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  1. Astronomy | Definition, History, Discoveries, & Facts | Britannica

    Nov 14, 2025 · Astronomy, science that encompasses the study of all extraterrestrial objects and phenomena. Since the late 19th century, astronomy has expanded to include astrophysics, the …

  2. Astronomy Definition & Meaning | Britannica Dictionary

    ASTRONOMY meaning: the scientific study of stars, planets, and other objects in outer space

  3. Astronomy Portal | Britannica

    Astronomy, science that encompasses the study of all extraterrestrial objects and phenomena. Until the invention of the telescope and the discovery of the laws of motion and gravity in the …

  4. astronomy - Kids | Britannica Kids | Homework Help

    The study of astronomy involves all of the objects outside Earth’s atmosphere. These include the Sun, Moon, planets, stars, galaxies, and all other matter in the universe.

  5. Astronomy - Techniques, Observations, Measurements | Britannica

    Nov 14, 2025 · Astronomy - Techniques, Observations, Measurements: Astronomical observations involve a sequence of stages, each of which may impose constraints on the type …

  6. History of astronomy and contributions of Ptolemy, Nicolaus …

    astronomy, Science dealing with the origin, evolution, composition, distance, and motion of all bodies and scattered matter in the universe. The most ancient of the sciences, it has existed …

  7. Astronomy - Ancient, Celestial, Observations | Britannica

    Nov 14, 2025 · Astronomy - Ancient, Celestial, Observations: Astronomy was the first natural science to reach a high level of sophistication and predictive ability, which it achieved already …

  8. Dark matter | Definition, Discovery, Distribution, & Facts | Britannica

    Nov 29, 2025 · The rate at which galaxies and large structures composed of galaxies coalesced from density fluctuations in the early universe indicates that the nonbaryonic dark matter is …

  9. astronomy - Students | Britannica Kids | Homework Help

    Before the dawn of history someone noticed that certain celestial bodies moved in orderly and predictable paths, and astronomy—an ancient science—was born. Yet some of science’s …

  10. Star | Definition, Light, Names, & Facts | Britannica

    Oct 27, 2025 · Astronomers define stellar brightness in terms of magnitudes: the apparent magnitude (the perceived and measured brightness of a star) and the absolute magnitude of …