Astronony presention for css exams .pptx

Astronomy

1. Astronomy Imran Umar Abbasi

2. What is Astronomy Astronomy is the study of everything in the universe beyond Earth's atmosphere. That includes objects we can see with our naked eyes, like the Sun , the Moon , the planets, and the stars.

3. Dark Matter Everything around us is made of matter. 5% of normal matter rest of other is dark matter and dark energy They are invisible in nature Dark Matter does not reflect light Fritiz Zwicky ( Concept on Dark Matter)

4. Block Hole Star Dies A black hole is formed when the core of a star collapses the star explodes and the star dies. Star can no longer sustain energy. This phenomenon generates a mini black hole in which stars eat the star from inside. Explosions release tremendous amounts of energy. Gravitational Field High magnetic field Nothing can escape from a Black Hole Super humungous magnetic field Even light cannot escape Nearest Black hole to Earth 1600 Lights years away

5. Big Bang Theory Universe began 13.7 Billion years ago with a massive explosion of extremely hot bubble. After the explosion the universe was born time, space and matter all these came into form. It kept on expanding at phenomenal rate. As the universe cooled down the energy converted into particles of matter and antimatter. When it was more cooled enough it form stable particle called proton and neutron and temperature fell below 1 billion degree C elsius. Hydrogen gas was formed because of atoms and stars and galaxies are formed. Their radiation dissolve hydrogen atoms into plasma that allowed visible light to pass and universe came into being.

6. Galaxy Galaxy is group of billion of stars that moves through space as a unit and Milky way is the large disk shaped galaxy that includes our solar system. The milky way is about 100,000 light years in diameter The spiral galaxy formed 13.7 billion years ago Near milky way there is Andromeda Our solar system is 300,000 light year away from milky way.

7. How to Estimate age of Universe Age of Oldest Stars This method is based on observations of globular clusters Individual distances from the earth can be taken as equal Stars can have different masses Globular clusters have stars with masses lower than 0.7 times the solar mass Stars are dimmer than our sun, and they have been burning for around 11-18 billion years.

8. Hubble’s Law A direct linear equation between galaxy velocity and distance V= H x d According to this law, since the Big Bang, the universe has been expanding at a constant rate. Thus, from an extremely small region where things were compact and close to each other, the universe and everything in it has moved away from each other at a steady rate to reach where they are today.

9. Solar System

10. Characteristics Sun The Sun is the center of Solar System Sun contain 91% of Hydrogen 8% of Helium and 1% other metals Diameter 1,398,000 Km Temperature 15,000,000 K

11. Region of Sun The centermost region of the Sun is known as the core; this is the region where Hydrogen turns into Helium through the  nuclear reaction. Between the core and the convection zone, there lies the radiative zone; by means of radiative diffusion and thermal conduction. The outermost layer of the Sun’s interior is known as the convection zone. This zone uses convection mode to transfer energy . The Photosphere has a thickness of about 500 KM, and all the visible light from the Sun comes from this layer. The Chromosphere is visible as a dim red ring, and it lies just above the Photosphere.

12. Planets A planet is  a large celestial body that revolves around the sun in fixed orbits .

13. Dwarf Planets A planet is a large celestial body that revolves around the sun in fixed orbits, Ceres, Pluto, Eris, Haumea, and Makemake , have been discovered.

14. Natural Vs Artificial Satellite Natural Satellite Artificial Satellite They are formed by nature They are man-made They are not controlled by human They are controlled by humans They are permanent They are temporary They are not used for communication The are used for communication

15. Moon Eclipse When the sun the earth and the moon come in a straight line with the earth in between the moon and the sun, then the shadow of the earth falls on the moon This results in a lunar eclipse. When the Moon is completely in the dark shadow of the Earth is called a total lunar eclipse. When the Moon is not partly hidden by the dark shadow of the Earth is called a partial lunar eclipse. A lunar eclipse takes place on a full moon day. The shadow consists of two parts One part is the darkest part of the shadow where light does not reach from the source of light and this part is known as the umbra. Another part is not completely dark where some light reaches from the source of light this part is known as the penumbra and it surrounds the umbra.

16. Solar Eclipse A solar Eclipse occurs when the moon comes in between the sun and the Earth. As a result, the moon blocks the light of the sun from reaching the earth’s surface and casts a shadow on it . Partial:  When the moon does not align completely with the sun, and so only a portion of the sunlight is blocked from reaching the earth. Annular:  When the moon covers the sun, but the sun can be seen around the edges of the moon Total :  When the sun is completely covered by the moon.

17. Difference Between Asteroid and Metroid Asteroids Metroid's Asteroids are minor planets. Meteoroids are falling stars. Does not have an atmosphere Does not produce an atmosphere, but burn up when falling into a planet. 1 to more than 100 kilometres in diameter Typically, less than 10 metres . The orbital shape is elliptical and orbits the Sun The orbital shape is elliptical and orbits the Sun but gets pulled into larger bodies.

18. Comet Comets are cosmic snowballs of frozen gases, rock and dust roughly the size of a small town. When a comet's orbit brings it close to the sun, it heats up and spews dust and gases into a giant glowing head larger than most planets. The dust and gases form a tail that stretches away from the sun for millions of kilometers.

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20. CSS Questions Differentiate between occurrence of Lunar and Solar eclipse. Describe difference method of estimate the age of universe Explain the formation of Lunar Eclipse Explain the dark energy and dark matter Define the term black whole. What is expected inside it How can have sun have strong gravitational field if its made up of gases? Differentiate between a start and a planet. What is the magnitude of a star and how the color of stars is correlated with their temperatures ? Briefly describe the most popular and accepted theory about the origin of the Universe . Differentiate between natural and artificial satellites. Briefly describe the working of communication satellites with some applications . What is Black Hole? How black hole are formed and discovered?