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Across the board, stars are uniformly spherical in shape - but they come in many colors (white, blue, orange, yellow and red) and sizes depending on where a star is in its lifespan.
Stars are born in stellar nebulas, such as the Orion Nebula (also known as the middle "star" in Orion's sword). As gravity causes its gases to coalesce, an average star will burn yellow, like our sun, while a massive star will burn blue - extra hot.
As they age, an average star becomes a red giant while a massive star becomes a red supergiant. An average star turns into a planetary nebula and dies as a white dwarf.
A typical white dwarf is slightly bigger than Earth but 200,000 times as dense. These form when average stars have burned through all their fuel and lack the temperature and pressure to continue fusion in their core. Ninety-seven percent of stars will end as white dwarfs.
The most massive stars in the universe morph into supernovae and die violently as either neutron stars or black holes.
Stars can be much smaller than our sun or large enough to push the bounds of comprehension. The largest known star in the universe is a red hypergiant called VY Canis Majoris (VY CMa), located in the constellation Canis Major, which also hosts Sirius, the brightest star in the night sky.
An airplane traveling 600 mph would take 1,100 years to circle VY CMa once. The star is almost 2 billion miles in diameter and roughly 5,000 light years from Earth.
VY CMa is a hypergiant exhibiting tremendous mass and luminosity and showing signs of a very high rate of mass loss. In other words, this star is on its deathbed. One step down from this red hypergiant is Betelgeuse, a red supergiant, which can be viewed as the orange star at Orion's left shoulder.
Astronomers, with the help of the Hubble Space Telescope, believe VY Canis Majoris will explode as a hypernova within the next 100,000 years. A hypernova could, in theory, cause gamma ray bursts that would eliminate all cellular life within a number of light years, but no hypergiant is close enough to Earth to do this. VY CMa is likely to create an enormous black hole as its final act.
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