comets

The brightest members of the Kreutz Sungrazers have been spectacular objects, easily visible in the daytime sky. The three most impressive have been the Great Comet of 1843, the Great Comet of 1882 and Comet Ikeya-Seki. Another very notable Kreutz Sungrazer was the Eclipse Comet of 1882. Kreutz Sungrazers - The Great Comet of 1843. The Great Comet of 1843 was first noticed in early February of that year, just over three weeks before its perihelion passage. By February 27 it was easily visible in the daytim ...

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Kreutz Sungrazers, Kreutz Sungrazers - Discovery and historical observations, Kreutz Sungrazers - Notable members, Kreutz Sungrazers - The Great Comet of 1843, Kreutz Sungrazers - The Eclipse Comet of 1882, Kreutz Sungrazers - The Great Comet of 1882, Kreutz Sungrazers - Comet Ikeya-Seki, Kreutz Sungrazers - Dynamical history and evolution, Kreutz Sungrazers - Current observations, Kreutz Sungrazers - Future of the Kreutz Sungrazers

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History of astrology - Western astrology's Babylonian origins. The history of western astrology can now be traced back to ancient Babylonia, and indeed to the earliest phases of Babylonian history, i.e. to about 3000 B.C. In Babylonia as well as in Assyria as a direct offshoot of Babylonian culture (or as we might also term it "Euphratean" culture), astrology takes its place in the official cult as one of the two chief means at the disposal of the priests (who were called bare or "inspectors") for ascertaining the will and intention of the gods, the other being through the inspection of ...

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History of astrology, History of astrology - Overview, History of astrology - History, History of astrology - Western astrology's Babylonian origins, History of astrology - The spread of astrology from Babylonia, History of astrology - Greek and Egyptian contributions to astrology, History of astrology - Medieval and Renaissance astrology, History of astrology - Astrology's 20th century expansion, History of astrology - Astrology in the Jewish community, History of astrology - Noted predictions, History of astrology - Historical proponents of astrology, History of astrology - Historical opponents of astrology, History of astrology - Other miscellany

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Most planets, including Earth, spin in the prograde sense: They spin in the same direction as they orbit the Sun (that is, their north rotational pole and north orbital pole point in similar directions, more or less in the direction of the Solar north pole). The exceptions are Venus, Uranus, and Pluto. Uranus rotates nearly on its side relative to its orbit. It has been described as having an axial tilt of 82° and a negative rotation of −17 hours, or, equivalently, of having an axis tilted at 98° and a positive rotation. Since current sp ...

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Prograde and retrograde motion, Prograde and retrograde motion - Two notations, Prograde and retrograde motion - Retrograde orbits, Prograde and retrograde motion - Retrograde rotation, Prograde and retrograde motion - Retrogradation or apparent retrograde motion, Prograde and retrograde motion - Examples, Prograde and retrograde motion - Reference

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A Natural phenomenon can easily cause a natural disaster. Appearing to arise without direct human involvement, natural disasters are sometimes called an act of God. A natural disaster may become more severe because of human actions prior, during or after the disaster itself. A specific disaster may spawn different types of events and may reduce the survivability of the initial event. A classic example, is an earthquake that collapses homes, trapping people and breaking gas mains that then ignite, and burn people alive while trapped under deb ...

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Disaster, Disaster - Natural disasters, Disaster - Avalanche, Disaster - Cold, Disaster - Disease, Disaster - Drought, Disaster - Earthquake, Disaster - Famine, Disaster - Fire, Disaster - Flood, Disaster - Hail, Disaster - Heat, Disaster - Hurricane, Disaster - Impact event, Disaster - Limnic eruption, Disaster - Landslide, Disaster - Mudslide, Disaster - Sink hole, Disaster - Solar flare, Disaster - Storm surge, Disaster - Thunderstorm, Disaster - Tornado, Disaster - Tsunami, Disaster - Volcanic eruption, Disaster - Waterspout, Disaster - Winter storm, Disaster - Man-made disasters, Disaster - Aviation, Disaster - Arson, Disaster - CBRNs, Disaster - Civil disorder, Disaster - Power outage, Disaster - Public relations crisis, Disaster - Radiation Contamination, Disaster - Space Disasters, Disaster - Telecommunication outage, Disaster - Terrorism, Disaster - War, Disaster - Surviving a disaster, Disaster - Personal and family disaster preparation, Disaster - Local government and emergency services disaster preparation and management, Disaster - Business disaster preparation and management, Disaster - National disaster preparation, Disaster - Humanitarian disaster preparation, Disaster - Information security disaster preparation

