The time indicated by the stars is called what?

• A. Solar time
• B. Lunar time
• C. Atomic time
• D. Sidereal

Answer: (D)

Time indicated by the stars is sidereal time. It’s defined by Earth’s rotation relative to distant stars rather than the Sun. A sidereal day lasts about 23 hours 56 minutes, roughly four minutes shorter than a solar day, which is why solar time drifts with respect to stellar positions. Local sidereal time tells you which celestial longitude (right ascension) is on the local meridian, a crucial reference for astronomers when pointing telescopes and tracking stars. Atomic time, by contrast, is a highly precise clock time based on atomic transitions, not celestial positions; solar time is based on the Sun’s position for our civil clocks; there isn’t a standard lunar time used in practice. So the time indicated by the stars is sidereal time.