Complete Notes of Solar System And Universe!Physical Features Of India
Best Notes for SSC and B.ED
The universe is commonly defined as the totality of everything that exists including all physical matter and energy ,the planted ,stars galaxies and the contents of intergalactic space.
The study of universe is known as Cosmology.
Galaxy
A galaxy contains a large number of gas clouds ( mainly of hydrogen gas ) and dust.
There are about 100 billion galaxies ( 10 ¹¹ galaxies ) in the universe.
Each galaxy has on an average 100 billion stars ( 10¹¹ stars ) .
So the total number of stats in the universe is 10²² stars.
The milky way galaxy is the home of the earth and our solar system.
The milky way galaxy is spiral in shape.
Milky way galaxy was formed 5 billion years after the big bang.
Latest known galaxy is the Dwarf Galaxy.
Universe can be classified into two parts.
1. Atmosphere
2. Space
Origin of the universe is explained by the big bang theory.
Big bang theory proposed by the Belgian astronomer and cosmologist Georges Lemaitre.
Andromeda is our nearest galaxy.
Star
Clumps of dust and gas in a nebula come together due to gravity and form stars.
They are made of hot burning gases.
Star emit light of their own and very large and very hot.
Light takes about 4.3 years to reach us from the next nearest star proxima centauri.
Solar system
Solar system consists
1. Sun
2. 8 planets and their satellites
3. Asteroid
4. Comets
5. Meteors
The sun is at the centre of the solar system and all these bodies are revolving around it.
The gravitational pull of the sun keeps all the planets and their objects revolving round it.
Thus the motion of all the members of the solar system is governed by the gravitational force of the sun.
Planets revolve around the sun in elliptical orbit.
Order : sequence of distance from sun
Sun > Mercury > Venus > earth > mars > Jupiter > Saturn > Uranus > Neptune
The planet nearest to the sun is Mercury.
Planet farthest from the sun is is Neptune ( not Pluto ).
The size of solar system has been estimated to at about 10⁴ A. U.
Pluto is a dwarf planet.
Terrestrial planet :
1. Mercury
2. Venus
3. Earth
4. Mars
Gaseous planet :
1. Jupiter
2. Saturn
3. Uranus
4. Neptune
Member of the solar system :
The Sun :
It is at the centre of the solar system.
Its size 13 lakh times as that of the earth.
It is the nearest star to the earth.
Its diameter is 14 lakh kms.
It is composed of
Hydrogen = 71 ℅
Helium = 26.5 %
Other elements = 2.5 %
Hydrogen and Helium are the main gases present in the sun.
Within the sun , hydrogen is converted to helium due to nuclear fusion releasing a tremendous amount of heat and light.
Its surface temp. Of 5778K or 5504.85°C.
The temp. at the centre is around 1.571 × 10^7 or 15 ,000,000°C.
Shining surface of the sun is called photosphere, it radiates energy and acts as a source of energy.
The outer layer of sun's atmosphere made up of thin hot gases , is called Corona.
Corona is visible only during a total eclipse of the sun or with a special solar telescope called coronagraph.
The planet travels with the sun through millions of stars in our galaxy at a speed of about 70,000 km/ h.
The sun is about 150 million kms away from the earth .
Light (at the speed of 3,00,000 km/sec)
takes about 8.5 min to reach the earth from the sun.
The Planet
8 planets in the solar system.
9th planet has been recently discovered by NASA named as Carla.
The sequence of planet to their distance from the sun is
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
The sequence of planet to their size ( in descending order i.e. from big to small ) is
Jupiter
Saturn
Uranus
Neptune
Earth
Venus
Mars
Mercury
Jupiter is the biggest and mercury is the smallest planets of our solar system.
Planets is of two types.
1. Terrestrial planets / Rocky planets
2. Jovian planets / Gaseous planets
Terrestrial planets :
4 planets are terrestrial.
Mercury
Venus
Earth
Mars
These planets are called terrestrial because their structure is similar to the earth and these four planets are nearest to the sun.
Jovian planets :
4 planets are jovian.
Jupiter
Saturn
Uranus
Neptune
Note :
Terrestrial planets are also called inner planets.
Jovian planets are also called outer planets.
Inner planets :
1. These planets are Mercury ,Venus , Earth , Mars.
2. They are nearest to the sun.
3. They are made up of dense metallic minerals.
4. They move faster and have a shorter period of revolution.
5. They have thin , rocky crust .
6. They have a mantle , rich in iron and magnesium.
7. They have a core of molten metals.
8. They have thin atmosphere.
9. They have very few natural satellites or moons or no satellites.
Outer planets :
1. They include Jupiter , Saturn , Uranus , Neptune.
2. They are far away from the sun.
3. They are made up of hot gases mainly hydrogen & helium.
4. They move rather slowly and have a longer period of revolution.
5. They are all gaseous bodies.
6. Made of gases.
7. They have ring systems around them.
8. They have large number of natural satellites or moons.
Mercury :
* Closest to the sun.
* Hot planet.
* Has no water on it.
* Has no gases like CO2 , O2 , N2 and H2 which can acts as building blocks of life.
* Mercury planet has no protective blanket like ozone around it to prevent us from harmful radiation.
Venus :
* 2nd planet in distance from the sun.
It is nearest to the earth.
* Venus is also known as brightest planet.
* Venus is also known as the "morning star" as well as "evening star".
* Venus is surrounded by a thick cloud cover hence known as the "Veiled planet".
Venus is like the earth in size and mass and hence also known as the "Earth's twin".
