A stellar explosion that occurs when a white dwarf star exceeds the Chandrasekhar limit (about 1.4 solar masses) through mass accretion, causing complete thermonuclear destruction of the star. These supernovae have remarkably uniform peak brightness, making them excellent standard candles for cosmological distance measurements.
Classification system developed by Walter Baade and Fritz Zwicky in 1941, with 'Type I' indicating absence of hydrogen lines and 'a' subtype showing strong silicon absorption. The Roman numeral system was adopted to distinguish different supernova mechanisms based on spectroscopic features.
Type Ia supernovae are cosmic lighthouses that helped us discover dark energy! Because they all explode at the same mass limit, they shine with nearly identical brightness, allowing astronomers to measure that the universe's expansion is actually accelerating - a discovery that won the 2011 Nobel Prize.
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