Introduction
The space between the stars may appear black but it is certainly not empty. A handful of space contains, on average, 30 hydrogen atoms and several specks of dust. This may not seem much, but it is this interstellar medium that is constantly giving birth to new stars. Light from these new stars shines through the clouds to produce incredible shapes called nebulae.
Interstellar medium
The space between the stars in a galaxy is not empty. It contains small quantities of dust and gas called interstellar medium. This gas is what remains of stars that have exploded. It will in turn give birth to new stars when conditions are right. Most interstellar medium can be found in clouds and can rise to temperatures greater than 8,000oC (14,400oF). However, there are pockets of very thin gas between the stars where temperatures can reach higher than one millionoC (1.8 millionoF)! These bubbles are created by the force of supernovae.
Types of Nebulae
Nebulae come in many different shapes and sizes and colours. Most are illuminated by the light of the stars inside them, but some do not give off any light at all and can only be seen as dark shadows that block out the light of distant stars.
Some important facts
1) Even in nebulae the interstellar medium can only amount to several hundred atoms per cubic centimeter. We can still see interstellar medium because we are looking through a great thickness of it.
2) Much of the starlight in the milky way is blocked out by clouds of gas and dust. If these clouds were not there, the light from the stars at night would be bright enough to read a book by!
3) Emission nebulae : These are the most beautiful and colourful of all the nebulae. Their striking colours come from the presence of hydrogen atoms that release light red light. These clouds are very hot, often over 10,000
4) Reflection nebulae : Reflection nebulae are illuminated by light that is reflected from nearby stars. They appear blue because the light is scattered by dust grains. This produces the same effect as the sun's light shining through the Earth's atmosphere and making the sky blue.
5) Dark nebulae : These nebulae, also called absorption nebulae, appear dark because there are no nearby stars to light them. They can be spotted because they blot out the light from more distant stars, appearing like black voids in the sky.
6) Planetary nebulae : After stars like our suns become red giants and die, they blow off their outer layers in a large, expanding cloud. Early astronomers believed these clouds looked like Uranus and Neptune, but now we know they have nothing to do with planets.
The space between the stars may appear black but it is certainly not empty. A handful of space contains, on average, 30 hydrogen atoms and several specks of dust. This may not seem much, but it is this interstellar medium that is constantly giving birth to new stars. Light from these new stars shines through the clouds to produce incredible shapes called nebulae.
Interstellar medium
The space between the stars in a galaxy is not empty. It contains small quantities of dust and gas called interstellar medium. This gas is what remains of stars that have exploded. It will in turn give birth to new stars when conditions are right. Most interstellar medium can be found in clouds and can rise to temperatures greater than 8,000oC (14,400oF). However, there are pockets of very thin gas between the stars where temperatures can reach higher than one millionoC (1.8 millionoF)! These bubbles are created by the force of supernovae.
Types of Nebulae
Nebulae come in many different shapes and sizes and colours. Most are illuminated by the light of the stars inside them, but some do not give off any light at all and can only be seen as dark shadows that block out the light of distant stars.
Some important facts
1) Even in nebulae the interstellar medium can only amount to several hundred atoms per cubic centimeter. We can still see interstellar medium because we are looking through a great thickness of it.
2) Much of the starlight in the milky way is blocked out by clouds of gas and dust. If these clouds were not there, the light from the stars at night would be bright enough to read a book by!
3) Emission nebulae : These are the most beautiful and colourful of all the nebulae. Their striking colours come from the presence of hydrogen atoms that release light red light. These clouds are very hot, often over 10,000
4) Reflection nebulae : Reflection nebulae are illuminated by light that is reflected from nearby stars. They appear blue because the light is scattered by dust grains. This produces the same effect as the sun's light shining through the Earth's atmosphere and making the sky blue.
5) Dark nebulae : These nebulae, also called absorption nebulae, appear dark because there are no nearby stars to light them. They can be spotted because they blot out the light from more distant stars, appearing like black voids in the sky.
6) Planetary nebulae : After stars like our suns become red giants and die, they blow off their outer layers in a large, expanding cloud. Early astronomers believed these clouds looked like Uranus and Neptune, but now we know they have nothing to do with planets.
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