241 relations: Absorption spectroscopy, Accelerating expansion of the universe, Accretion disk, Age of the universe, Alexander Friedmann, American Journal of Physics, Andromeda Galaxy, Angle, Aristarkh Belopolsky, Astronomical spectroscopy, Astronomy, Astronomy & Astrophysics, Astrophysics and Space Science, Asymptote, Atmosphere of Earth, Atom, Barycenter, Big Bang, Binary star, Black body, Black hole, Blueshift, Brady Haran, Brightness, C. H. D. Buys Ballot, Cambridge University Press, Carnegie Institution for Science, Celestial sphere, CfA Redshift Survey, CfA2 Great Wall, Chemical element, Christian Doppler, Circular symmetry, Classical physics, Color, Color temperature, Comoving and proper distances, Conservation of energy, Coordinate system, Copernican principle, Cosmic Background Explorer, Cosmic distance ladder, Cosmic microwave background, Cosmic neutrino background, Cosmic time, Cosmological principle, Cosmology, Cosmos Redshift 7, Curvature, Dark matter, ..., Data set, DEEP2 Redshift Survey, Dielectric, Dimensionless quantity, Distance, Doppler broadening, Doppler effect, Doppler radar, Dynamics (mechanics), Edward Robert Harrison, Edwin Hubble, Einstein field equations, Electric charge, Electromagnetic radiation, Electromagnetic spectrum, Elementary particle, Emission spectrum, Energy, Entropy, Equivalence principle, Event horizon, Exoplanet, Expansion of the universe, Extinction (astronomy), FAQ, Frame of reference, Fraunhofer lines, Frequency, Friedmann equations, Friedmann–Lemaître–Robertson–Walker metric, Fritz Zwicky, Function (mathematics), Galaxy, Galaxy rotation curve, Gamma-ray burst, General relativity, General Relativity and Gravitation, Geodesic, Geoffrey Burbidge, GN-z11, Gravitational constant, Gravitational field, Gravitational redshift, Gravitational wave background, Gravity, GRB 090423, Halton Arp, Helios (spacecraft), Helioseismology, Hermann Carl Vogel, Hippolyte Fizeau, Hubble Deep Field, Hubble Space Telescope, Hubble Ultra-Deep Field, Hubble's law, Hydrogen, Hydrogen line, Hydrogen spectral series, Inflation (cosmology), Infrared, Interstellar cloud, Interstellar medium, Ives–Stilwell experiment, Jan Oort, John C. Baez, Journal of the Royal Astronomical Society of Canada, K correction, Kinetic theory of gases, Laboratory, Lambda-CDM model, Life, Light, Light intensity, Light-year, Line-of-sight propagation, Local Group, Local reference frame, Lorentz covariance, Lorentz factor, Lowell Observatory, Luminosity, Lyman-break galaxy, MacTutor History of Mathematics archive, Magnitude (mathematics), Mass, Mass-to-light ratio, Matter, Mössbauer effect, Methods of detecting exoplanets, Metre per second, Metric (mathematics), Metric tensor, Milky Way, Minkowski space, Monotonic function, Monthly Notices of the Royal Astronomical Society, Motion (physics), NASA, Nature (journal), Neil Gehrels Swift Observatory, Netherlands, Neutron star, Non-standard cosmology, Observable universe, Observational error, Optical filter, Orange (colour), Orbit, Parsec, Peculiar velocity, Philosophical Transactions of the Royal Society, Photometric redshift, Photometry (astronomy), Photon energy, Photosphere, Physical optics, Physics, Pitch (music), Planet, Popular Astronomy (US magazine), Pound–Rebka experiment, Proceedings of the National Academy of Sciences of the United States of America, Quasar, Radar gun, Radiative transfer, Randomness, Rayleigh scattering, Recessional velocity, Redshift-space distortions, Refractive index, Relativistic Doppler effect, Right angle, Rossiter–McLaughlin effect, Rotation, Sachs–Wolfe effect, Scale factor (cosmology), Scattering, Schwarzschild coordinates, Schwarzschild metric, Scientific American, Sloan Digital Sky Survey, Sound, Space telescope, Spacetime, Spacetime topology, Special relativity, Spectral line, Spectrograph, Spectroscopy, Speed of light, Spiral galaxy, Star, Stationary spacetime, Stellar population, Steven Weinberg, Sun, Supercluster, Telescope, Temperature, The Astrophysical Journal, The Feynman Lectures on Physics, The First Three Minutes, The New York Times, Time dilation, Tired light, Type Ia supernova, UDFy-38135539, ULAS J1342+0928, Universe, University of Nottingham, University of St Andrews, Variance, Vector projection, Velocity, Venus, Vesto Slipher, Virgo Cluster, Virial theorem, Visible spectrum, W. M. Keck Observatory, Walter Sydney Adams, Wave, Wavelength, Whistler (radio), White noise, Wilkinson Microwave Anisotropy Probe, Willem de Sitter, William Huggins, Wolf effect, Zeitschrift für Physik, 2dF Galaxy Redshift Survey. Expand index (191 more) » « Shrink index
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample.
