Final answer:
The first exoplanet, 51 Pegasi B, was discovered in 1995 by Didier Queloz and Michel Mayor of the Geneva Observatory using the Doppler effect.
Step-by-step explanation:
The first exoplanet, 51 Pegasi B, was discovered in 1995 by Didier Queloz and Michel Mayor of the Geneva Observatory using the Doppler effect.They found a planet orbiting a star called 51 Pegasi, which is about 40 light-years away from us.This discovery was significant because it was the first confirmation of a planet orbiting a regular star outside our solar system.