The waves detected came from the merger of what?

• A. Two black holes
• B. Two neutron stars
• C. One black hole and one neutron star
• D. Two white dwarfs

Answer: (A)

Gravitational waves carry a signature of the system that produced them, especially the masses and whether matter is involved. The first detection showed a distinctive chirp: the waves increased in frequency and amplitude as two compact objects spiraled together and merged, releasing a huge amount of energy in gravity waves. The inferred masses were tens of solar masses, and the final object was a larger black hole. There’s little light expected from a black hole merger, so no strong electromagnetic counterpart was observed, which matches the black hole scenario. Mergers of neutron stars would involve matter and typically produce gamma rays and other light, and white-dwarf mergers would emit in a different, lower-frequency range. Based on the waveform and the mass range, the waves came from two black holes merging.