A supernova is a stella explosion. Supernova's are extremly luminous and cause a burst of radiation that often briefly outshines an entire galaxy before fading from veiw over several weeks or months. During this short interval, a supernova can radiate as much energy as the sun could emit over its entire life span.

A supernova eplosion expels much or all the stars material at a velocity of up to 30,000 km/s (a tenth the speed of light) driving a shock wave into the surrounding inter stellar medium/ this shock wave sweeps up an exploding shell of gas and dust called a supernova remnant.

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The mass of the expelled material may exceed 10 times the mass of the sun. Type 1 supernova may occur in certain binary stars. A type 2 supernova results from the death of a single star much more massive than the sun.

Supernova deffers in an amount and composition of the material that they expel. After some supernova explosions the remains are small dense star composed mainly of neutrons or perhaps of elementery particals called quarks.

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W49B which sits 35,000 light-years from Earth is the glowing cloud of gas and dust left behind the death of a massive star. As such stars age, they shed their outer layers forming cocoons of gas and dust around dense cores.