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Universe – 01

CHAPTER 1: UNIVERSE
The universe is a vast endless space which includes galaxies, stars, planets and other forms of matter and energy in it.

ORIGIN OF UNIVERSE: BIG BANG THEORY :-

The most popular argument regarding the origin of the universe is the Big Bang Theory. It is also called expanding universe hypothesis.  In 1927, Abbe Georges Lemaitre, a Belgian astronomer was the first to propose, a theory on the origin of the universe. It was Edwin Hubble who provided the evidence that the universe is expanding It was called, ‘the Big Bang Theory’. According to it, the universe was formed about 13.75 billion years ago. In the beginning, all matter forming the universe existed in one place in the form of tiny ball (singular atom).  At the big bang, the tiny ball exploded violently. It led to huge expansion and temperature dropped to 4500K and gave rise to atomic matter. The universe became transparent.

HOYLE’S CONCEPT OF STEADY STATE  :- 

It considered the universe to be roughly the same at any point of time. It did not have a beginning and did not have an end.However, with  evidence  available about the expanding universe, scientific community favours the argument of expanding universe.

NEBULAR HYPOTHESIS: 

One of the earlier and popular arguments of the earth’s origin was by a German professor Immanuel Kant. Mathematician Laplace revised it in 1796. It was known as Nebular Hypothesis. It considered that planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating.

Galaxy:

A galaxy is a system of billions of stars, stellar remnants, interstellar gas, dust, and dark matter. The Milky Way is the galaxy that contains our Solar System.

UNITS  OF  MEASURING  DISTANCE  IN  THE  UNIVERSE.

Astronomical unit (AU) It is defined as the mean distance from the earth to sun. 1AU =1.5 X 10^8 kms.

LIGHT YEAR 

It is the distance travelled by light in one year.Light year =9.46X 10^12kms. 3) PARSEC It is a unit of length used to measure the astronomically large distances between objects beyond our solar system. one parsec is the distance at which one astronomical unit subtends an angle of one arc second. 1Parsec =3.26 light years.

STAR  AND  CONSTELLATIONS

Star is a type of astronomical object which has its  own light and heat. The nearest star to the earth is sun. Proxima centuari   is the closest star to the sun; stars are made up of vast clouds of hydrogen gas, some helium and dust. In ancient times, people used to determine directions during the night with the help of stars. The North Star indicates the north direction. It is also called the Pole Star. Some astronomical objects do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets.

CONSTELLATION : –  

Constellation is the group of star that forms a particular shape in the sky.  Ursa Major is a constellation that can be seen in the northern hemisphere.

BLACK HOLE

A black hole is an object with such a strong gravitational field that even light cannot escape from its surface. A black hole may be formed when a massive object undergoes uncontrolled contraction because of the inward pull of its own gravity. SOLAR SYSTEM  A solar system consists of a sun at the centre and the eight planets, moons, asteroids, comets and meteoroids that revolve it. The eight planets, namely the Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.  These planets  revolve around the sun in fixed elliptical path       known as ‘orbits’. The solar system is believed to have been formed about 4.6 billion years ago. The solar system also includes the Kuiper Belt that lies past Neptune’s orbit. Of the eight planets, Mercury and Venus are the only planets with no satellites while the Jupiter and Saturn have the highest number of satellites in our solar system.

THE SUN

The sun is in the centre of the solar system. It is huge and made up of extremely hot gases. It provides the pulling force that binds the solar system. The sun is the ultimate source of heat and light for the solar system. But that tremendous heat is not felt so much by us because despite being our nearest star, it is far away from us. The sun is about 150 million km away from the earth and light travelling at the speed of 3X10^5 km per second and takes about 8 min and 20 sec to reach the earth surface. You Can show the below one in a better pic or video . google as Anatomy of sun .

PLANETS

There are eight planets in our solar system. In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.  The planets are classified in order of their distance from the sun and based on their characteristics. They are:
  1. The inner planets or terrestrial planets or rocky planets.
 Mercury, Venus, Earth and Mars are called inner or terrestrial planets.
  1. The outer planets or gaseous planets or giant planets. 
Jupiter, Saturn, Uranus and Neptune are called outer or gaseous planets.