The accelerating expansion of the universe is the observation that the universe appears to be expanding at an increasing rate, so that the velocity at which a distant galaxy is receding from the observer is continuously increasing with time.
An accretion disk is a structure (often a circumstellar disk) formed by diffused material in orbital motion around a massive central body.
In physical cosmology, the age of the universe is the time elapsed since the Big Bang.
Alexander Alexandrovich Friedmann (also spelled Friedman or Fridman; Алекса́ндр Алекса́ндрович Фри́дман) (June 16, 1888 – September 16, 1925) was a Russian and Soviet physicist and mathematician.
The American Journal of Physics is a monthly, peer-reviewed scientific journal published by the American Association of Physics Teachers and the American Institute of Physics.
The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.
In plane geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle.
Aristarkh Apollonovich Belopolsky (Аристарх Аполлонович Белопольский), Moscow – 16 May 1934, Pulkovo, Leningrad) was a Russian astronomer. He was born in Moscow but his father's ancestors are from a Serbian town called Belo Polje.
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects.
Astronomy (from ἀστρονομία) is a natural science that studies celestial objects and phenomena.
Astronomy & Astrophysics is a peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics.
Astrophysics and Space Science is a bimonthly peer-reviewed scientific journal covering astronomy, astrophysics, and space science and astrophysical aspects of astrobiology.
In analytic geometry, an asymptote of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the x or y coordinates tends to infinity.
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.
The barycenter (or barycentre; from the Ancient Greek βαρύς heavy + κέντρον centre) is the center of mass of two or more bodies that are orbiting each other, which is the point around which they both orbit.
The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.
A binary star is a star system consisting of two stars orbiting around their common barycenter.
A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift.
Brady John Haran (born 18 June 1976) is an Australian-born British independent filmmaker and video journalist who is known for his educational videos and documentary films produced for BBC News and his YouTube channels, the most notable being Periodic Videos and Numberphile.
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.
Christophorus Henricus Diedericus Buys Ballot (October 10, 1817 – February 3, 1890) was a Dutch chemist and meteorologist after whom Buys Ballot's law and the Buys Ballot table are named.
Cambridge University Press (CUP) is the publishing business of the University of Cambridge.
The Carnegie Institution of Washington (the organization's legal name), known also for public purposes as the Carnegie Institution for Science (CIS), is an organization in the United States established to fund and perform scientific research.
In astronomy and navigation, the celestial sphere is an abstract sphere with an arbitrarily large radius concentric to Earth.
The Center for Astrophysics (CfA) Redshift Survey was the first attempt to map the large-scale structure of the universe.
The Great Wall (also called Coma Wall), sometimes specifically referred to as the CfA2 Great Wall, is an immense galaxy filament.
A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z).
Christian Andreas Doppler (29 November 1803 – 17 March 1853) was an Austrian mathematician and physicist.
In geometry, circular symmetry is a type of continuous symmetry for a planar object that can be rotated by any arbitrary angle and map onto itself.
Classical physics refers to theories of physics that predate modern, more complete, or more widely applicable theories.
Color (American English) or colour (Commonwealth English) is the characteristic of human visual perception described through color categories, with names such as red, orange, yellow, green, blue, or purple.
The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source.
In standard cosmology, comoving distance and proper distance are two closely related distance measures used by cosmologists to define distances between objects.
In physics, the law of conservation of energy states that the total energy of an isolated system remains constant, it is said to be ''conserved'' over time.
In geometry, a coordinate system is a system which uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space.
