Supernova A supernova (abbreviated SN, plural SNe after "supernovae") is a stellar explosion that is more energetic than a nova. It is pronounced /ˌsuːpəˈnoʊvə/ with the plural supernovae /ˌsuːpəˈnoʊviː/ or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this interval a supernova can radiate as much energy as the Sun is expected to emit over its entire life span.[1] The explosion expels much or all of a star's material[2] at a velocity of up to 30,000 km/s (10% of the speed of light), driving a shock wave[3] into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant. Nova means "new" in Latin, referring to what appears to be a very bright new star shining in the celestial sphere; the prefix "super-" distinguishes supernovae from ordinary novae which are far less luminous. Discovery[edit]
Solar System Discovery and exploration Andreas Cellarius's illustration of the Copernican system, from the Harmonia Macrocosmica (1660) For many thousands of years, humanity, with a few notable exceptions, did not recognize the existence of the Solar System. People believed Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Structure and composition The orbits of the bodies in the Solar System to scale (clockwise from top left) The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally.[13] The Sun's four largest orbiting bodies, the gas giants, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic. Distances and scales Planets of the Solar System to scale.
Spiral Galaxy An example of a spiral galaxy, the Pinwheel Galaxy (also known as Messier 101 or NGC 5457) Spiral galaxies are named for the spiral structures that extend from the center into the disk. The spiral arms are sites of ongoing star formation and are brighter than the surrounding disk because of the young, hot OB stars that inhabit them. Roughly two-thirds of all spirals are observed to have an additional component in the form of a bar-like structure,[2] extending from the central bulge, at the ends of which the spiral arms begin. Our own Milky Way has recently (in the 1990s) been confirmed to be a barred spiral, although the bar itself is difficult to observe from our position within the Galactic disk.[4] The most convincing evidence for its existence comes from a recent survey, performed by the Spitzer Space Telescope, of stars in the Galactic center.[5] Structure[edit] Spiral galaxies consist of four distinct components: Spiral arms[edit] Galactic bulge[edit] Galactic spheroid[edit] Other
Planet The planets were thought by Ptolemy to orbit Earth in deferent and epicycle motions. Although the idea that the planets orbited the Sun had been suggested many times, it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations, performed by Galileo Galilei. By careful analysis of the observation data, Johannes Kepler found the planets' orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics, and even hydrology. History Printed rendition of a geocentric cosmological model from Cosmographia, Antwerp, 1539 Babylon Greco-Roman astronomy India Medieval Muslim astronomy European Renaissance 19th century 20th century
Galaxy Galaxies contain varying numbers of planets, star systems, star clusters and types of interstellar clouds. In between these objects is a sparse interstellar medium of gas, dust, and cosmic rays. Supermassive black holes reside at the center of most galaxies. They are thought to be the primary driver of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy is known to harbor at least one such object.[5] Galaxies have been historically categorized according to their apparent shape, usually referred to as their visual morphology. Etymology[edit] The word galaxy derives from the Greek term for our own galaxy, galaxias (γαλαξίας, "milky one"), or kyklos ("circle") galaktikos ("milky")[11] for its appearance as a lighter colored band in the sky. In the astronomical literature, the capitalized word 'Galaxy' is used to refer to our galaxy, the Milky Way, to distinguish it from the billions of other galaxies. Nomenclature[edit] Observation history[edit] Milky Way[edit]
Gravitational singularity A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system. These quantities are the scalar invariant curvatures of spacetime, which includes a measure of the density of matter. The two most important types of spacetime singularities are curvature singularities and conical singularities.[2] Singularities can also be divided according to whether they are covered by an event horizon or not (naked singularities).[3] According to general relativity, the initial state of the universe, at the beginning of the Big Bang, was a singularity. Interpretation[edit] Many theories in physics have mathematical singularities of one kind or another. Some theories, such as the theory of loop quantum gravity suggest that singularities may not exist. Types[edit] Curvature[edit] , which is diffeomorphism invariant, is infinite. Conical[edit] Naked[edit] Entropy[edit]
Black hole A black hole is defined as a region of spacetime from which gravity prevents anything, including light, from escaping.[1] The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole.[2] Around a black hole, there is a mathematically defined surface called an event horizon that marks the point of no return. The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics.[3][4] Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater. Objects whose gravity fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. History General relativity
Universe There are many competing theories about the ultimate fate of the universe. Physicists remain unsure about what, if anything, preceded the Big Bang. Many refuse to speculate, doubting that any information from any such prior state could ever be accessible. There are various multiverse hypotheses, in which some physicists have suggested that the Universe might be one among many or even an infinite number of universes that likewise exist.[11][12] Historical observation XDF size compared to the size of the Moon – several thousand galaxies, each consisting of billions of stars, are in this small view. XDF (2012) view – each light speck is a galaxy – some of these are as old as 13.2 billion years[13] – the visible Universe is estimated to contain 200 billion galaxies. XDF image shows fully mature galaxies in the foreground plane – nearly mature galaxies from 5 to 9 billion years ago – protogalaxies, blazing with young stars, beyond 9 billion years. History Etymology, synonyms and definitions
Nebula Portion of the Carina nebula A nebula (from Latin: "cloud";[1] pl. nebulae or nebulæ, with ligature, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others. Observational history The "Pillars of Creation" from the Eagle Nebula. On November 26, 1610, Nicolas-Claude Fabri de Peiresc discovered the Orion Nebula using a telescope. In 1715, Edmund Halley published a list of six nebulae.[8] This number steadily increased during the century, with Jean-Philippe de Cheseaux compiling a list of 20 (including eight not previously known) in 1746. Formation The Triangulum Emission Garren Nebula NGC 604 Types of nebulae
Gravitational wave Aspect of relativity in physics Gravitational waves are waves of spacetime curvature that propagate at the speed of light and are produced by the relative motion of gravitating masses. They were first predicted by Albert Einstein[1][2] as a consequence of his general theory of relativity, appearing as "ripples in spacetime curvature".[3][4]: 326 [5]: 117 Hundreds of these gravitational waves have since then been observed, first indirectly using binary-pulsar observations[6] and, since 2015[7], directly through dedicated observatories. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation.[8] Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, instead asserting that gravity has instantaneous effect everywhere. Gravitational waves therefore stand as an important relativistic phenomenon that is absent from Newtonian physics. -significance. with the initial radius and
Virgo The Virgo Supercluster (Virgo SC) or Local Supercluster (LSC or LS) is the irregular supercluster that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs (110 million light-years). It is one of millions of superclusters in the observable universe. Background[edit] Beginning with the first large sample of nebulae published by William and John Herschel in 1863, it was known that there is a marked excess of nebular fields in the constellation Virgo (near the north galactic pole). Structure[edit] Galaxy distribution[edit] The number density of galaxies in the LS falls off with the square of the distance from its center near the Virgo Cluster, suggesting that this cluster is not randomly located. Cosmology[edit] Large scale dynamics[edit] Dark matter[edit] Maps[edit] Diagrams[edit] See also[edit] References[edit] External links[edit]
Gravitation Gravitation, or gravity, is a natural phenomenon by which all physical bodies attract each other. It is most commonly recognized and experienced as the agent that gives weight to physical objects, and causes physical objects to fall toward the ground when dropped from a height. During the grand unification epoch, gravity separated from the electronuclear force. History of gravitational theory Scientific revolution Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries. Newton's theory of gravitation In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newton's theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Equivalence principle Formulations of the equivalence principle include: General relativity Specifics