Night sky
The appearance of the sky after sunset, including celestial objects and lights produced by Earth's atmosphere or human activity.
Celestial sphere: An imaginary sphere centered on Earth onto which celestial objects appear projected. It provides the framework for describing where stars and planets appear across the sky.
Earth's rotation: The spinning of Earth around its axis, completed in roughly one day. It carries observing locations through night and makes celestial objects appear to move westward.
Astronomy: The scientific study of celestial objects, space, and the universe. Night-sky observations provide direct evidence about stars, planets, and distant galaxies.
Milky Way: The barred spiral galaxy containing the Solar System, visible from Earth as a diffuse band of light. Its bright central plane dominates a dark sky far from artificial lights.
Star lore: Cultural stories, names, and traditions associated with stars and constellations. Different societies have interpreted the same visible star patterns in distinct ways.
Star: A luminous ball of plasma held together by gravity and powered by nuclear fusion. Stars form the countless points of light visible on clear, dark nights.
Sidereal time: A timekeeping system based on Earth's rotation relative to distant stars. It predicts which stars cross the night sky at a given moment.
Astrophotography: The practice of photographing celestial objects and phenomena. Long exposures record faint stars, nebulae, and the Milky Way beyond naked-eye visibility.
Aurora: A natural light display caused by charged particles interacting with gases in Earth's upper atmosphere. Its shifting curtains add vivid atmospheric light to high-latitude night skies.
Constellation: A formally defined region of the celestial sphere, often associated with a recognizable star pattern. Constellations organize the visible sky and carry scientific and cultural meanings.