Final answer:
A Type Ia supernova is the explosion of a white dwarf in a binary system after accruing enough mass from its companion. It is marked by distinct silicon absorption lines and serves as a standard bulb for measuring cosmic distances.
Step-by-step explanation:
A Type Ia supernova is the explosion of a white dwarf in a binary star system after it has accreted sufficient mass from its companion star to exceed the Chandrasekhar limit. When this mass transfer occurs, the white dwarf becomes unstable and undergoes a thermonuclear explosion, resulting in a supernova that can outshine entire galaxies. Unlike the remnants left by the explosion of high-mass stars, the white dwarf is completely obliterated in a Type Ia supernova, leaving no remnant behind. These explosions are characterized by strong silicon absorption lines in their spectra, which distinguish them from other types of supernovae that result from the collapse of massive stars. Type Ia supernovae are significant astronomical events because they serve as standard bulbs due to their consistent peak luminosity, allowing astronomers to measure vast distances in the universe.