* It rotates clockwise like Uranus.
* Venus is the hottest planet even hotter than Mercury.
It has no water on it. No sufficient oxygen on the Venus.
The Earth :
* Earth is the largest of the inner planets.
* Earth is 23½° tilted on its axis and thus makes 66½° angle.
* It takes 23 hour 56 min and 4.091 sec to rotate on its axis.
* It rakes 365 days , 5 hours and 48 min to revolve around the sun.
* Earth is known as the "Watery planet" or the "blue planet" due to the presence of huge amount water on it.
The Moon :
* Moon is the only satellite of the earth.
* It has a diameter of 3,475 km and its circumference is 10,864 km.
* Its orbit is elliptical.
* The maximum distance ( apogee ) of the moon from the earth is 4,06,000 km and the minimum distance (perigee) is 3,64,000 km.
* It takes 27 days , 7 hours and 43 min to rotate on its axis.
* This period of about 27½ days is called the sideral month.
* It takes same period of time to revolve around the earth.
* The moon's period of revolution with reference to the sun is about 29.53 days.
* (29 days,12 hours,44 min and 2.8 sec)
This period is called a "synodic month".
* The bright part of the moon is full of mountains whereas the dark patches are low lying plains.
"Sea of tranquility" made of the plain of dust particles, is on near side of the moon, which always remains dark.
* The highest mountain on the moon is "liebuity mountain" which is 10,660 meter high.
* The moon has no atmosphere , no twilight and no sound.
* The temperature during day time is about 100°C and during night it drops down to about -180°C.
* The light from the moon takes 1.3 sec to reach the earth.
* The size of the moon is ¼th the size of the Earth.
* Gravitational pull of the moon is 1/6th that of the Earth.
* Silicon , iron , magnesium etc elements are found on the moon's surface.
* The study of the Moon is called "Selenology".
* Moon is also known as the fossil planet.
Mars :
* Mars is also called "Red Planet" due to because iron-rich red soil and pink sky.
* 2 Satellites of Mars.
1. Phobes
2. Demos
Jupiter :
* It is the largest planet of the solar system.
* It is also known as "winter planet"
* Its average temp. is very low -148°C.
* "Gannymeda" is the satellite of Jupiter. It is the largest satellite of the solar system.
Saturn :
It is the second largest planet.
* Saturn has bright concentric rings which are made up of ice and ice-covered dust particles which revolve around it.
* Titan is the largest satellite of Saturn
Uranus :
Uranus is about four times the size of the Earth.
* This planet appears greenish in colour because of methane gas present in its atmosphere.
* Uranus is discovered in 1781 by Sir William Hersiel.
* Uranus is the 7th planet from the sun.
* Uranus is the first planet to have been discovered by the use of a telescope.
* Uranus is the third biggest planet of the solar system.
* Uranus is extremely cold having surface temperature -190°C .
* Uranus is surrounded by 13 rings.
1. Zeta/ R1986U2,6,5,4
2. Alpha
3. Beta
4. Eta
5. Gamma
6. Delta
7. Lambda
8. Epsilon
9. Nu
10. Mu
Uranus rotates from east to west on its axis, which is opposite to other planets except Venus.
The axis of Uranus has large inclination so that it appears to be lying down.
* Hence it bears the name
" A planet on its Side".
Neptune :
* The temp. on the surface of Neptune remains low.
* Neptune is very similar to Uranus that's why they are called "twins".
Pluto is not a Planet now
On the basis of the new definition of planet given by the IAU
( International Astronomical Union ),
the worlds top institution on space science research , leading astronomers participating in IAU's meet at Prague ( Czech Republic )
On Aug 24, 2006 declared that Pluto would no longer remain a Planet.
Under the IAU's new guidelines ,the number of planets in the solar system has thus been reduced from nine to eight.
Pluto had been holding the planetary status since its discovery in 1930 by Clyde Tombaugh.
Some facts and figures about the planets :
1. Name of the planet - Mercury
Distance from the sun - 58 × 10^6 km
Time taken - 88 days
Time taken on its axis - 58.6 days
Diameter - 4878 km
No. of satellites - None
2. Name - Venus
Distance - 108 × 10^6 km
Time taken - 224.7days
Time taken on its axis - 243 days
Diameter- 12,100 km
No. of satellites - None
3. Name - Earth
Distance - 150 × 10^6 km
Time taken - 365.26 days
Time taken on its axis - 23.9 hours
Diameter - 12,760 km
No of satellites - 1
4. Name - Mars
Distance - 228 × 10^6 km
Time taken - 687 days
Time taken to its axis - 24.6 hours
Diameter - 6780 km
No of satellites - 2
5. Name - Jupiter
Distance - 778 × 10^6 km
Time taken - 11.9 years
Time taken to its axis - 9.9 hours
Diameter - 1,42,800 km
No of satellites - 67 ( 50 + 17 )
6. Name - Saturn
Distance - 1427 × 10^6 km
Time taken - 29.5 years
Time taken to its axis - 10 hours
Diameter- 1,20,000 km
No of satellites - 62 ( 53 + 9 )
7. Name - Uranus
Distance - 2870 × 10^6 km
Time taken - 84 years
Time taken to its axis - 16.2 hours
Diameter - 50,800 km
No of satellites - 15
8. Name - Neptune
Distance - 4504 × 10^6 km
Time taken - 164.8 years
Time taken to its axis - 18.5 hours
Diameter - 48,600 km
No of satellites - 8
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