Type Ia supernovae are used as standard candles because they result from thermonuclear explosion of _______.
- Massive stars >8 solar masses
- White dwarfs reaching Chandrasekhar limit
- Neutron star mergers
- Red supergiants
Answer: White dwarfs reaching Chandrasekhar limit
Type Ia supernovae occur when carbon-oxygen white dwarfs accrete mass to ~1.4 solar masses, triggering uniform explosions useful for measuring cosmic distances.