Universe and Solar System

The universe is a vast expanse of free space that contains everything from the tiniest particle to the most massive galaxies. The Solar system is a planetary system that occurs in the Milky Way galaxy, which is part of the Universe itself. It includes all galaxies, clusters of galaxies etc. The solar system is 4.6 billion years old. The solar system has a diameter more than 40 times greater than the distance to the sun, but the solar system is a tiny part of a much larger galaxy.

The Universe
Composition of the Universe
Galaxy
The Solar System
Formation of Solar System
The Sun
Other Objects in the Solar System
Constellation
Formation of Planets
Earth and its Properties
Theories of Earth’s and Universe’s Origin
Big bang theory
Conclusion
FAQs
MCQs

The Universe

All the existing matter and space including stars, planets, galaxies etc. is termed as Universe.
The word “universe” is derived from the Latin word “universum,” which was used by the Romans to describe the globe and cosmos.
The Universe is made up of everything that exists, from Galactic Mega Clusters to subatomic particles.
Scientists agree that the Universe is roughly 13.79 billion years old as of 2015.
A large number of galaxies exist in the universe.
The visible universe contains about 100 billion galaxies, according to optical and radio telescope studies.
For the origin of the Universe, the Big Bang Theory is the most acceptable one.

Composition of the Universe

The cosmological composition of the Universe

Dark energy (73%): A mysterious form of energy that is spread out uniformly throughout space and which has anti-gravitational properties.
Dark Matter (23%): We can’t see matter since it doesn’t emit visible radiation, but it can be detected gravitationally.
Hydrogen & Helium Gas (4%): Hydrogen & Helium are the most abundant element in the universe.
Star (0.5%): A brightly shining ball made largely of hydrogen and helium gas. Our Sun is a celestial body.
Neutrino (0.3%): A small particle that has no charge and is thought to have very little mass. Neutrinos are created in energetic collisions between nuclear particles.
Heavy elements (0.03%): Planets etc.

Galaxy

A galaxy is made up of millions or billions of stars and planets held together by gravity.
One of these galaxies is our Milky Way. This galaxy contains the planet Earth. It is known as the Milky Way because it resembles a river of milky light flowing from one corner of the sky to another.
It takes the form of a spiral.
Andromeda is the closest galaxy to our own.
Andromeda is a spiral galaxy 2.5 million light-years away from Earth.

The Solar System

The solar system is enormous, with a diameter of at least 100 Astronomical Units (15 trillion km). Our Solar System is thought to be over 4.6 billion years old, according to several experts.
The enormous gravitational force of the sun holds it together, keeping planets and asteroids in orbit around it. The earth is the densest of all the planets in our solar system.
The nine known planets and their moons, as well as smaller objects orbiting the sun known as comets, asteroids, and meteoroids, make up the solar system’s largest and most important components.

Formation of Solar System

The solar system, according to scientists, was formed when a cloud of gas and dust in space was disturbed, possibly by the explosion of a nearby star known as SUPERNOVA.
This explosion sent shockwaves into space, compressing the gas and dust cloud. Gravity drew the gas and dust together, forming a solar nebula, as the cloud began to collapse.
At the dense center of this nebula, the sun’s nuclear flames erupted. In the churning currents of the vast cloud, the planets were created.
Mercury, Venus, Earth, and Mars all began as rock globes orbiting the Sun. It was impossible to capture them since they were too small and had weak gravitational fields.
The enormous planets Jupiter and Saturn, which are far from the sun and have powerful gravitational fields, did, nevertheless, draw and hold thick gaseous atmospheres of Hydrogen and Helium.

The Sun

Our solar system’s largest object is the sun. It is roughly 109 times the size of Earth. The Sun has a diameter of 1,392,000 kilometres. It comprises 99.8% of the mass of the solar system.
The sun is a star with a surface temperature of 60000 degrees Celsius. It is largely made up of hydrogen gas, with a minor quantity of helium thrown in for good measure.
The Sun is the solar system’s closest star. It belongs to the Milky Way galaxy. It’s thought to be more than 4 billion years old. The Sun is a yellow dwarf, a medium-sized star. As it rotates around the galaxy, the Sun spins gently on its axis.
The Earth would be a dead sphere of rock and ice if it were not for the Sun. The Sun warms our globe, influences our weather, and provides energy to plants, which provides food and energy for life on Earth.
The Sun’s energy reaches the Earth and other planets in all directions. The planet absorbs less energy as it gets further away from the Sun.

