There are numerous different main types of stars, considering their size, brightness and life cycle. Brown dwarfs – ‘failed stars’, which form from clouds of stellar gas, just like other stars do, but never stretch to sufficient mass, density and interior heat to start the nuclear fusion practice i.e. less than 8 percent of the mass of our Sun. Even though they may glow faintly when freshly formed and are therefore actually red not brown, they begin to cool soon after and so are very difficult to detect. They might actually be among the best common type of stars.
Yellow dwarfs – main-structure stars like our own Sun, Alpha Centauri A, Tau Ceti, etc. Normally about 80 to 100 percent of the size of the Sun, and in fact more white than yellow. They are also identified as G V stars for their ghostlike type G and luminosity class V.
White stars - bright, main-structure stars with masses from 1.4 to 2.1 times the mass of our Star and external temperatures between 7,600°C to 10,000°C, such as Sirius A and Vega.
Red giants - bright giant stars of low or middle mass (generally between 0.5 and 10 solar masses) in a late stage of stellar development, such as Aldebaran and Arcturus. When a main-structure star has fused all its hydrogen into helium, it then begins to burn its helium to produce oxygen and carbon, and grows to many times its earlier volume to grow into a red giant. After a comparatively short time (in almost two hundred million years), the red giant wisps out its exterior layers in a gas cloud termed as a nebula and falls in on itself to become a white dwarf. The biggest red giants are known as red supergiants, and are the biggest stars in the cosmos in terms of volume, recognized examples are Antares and Betelgeuse.
White dwarfs - small, thick, burnt-out crusts of stars, no longer undertaking fusion reactions, and signifying the final evolutionary stage of most of the stars in Milky Way Galaxy. When a red giant has fused all of its helium to produce oxygen and carbon, and has not enough mass to produce the core temperatures compulsory to fuse carbon, it sheds its external layers to become a planetary nebula, and leaves behind an inactive mass of oxygen and carbon. A white dwarf is naturally only the size of the Earth, but 200,000 times more thick and dense.
Black dwarfs - theoretical stellar fragments formed when a white dwarf becomes cool and dark after approximately ten billion years of life. Black dwarfs are very difficult to spot, and very a small number of them would exist yet in any case in a universe only 13.7 billion years old.
Blue giants – sunny and bright, massive stars, between 10 and 100 times the size of our Sun, and between 10 and 1,000 times its brightness. Because of their mass and warmness, they are comparatively short-lived and quickly finish their hydrogen fuel, concluding as red supergiants or neutron stars. The largest and greatest luminous stars are mentioned to as blue super-giants and hyper-giants. The best recognized blue super-giant is Rigel, the brightest star in the Orion-constellation, which has a mass roughly 20 times that of the Sun and a luminosity more than 60,000 times better. The largest and brightest ever discovered is 10 million times as luminous as the Sun.
Neutron stars - cosmological tiny fragments that can be formed from the gravitational collapse of enormous stars during a supernova incident. They are collected almost of rumpled neutrons, and are very hot and very dense. Though a usual neutron star has a mass of only between 1.35 and almost 2.1 times that of Sun, it is 60,000 times smaller in mass than the Sun (typically in the region of just 20 to 30 kilometers across) and, because of this enormous density, has a gravity of more than 200 billion times that we feel on Earth. They revolve very fast (particularly soon after the supernova blast) and some produce steady pulses of radiation and are recognized as pulsars. Smaller collapsed-stars will generally become white dwarfs, and larger ones (over almost 5 solar masses) will collapse entirely into a black hole singularity.
Variable stars - stars that develop and shrink in size occasionally and seem to pulsate. The changes in obvious brightness may be due to differences or variations in the star's real luminosity, or to variations in the amount of the star's brightness that is obstructed from reaching Earth.
Binary stars - two stars in adjacent proximity which orbit around their common center of mass. Actually, the majority of stars are part of binary system, triplet or numerous star systems, and recognized examples are Alpha Centauri and Sirius in the Canis Major constellation.