In physical cosmology, the Copernican principle, is an alternative name of the mediocrity principle, or the principle of relativity, stating that humans (the Earth, or the Solar system) are not privileged observers of the universe.
The Cosmic Background Explorer (COBE), also referred to as Explorer 66, was a satellite dedicated to cosmology, which operated from 1989 to 1993.
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects.
The cosmic microwave background (CMB, CMBR) is electromagnetic radiation as a remnant from an early stage of the universe in Big Bang cosmology.
The cosmic neutrino background (CNB, CνB) is the universe's background particle radiation composed of neutrinos.
Cosmic time (also known as time since the big bang) is the time coordinate commonly used in the Big Bang models of physical cosmology.
In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is homogeneous and isotropic when viewed on a large enough scale, since the forces are expected to act uniformly throughout the universe, and should, therefore, produce no observable irregularities in the large-scale structuring over the course of evolution of the matter field that was initially laid down by the Big Bang.
Cosmology (from the Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is the study of the origin, evolution, and eventual fate of the universe.
Cosmos Redshift 7 (also known as COSMOS Redshift 7, Galaxy Cosmos Redshift 7, Galaxy CR7 or CR7) is a high-redshift Lyman-alpha emitter galaxy (meaning CR7 is one of the oldest, most distant galaxies), in the constellation Sextans, about 12.9 billion light travel distance years from Earth, reported to contain the first stars (first generation; Population III)—formed soon after the Big Bang during the reionisation epoch (redshift, z ∼ 6−7), when the Universe was about 800 million years old—to have provided the chemical elements (like oxygen, nitrogen, carbon, calcium and iron) needed for the later formation of planets and life as it is known.
In mathematics, curvature is any of a number of loosely related concepts in different areas of geometry.
Dark matter is a theorized form of matter that is thought to account for approximately 80% of the matter in the universe, and about a quarter of its total energy density.
A data set (or dataset) is a collection of data.
The DEEP2 Survey or DEEP2 was a two-phased Redshift survey of the Redshift z.
A dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field.
In dimensional analysis, a dimensionless quantity is a quantity to which no physical dimension is assigned.
Distance is a numerical measurement of how far apart objects are.
In atomic physics, Doppler broadening is the broadening of spectral lines due to the Doppler effect caused by a distribution of velocities of atoms or molecules.
The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave in relation to observer who is moving relative to the wave source.
A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance.
Dynamics is the branch of applied mathematics (specifically classical mechanics) concerned with the study of forces and torques and their effect on motion, as opposed to kinematics, which studies the motion of objects without reference to these forces.
Edward R. "Ted" Harrison (8 January 1919 – 29 January 2007) was a British astronomer and cosmologist, noted for his work about the increase of fluctuations in the expanding universe, for his explanation of Olbers' Paradox, and for his books on cosmology for lay readers.
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer.
The Einstein field equations (EFE; also known as Einstein's equations) comprise the set of 10 equations in Albert Einstein's general theory of relativity that describe the fundamental interaction of gravitation as a result of spacetime being curved by mass and energy.
Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space-time, carrying electromagnetic radiant energy.
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
In particle physics, an elementary particle or fundamental particle is a particle with no substructure, thus not composed of other particles.
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state.
In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.
In statistical mechanics, entropy is an extensive property of a thermodynamic system.
In the theory of general relativity, the equivalence principle is any of several related concepts dealing with the equivalence of gravitational and inertial mass, and to Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.
In general relativity, an event horizon is a region in spacetime beyond which events cannot affect an outside observer.
An exoplanet or extrasolar planet is a planet outside our solar system.
The expansion of the universe is the increase of the distance between two distant parts of the universe with time.
In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer.
Frequently asked questions (FAQ) or Questions and Answers (Q&A), are listed questions and answers, all supposed to be commonly asked in some context, and pertaining to a particular topic.
In physics, a frame of reference (or reference frame) consists of an abstract coordinate system and the set of physical reference points that uniquely fix (locate and orient) the coordinate system and standardize measurements.
In physics and optics, the Fraunhofer lines are a set of spectral lines named after the German physicist Joseph von Fraunhofer (1787–1826).
Frequency is the number of occurrences of a repeating event per unit of time.
The Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity.
The Friedmann–Lemaître–Robertson–Walker (FLRW) metric is an exact solution of Einstein's field equations of general relativity; it describes a homogeneous, isotropic, expanding or contracting universe that is path connected, but not necessarily simply connected.
