starfræði

Starfræði, known in English as astronomy, is the scientific study of celestial objects and phenomena beyond Earth's atmosphere. It includes the observation and interpretation of stars, planets, galaxies, nebulae, black holes, and the cosmic background radiation. The aim is to understand the origin, evolution, and physical laws that shape the universe, from our solar system to the largest scales of space and time.

Historically, starfræði emerged from ancient sky-watching traditions and matured during the scientific revolution, when instruments such as the telescope enabled detailed measurements. Copernicus, Kepler, and Galileo helped shift understanding away from a geocentric model. In the 19th and 20th centuries, spectroscopy and astrometry revealed the composition and motions of celestial bodies, while the development of radio, infrared, X-ray, and gamma-ray astronomy, including space-based observatories, expanded observational reach. Modern cosmology combines observations with physical theory to explain the origin and fate of the universe.

Starfræði is practiced through two broad approaches: observational astronomy, which gathers data across wavelengths from the ground and space, and theoretical astronomy, which uses physics and mathematics to explain celestial phenomena. Its subfields include planetary science, stellar astronomy, galactic astronomy, extragalactic astronomy, cosmology, and astrobiology. Techniques such as spectroscopy, photometry, astrometry, and computer simulations are fundamental tools.

Applications of starfræði range from fundamental knowledge about the universe to practical technologies derived from imaging, timekeeping, and satellite navigation. The field continues to address major questions, including the nature of dark matter and dark energy, the conditions for planet formation, and the possibility of life beyond Earth.