Astrophysics, Cosmology & Relativity
60 terms · page 1 of 3
Accretion Disk
A rotating disk structure formed by infalling diffuse matter orbiting a massive central body like a white dwarf, neutron star, or black…
Astrophysics, Cosmology & RelativityAstronomical Unit (AU)
An astronomical unit of length defined as exactly 149,597,870,700 meters, representing the mean distance from Earth to the Sun.
Astrophysics, Cosmology & RelativityBig Bang
The prevailing cosmological model describing the universe as originating from an extremely hot, dense state ~13.8 billion years ago and…
Astrophysics, Cosmology & RelativityBinary Star System
A stellar system consisting of two gravitationally bound stars orbiting around their common center of mass.
Astrophysics, Cosmology & RelativityBlack Hole
A region of spacetime where gravitational acceleration is so intense that nothing, including light, can escape beyond its event horizon.
Astrophysics, Cosmology & RelativityBrown Dwarf
A substellar object intermediate in mass between giant gas planets and low-mass stars, incapable of sustaining stable core hydrogen fusion.
Astrophysics, Cosmology & RelativityChandrasekhar Limit
The maximum mass that a stable white dwarf star can support against gravitational collapse via electron degeneracy pressure.
Astrophysics, Cosmology & RelativityCosmic Inflation
A cosmological theory proposing a brief phase of exponential spatial expansion in the early universe (~10⁻³⁶ to 10⁻³² seconds after the Big…
Astrophysics, Cosmology & RelativityCosmic Microwave Background (CMB)
The electromagnetic thermal radiation leftover from the recombination epoch of the early universe (~380,000 years after the Big Bang).
Astrophysics, Cosmology & RelativityCosmic Strings
Hypothetical 1D subatomic-width topological line defects that may have formed during GUT phase transitions in the early universe.
Astrophysics, Cosmology & RelativityCosmological Redshift
The stretching of photon wavelengths to longer, redder values as light travels across the expanding space of the universe.
Astrophysics, Cosmology & RelativityDark Energy
An unknown form of energy with negative pressure that permeates all space and drives the accelerated expansion of the universe.
Astrophysics, Cosmology & RelativityDark Matter
A non-baryonic form of matter that does not absorb, reflect, or emit electromagnetic radiation, detectable solely through its gravitational…
Astrophysics, Cosmology & RelativityDark Matter Halo
An extended, nearly spherical region of dark matter enveloping a galaxy or galaxy cluster that extends far beyond the visible stellar disk.
Astrophysics, Cosmology & RelativityDrake Equation
A probabilistic equation formulated by Frank Drake in 1961 to estimate the number N of active, communicative extraterrestrial civilizations…
Astrophysics, Cosmology & RelativityEinstein Field Equations
The set of 10 non-linear partial differential equations in general relativity relating spacetime curvature (Ricci tensor R_μν) to…
Astrophysics, Cosmology & RelativityEquivalence Principle
The foundational postulate of general relativity asserting that the physical effects of a uniform gravitational field are locally…
Astrophysics, Cosmology & RelativityEvent Horizon
The boundary surrounding a black hole beyond which escape velocity exceeds the speed of light, preventing any matter or signal from…
Astrophysics, Cosmology & RelativityExoplanet
A planet situated outside the Solar System that orbits a star, stellar remnant, or brown dwarf.
Astrophysics, Cosmology & RelativityFermi Paradox
The apparent contradiction between high probabilistic estimates for the existence of extraterrestrial civilizations and the complete lack…
Astrophysics, Cosmology & RelativityGalaxy
A massive, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter.
Astrophysics, Cosmology & RelativityGalaxy Cluster
A gravitationally bound structure containing hundreds to thousands of individual galaxies bound together by gravity.
Astrophysics, Cosmology & RelativityGeneral Relativity
Albert Einstein's 1915 geometric theory of gravitation describing gravity not as an attractive force, but as the curvature of 4D spacetime…
Astrophysics, Cosmology & RelativityGeodesic
The path of shortest (or extreme) spacetime interval between two points in curved spacetime, representing the free-fall trajectory of…