Other Objects in the Solar System

Asteroids: Asteroids are rocky and metallic objects that orbit the Sun but aren’t large enough to be termed planets. Minor planets are what they’re called.
The majority of the asteroids in our solar system orbit the Sun between Mars and Jupiter’s orbits. The “asteroid belt” is a term used to describe this region. A few asteroids are getting closer to the Sun.
Asteroid belt: The asteroid belt is a doughnut-shaped cluster of asteroids orbiting the Sun between Mars and Jupiter’s orbits, closer to Mars’ orbit.
Meteorites: Aside from asteroids, the Sun is also orbited by smaller rocks and dust particles. These particles of rock or dust make their way into the atmosphere. They come into contact with a lot of friction as they pass, which causes them to heat up and burn out. Meteors are little shards of rock or dust that burn.
The majority of meteors burn up before they reach Earth. Some are so massive that a piece of it falls to Earth as a meteorite. A meteorite is a piece of debris that collides with the Earth. When it collides with the ground, it can create a hole or crater. The hole gets bigger as the meteorite gets bigger.
Satellites: Satellites are celestial objects that orbit planets and are part of the solar system. The Moon is the Earth’s satellite. Some satellites, like Ganymede (which orbits Jupiter), are larger than Mercury and have atmospheres.
Artificial satellites: Artificial satellites, which are man-made, are also an important part of the solar system. These satellites orbit the Earth far closer than the moon, which is the Earth’s natural satellite. Aryabhata is India’s first artificial satellite. India has launched a number of other satellites, including INSAT, IRS, and EDUSAT.
Comets: Comets are small icy objects with irregular shapes. They usually come from the Kuiper Belt, which is located beyond Neptune in the solar system’s far reaches. When these objects approach the sun, the ice evaporates, leaving behind a lovely tail. Some of these comets return on a regular basis, such as Halley’s Comet, which returns every 76 years. The next time in 2061.

Constellation

A constellation is a group of stars in the night sky that form an imagined shape.
It aids in the navigation of maritime vessels at night because they are visible in a fixed direction at a specific time of year.
Constellations such as Orion, Big Dipper, Great Bear, and Cassiopeia are examples.

Formation of Planets

Planets were formed at least 4.6 billion years ago when gravity caused discs of dust and gas orbiting the sun to collapse and clump together. This disc, known as the solar nebula, was primarily made up of hydrogen and helium, with minor amounts of other elements. Planets are divided into two categories: terrestrial and extra-terrestrial.
Mercury, Venus, Earth, and Mars are rocky planets that are largely formed of solid rock and metal.
Jupiter, Saturn, Uranus, and Neptune are gas giants that are largely made up of gases like hydrogen, helium, and methane. In comparison to rocky planets, these worlds are enormous.

Earth and its Properties

Earth, like the other planets, is thought to have formed 4.5 billion years ago from a solidified cloud of dust and gases left over from the Sun’s formation.
Almost every discipline of natural science has contributed to a better knowledge of the major events of Earth’s history, which has been marked by ongoing geological change and biological development.
The study of the record of the earth’s magnetic field using magnetic fields preserved in rocks, silt, or archaeological materials is known as Palaeomagnetism.
Geomagnetism, also known as the geomagnetic field, is the study of all aspects of the Earth’s magnetic field which surrounds our planet in the magnetosphere.
Earth has numerous characteristics that distinguish it from other planets and planetary bodies in the solar system and the Milky Way galaxy. Along with Venus, Mercury, and Mars, it is one of four rocky planets and the fifth largest planet after Neptune, Uranus, Saturn, and Jupiter.
With a density of 5.52 grams per cubic inch, Earth is the densest large body in the solar system. 34.6 percent iron, 29.5 percent oxygen, 15.2 percent silicon, 12.7 percent magnesium, 2.4 percent nickel, 1.9 percent sulfur, and 0.05 percent titanium make up this alloy.
The availability of water and oxygen are two distinguishing characteristics of the Earth. Water comprises around 71% of the Earth’s surface, with the majority of that water being in the oceans. Oxygen, which is created by plants, makes up around a fifth of Earth’s atmosphere.
The temperature, pressure, and density of the Earth’s interior gradually rise with depth. A specific Earth material may act as a brittle solid, distort like plastic, or melt and become liquid depending on the temperature and depth.

