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Astronomy is a natural science studying of celestial objects and phenomena originating outside the Earth's atmosphere.


Astronomy is the scientific study of celestial objects and phenomena that originate outside the Earth’s atmosphere. These objects and phenomena include the study of stars, planets, moons, comets, nebulae, galaxies, and cosmic background radiation. Astronomy is concerned with the physics, chemistry, meteorology, and motion of celestial objects as well as the universe as a whole, its formation, and development.

Astronomy is one of the oldest sciences, with early civilizations making astronomical observations. In 700 BC the Babylonians recorded and could predict future lunar eclipses. The invention of the telescope in 1608 transformed the world of astronomy. While early telescopes were primarily used for terrestrial observations, a small group of astronomers, including Galileo Galilei, began pointing them to the skies. The increased magnification of heavenly objects produced a significant and immediate impact with observations and interpretations of stars, the moon, Jupiter, the sun, and the phases of the planet Venus, transforming civilization's understanding of the universe.

Modern astronomy is split into two fields: observational and theoretical. Observational astronomy focuses on acquiring and analyzing data from celestial objects. Theoretical astronomy develops computer or analytical models describing astronomical objects and phenomena. The two fields complement one another, with theoretical astronomy seeking to explain observational data, and observational astronomy confirming theoretical results.

Astronomy is a natural science in which amateurs still play an active role, and amateur astronomers have contributed to many important astronomical discoveries.

Observational astronomy

Observational astronomy measures and records data from the observable universe. This means the electromagnetic radiation emitted from stars and other celestial objects as well as signals they produce such as neutrinos, and gravitational waves.

Observational astronomy using light utilizes optical telescopes (which come in two types: reflectors and refractors) to gather light and reveal more detail. Observational astronomy can be divided into fields based on the wavelength of light being measured including: radio, infrared (IR), ultraviolet (UV), x-ray, and gamma-ray telescopes.

Theoretical astronomy

Motivated by observational data, theoretical astronomers utilize numerical simulations to explain astronomical phenomena. Astronomical simulations and models help investigate phenomena in detail, examining ideas and viewpoints impossible to observe. Theoretical astronomy studies a wide range of objects including: moons, planets, stars, space plasma, galaxies, clusters of galaxies, active galactic nuclei, large-scale structures of the Universe, and the Universe itself.


Studies in astronomy can be divided into four subfields:

  • Astrophysics
  • Astrometry
  • Astrogeology
  • Astrobiology

Astrophysics relates the principles of physics to astronomy to understand the physical processes of celestial bodies and the surrounding space. Astrophysics encapsulates the following subjects:

  • Cosmology—How the universe was created and evolved.
  • Spectroscopy—How light is reflected, absorbed, and transferred between matter
  • Photometry—How luminous astronomical objects are based on electromagnetic radiation
  • Heliophysics—The study of the sun
  • Asteroseismology—Observations of stars to study their interior structure and dynamics
  • Helioseismology—‚Asteroseismology specific to the sun.

Astrometry is the study of the position and motion of celestial bodies in space. It provides a frame of reference for the movement of celestial objects. Areas within astrometry include planetary science (planetology) and exoplanetology, the study of planets outside of our solar system.


Astrogeology studies the geology of celestial bodies such as planets, moons, asteroids, meteorites, and comets.


Astrobiology is a field looking for signs of life in the universe.


Further Resources



November 5, 2021
HILO, Hawaii (AP) -- An independent review of the state of astronomy and astrophysics in the U.S. has recommended federal funding of a giant telescope in Hawaii. The Astronomy and Astrophysics Decadal Survey warned it could be "disastrous" for U.S.
August 30, 2021
Brown dwarfs are astronomical objects with masses between those of planets and stars.
WION Web Team
July 26, 2021
Astronomers have just detected a disk of dust forming around a planet outside our solar system for the first time.
Science X staff
July 21, 2021
Results from a new survey of astronomers and geophysicists show that these sciences have a systemic bullying problem; one that is disproportionately worse for women and those from minority groups. In a survey carried out by the Royal Astronomical Society (RAS) last year of over 650 people in the field, 44% of respondents had suffered bullying and harassment in the workplace within the preceding 12 months. Aine O'Brien, RAS Diversity Officer, will present the key results in a talk at the virtual National Astronomy Meeting on Thursday 22 July.
Science X staff
May 24, 2021
Three dozen dwarf galaxies far from each other had a simultaneous 'baby boom' of new stars, an unexpected discovery that challenges current theories on how galaxies grow and may enhance our understanding of the universe.


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