Nebula

A nebula (which in Latin means cloud) is an interstellar cloud of dust, hydrogen gas & plasma. It is the place where stars & planets are formed. Gravity pulls together dust, gas & other materials to form a huge ball of mass. When the mass is great enough it forms a star. The leftover material becomes planets which orbit this star. Eventually these stars form galaxies which includes our own Milky Way Galaxy. A nebula is the birth place of Galaxies. Nebula's vary in sizes & shapes. The four major ones are Planetary nebula, Reflection nebula, Emission nebula & Absorption nebula.
 * Nebula**

A famous picture of the Eagle Nebula
 * "Pillars of Creation"**
 * Types of Nebulas**


 * Planetary Nebula-** This nebula is when the sun's outer layer get's blown off after it's out of fuel to burn. It usually takes form of a bubble or ring. About 200 years ago William Herchel named these types of nebula as Planetary nebulas as it was a shape of a planet. At the centre of the nebula is the inner core of that particular star.

A planetary Nebula, the glowing part is the core of that star.


 * Reflection Nebula-** This nebula is a cloud of gas and dust which does not create its own light, but instead shines by reflecting the light from nearby stars. The brightest nebulas are found where new stars are being formed. Here the gas is thick and shines brightly as the light is new.

A reflection Nebula
 * Emission Nebula-** This nebula hot glowing cloud of gas & dust. These nebulas absorb the heat and light form nearby planets which makes them reach very high temperatures. This is why emission nebulas glow so bright. It is found in places where new stars are forming.

An Emission Nebula
 * Absorption Nebuals-** This nebula is made up of dark clouds which absorbs the light & blocks light passing through it. This keeps things behind it invisible. It is very hard to find Absorption Nebulas unless it is nearby a very powerful light source.

An Absorption Nebula
 * Examples of Nebulas**


 * Planetary

Cat's Eye Nebula**

This is a planetary nebula situated in the Draco constellation. It is one of the most complex nebulas ever found. The structure of it is so complex with ties, knots & sinewy arc-like features. It was discovered by William Herschel on February 15th 1786. It has a density of 5000 particles/cm3 & temperatures between 8000K - 15000K. The centre of the nebula has temperatures upto 80000K. It is between 100 - 260 years old. It is hard to determine the distance from earth, but due to research & the Hubble telescope, astronomers devised a new method to calculate the distance. This nebula is 3300 light years away. At Voyager 1 speed (55000km/h) it would take 18000 years to get there.


 * Reflection**


 * Pleiades**

This is a reflection nebula and also one of the closest nebula to Earth situated in the constellation Taurus. On a clear night sky, you can actually see the nebula Pleiades. It is made of hot blue stars which were formed within the last 100 million years. It has a 1000 stars out of which 14 are naked to the human eye. Astronomers predict it will last another 250 million years. The exact temperature is not certain. The mass of this nebula is 800 solar mass and one salor mass is 3,324,946,000 trillion tonnes. The distance to Pleiades is roughly 440 light years away. At Voyager 1 speed (55000km/h) it will take 2400 years to get there. If you look closely it almost is the shape of an arrow


 * Emissions**


 * Omega**

This is an emission nebula discovered by Philippe Loys de Cheseaux in 1745. It is located in the rich starfields of the Sagittarius area of the Milky Way. Because it absorbs light from nearby stars it is made of young hot high temperature stars. Not much detail is available as it is very far. A cluster of 35 stars lies embedded in the nebulosity and causes the gases of the nebula to shine due to radiation from these hot, young stars. It's diameter alone is 15 light years & it's whole mass is about 800 solar mass and one solar mass is 3,324,946,000 trillion tonnes. This nebula is about 5000- 6000 light years away. At Voyager 1 speed (55000km/h) it will take 30000 years to reach there.


 * Absorption**


 * The Horsehead**

This is an absorption nebula discovered by William Fleming in 1888. The nebula is located just below Anlnitak, the star furthest left on Orion's Belt. It is one of the most easiest to identify due to it's shape of a horse head. It mainly consisted of thick dark clouds & gases mainly hydrogen. At the centre of the nebula there are two young red stars which have just been formed. If you look closely it seems as if they were the eyes of a horse. The physical aspects of this nebula is unknown. But we do know it is 1500 light years away.




 * The Eyes of the Nebula**


 * Can we survive in any nebula?**

No, we cannot survive in any Nebula in this whole universe. There are many reasons but mainly the reason **is it is too hot.** Other reasons include:-


 * No water
 * No atmosphere
 * No soil to grow food
 * Can't get there because the spaceship would dissolve into nothing because of the heat
 * Huge distances form the earth
 * No oxygen for us to breathe
 * To much Gravity


 * What are the astronomers trying to find out?**


 * NASA** is trying to find out more about the surface of the nebulas like it's temperatur, mass, size, how many stars & how they were made. Most of this information has not been found yet. If we do find out theses information, then we can get a better understanding of how nebulas were formed & more importantly a detailed information of how a star is born.


 * These are some videos on nebulas which will help you undesratnd more closley on what a nebula is**

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