Before the man started fireworks in the night sky on Independence Day or at New Year; our universe had shown many fireworks of its own and no doubt they were more powerful than we can even think of. In 1054 there was a huge explosion and it sure was the violent death of a star and the star was 10 times more massive than our sun. It was the outstanding eruption of a supernova. Chinese astronomers for the first time in history saw and recorded the star's death. The remains of this exploded star were later named as the Crab Nebula. The Crab Nebula is cloudy, glowing mass of gas and dust and it is about 7000 light years away from us. There was a star so bright that people saw it in the sky during the day for almost a month. The Chinese called it “the Guest Star”. Astronomers have viewed only two equal disasters in our Galaxy: the supernova explosions of 1572 and 1604.
A nebula is actually a bunch of molecules and atoms, floating in space like a dust cloud. More than one nebula are called nebulae. Nebula means cloud in Latin. The first Nebula formed after the Big Bang was 15 billion years ago. All forms of installer matter in the Milky Way Galaxy are Nebulae so far observed. Nebulae are mostly composed of hydrogen and other constituents are helium, oxygen, carbon, neon, and nitrogen.
On the basis of looks of nebulae, they are divided into two clear categories; Dark Nebulae and Bright Nebulae. Dark nebulae seem as on an irregular basis formed black patches in the sky and blot out the light of the stars that lie on the far side them. On the other hand, bright nebulae are very luminous and their brightness is mostly because they not just only emit their own light but also reflect light of nearby stars. Dark Nebula is a type of installer cloud and so dense that it obscures the light of background stars. The reason behind these phenomena’s is its internal dust grains and act like an opaque object.
Bright nebulae are also interstellar clouds of dust and gas where stars mostly are born and have died. Their rich colors and complex shapes made them interesting field for many amateur astronomers. Bright nebulae are also known as diffuse or Galactic nebulae. Planetary nebulae are common. A planetary nebula is kind of emission nebula and consists of a very shiny and glowing shell. This glowing shell of a planetary nebula made of ionized gas usually ejected by red old giants. At the end of the star’s life mostly at red giants phase; the outer layers of the star are ejected through strong stellar winds. The exposed hot, glowing core produces ultraviolet radiation that ionizes the ejected outer layers of the star and it appears as a Planetary Nebula.