It is the brightest & hottest planet. Its maximum surface temperature may
reach 900F. It is the brightest object in the sky after the sun and moon
because its atmosphere reflects sunlight so well. People often mistake it for
a star.
 It orbits the Sun once in about 225 Earth days.
 Venus reaches its maximum brightness shortly before sunrise or shortly
after sunset, so it is also known as the Morning Star or Evening Star.
 Venus is also known as “Sister” or “Twin” planet to earth because of its
similar size & mass to earth.
 Venus has no moon.

12. Earth –The Blue Planet
 It is also known as watery planet, because 70% of its surface is
covered by water.
 It reflects about 1/3rd of sunlight it receives .The earth’s
atmosphere scatters the light & creates a blue effect, so it is also
called Blue Planet.
 Only planet having life.
 It orbits the Sun once in about 365 Earth days.
 It rotates about its own axis, thus creating day & night. It takes 24
hours to do that.
 It revolves around sun, due to its tilt, seasons are created.
 Due to gravity, the layer of gases remains attached to it (which is
known as atmosphere), it prevents too much heat or UV rays from
Sun reaching earth.
 Moon is the only satellite of the Earth.

13. Earth –The Blue Planet
*Earths Moon
 It takes the moon approximately 29 days to
complete one rotation. The same side of the
moon always faces us.
The moon’s surface is covered in dust and
rocky debris from meteor impacts. It has no
water or atmosphere.
The moon reflects light from the sun onto
the earth’s surface.

14. Mars –The Red Planet
It is named after the Roman god of war.
It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives
it a reddish appearance
Mars has approximately half the diameter of Earth
It has two satellites.
The gravity of Mars is half of the earth .
The atmosphere of Mars consists of about 95% carbon dioxide,
3% nitrogen,1.6% argon
and contains some oxygen and water
Mars also has the largest dust storms in the Solar System
Like Earth, Mars has ice caps at its poles.
Mars has the largest volcano in our solar system: Olympus Mons. Olympus Mons is
approximately 15 miles high.
-iron oxide, or rust, in its soil.
Mars takes about two years to complete an orbit.

15. Jupiter –The Giant Planet
 It is named after the Roman god Jupiter (ruler of Roman gods)
Jupiter is the largest and most massive planet within the Solar
System. It’s diameter is 11 times bigger than that of the Earth’s.
It has a great Red Spot, it is rotating storm system inside the
planet.
 Jupiter rotates faster than any other planet. It completes one
rotation in 10 hours
Jupiter has a faint ring system, these rings appear to be made of
dust. This is also a windy planet as the fast rotation causes high
winds.
It has 16 known moons
It takes about 12 years for Jupiter to orbit the sun.

16. Saturn –The Jewel Planet
Saturn is the sixth planet from the Sun and the second largest planet in
the Solar System, after Jupiter.
It is named after the Roman god Saturn
Saturn is classified as a GAS GIANT planet. Saturn is composed almost entirely
of hydrogen and helium.
It has 22 known satellites .
It can be seen by naked eye
Saturn is 95 times heavier than earth
It takes Saturn 10,759 Earth days (or about 29½ years) to finish one revolution
around the Sun
Saturn has many rings made of ice. Saturn’s rings are very wide. They extend
outward to about 260,000 miles from the surface but are less than 1 mile thick.
Saturn has 18 known moons, some of which orbit inside the rings.
It takes Saturn about 30 years to orbit the sun.

17. Uranus –A planet on its side
Uranus appears to lie on its side.
It is named after the Roman god of the sky.
The only planet which rotates on its axis from east to west.
Uranus is blue in color due to methane gas in its
atmosphere.
Uranus has 11 dark rings surrounding it which are made of
dust.
Uranus has 21 known moons and takes 84 years to complete
one orbit.
It is a very cold planet ,it receives 370 times less sunlight
than Earth as it is far away from sun as compared to Earth.
Its core is very rocky.

18. Neptune –The Last Giant
Most distant gas planet.
It is named after the Roman god of the sea .
Most windy planet. Neptune has the fastest winds in the solar
system: up to 2,000 km/hr.
It has 8 known satellite
Can’t be seen with naked eye. As it is very far from Sun,it
completes an orbit on average every 164.79 years.
The average distance between Neptune and the Sun is 4.50
billion km.
Neptune was the first planet found by mathematical prediction.
Neptune is also blue in color due to methane gas in its
atmosphere.

20. Solar System- MOON
Phases of Moon
a. New Moon- The Moon's unilluminated side is facing the Earth. The
Moon is not visible (except during a solar eclipse).
b. Waxing Crescent- The Moon appears to be partly but less than one-
half illuminated by direct sunlight. The fraction of the Moon's disk
that is illuminated is increasing.
c. First Quarter- One-half of the Moon appears to be illuminated by
direct sunlight. The fraction of the Moon's disk that is illuminated is
increasing.
d. Waxing Gibbous- The Moon appears to be more than one-half but
not fully illuminated by direct sunlight. The fraction of the Moon's
disk that is illuminated is increasing.