Fritz Zwicky (February 14, 1898 – February 8, 1974) was a Swiss astronomer.
In mathematics, a function was originally the idealization of how a varying quantity depends on another quantity.
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre.
In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic explosions that have been observed in distant galaxies.
General relativity (GR, also known as the general theory of relativity or GTR) is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics.
General Relativity and Gravitation is a monthly peer-reviewed scientific journal.
In differential geometry, a geodesic is a generalization of the notion of a "straight line" to "curved spaces".
Geoffrey Ronald Burbidge FRS (24 September 1925 – 26 January 2010) was an English astronomy professor and theoretical astrophysicist, most recently at the University of California, San Diego.
GN-z11 is a high-redshift galaxy found in the constellation Ursa Major.
The gravitational constant (also known as the "universal gravitational constant", the "Newtonian constant of gravitation", or the "Cavendish gravitational constant"), denoted by the letter, is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's general theory of relativity.
In physics, a gravitational field is a model used to explain the influence that a massive body extends into the space around itself, producing a force on another massive body.
In astrophysics, gravitational redshift or Einstein shift is the process by which electromagnetic radiation originating from a source that is in a gravitational field is reduced in frequency, or redshifted, when observed in a region at a higher gravitational potential.
The gravitational wave background (also GWB and stochastic background) is a random gravitational wave signal produced by a large number of weak, independent, and unresolved sources.
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another.
GRB 090423 was a gamma-ray burst (GRB) detected by the Swift Gamma-Ray Burst Mission on April 23, 2009 at 07:55:19 UTC whose afterglow was detected in the infrared and enabled astronomers to determine that its redshift is z.
Halton Christian "Chip" Arp (March 21, 1927 – December 28, 2013) was an American astronomer.
Helios-A and Helios-B (also known as and), are a pair of probes launched into heliocentric orbit for the purpose of studying solar processes.
Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations.
Hermann Carl Vogel (April 3, 1841 – August 13, 1907) was a German astrophysicist.
Armand Hippolyte Louis Fizeau FRS FRSE MIF (23 September 181918 September 1896) was a French physicist, best known for measuring the speed of light in the namesake Fizeau experiment.
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope.
The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.
The Hubble Ultra-Deep Field (HUDF) is an image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies.
Hubble's law is the name for the observation in physical cosmology that.
Hydrogen is a chemical element with symbol H and atomic number 1.
The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms.
The emission spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula.
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe.
Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.
An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies.
In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.
The Ives–Stilwell experiment tested the contribution of relativistic time dilation to the Doppler shift of light.
Jan Hendrik Oort (or; 28 April 1900 – 5 November 1992) was a Dutch astronomer who made significant contributions to the understanding of the Milky Way and who was a pioneer in the field of radio astronomy.
John Carlos Baez (born June 12, 1961) is an American mathematical physicist and a professor of mathematics at the University of California, Riverside (UCR) in Riverside, California.
The Journal of the Royal Astronomical Society of Canada is a bimonthly peer-reviewed scientific journal published by the Royal Astronomical Society of Canada since 1907.
K correction is a correction to an astronomical object's magnitude (or equivalently, its flux) that allows a measurement of a quantity of light from an object at a redshift z to be converted to an equivalent measurement in the rest frame of the object.
The kinetic theory describes a gas as a large number of submicroscopic particles (atoms or molecules), all of which are in constant rapid motion that has randomness arising from their many collisions with each other and with the walls of the container.
A laboratory (informally, lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed.
The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parametrization of the Big Bang cosmological model in which the universe contains a cosmological constant, denoted by Lambda (Greek Λ), associated with dark energy, and cold dark matter (abbreviated CDM).
Life is a characteristic that distinguishes physical entities that do have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate.
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
Several measures of light are commonly known as intensity.
The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles.
Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver.
The Local Group is the galaxy group that includes the Milky Way.
In theoretical physics, a local reference frame (local frame) refers to a coordinate system or frame of reference that is only expected to function over a small region or a restricted region of space or spacetime.
In relativistic physics, Lorentz symmetry, named for Hendrik Lorentz, is an equivalence of observation or observational symmetry due to special relativity implying that the laws of physics stay the same for all observers that are moving with respect to one another within an inertial frame.
