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The Sun is a weakly variable star, and its actual luminosity therefore fluctuates. [3] The major fluctuation is the eleven-year solar cycle (sunspot cycle) that causes a quasi-periodic variation of about ±0.1%. Other variations over the last 200–300 years are thought to be much smaller than this. [4]
In contrast, the term brightness in astronomy is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to ...
Bright sunlight 120 kilolux: Brightest sunlight Luminance. This section lists examples of luminances, measured in candelas per square metre and grouped by order of ...
A more complex definition of absolute magnitude is used for planets and small Solar System bodies, based on its brightness at one astronomical unit from the observer and the Sun. The Sun has an apparent magnitude of −27 and Sirius, the brightest visible star in the night sky, −1.46. Venus at its brightest is -5.
Notable features: Brightness variable from 0%-100% | Sunset simulation | 13 preloaded alarm sounds | Numerous relaxation sounds | Night-light setting The Hatch Restore 2 is a full-featured sunrise ...
[1] [2] During these times, the brightness of the sky matches the brightness of streetlights, signs, car headlights and lit windows. The period of time shortly before the magic hour at sunrise, or after it at sunset, is called the "blue hour". This is when the sun is at a significant depth below the horizon, when residual, indirect sunlight ...
Along the ecliptic plane there are enhancements in the zodiacal light where it is much brighter near the Sun and with a secondary maximum opposite the Sun at 180 degrees longitude (the gegenschein). In extreme cases natural zenith sky brightness can be as high as ~21.0 mag/arcsec², roughly twice as bright as nominal conditions.
Former Google CEO Eric Schmidt says human-directed AI-controlled drones are the future of war. Schmidt's startup, White Stork, is developing drones for Ukraine to use in its war with Russia.