The Earth

The earth is the third nearest planet to the sun.  In size, it is the fifth largest planet. It is slightly flattened at the poles. And so its shape is described as a Geoid. Geoid means an earth-like shape. Conditions favourable to support life are probablyfound only on the earth.  The earth is neither too hot nor too cold. It has water and air, which are very essential for our survival. The air has life-supporting gases like oxygen. Because of these reasons, the earth is a unique planet in the solar system. From the outer space, the earth appears blue because its two-thirds surface is covered by water. Itis, therefore, called a blue planet. The planet known as the “Earth’s Twin” is Venus why because it has similar mass, size and proximity to sun.All the planets rotates in the  anti-clock wise except for Venus and Uranus who will make the spin in the clock-wise direction.(east to west).

MERCURY

Mercury is the nearest planet to the sun and it is the smallest planet in the solar system. Mercury is the smallest planet in the Solar System and the closest planet to the Sun. Though it is very close to the Sun, it is not the hottest planet, that title belongs to Venus, but Mercury is the second-hottest nonetheless.
  • Mercury is the closest planet to the Sun at a distance of 57 million kilometers / 35 million miles.
  • Out of all the terrestrial planets, Mercury is the smallest. It is also the smallest planet in the Solar System.
  • Despite being so small, Mercury is the second-densest planet in the Solar System after Earth. This means it is very compact.
  • Mercury does not have any satellites or ring systems.
  • The surface of Mercury is similar to the Moon. It is the most heavily cratered planet and this means that it hasn’t been geologically active for many years.
  • Mercury has a radius of 2.439 km / 1.516 mi and a diameter of 4.879 km / 3.032 mi.
  • Though it is the closest planet to the Sun, temperatures on Mercury are both hot and cold.
  • During the day, Mercury’s average surface temperatures can reach up to 800 degrees Fahrenheit / 430 degrees Celsius.
  • At night, Mercury’s surface temperatures can drop to as low as -290 degrees Fahrenheit / -180 degrees Celsius.
  • Mercury’s changes in temperature are the most drastic in the Solar System.
  • Mercury formed around 4.5 billion years ago after gravity pulled swirling gases and dust together.
  • After Mercury was formed, scientists believe that it suffered heavy bombardments by comets and asteroids shortly after. Another event called the Late Heavy Bombardment which ended around 3.8 billion years ago, may also be responsible for Mercury’s cratered surface.
  • Almost 85% of Mercury’s radius is represented by its enormous iron core.
  • Due to the core’s unusual size, Mercury began to shrink as the core cooled and contracted pulling the surface inwards
VENUS’ Venus is the second planet from the Sun, and the sixth largest of all the planets. It is named after the Roman goddess of love and beauty. It is also called as ‘Earth’s Sister’ planet due to its similar size and mass as that of our Earth. It is the hottest planet in the solar system. It is Popularly known as “Morning star and Evening star” It is seen in the east sky before sunrise (dawn) in the morning and in the west sky after the sunset (twilight).It rotates clockwise i.e. east to west direction on its own axis.
  • Venus and Mercury are the only planets in the Solar System that do not have a moon.
  • Venus is the second brightest object in the sky after the Moon, and the Sun.
  • It is the only planet named after a female deity and the brightest planet in the Solar System.
  • Venus is 62 degrees hotter than Mercury, the closest planet to the Sun.
  • Venus has a radius of 6.051 kilometers / 3.760 miles, and a diameter of 12.104 km / 7.521 mi. It is only slightly smaller than Earth.
  • Venus is at a distance of 108 million km / 68 million mi away from the Sun.
  • One day on Venus lasts for about 243 Earth days. This is the slowest rotation of any planet making it the most spherical object in the Solar System, after the Sun.
  • Venus and Uranus rotate in the opposite direction than the other planets. They both move from East to West, clockwise.
  • Venus has montains, valleys, and tens of thousands of volcanoes. The highest mountain on Venus, Maxwell Montes, is 20,000 feet / 8.8 kilometers high – very similar to the highest mountain on Earth, Everest.
  • Apart from lacking any moons, Venus also doesn’t have a ring system, and because it rotates very slowly, its magnetosphere is also very weak.
  • The average temperatures on Venus have been estimated to be at around 465 degrees Celsius / 900 degrees Fahrenheit, this is hot enough to melt lead. 
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