Night sky
Natural light sources in a night sky include moonlight, starlight, and airglow, depending on location and timing.
Occasionally, a large coronal mass ejection from the Sun or simply high levels of solar wind may extend the phenomenon toward the Equator.
The history of astrology has generally been based on the belief that relationships between heavenly bodies influence or explain events on Earth.
The scientific study of objects in the night sky takes place in the context of observational astronomy.
Optical filters and modifications to light fixtures can help to alleviate this problem, but for optimal views, both professional and amateur astronomers seek locations far from urban skyglow.
[5] In ancient times the stars were often assumed to be equidistant on a dome above the Earth because they are much too far away for stereopsis to offer any depth cues.
It takes several minutes for eyes to adjust to the darkness necessary for seeing the most stars, and surroundings on the ground are hard to discern.
[6] The Big Dipper (which has a wide variety of other names) is helpful for navigation in the northern hemisphere because it points to Polaris, the north star.
It spans, depending on its exact location, 29–33 arcminutes – which is about the size of a thumbnail at arm's length, and is readily identified.
They tend to be visible only shortly before sunrise or after sunset because those are the times they are close enough to the Sun to show a tail.
Thicker cloud cover obscures celestial objects entirely, making the sky black or reflecting city lights back down.
On clear dark nights in unpolluted areas, when the Moon appears thin or below the horizon, the Milky Way, a band of what looks like white dust, can be seen.
Zodiacal light is a glow that appears near the points where the Sun rises and sets, and is caused by sunlight interacting with interplanetary dust.
Gegenschein is a faint bright spot in the night sky centered at the antisolar point, caused by the backscatter of sunlight by interplanetary dust.
Shortly after sunset and before sunrise, artificial satellites often look like stars – similar in brightness and size – but move relatively quickly.
