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Night sky

space Maturity 9-11 Next article →

The night sky is the collection of celestial objects visible between sunset and sunrise. This view includes stars, planets, the Moon, and even distant galaxies. It appears when the Sun is below the horizon, allowing us to see light from other sources. These sources include moonlight, starlight, and a natural phenomenon called airglow. In polar regions, aurorae can light up the sky. Sometimes, large coronal mass ejections or solar winds from the Sun can push these lights toward the Equator.

Свет от деревни - panoramio
Свет от деревни - panoramio

Understanding the brightness of the sky requires looking at how light scatters. During the day, Rayleigh scattering of sunlight makes the sky bright. After sunset, we enter a period called twilight, which has three distinct stages. First is civil twilight, which ends when the Sun is 6 degrees below the horizon. Next is nautical twilight, occurring between 6 and 12 degrees. Finally, astronomical twilight lasts from 12 to 18 degrees below the horizon. Once the Sun drops past 18 degrees, the sky reaches its minimum brightness.

Паранальские ночи
Паранальские ночи

Humanity has a long history of observing these patterns. Ancient farmers used the sky as a calendar to time their crop planting. Many cultures created constellations, which are groupings of stars used to represent mythology or deities. Because stars are so distant, they lack depth cues, leading ancient people to believe they sat on a dome above Earth. Some stars, known as pole stars, appear stationary because they align with Earth's axis of rotation. For example, the Big Dipper helps navigators find Polaris, the North Star.

Starry Night at La Silla
Starry Night at La Silla

Planets are often called "wanderers" because they move through the starfield daily. Unlike stars, planets shine by reflecting or scattering sunlight. Their brightness changes based on the positions of the Sun, the planet, and the Earth. Venus is the most prominent planet and is often called the "morning star" or "evening star." The Moon is another major object, appearing as a grey disc with visible craters. It undergoes a cycle of lunar phases that lasts about 29.53 days on average.

Where Heaven and Earth Collide
Where Heaven and Earth Collide

Other fascinating objects occasionally appear in our view. Comets are rare visitors that show tails pointing away from the Sun. You might also see meteors, which are bright, fleeting streaks of light. Some people mistake the Magellanic Clouds for Earth-based clouds, but they are actually dwarf galaxies outside the Milky Way. The Milky Way itself looks like a band of white dust in very dark areas. This galaxy is composed of billions of stars arranged in a halo and a disc structure.

Modern technology has changed how we see the sky. Artificial light pollution from cities creates "skyglow," which makes it harder to see faint stars. Astronomers often seek locations far from urban areas to find optimal views. They may also use optical filters to help reduce this interference. We can also see man-made objects like artificial satellites. Some satellites, including space debris, may blink due to rotation. Others, like the International Space Station, can produce bright satellite flares.

Паранальские ночи
Паранальские ночи

To see the most detail, observers must practice dark adaptation. It takes several minutes for the eyes to adjust to the darkness. Using a red flashlight can help you read star charts without ruining this adjustment. This is important because stars can appear as hundreds or even tens of thousands of pinpoints. Even the sky itself will change over massive timescales. Eventually, tens of billions of years from now, the Milky Way and the Andromeda Galaxy will merge. This event will create a single elliptical galaxy and transform the night sky forever.

Andromeda and Milky Way collision sequence
Andromeda and Milky Way collision sequence
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🖼️ Images & Media (6)
File:Свет от деревни - panoramio.jpg
Свет от деревни - panoramio.jpg
File:Starry Night at La Silla.jpg
Starry Night at La Silla.jpg
File:Паранальские ночи.jpg
Паранальские ночи.jpg
Milky_way_-route_292_shiga_kusatsu_road-_1...
File:Where Heaven and Earth Collide.jpg
Where Heaven and Earth Collide.jpg
File:Andromeda and Milky Way collision sequence.jpg
Andromeda and Milky Way collision sequence.jpg
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