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Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, meteoroids, asteroids, and comets.
In astronomy, absolute magnitude (M) is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale; the more luminous (intrinsically bright) an object, the lower its magnitude number.
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.
11 must-see astronomy events in 2025. The new year will be a busy one in the night sky with celestial sights of all types for everyone to enjoy, many of which can be viewed without needing a ...
An illustration of light sources from magnitude 1 to 3.5, in 0.5 increments. In astronomy, magnitude is a measure of the brightness of an object, usually in a defined passband.
The Friedmann equations start with the simplifying assumption that the universe is spatially homogeneous and isotropic, that is, the cosmological principle; empirically, this is justified on scales larger than the order of 100 Mpc.
They provide a precise formulation of the relationship between spacetime geometry and the properties of matter, using the language of mathematics. More concretely, they are formulated using the concepts of Riemannian geometry , in which the geometric properties of a space (or a spacetime) are described by a quantity called a metric .
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars, binary systems, [1] nebulae, [2] and black holes.. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial velocity method or Doppler spectroscopy, and is determined using the binary mass function.