CSS Exam Pakistan EDS Notes : Universe, Galaxy and Solar System

Universe, Galaxy and Solar System

CSS EXAM PAKISTAN EDS PAPER 2013

Universe:

• The totality of everything that exists or is known to exist is called universe.
• It includes all matter and energy, stars, planets and galaxies and contents of intergalactic space.
• The branch of science that deals with the study of universe is called cosmology.

Origin of Universe Theories:

1. Bigbang Theory:

According to this theory, the universe came into existence 15 to 20 billion years ago when a cataclysmic explosion took place.

2. The 3K Microwave background theory:

This theory supported bingbang theory and stated that the echo of that explosion can still be heard in the form of microwave radio signal from radiation.

Future of Universe Theories:

1. Open Universe Theory:

The universe will keep expanding.

2. Close Universe Theory:

The universe will shrink and close.

3. The cycle Theory:

The universe will expand and close.

4. Steady state Theory:

The universe will always exist.


                                                                      GALAXY

• Galaxy is the fundamental unit of universe.
• A system of starts and planets together with the intergalactic space and dust held together with the gravitational attraction.
• There are billions of galaxies in the universe. Some of them have only a few millions stars while others have as many as 400 billion stars or even more.
•  There are three kinds of galaxies. Spiral, Elleptical and Irregular.  The only difference is their shape.

OUR GALAXY

• Our galaxy is called milky way.
• Milky way is a spiral galaxy.
• The region in space occupied by the spiral galaxy is called galactic plane.
• The sun is not present at the centre of our galaxy.
• The arms of spiral galaxy are called galactic arms.
• The sun revolves around the nucleus of the milky way galaxy once in 225 to 250 million years. This duration is called cosmic year or galactic year.
• The nearest spiral galaxy to milky way galaxy is Andromeda galaxy.

SOLAR SYSTEM

• Solar system is a tiny part of the universe.
• It includes the sun and all other objects that travel around it.
• It includes earth and 7 to 8 other planets together will satellites that travel around most of them.
• It further includes asteroids, meteoroids, comets and interplanatery dust and interplanatery plasma.

Planets of our solar system

• Mercury
• Venus
• Earth
• Mars
• Jupiter
• Satrun
• Uranus
• Naptune
• Platu 

Mercury:

• Mercury is the 2nd smallest planet.
• Mercury is nearest to the Sun
• Its mean distance from the sun is 0.837 AU.
• Its diameter is 4,880 kilo meter.
• Mercury takes 88 earth days to complete one revolution round the sun.
• Mercury has holes called crackers
• Mercury has no moon
• Mercury has no atmosphere
• Mercury is of the same size as our moon.