21. Solar System- MOON
Phases of Moon
a. New Moon- The Moon's unilluminated
side is facing the Earth. The Moon is not
visible (except during a solar eclipse).

22. Solar System- MOON
Phases of Moon
b. Waxing Crescent- The Moon appears to
be partly but less than one-half illuminated
by direct sunlight. The fraction of the
Moon's disk that is illuminated is
increasing.

23. Solar System- MOON
Phases of Moon
c. First Quarter- One-half of the Moon
appears to be illuminated by direct
sunlight. The fraction of the Moon's disk
that is illuminated is increasing.

24. Solar System- MOON
Phases of Moon
d. Waxing Gibbous- The Moon appears to
be more than one-half but not fully
illuminated by direct sunlight. The fraction
of the Moon's disk that is illuminated is
increasing.

25. Solar System- MOON
Phases of Moon
e. Full Moon- The Moon's illuminated side
is facing the Earth. The Moon appears to be
completely illuminated by direct sunlight

26. Solar System- MOON
Phases of Moon
f. Waning Gibbous- The Moon appears to
be more than one-half but not fully
illuminated by direct sunlight. The fraction
of the Moon's disk that is illuminated is
decreasing.

27. Solar System- MOON
Phases of Moon
g. Last Quarter- One-half of the Moon
appears to be illuminated by direct
sunlight. The fraction of the Moon's disk
that is illuminated is decreasing.

28. Solar System- MOON
Phases of Moon
h. Waning Crescent- The Moon appears to
be partly but less than one-half illuminated
by direct sunlight. The fraction of the
Moon's disk that is illuminated is
decreasing.

29. Solar System- CONSTELLATION
CONSTELLATION
Late Latin term "constellatio," which can be translated as "set of
stars".
Is an area of the sky with defined boundaries, all stars and any other
objects within that boundary are considered part of the constellation.
There are 88 official constellations which are recognized by the
International Astronomical Union
STARS and GALAXY
-Our Sun is one of several hundred million stars in the Milky Way. It
lies in an arm of the galaxy called the Orion Arm, and is about 26,000
light-years from the galaxy's center.

30. Solar System- CONSTELLATION
1. Proxima Centauri
The closest star to our own solar system is called Proxima Centauri. It will not always be closest,
since stars do move through space. Proxima Centauri is the third star in the Alpha Centauri star
system, also known as Alpha Centauri C. Distance: 4.2 light-years
but even if it is only 4.28 light years away this red duarf is only of magnitude 11

31. Solar System- CONSTELLATION
1. Proxima Centauri
The closest star to our own solar system is called Proxima Centauri. It will not always be closest,
since stars do move through space. Proxima Centauri is the third star in the Alpha Centauri star
system, also known as Alpha Centauri C. Distance: 4.2 light-years
2. Rigil Kentaurus
The second closest star is a tie between the sister stars of Proxima Centauri. Alpha Centauri A and
B make up the other two stars of the triple star system Alpha Centauri. Distance: 4.3 light-years
3. Barnard's Star
This is a faint red dwarf star, discovered in 1916 by E. E. Barnard. Recent efforts to discover
planets around Barnard's Star have failed. Distance: 5.9 light-years
4. Wolf 359
This star is known to many as the location of a famous battle on Star Trek the Next generation.
Wolf 359 is a red dwarf. It is so small that if it were to replace our Sun, an observer on Earth
would need a telescope to see it clearly. Distance: 7.7 light-years
5. Lalande 21185
While it is the fifth closest star to our own Sun, Lalande 21185 is about three times too faint to be
seen with the naked eye. You'd need a good telescope to pick it out of the night sky. Distance:
8.26 light-years

32. Solar System- CONSTELLATION
6. Luyten 726-8A and B
Discovered by Willem Jacob Luyten (1899-1994), both Luyten 726-8A 726-8B are red
dwarfs and too faint to be seen with the naked eye. Distance: 8.73 light-years
7. Sirius A and B
Sirius, also known as the Dog Star, is the brightest star in the night sky. It has a
companion called Sirius B, which is a white dwarf. Distance: 8.6 light-years
8. Ross 154
Ross 154 appears to be a flare star, which means that it can increase its brightness by a
factor of 10 or more before reverting to its normal state, a process which takes only a
few minutes. Distance: 9.693 light-years
9. Ross 248
While it is now the ninth closest star to our solar system, around the year 38000AD, the
red dwarf Ross 248 will take the place of Proxima Centauri as the closest star to us.
Distance: 10.32 light-years
10. Epsilon Eridani
Epsilon Eridani is among the closest stars known to have a planet, Epsilon Eridani b. It is
the third closest star that is viewable without a telescope. Distance: 10.5 light-years