Probing the Universe
The universe is vast beyond our imagination. It is mostly empty space and dark. This space contains everything, from the tiniest subatomic particle to galactic superstructures like Black hole. It is estimated that the Universe contains 100 billion galaxies, each of which comprises 100 billion stars. The Universe probably came into existence about 10-20 billion years ago.
The prevailing theory of cosmological explanation is Big Bang Theory, it states that the universe is started with a singularity which is incessantly expanding and it is 13.8 billions year old.
The life of a Star
The Universe comprises of billions of galaxies and these galaxies comprises a huge number of stars, nebulae and interstellar dust and gases. Nebulae are clouds of dust and gas ( mainly hydrogen and ionized hydrogen ) that float in space. Often, the force of gravity pulls the particles of the gas and dust closer into swirling mass. If the mass is heavy enough, the spinning cloud will start to glow. This is a Protostar, or the first stage before a star is born.
The protostellar phase is the earliest one in the process of stellar evolution (process of star formation).
Stars are self-luminous bodies of hot and glowing gas (hydrogen) born inside the nebulae itself as the most abundant gas in universe is Hydrogen. Our Sun is a small star. Massive stars may have a mass of at least three times that of the Sun and some stars as massive as 50 times the Sun exist. Stars produce energy by nuclear fusion at the core. After millions to billions of years, when the hydrogen starts running out, the core contracts while the outer portion continues to expanding. The star is now called a Red Giant. The amount of mass a star has determines the rest of its life cycle. The cores of low-mass stars collapse, expelling the outer layers, which forms nebula. The core remains as white dwarf and eventually cools to become a black dwarf.
Red giant stars have a yellow-orange to red appearance and the average surface temperature of a red giant is between 4,000 and 5,800 degrees Fahrenheit.
A massive star will undergo a supernova explosion. If the remnant of the explosion is 1.43 times as massive as the Sun, it will become a Neutron star. After the explosion, a star with a core more than three times the Sun, will be swallowed by its own gravity. It now becomes a Black hole which can readily attract any matter or energy that comes near it.
Approximately one supernova occurs every second, and sometimes they’re brighter than a galaxy.