General Awareness Universe and Solar System

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Universe and Solar System

Universe

• The study of universe is known as Cosmology.
• Cosmology comes from Cosmos (Universe) + Logos (Study).
• All physical matters, energy, planets, stars, galaxies and the contents of intergalactic space constitute universe.
• It comprises of billions of galaxies which are made up of millions of stars held together by the force of gravity.
• Andromeda is our nearest galaxy. Our own galaxy is called the Milky Way (or the Akash Ganga) and it contains about 100 billion stars and one of these is our Sun.
• Planets and other objects go round the Sun and those make up the solar system with the Sun at the centre: Latest known galaxy is the Dwarf Galaxy.
• Evolution of universe is explained by the Big Bang Theory. Big Bang was basically an explosion that occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.

Solar System

• The solar system comprises the Sun and its eight planets, which are believed to have been developed from the condensation of gases and other lesser bodies.
• The Sun is the center of solar system. It is huge and made of extremely hot gases. It provides the pulling force that binds the Solar System.
• The eight planets in the Solar System are Mercury, Venus, Earth, Mars Jupiter Saturn, Uranus & Neptune.

Components of the Solar System

1. All the planets revolve around the Sun in their elliptical orbit.
2. The size of solar system has been estimated to about 10'' AU.
3. Other components of solar system are
• The Sun, eight planets (excluding Pluto) and their respective satellites.
• Five Dwarf planets (Ceres, Pluto, Eris, Makernake and Haumea).
• Interstellar debris such as asteroids, rneteoroids, cornets.
• The electrically charged gases called Plasma.
• Interplanetary dust particles are cosmic dust which pervade between planets in the Solar System.
• Components other than these are known as Small Solar System Bodies (SSSB).

The Sun

• The Sun accounts for more than 99% of the mass of the solar system and due to this, the Sun exerts immense gravitational pull to keep the planets rotating around it in a definite elliptical orbit.
• The Sun is the major source of energy of the solar system. The nuclear fusion reaction that converts hydrogen into helium in the core of the Sun provides the energy.
• The glowing surface of the Sun that we see is known as Photo sphere. Above the Photo sphere is the red coloured Chromosome and beyond it is the magnificent corona, which is visible during eclipses.
• Super imposed on Sun's white light are hundred of dark lines called Fraudster lines. Each line indicates some elements present in the solar system.

Concepts Associated with Sun

• Solar Winds and Solar Flares - The Sun is continuously emitting streams of proton in all directions either as spiral streams called Solar Winds or bouts of incandescent material called Solar Flares.
• Aurora - The constituent particles of the solar wind are trapped by the Earth's magnetic field and enter the Earth's upper atmosphere as Aurora. It is described as Aurora Borealis in the Northern hemisphere and Aurora Australis in Southern hemisphere.
• Plages and Sunspots - The surface of the Sun is continuously changing. Bright spots are called Plages and dark spots are called Sunspots. The sunspots are cold and dark regions on the Sun's surface with a periodicity of 11 years.

Planets

• Planets are opaque bodies which continuously revolve around and are lighted by the Sun. There are eight planets in the solar system.
• The sequence of planets according to their size (in descending order) is Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars and Mercury.
• The sequence of planets according to their distance from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Types of Planets

Classification of Planets

1. Inner Planets -It consists of Mercury, Venus, Earth and Mars.
2. Outer Planets - It consists of Jupiter, Saturn, Uranus and Neptune.

A Comparative Study of the Planets of the Solar System

Moon

• The study of Moon is called speleology.
• It is also known as the fossil planet.
• The Moon is the only natural satellite of the Earth which has no atmosphere, no twilight and no sound.
• The size of the Moon is one-fourth the size of the Earth.
• Gravitational pull of Moon is one-sixth that of the Earth. Mainly silicon, iron, magnesium etc, elements are found on the Moon's surface.

Stars

• Stars are heavenly bodies made up of burning gases, thus, shining by their own light.
• lf the star is bigger than the Sun, but not more than twice as big, it will turn into a Neutron star or Pulsar. They are formed due to Novae or super novae explosion.
• A star's colour indicates the temperature of its surface. Blue colour denotes maximum temperature. Then comes yellow, then red etc.

Concept of Black Hole and Chandrasekhar Limit

1. There is an upper limit to the mass of stars, above which two things are possible
• Explosion of the star to form neutron stars called Pulsar.
• Collapse and compaction of the star to form Black Holes.
2. wherefore, the bleak holes are formed due to collapse and compaction under gravity, at the end of the life cycle.
3. A renovated Indian Physicist Chandrasekhar had predicted an upper limit to the mass of stars, which is called as Chandrasekhar limit. A star having a mass above 1.44 solar masses will continue to collapse to form a neutron star is Chandrasekhar limit.

Units of Distance

• Halley's Comets Reappears after 76 years, last seen in 1986.
• Comet Shoemaker Levy-9 Collided with Jupiter between 16th and 21st July, 1994.
• Comet Smith-Tittle Can collide with Earth on 14th August, 2116. It creates an impact of about 1.6 million times that of Hiroshima bomb.
• Asteroid Apoptosis NASA has authenticated the impact of asteroid called Apoptosis, which is having a probability of impact on Earth is dated on April, 2036.

The Earth

• The Earth is a unique planet. It is the third planet from the Sun and the densest as well as the fifth-largest of the eight planets in the solar system. It is also the largest of the solar system's four terrestrial planets, also known as Blue Planet.

Tilt of the Earth's Axis

• The axis of the Earth is inclined to the plane of ecliptic (the plane, in which the Earth orbits round the Sun) at an angle of `661/2` giving rise to different seasons and varying lengths of day and night.
• If the axis were perpendicular to this plane, all parts of the globe would have equal days and nights at all times of the year.
• The Earth is tilted about "23.5" from a line perpendicular to ecliptic plane.