Which device is used primarily for studying electromagnetic radiation emitted by celestial bodies?

The correct choice is the radiotelescope, which is specifically designed to observe and study the electromagnetic radiation emitted by celestial bodies. Radiotelescopes detect radio waves, which are a form of electromagnetic radiation, allowing astronomers to gather information about various astronomical phenomena such as stars, galaxies, and cosmic background radiation. The ability to analyze these radio signals is crucial for understanding the behaviors, compositions, and distances of celestial objects, making radiotelescopes a fundamental tool in the field of astrophysics.

Other devices, while useful for different scientific purposes, do not primarily focus on studying electromagnetic radiation from space. For instance, radar is primarily used for detecting objects and measuring distances, seismometers monitor seismic activity, and laser interferometers are utilized in precision measurements, such as detecting gravitational waves. Each of these instruments serves valuable functions in their respective fields but lacks the specific focus on the electromagnetic spectrum that radiotelescopes provide in the study of astronomy.