Question

How did astronomers use technology to identify characteristics of the Crab nebula?

technology that detects ultraviolet light found hydrogen in the nebula
technology that detects radio waves identified a pulsar at the center of the nebula
technology that detects microwaves revealed the behavior of electrons in the nebula
technology that detects gamma rays measured the distance of the nebula from Earth

Answer 1

Briefly evaluating each statement:

- Technology that detects ultraviolet light found hydrogen in the nebula — True (with a caveat). UV spectroscopy detects emission lines (including hydrogen Lyman‑α and other ionized species) that help identify the nebula’s gas composition and ionization state. Optical spectroscopy also shows strong hydrogen lines.

- Technology that detects radio waves identified a pulsar at the center of the nebula — True. Radio observations revealed the 33‑ms pulses from the Crab pulsar; pulsars were first discovered via radio telescopes.

- Technology that detects microwaves revealed the behavior of electrons in the nebula — True. Microwave (and radio) observations trace the synchrotron emission from relativistic electrons spiraling in magnetic fields, letting astronomers infer electron energies and magnetic structure.

- Technology that detects gamma rays measured the distance of the nebula from Earth — False. Gamma‑ray observations probe high‑energy processes but do not give distance. The Crab’s distance is estimated from expansion measurements (proper motions combined with radial velocities) and other distance‑measurement techniques.