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Night sky

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The night sky is the view of space we see when the Sun is below the horizon.

Свет от деревни - panoramio
Свет от деревни - panoramio

It includes many objects like stars, planets, and the Moon. These objects appear in a clear sky between sunset and sunrise. Natural light comes from moonlight, starlight, and a glow called airglow. Sometimes, aurorae light up the skies near the polar circles. Large bursts from the Sun can even send light toward the Equator. The sky is never truly dark. If it were, we could not see the shape of objects against it.

Паранальские ночи
Паранальские ночи

Light in the sky changes in many ways. During the day, sunlight scatters to make the sky bright. After sunset, we enter a period called twilight. This happens in three segments based on the Sun's position. Civil twilight is the first stage after the Sun sets. This is followed by nautical twilight and then astronomical twilight. The sky reaches its darkest point when the Sun is 18 degrees below the horizon.

Other light sources include starlight and artificial light pollution. Light pollution comes from city lights and makes it hard to see stars. People use special filters or move to dark places to fix this.

Humans have studied the sky for a very long time.

Starry Night at La Silla
Starry Night at La Silla

Ancient farmers used the stars as a calendar to know when to plant crops. Many cultures drew constellations between stars to tell stories about their gods. These groupings of stars are called constellations. People once thought stars were all on a flat dome above Earth. They thought this because stars are too far away to see depth. Some stars, called pole stars, stay in one place as Earth rotates. The Big Dipper is a famous group that helps people find the north star, Polaris.

Many different objects move through the night sky. Planets are called "wanderers" because they move through the starfield each day. They shine because they reflect light from the Sun. Venus is the brightest planet and is often called the morning or evening star. The Moon is a grey disc that shows phases over 29.53 days.

Where Heaven and Earth Collide
Where Heaven and Earth Collide

You can even see the Moon during the day. Comets are rare visitors that show long tails pointing away from the Sun. You might also see meteors streaking across the sky or satellites moving quickly. Even the Milky Way looks like a band of white dust in dark areas.

Our view of the sky will change over many years. The Moon moves around Earth, and Earth moves around the Sun. Stars also move and change brightness over time. This is called proper motion. In the very distant future, the Milky Way and the Andromeda Galaxy will merge. They will become one single, huge galaxy.

Andromeda and Milky Way collision sequence
Andromeda and Milky Way collision sequence

This will change the night sky forever. For now, we can use star charts to help us find our way. Using a red flashlight can help you read these charts without losing your dark adaptation. This helps your eyes stay ready to see the most stars.

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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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