heleduseväärtuse

Heleduseväärtus refers to the apparent brightness of a celestial object as seen from Earth. It is a logarithmic scale that quantifies how bright something appears in the sky. The scale is inverted, meaning that brighter objects have lower or more negative magnitudes, while dimmer objects have higher positive magnitudes. For example, Sirius, the brightest star in the night sky, has a magnitude of about -1.46, while the Andromeda Galaxy has a magnitude of about 3.4. The human eye can typically see stars down to a magnitude of about 6.5 under ideal dark sky conditions.

The concept of magnitude was first developed by the ancient Greek astronomer Hipparchus, who classified stars into six classes based on their brightness. Modern astronomers use a more precise and extended version of this system. Apparent magnitude is distinct from absolute magnitude, which is a measure of an object's intrinsic luminosity. Absolute magnitude is the apparent magnitude an object would have if it were located at a standard distance of 10 parsecs (about 32.6 light-years) from Earth. This distinction is crucial for comparing the true brightness of stars and other celestial bodies. Factors such as distance, interstellar dust, and the object's own energy output influence its apparent brightness.