Theories of Earth’s and Universe’s Origin

Nebular Hypothesis of Laplace

Kant’s theory was revised in 1976 by mathematician Laplace. According to the nebular hypothesis, the Sun was encircled by a solar nebula made up primarily of hydrogen and helium, as well as dust.
The development of a disk-shaped cloud is caused by particle impact and friction.
Planets were formed from material associated with the young sun as a result of the accretion process.

Binary theory or Planetesimal Hypothesis of Chamberlin

In 1900, Chamberlain and Moulton gave this theory.
Another wandering star, according to theory, approached the sun. As a result, the material’s cigar-shaped extension from the solar surface was separated.
The sun with its very high-temperature projects hot material called the prominences, thousands of kilometers away from it.
The particles of this material got coalesced to form the planets. A lot of heat was generated in the process.
Separated material slowly condensed into a planet as the passing star moved away, and the sun continued to spin.

Big Bang Theory TimeLine

Big bang theory

Big Bang Theory

The expanding universe hypothesis is another name for this theory. Edwin Hubble demonstrates the expansion of the universe in 1920. The distance between galaxies is getting longer over time.
According to the big bang theory, all of the matter that made up the universe resided in a single location with a volume smaller than an atom, an unlimited temperature, and an infinite density.
Around 13.7 billion years ago, it burst with a huge bang. The first atom was produced within three minutes of the big bang event. The energy was transformed into matter over time.
Around 3 lakh years after the big bang, the universe turns transparent due to the production of atomic matter

Conclusion

To summarise, everything expands (or contracts) at different rates in an expanding universe, depending on the interactions that hold the various bodies together. The expansion (contraction) rates are small in general and can be ignored for all practical purposes.

FAQs

Question: What is Galaxy?

Answer:

A galaxy is made up of millions or billions of stars and planets held together by gravity.

Question: What is the view of the Nebular hypothesis on the formation of the solar system?

Question: What is Palaeomagnetism?

MCQs

Question: What is the difference between asteroids and comets? (UPSC CSE-2011)

Asteroids are small rocky planetoids, while comets are formed of frozen gases held together by rocky and metallic material.
Asteroids are found mostly between the orbits of Jupiter and Mars, while comets are found mostly between Venus and Mercury.
Comets show a perceptible glowing tail, while asteroids do not.

Select Codes:

(a) 1 and 2 only

(b) 1 and 3 only

(d) 1, 2 and 3

Answer: (b) See the Explanation

Asteroids are small, rocky objects that orbit the Sun. Although asteroids orbit the sun like planets, they are much smaller than planets whereas Comets are frozen leftovers from the formation of the solar system composed of dust, rock and ices. Hence statement 1 is correct.
Most of this ancient space rubble can be found orbiting the Sun between Mars and Jupiter within the main asteroid belt. Since comets are not restricted to Venus and Mercury. Hence statement 2 is incorrect.
Asteroids do not show a perceptible glowing tail, while comets do. Hence statement 3 is correct. Therefore (b) is the correct option.

Question: Which one of the following planets has the largest number of natural satellites or moons? (UPSC CSE- 2009)

(a) Jupiter

(b) Mars

(d) Venus

Answer: (c) See the Explanation

Saturn: It is the largest planet in our solar system at nearly 11 times the size of Earth and 317 times its mass. It is mostly composed of hydrogen and helium. It has 53 named moons and another 26 awaiting official names. Therefore (c) is the correct option.

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