The Big Bang theory is a theory that states that the universe originated as a single mass, which subsequently exploded. The entire universe was once all in a hot and dense ball, but about 20 million years ago, it exploded. This explosion hurled material all over the place and all mater and space was created at that point in time. The gas that was hurled out cooled and became our stellar system. A red shift is a shift towards longer wavelengths of celestial objects. An example of this is the “Doppler shift. ” Doppler shift is what makes a car sound lower-pitched as it moves further away.
As it turns out, a special version of this everyday life effect applies to light as well. If an astronomical object is moving away from the Earth, its light will be shifted to longer (red) wavelengths. This is significant because this theory indicates the speed of recession of galaxies and the distances between galaxies. Small regions within an instellar cloud about a fraction of a light year across begin to collapse under their own gravity. As the collapse continues, the center of this core region becomes denser and denser climbing from only 100 atoms per cubic centimeter to millions of atoms per cubic centimeter and higher.
As it collapses, whatever very slight rotation it originally had gets amplified so that it spins faster and faster. Although the gas falling along the axis of the collapsing cloud feels nothing more than the gravitational force of the central core, along the equator of the object, centrifugal forces due to its spinning become so strong that they strengthen the collapse along this direction. The cloud collapses into a flattened disk with a central bulge containing most of the mass, and it is in this central objects that the star will be formed.
A star is born in a high-density nebula and condenses into gas and dust and contracts under its own gravity. Next, a region of condensing matter will begin to heat up and star to glow, forming protostars. The temperature at this point is 5 million degrees centigrade. When this temperature is reached, hydrogen fuses and forms helium. A star then begins to release energy which causes it to contract and shine. After millions of years, the core of the star which is helium, contracts and a reaction begins to occur in a shell around the core.
The core is at a high enough temperature for helium to form into carbon and the out layer of the star expands, cools and becomes less bright. The core then burns out and the outer layer leaves the core as a gaseous shell. The rest of the core cools and becomes a white dwarf and is less bright. When the white dwarf stops shining, it is called a black dwarf. Every now and then, a large star reaching the end of its life collapses in on itself, and then explodes very violently. The star explodes so violently that for a few weeks the star can out shine its parent galaxy. This type of explosion is known as a supernova.
Neutron stars form during a supernova. Nebula are clouds of gas and dust many light years across. They can be formed by dying stars as in supernova remnants or planetary nebula. They can be formed by young stars just emerging from their nurseries and beginning to illuminate the surrounding gas cloud. A nebula is comprised of interstellar gas, such as hydrogen, helium and other heavy elements. The crab nebula, for example, formed when a supernova exploded. Chinese astronomers saw this explosion and also saw a star six times brighter than Venus in the southern horn of the constellation Taurus.
The star was then later named the crab because of its tentacle-like structure resembling the legs of a crustacean. M42 or the Orion Nebula is located in the Orion constellation. It is in the middle of the region known as the Sword of Orion. It is visible to humans through binoculars. Galaxies formed from a diluted but lumpy mixture of hydrogen and helium gas – the main components which formed the Big Bang. The galaxy in which we live, usually referred to as the Milky Way, is a giant spiral assembly of several billion stars, including the sun.
The galaxy is now known to be an immense disk shaped object, with its visible disk having a diameter of about 1,000 light-years and a height above its principal plane of about 1,00 light-years. Most astronomers believe that galaxies like the Milky Way were formed from a large cloud of gas, which collapsed and broke up into individual stars. The stars are packed together most tightly in the center, or nucleus. Scientists believe it is possible that at the very center there was too much matter to form an ordinary star, or that the stars which did form were so close to each other that they coalesced to form a black hole.
It is argued that really massive black holes, equivalent to a hundred million stars like the Sun, could exist at the center of some galaxies Photons always travel at the speed of light, but they lose energy when traveling out of a gravitational field and appear to be redder to an external observer. The stronger the gravitational field, the more energy the photons lose because of this gravitational red shift. The extreme case is a black hole where photons from within a certain radius lose all their energy and become invisible.
