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Milky Way Galaxy
Milky Way Galaxy: Milky way galaxy is a giant family of millions of stars. It consists of gas, dust, stars, and solar systems. All these in a galaxy are held together by the gravitational pull from within the galaxy. There are uncountable galaxies in the universe. According to some scientists, there are more than 100 billion galaxies in the universe!
Generally, galaxies are either spiral-shaped or elliptical-shaped.
The Milky Way is a spiral-shaped galaxy. Elliptical galaxies are the most abundant in the universe. Again, some galaxies are neither spiral nor elliptical. They have an irregular shape and are called Irregular Galaxies.
Milky Way Our Galaxy
There are few places on earth where we can even see the dusty bands of the Milky Way. Dust, gas, energy, a Solar System, and stars make up the Milky Way Galaxy. A spiral galaxy is what it is. From the top, it appears to be a spinning wheel. According to NASA, our Galaxy contains 100 billion stars.
The planets revolve around the Sun, which revolves around the Milky Way Galaxy. It takes the Sun 250 million years to reach the Milky Way’s centre.
The Universe contains billions of galaxies. With clear eyes, we can only see two or three galaxies. Andromeda is the nearest Galaxy visible with unaided eyes. Scientists discovered that Andromeda is approaching our Galaxy. As a result, Andromeda and the Milky Way may collide in 4.5 billion years.
Milky Way Galaxy Size
The Milky Way is vast, and its size is around 1,00,000 light-years across (1 light year= 9,460 billion kilometres). It is believed to be 13.6 billion years old. In the middle of the Milky Way, Sagittarius A* is a supermassive black hole in the centre of the Milky Way. Everything in the galaxy revolves around this. In the immediate surrounding of the Sagittarius A*, there is a tightly packed region of gas, dust, and stars. This space is known as the galactic bulge. Beyond this bulge, there is the galactic disc. The galactic disc hosts billions of stars, including our Sun.
The Sun is located comparatively far away from the centre of the galaxy. It completes one lap around the universe about every 230 million years. The galaxy named Andromeda is our nearest neighbour. Andromeda is located about 2.5 million light-years away from Earth.
The galactic centre is the centre of any galaxy. Astronomers believe that every Galaxy contains a massive black hole. A massive black hole in the Milky Way Galaxy, for example, has 4 million solar masses.
Milky Way Galaxy Black Hole
In the 1940s, Isaac Newton predicted the existence of a black hole.NASA scientists later discovered a massive black hole in the Milky Way Galaxy. The black hole was seen to be erupting with hot bubbles and bright gas. This black hole is approximately 900 million light-years from Earth. The black holes consume the stars or solar systems that surround them. The black hole in the Milky Way Galaxy is the size of billions of suns. Two or more black holes are fairly common. An astronomer recently predicted that the Milky Way Galaxy may contain more than one black hole.
Milky Way Galaxy Stars
A star is a giant, glowing ball of gas and dust held together by gravity. They are mainly composed of hydrogen and helium. They vary in size, mass, and temperature. The colour of the star is determined by its temperature. The hottest stars appear blue, while the coldest stars appear red.
Birth and Death of a Star
They are born from clouds of gas and dust called the Nebula. Due to gravity, pockets of dense matter within the nebula collapse under their weight. A dense region is formed called a Protostar. The protostar further condenses, and nuclear fusion starts to form a star. Due to this nuclear fusion, an enormous amount of energy is emitted, making stars hot and bright.
We already know that stars are made up of Helium and Hydrogen. As stars move toward the ends of their lives, much of the hydrogen gets converted into helium. Helium sinks to the star’s core, raising the star’s temperature. The hot interior core raises the temperature of the surrounding gases. As a result, the outer shell of hot gases expands, and the star changes colour to form a Red Giant star. What happens to the star now depends on its mass.
When the star has a lower mass, around the mass of the earth they form white dwarfs. The nuclear fusion and energy production inside the core gradually stops. As a result, the core of the star contracts under its weight. The remnant is a highly dense body called White Dwarfs. These white dwarf stars eventually stop emitting any heat or light and turn into Black Dwarf.
When the star is massive, it explodes at the end of its life. This explosion, called a Supernova, may result in neutron stars or black holes. After the explosion core of the star remains. If the surviving core is between 1.5 – 3 solar masses, it contracts to become a Neutron Star. If the surviving core is more significant than 3 solar masses, it may form a Black Hole. Black holes are places in space that are so dense and have such immense gravity that even light cannot pass through them. The area beyond which nothing can escape a black hole is called the Event Horizon.
Milky Way Galaxy UPSC
Event Horizon Telescope is an international collaboration of a group of observatories. It aims to capture images of black holes. In 2019, it released the first-ever image of a black hole. The black hole was located in the centre of galaxy M87. Scientists from the Event Horizon Telescope (EHT) facility recently revealed the first image of the Sagittarius A* black hole at the centre of our galaxy, the Milky Way.
Nearly all galaxies have these massive black holes at their centres, where light and matter cannot escape, making images of them extremely difficult. The black hole was dubbed “the gentle giant in the centre of our galaxy” by researchers.
The Expansion of the Universe is a critical concept for the UPSC science and technology section. Both Indian and global scientists are conducting extensive research in this field to determine how the universe began billions of years ago. In this article, you will learn about the Milky Way and galaxies in a nutshell in preparation for the UPSC IAS exam.