What did graduate student Jocelyn Bell Burnell discover in 1967?

• A. A neutron star
• B. A black hole
• C. A pulsar
• D. A quasar

Answer: (A)

The key idea is that the discovery was a pulsar—a rotating neutron star that beams radio waves like a lighthouse. Bell Burnell and her team detected highly regular radio pulses from a single sky location, with a period of about 1.337 seconds. That regularity can only come from a compact, rapidly spinning object with a strong magnetic field, so the pulses we see occur as the star’s beams sweep past Earth. A neutron star is the type of object involved, but the phenomenon that explains the observations is the pulsed emission from a rotating neutron star, i.e., a pulsar. Black holes don’t produce these steady, periodic radio pulses, and quasars are distant active galactic nuclei with different emission behavior, not the precise, repeating pulses seen here.