4-Nebulae and star clusters

 

Nebulae and star clusters 

A nebula is a cloud of dust and gas inside a Galaxy. nebula become visible if the gas glows, Or if the cloud reflects Starlight or obscures light from more distant objects. Emission nebulae shine because their gass emits light when it is stimulated by radiation from hot young stars.

 

 


 

Reflection nebulae because Shine because their best reflects light from stars in or around the nebula. Dark nebulae appear as silhousettes because they block out light from shining nebulae or stars behind them.Two types of nebula are associated with dying stars: planetary nebulae and supernova remnants.

 


Both consists of expanding shells of gas that  were once the outer layers of a star.A planetary nebula is gas shell drifting away from a dying stella rcore. A supernova remnant is a gas shell moving away from steller core at great speed following a violent explosion called a supernova.

 

 


Stars are often found in groups knows us clusters.Open clusters are loose groups of few 1000 young stars that were born from the same cloud and are drifting apart. Globular clusters are densely packed, roughly spherical groups of hundreds of thousands of older stars….

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