Fotometriaa

Fotometriaa refers to the branch of astronomy and astrophysics concerned with measuring the intensity of light emitted or reflected by celestial objects. The term originates from the Greek words *phōs* (light) and *métron* (measure), reflecting its core purpose: quantifying luminosity, brightness, and other photometric properties of stars, galaxies, and other astronomical phenomena. Unlike spectroscopy, which analyzes the composition and velocity of objects through light wavelengths, photometry focuses solely on the total amount of light received, typically within specific wavelength bands.

Photometric observations are fundamental in determining key properties of astronomical objects. For instance, the apparent magnitude of a star—a measure of its brightness as seen from Earth—is a primary photometric parameter. By comparing apparent magnitudes with intrinsic luminosity, astronomers infer distances using standard candles like Cepheid variables or Type Ia supernovae. Photometry also aids in classifying stars based on their color indices (e.g., B-V, U-B), which correlate with temperature and spectral type.

Modern photometry relies on sensitive detectors such as charge-coupled devices (CCDs) or photomultiplier tubes, often mounted on telescopes. Filters select narrow wavelength ranges to isolate specific features, such as the Johnson-Cousins UBVRI system or broader bands like SDSS (Strömgren). Time-series photometry tracks variations in brightness, revealing phenomena like eclipsing binaries, pulsating stars, or exoplanet transits. Automated surveys, such as the Pan-STARRS or Kepler missions, have expanded photometric data collection, enabling large-scale studies of stellar populations and cosmic structures.

Beyond astronomy, photometry principles extend to fields like photochemistry and remote sensing, where light intensity is measured to analyze chemical compositions or environmental conditions. Advances in instrumentation and computational techniques continue to refine photometric techniques, enhancing precision and broadening applications in both fundamental and applied sciences.