Observational astronomy

Observational astronomy collects and analyzes data from celestial sources using instruments that detect electromagnetic radiation, particles, and gravitational waves.

Telescope: An instrument that collects and focuses radiation or particles to reveal distant objects. Telescopes gather faint signals that observational astronomy measures.
Angular resolution: The ability of an instrument to distinguish two nearby sources on the sky. It determines which celestial structures an observation can separate.
Radio astronomy: The study of celestial sources through radio-frequency radiation. Radio observations reveal cold gas, pulsars, and emissions from energetic particles.
Theoretical astronomy: The use of physical models and mathematics to explain astronomical systems and predict their behavior. It develops explanations and predictions rather than collecting celestial data directly.
Electromagnetic spectrum: The full range of electromagnetic radiation, from radio waves to gamma rays. Astronomers select wavelength bands to probe different sources and physical conditions.
Sensitivity (astronomy): An instrument’s ability to detect weak astronomical signals. Sensitivity determines how faint a source an observation can measure.
Infrared astronomy: The study of celestial sources through infrared radiation. Infrared instruments detect cool objects and see through some dust-obscured regions.
Space telescope: A telescope operated beyond Earth’s atmosphere, usually in orbit or deep space. It avoids atmospheric absorption and blurring, unlike ground-based observatories.
Spectroscopy: The study of how matter interacts with radiation as a function of wavelength or frequency. Spectra reveal celestial objects’ composition, temperature, motion, and physical conditions.
Atmospheric seeing: The blurring of astronomical images caused by turbulence in Earth’s atmosphere. Seeing limits the sharpness of ground-based observations in visible light.

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