The Universe, the Solar System and Earth’s Galaxy

By Saroj Singh|Updated : February 27th, 2020

NASA has bid goodbye to the Spitzer space telescope after 16 years of service using infrared light to unveil otherwise invisible features of the universe, including the planets in our galaxy solar system and innumerable stars in the galaxy. It gave us new views of distant galaxies, newborn stars and nearby exoplanets, as well as of asteroids, comets and other objects in our solar system. In this article, let us understand some basics regarding the Universe and related aspects.

The Universe is everything that surrounds us. The totality of everything that exists, including all physical matter and energy. The planets, stars, galaxies and the contents of intergalactic space comprise the Universe.

The Universe, the Solar System and Earth’s Galaxy

Broadly universe in modern times can be classified into two parts i.e. atmosphere and space. The spatial size of entire universe is unknown and is possible to measure the size of the observable universe, which is estimated to be 93 billion light-years in diameter. The study of the universe is called Cosmology. The Big Bang Theory is the prevailing cosmological description of the origin and development of the Universe.

What is a galaxy?

A galaxy is a vast system of billions of stars, which also contains a large number of gas clouds and dust, isolated in space from similar systems. A large group of stars, dust, and light gases bound together by their own gravity is called a galaxy. There are about 100 billion galaxies (1011 galaxies) in the universe, and each galaxy has, on an average 100 billion stars (1011 stars).

  • The latest known galaxy is ‘Dwarf galaxy’.
  • The ‘Milky Way’ is the home of the earth and its solar system.
  • Big Bang was an explosion that occurred 15 billion years ago, leading to the formation of galaxies of stars and other cosmic bodies.
  • All the galaxies have been flying away from one another causing expansion of the universe.

According to Big Bang theory at starting the whole mass of the universe concentrated in an extremely dense and hot fireball like structure 13.7 billion years ago it exploded (Big Bang). The matter was broken into pieces, which were thrown out with high speed in all directions forming stars and galaxies which are still moving away from one

Contemporary Developments

Higgs Boson experiment: A historical mega experiment was conducted in 100 ft deep and 27 km long tunnel in Large Hadron Collider (LHC) in Geneva by European Centre for Nuclear Research (CERN) on 30th March 2010 to unravel the mysteries of the Universe.

  • Proton beams of the same velocity of light were collided to produce Higgs Boson.
  • This was carried out to know about the dark matter, dark energy, extra dimension, Higgs boson and god particle.

Basically, through this experiment scientists tried repeating the phenomena that occurred prior to 15 billion years ago known as ‘Big Bang’ in the field of science.


Stars are made up of hot burning gases. The dust particles and gas in nebula come together due to gravity and form stars. They emit light of their own and are extremely hot.

Solar System

The solar system is dominated by the sun which accounts for almost 99.9% of the matter in the whole solar system. The solar system consists of the sun, the eight planets and their satellites and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.


These are opaque bodies which continuously revolve around and are lighted by the Sun. Mercury, Venus, Earth, Mars are called terrestrial planets and Jupiter, Saturn, Uranus and Neptune are called gaseous planets. A ninth planet has been recently discovered by NASA named Carla. Terrestrial planets are also called as ‘Rocky planets’/Jovian planets/Gaseous planets. The planets are also classified as inner and outer planets based on nearness to the Sun. The inner planets are Mercury, Venus, Earth, Mars and the outer planets are Jupiter, Saturn, Uranus and Neptune.


Peculiarities of planets:

  • Mercury is closest to the Sun and devoid of gases like CO2, N2, H2, and O2, meaning atmosphere is absent in Mercury.
  • Venus is the second planet from the Sun, but nearest to the Earth and is the brightest planet. Venus is known as ‘Evening Star’ as well as ‘Morning Star’. It is also regarded as ‘Earth’s Twin’. Venus is the hottest planet.
  • Earth is the only known planet which provides sustenance or life on it. It has a large quantity of oxygen which supports life.
  • ‘Sea of tranquillity’ made of the plain of dust particles, is on the rear side of the moon (satellite of Earth), which always remains dark. Moon is also devoid of the atmosphere with daytime temperature is about 100OC and during the night it drops down to about -180O Moon is also known as fossil planet.

Chandrayan 1

·       Indian Space Research Organization (ISRO) has successfully established Chandrayan-1 in the moon’s orbit from Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh by Polar Satellite Launch Vehicle -PSLVC1 on 22nd Oct 2008.

·       This takes pictures of moon’s surface even of the whole of its chemical environment and provides information about its soil, mineral, ice, heat and weather etc.

Chandrayan 2

·       India’s second mission to the Moon is a totally indigenous mission comprising of an Orbiter, Lander and Rover with the goal of exploring south pole of the moon.

Why do we go to the moon?

The moon is the closest cosmic body at which space discovery can be attempted and documented. It is also a promising testbed to demonstrate the technologies required for deep-space missions. Chandrayaan- 2 aims for enhancing our understanding of the Moon, stimulate the advancement of technology, promote global alliances and inspire a future generation of explorers and scientists.

  • Mars is one of the most explored planets in our solar system. It is a rocky planet and its solid surface has been altered by volcanoes, impacts, winds, crustal movements and chemical reactions. The predominance of red soil and the pink sky gave its name as ‘Red Planet’. Phoebes and Demos are two satellites of Mars.
  • Jupiter is the largest planet of the solar system. It is also known as the winter planet as its average temperature is very low (-148OC). Ganymede, the satellite of Jupiter is the largest satellite in the Solar system.
  • Saturn is the second-largest planet in the Solar System. It is circumference by the concentric rings which are made up of ice-covered dust particles which revolve around it. Titan is the largest satellite of Saturn
  • Uranus is four times the size of the earth. The predominance of methane gas makes it appear greenish in colour. It was the first planet to have discovered using a telescope. It rotates east to west on its axis, which is opposite to other planets except for Venus.
  • Neptune is the 8th planet of the Solar System and is very similar to Uranus and can be considered as its twin.

Note: Pluto is not a planet now. On the basis of the new definition of the planet given by the top institution on space science research, leading astronomers participating in IAU’s meet at Prague, the Czech Republic on August 24, 2006, declared that Pluto would no longer remain a planet.

Some Quick facts:

  • 1929, Hubble discovered a correlation between distance and radiation velocities as determined from their redshifts.
  • 1949, Fred Hoyle coined the phrase "Big Bang" for Lemaitre
  • 1965: The discovery of cosmic microwave background radiation constitutes a major development in modern physical cosmology. 
  • Since the 1990s dark energy is a term that describes an unknown form of energy, received worldwide acceptance. Dark energy affects the universe on the largest scales. 
  • Some other experiments also supported the Big Bang:
    1. Cosmic Background Explorer (COBE)
    2. Hubble Space Telescope
    3. Wilkinson Microwave Anisotropy Probe (WMAP)
    4. Planck observatory
    5. Large Hadron collider experiment (LHC)

The purpose of this post was to develop an understanding of the space sciences and the position of the earth in the universe



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