The Lorentz factor or Lorentz term is the factor by which time, length, and relativistic mass change for an object while that object is moving.
Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States.
In astronomy, luminosity is the total amount of energy emitted per unit of time by a star, galaxy, or other astronomical object.
Lyman-break galaxies are star-forming galaxies at high redshift that are selected using the differing appearance of the galaxy in several imaging filters due to the position of the Lyman limit.
The MacTutor History of Mathematics archive is a website maintained by John J. O'Connor and Edmund F. Robertson and hosted by the University of St Andrews in Scotland.
In mathematics, magnitude is the size of a mathematical object, a property which determines whether the object is larger or smaller than other objects of the same kind.
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
In astrophysics and physical cosmology the mass to light ratio, normally designated with the Greek upsilon symbol \Upsilon, is the quotient between the total mass of a spatial volume (typically on the scales of a galaxy or a cluster) and its luminosity.
In the classical physics observed in everyday life, matter is any substance that has mass and takes up space by having volume.
The Mössbauer effect, or recoilless nuclear resonance fluorescence, is a physical phenomenon discovered by Rudolf Mössbauer in 1958.
Any planet is an extremely faint light source compared to its parent star.
Metre per second (American English: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.
In mathematics, a metric or distance function is a function that defines a distance between each pair of elements of a set.
In the mathematical field of differential geometry, a metric tensor is a type of function which takes as input a pair of tangent vectors and at a point of a surface (or higher dimensional differentiable manifold) and produces a real number scalar in a way that generalizes many of the familiar properties of the dot product of vectors in Euclidean space.
The Milky Way is the galaxy that contains our Solar System.
In mathematical physics, Minkowski space (or Minkowski spacetime) is a combining of three-dimensional Euclidean space and time into a four-dimensional manifold where the spacetime interval between any two events is independent of the inertial frame of reference in which they are recorded.
In mathematics, a monotonic function (or monotone function) is a function between ordered sets that preserves or reverses the given order.
Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics.
In physics, motion is a change in position of an object over time.
The National Aeronautics and Space Administration (NASA) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.
Nature is a British multidisciplinary scientific journal, first published on 4 November 1869.
The Neil Gehrels Swift Observatory, previously called the Swift Gamma-Ray Burst Mission, is a NASA space telescope designed to detect gamma-ray bursts (GRBs).
The Netherlands (Nederland), often referred to as Holland, is a country located mostly in Western Europe with a population of seventeen million.
A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses.
A non-standard cosmology is any physical cosmological model of the universe that was, or still is, proposed as an alternative to the then-current standard model of cosmology.
The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion.
Observational error (or measurement error) is the difference between a measured value of a quantity and its true value.
An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings.
Orange is the colour between yellow and red on the spectrum of visible light.
In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet.
The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.
Peculiar motion or peculiar velocity refers to the velocity of an object relative to a rest frame — usually a frame in which the average velocity of some objects is zero.
Philosophical Transactions, titled Philosophical Transactions of the Royal Society (often abbreviated as Phil. Trans.) from 1776, is a scientific journal published by the Royal Society.
A photometric redshift is an estimate for the recession velocity of an astronomical object, such as a galaxy or quasar, without measuring its spectrum.
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation.
Photon energy is the energy carried by a single photon.
The photosphere is a star's outer shell from which light is radiated.
In physics, physical optics, or wave optics, is the branch of optics that studies interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid.
Physics (from knowledge of nature, from φύσις phýsis "nature") is the natural science that studies matterAt the start of The Feynman Lectures on Physics, Richard Feynman offers the atomic hypothesis as the single most prolific scientific concept: "If, in some cataclysm, all scientific knowledge were to be destroyed one sentence what statement would contain the most information in the fewest words? I believe it is that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another..." and its motion and behavior through space and time and that studies the related entities of energy and force."Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves."Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (...) You will come to see physics as a towering achievement of the human intellect in its quest to understand our world and ourselves."Physics is an experimental science. Physicists observe the phenomena of nature and try to find patterns that relate these phenomena.""Physics is the study of your world and the world and universe around you." Physics is one of the oldest academic disciplines and, through its inclusion of astronomy, perhaps the oldest. Over the last two millennia, physics, chemistry, biology, and certain branches of mathematics were a part of natural philosophy, but during the scientific revolution in the 17th century, these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy. Advances in physics often enable advances in new technologies. For example, advances in the understanding of electromagnetism and nuclear physics led directly to the development of new products that have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization; and advances in mechanics inspired the development of calculus.
Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale, or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" in the sense associated with musical melodies.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
Popular Astronomy is an American magazine published by John August Media, LLC and hosted at TechnicaCuriosa.com for amateur astronomers.
The Pound–Rebka experiment is a well known experiment to test Albert Einstein's theory of general relativity.
Proceedings of the National Academy of Sciences of the United States of America (PNAS) is the official scientific journal of the National Academy of Sciences, published since 1915.
A quasar (also known as a QSO or quasi-stellar object) is an extremely luminous active galactic nucleus (AGN).
A radar speed gun (also radar gun and speed gun) is a device used to measure the speed of moving objects.
Radiative transfer is the physical phenomenon of energy transfer in the form of electromagnetic radiation.
Randomness is the lack of pattern or predictability in events.
Rayleigh scattering (pronounced), named after the British physicist Lord Rayleigh (John William Strutt), is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.
Recessional velocity is the rate at which an astronomical object is moving away, typically from Earth.
Redshift-space distortions are an effect in observational cosmology where the spatial distribution of galaxies appears squashed and distorted when their positions are plotted in redshift-space (i.e. as a function of their redshift) rather than in real-space (as a function of their actual distance).
In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how light propagates through that medium.
The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity.
In geometry and trigonometry, a right angle is an angle of exactly 90° (degrees), corresponding to a quarter turn.
The Rossiter–McLaughlin effect is a spectroscopic phenomenon observed when either an eclipsing binary's secondary star or an extrasolar planet is seen to transit across the face of the primary or parent star.
A rotation is a circular movement of an object around a center (or point) of rotation.
The Sachs–Wolfe effect, named after Rainer K. Sachs and Arthur M. Wolfe, is a property of the cosmic microwave background radiation (CMB), in which photons from the CMB are gravitationally redshifted, causing the CMB spectrum to appear uneven.
The relative expansion of the universe is parametrized by a dimensionless scale factor a. Also known as the cosmic scale factor or sometimes the Robertson–Walker scale factor, this is a key parameter of the Friedmann equations.
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more paths due to localized non-uniformities in the medium through which they pass.
In the theory of Lorentzian manifolds, spherically symmetric spacetimes admit a family of nested round spheres.
In Einstein's theory of general relativity, the Schwarzschild metric (also known as the Schwarzschild vacuum or Schwarzschild solution) is the solution to the Einstein field equations that describes the gravitational field outside a spherical mass, on the assumption that the electric charge of the mass, angular momentum of the mass, and universal cosmological constant are all zero.
Scientific American (informally abbreviated SciAm) is an American popular science magazine.
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States.
In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.
A space telescope or space observatory is an instrument located in outer space to observe distant planets, galaxies and other astronomical objects.
In physics, spacetime is any mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum.
Spacetime topology is the topological structure of spacetime, a topic studied primarily in general relativity.
In physics, special relativity (SR, also known as the special theory of relativity or STR) is the generally accepted and experimentally well-confirmed physical theory regarding the relationship between space and time.
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies.
A spectrograph is an instrument that separates light into a frequency spectrum and records the signal using a camera.
Spectroscopy is the study of the interaction between matter and electromagnetic radiation.
The speed of light in vacuum, commonly denoted, is a universal physical constant important in many areas of physics.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae(pp. 124–151) and, as such, form part of the Hubble sequence.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
In general relativity, specifically in the Einstein field equations, a spacetime is said to be stationary if it admits a Killing vector that is asymptotically timelike.
During 1944, Walter Baade categorized groups of stars within the Milky Way into bluer stars associated with the spiral arms and the general position of yellow stars near the central galactic bulge or within globular star clusters.
Steven Weinberg (born May 3, 1933) is an American theoretical physicist and Nobel laureate in Physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic interaction between elementary particles.
The Sun is the star at the center of the Solar System.
A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest-known structures of the cosmos.
A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).
Temperature is a physical quantity expressing hot and cold.
The Astrophysical Journal, often abbreviated ApJ (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler.
The Feynman Lectures on Physics is a physics textbook based on some lectures by Richard P. Feynman, a Nobel laureate who has sometimes been called "The Great Explainer".
