Universe Solar System - Origin and Evolution

Universe Solar System: The Universe comprises billions of galaxies. A galaxy is a giant assembly of stars, planets, gases, and dust. These galaxies are made up of millions of stars held together by the force of gravity and these stars account for most of the masses of the galaxy. Our galaxy is named the Milky Way and it contains about 300 billion stars and one of these is our Sun. Planets and other objects go around the sun and make up the solar system with the sun at the center. Andromeda is the nearest major galaxy to the Milky Way.

In AD 140, Ptolemy propounded the theory that the Earth was at the center of the Universe, and the Sun and the other heavenly bodies revolved around it.
In 1543, Copernicus said that the Sun is the center of the Universe and not the Earth. Kepler supported Copernicus but said that the Sun is the center of the Solar system and not the Universe.
In 1924, Edwin Hubble first demonstrated the existence of galaxies beyond the Milky Way.
Structurally, the galaxies are found in 3 forms as follows: Spiral has a central nucleus with great spiral arms. The Milky Way and Andromeda are examples of it. Elliptical without spiral arms. Irregular with no shape.

Evolution of Universe Solar System

The three main theories put forward to explain the origin and evolution of the Universe are as follows:

Big Bang Theory: Proposed by Georges LeMaître, the Big Bang Theory suggests that around 13.8 billion years ago, there was a massive explosion. This explosion led to the formation of galaxies, stars, and other celestial bodies that we observe today.

Steady-State Theory: Developed by Bondi, Gold, and Fred Hoyle, the Steady-State Theory puts forth the idea that while the Universe is expanding, its appearance undergoes continuous changes. Importantly, this theory suggests that the Universe has no definitive beginning or end, presenting a constant state of transformation.

Pulsating Theory: The Pulsating Theory proposes a rhythmic pattern for the Universe. According to this idea, the Universe expands and contracts alternately, pulsating like a heartbeat. Currently, we find ourselves in a phase of expansion, contributing to the dynamic nature of the cosmos.

Solar System

Planets and other objects go around the Sun, and these make up the solar system, with the Sun at the center and thousands of other small heavenly bodies such as the asteroids, comets, and meteors.

The solar system contains different types of objects including:

A Star: the Sun
Planets: which go around the Sun
Satellites: which go around the planets

Stars

Stars are like cosmic campfires in the sky, providing warmth and light. Our Sun is actually one of them! Picture stars as huge gatherings of hydrogen, helium, and cosmic dust, like fluffy clouds in space. Sirius, the Dog Star, shines the brightest, while Proxima Centauri is our cosmic neighbor. Imagine stars as celestial beings born from these interstellar clouds, mostly made of hydrogen gas – the cosmic building blocks. Surprisingly, the bigger the star, the quicker it ages. Our Sun, at a spry 4.5 billion years old, is like the middle-aged cool parent of the cosmic neighborhood.

Supernova – Death of a Star

This happens when nuclear fusion can no longer happen in the core.
The heaviest element that can be formed in a star is iron. There isn’t enough energy for the iron atoms to combine.
Once this point is reached the core will contract and the outer parts will explode and send out a shockwave.
That explosion is called a supernova.
Supernovas can be a billion times as bright as the original star.

Constellation

Constellations are clusters of stars that appear in a specific form.
There are a total of 88 constellations officially recognised in the galaxy.
Most of the constellations are named after the names of the God and Goddess.
The International Astronomical Union officially listed around 88 constellations in their list in 1930.

Ursa Major:

It is also known as the Great Bear and the Big Dipper.
In the northern hemisphere, it is usually visible as the Bear.
It is the largest northern constellation.
It is also the third-largest constellation in the sky.

Ursa Minor:

It is also known as the little bear.
It was one of the 48 constellations that were listed by the Ptolemy in the early 2nd century.
It has been very important for mariners to navigate their pathways in the sea.
June is the best month to see the Ursa Minor in the Northern sky.

Orion:

It is also known as the hunter and called ‘the light of heavens’.
If you are in the Northern hemisphere, look at the southwest sky.
If you are in the southern hemisphere, then look at the northwestern sky.
If you are at the equator or near to it, look in the western sky, you will be able to see that.

Leo Major:

Ptolemy discovered this in the early 2nd century.
The constellation may be seen from January to June in the Northern hemisphere.
It is the 12th largest constellation in size.

Planets

Planets, those intriguing celestial bodies, are like cosmic wanderers dancing around the Sun. Unlike stars, they don’t have their own heat and light show. The term “planet” itself carries a whimsical touch, reflecting their nature as wanderers in the vastness of space. These cosmic globes, named after characters from Greek and Roman mythology (excluding our humble Earth), follow the beat of their own orbital rhythm.

In 2006, the International Astronomical Union (IAU) gave us a new cosmic rulebook for planets. According to this stellar handbook, a planet in our solar system is essentially a space traveler that meets a few criteria: it diligently orbits the Sun, has enough mass to take on a charmingly rounded shape, and has tidied up its cosmic neighborhood. So, think of planets as celestial friends twirling around the Sun, each with its unique character and style.

Satellites

The term satellite indicates a smaller companion to anything. True to their meaning, these satellites orbit around their planets and also accompany them in their revolution around the Sun. The Moon, for example, is a satellite of the Earth. It moves around the Earth and also around the Sun along with the Earth.

Asteroids

These are large rocky bodies in space, in orbit around the Sun. Between the orbits of Mars and Jupiter, there is a swarm of small bodies which also revolve around the Sun.
They are called asteroids. It is the debris left over from the formation of inner planets and also called ‘planetoids’ or ‘small planets’. They are the chunks of rock covered in frozen gases.

Comets

Comets are the most exciting of the heavenly bodies. They are composed up of loose collections of ice, dust, and small rocky particles. A well-developed comet has a tail that is always turned away from the Sun. The head develops the bright portion of the comet.
‘Halley’s Comet’ is one of the important comets. It revisits the Earth regularly and is visible once in 76 years. It was last seen in 1986. As comets advance the Sun, they exhibit enormous tails of luminous material that stretch for millions of kilometers from the head, away from the Sun.