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Stars in the night sky. The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include moonlight, starlight, and airglow, depending on location and timing.
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars. It is a commonly noticed aspect of light pollution . While usually referring to luminance arising from artificial lighting , skyglow may also involve any scattered light seen at night, including ...
Starry sky crossed with the Milky Way and a meteor. Starlight is the light emitted by stars. [1] It typically refers to visible electromagnetic radiation from stars other than the Sun, observable from Earth at night, although a component of starlight is observable from Earth during daytime.
Atmospheric refraction of the light from a star is zero in the zenith, less than 1′ (one arc-minute) at 45° apparent altitude, and still only 5.3′ at 10° altitude; it quickly increases as altitude decreases, reaching 9.9′ at 5° altitude, 18.4′ at 2° altitude, and 35.4′ at the horizon; [4] all values are for 10 °C and 1013.25 hPa ...
Stars in the night sky. The first star catalogue in Greek astronomy was created by Aristillus in approximately 300 BC, with the help of Timocharis. [10] The star catalog of Hipparchus (2nd century BC) included 1,020 stars, and was used to assemble Ptolemy's star catalogue. [11] Hipparchus is known for the discovery of the first recorded nova ...
The scientific study of the night sky and bodies observed within it, meanwhile, takes place in the science of astronomy. Within visible-light astronomy, the visibility of celestial objects in the night sky is affected by light pollution. The presence of the Moon in the night sky has historically hindered astronomical observation by increasing ...
Sky brightness refers to the visual perception of the sky and how it scatters and diffuses light. The fact that the sky is not completely dark at night is easily visible. If light sources (e.g. the Moon and light pollution ) were removed from the night sky , only direct starlight would be visible.
The twinkling of the brightest star in the night sky Sirius (apparent magnitude of -1.1), shortly before upper culmination at the meridian, at 20° above the southern horizon. In 29 seconds, Sirius appears to move 7.5 arcminutes from left to right.