The First Three Minutes: A Modern View of the Origin of the Universe (1977; second edition 1993) is a book by American physicist Steven Weinberg.
The New York Times (sometimes abbreviated as The NYT or The Times) is an American newspaper based in New York City with worldwide influence and readership.
According to the theory of relativity, time dilation is a difference in the elapsed time measured by two observers, either due to a velocity difference relative to each other, or by being differently situated relative to a gravitational field.
Tired light is a class of hypothetical redshift mechanisms that was proposed as an alternative explanation for the redshift-distance relationship.
A type Ia supernova (read "type one-a") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf.
UDFy-38135539 (also known as "HUDF.YD3") is the Hubble Ultra Deep Field (UDF) identifier for a galaxy which was calculated to have a light travel time of 13.1 billion years with a present proper distance of around 30 billion light-years.
ULAS J1342+0928 is the most distant known quasar detected and contains the most distant and oldest known supermassive black hole, at a reported redshift of z.
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
The University of Nottingham is a public research university in Nottingham, United Kingdom.
The University of St Andrews (informally known as St Andrews University or simply St Andrews; abbreviated as St And, from the Latin Sancti Andreae, in post-nominals) is a British public research university in St Andrews, Fife, Scotland.
In probability theory and statistics, variance is the expectation of the squared deviation of a random variable from its mean.
The vector projection of a vector a on (or onto) a nonzero vector b (also known as the vector component or vector resolution of a in the direction of b) is the orthogonal projection of a onto a straight line parallel to b. It is a vector parallel to b, defined as where a_1 is a scalar, called the scalar projection of a onto b, and b̂ is the unit vector in the direction of b. In turn, the scalar projection is defined as where the operator · denotes a dot product, |a| is the length of a, and θ is the angle between a and b. The scalar projection is equal to the length of the vector projection, with a minus sign if the direction of the projection is opposite to the direction of b. The vector component or vector resolute of a perpendicular to b, sometimes also called the vector rejection of a from b, is the orthogonal projection of a onto the plane (or, in general, hyperplane) orthogonal to b. Both the projection a1 and rejection a2 of a vector a are vectors, and their sum is equal to a, which implies that the rejection is given by.
The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time.
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.
Vesto Melvin Slipher (November 11, 1875 – November 8, 1969) was an American astronomer who performed the first measurements of radial velocities for galaxies, providing the empirical basis for the expansion of the universe.
The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo.
In mechanics, the virial theorem provides a general equation that relates the average over time of the total kinetic energy, \left\langle T \right\rangle, of a stable system consisting of N particles, bound by potential forces, with that of the total potential energy, \left\langle V_\text \right\rangle, where angle brackets represent the average over time of the enclosed quantity.
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.
The W. M. Keck Observatory is a two-telescope astronomical observatory at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii.
Walter Sydney Adams (December 20, 1876 – May 11, 1956) was an American astronomer.
In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport.
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
A whistler is a very low frequency or VLF electromagnetic (radio) wave generated by lightning.
In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density.
The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP), was a spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic microwave background (CMB) – the radiant heat remaining from the Big Bang.
Willem de Sitter (6 May 1872 – 20 November 1934) was a Dutch mathematician, physicist, and astronomer.
Sir William Huggins (7 February 1824 – 12 May 1910) was an English astronomer best known for his pioneering work in astronomical spectroscopy together with his wife Margaret Lindsay Huggins.
The Wolf Effect (sometimes Wolf shift) is a frequency shift in the electromagnetic spectrum.
Zeitschrift für Physik (English: Journal for physics) is a defunct series of German peer-reviewed German scientific journal of physics established in 1920 by Springer Berlin Heidelberg.
In astronomy, the 2dF Galaxy Redshift Survey (Two-degree-Field Galaxy Redshift Survey), 2dF or 2dFGRS is a redshift survey conducted by the Anglo-Australian Observatory (AAO) with the 3.9m Anglo-Australian Telescope between 1997 and 11 April 2002.
Cosmic redshift, Distance Redshift, Doppler redshift, Doppler-like redshifts, Galactic redshift, Galactic redshifts, Red Shift, Red shift, Red shift light, Red-shift, Redshifted, Redshifts, Relativistic Redshift, Spectral shift, Spectroscope redshift, Spectroscopic redshift.