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Awards Bruce Medal in 1942 Gold Medal of the Royal Astronomical Society in 1946 Henry Norris Russell Lectureship in 1951 Named after him Asteroid 1691 Oort Oort Cloud Oort constants of galactic structure ...

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Jan Oort, Jan Oort - A few of Oort's Discoveries, Jan Oort - Honors, Jan Oort - Online exhibition

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Planetary systems around sun-like stars are generally believed to form as part of the same process which results in star formation. Some early theories involved another star passing extremely close to the sun, and drawing material out from it which then coalesced to form the planets. However, the probability of such a near collision is now known to be far too low to make this a viable model. Accepted theories today argue that planetary systems form from a solar nebula. Some planetary systems are very unlike our own, however: planetary ...

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Planetary system, Planetary system - Origin and evolution of planetary systems, Planetary system - Significant planetary systems

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Water vapor - Evaporation/sublimation. Whenever a water molecule leaves a surface, it is said to have evaporated. Each water molecule that becomes water vapor takes a parcel of heat with it. This process is called evaporative cooling. The amount of water vapor in the air will determine how fast each molecule will return back to the surface or not. So, when a net evaporation occurs, that body of water ...

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Water vapor, Water vapor - General properties of water vapor, Water vapor - Evaporation/sublimation, Water vapor - Condensation, Water vapor - General Discussion, Water vapor - Water vapor in Earth's atmosphere, Water vapor - Radar and satellite imaging, Water vapor - Lightning generation, Water vapor - Extraterrestrial water vapor

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Water molecule - Density of water and ice. For most substances, the solid form of the substance is more dense than the liquid form; thus, a block of pure solid substance will sink in a tub of pure liquid substance. But, by contrast, a block of common ice will float in a tub of water because solid water is less dense than liquid water. This is an extremely important characteristic property of water. At room temperature, liquid water becomes denser with lowering temperature, just like ot ...

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Water molecule, Water molecule - Forms of water, Water molecule - A common substance, Water molecule - Water in the Universe, Water molecule - Water on Earth, Water molecule - Water in industry, Water molecule - Physics and chemistry of water, Water molecule - Density of water and ice, Water molecule - Density of saltwater and ice, Water molecule - Triple point, Water molecule - Mpemba effect, Water molecule - Hot ice, Water molecule - Surface tension, Water molecule - Electrical properties, Water molecule - Dipolar nature of water, Water molecule - Water as a solvent, Water molecule - Amphoteric nature of water, Water molecule - Acidity in nature, Water molecule - Hydrogen bonding in water, Water molecule - Quantum properties of Molecular Water, Water molecule - History, Water molecule - Systematic nomenclature and humor

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The foundations of the physical sciences rests upon key concepts and theories, each of which explains and/or models a particular aspect of the behavior of nature. As in other sciences, these key concepts and theories came to discovery using the scientific method. Natural sciences generally, and physical sciences particularly, tend to be more reductionist sciences, in contrast to the more holistic social sciences; i.e., physical science tends to explain the whole system from the system's fundamental parts, whereas social science tends to explain the whole syste ...

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Physical science, Physical science - Branches, Physical science - Basic principles, Physical science - Astronomy, Physical science - Chemistry, Physical science - Earth science, Physical science - Physics, Physical science - Notable physical scientists

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The Circumstellar habitable zone (or ecosphere) is a notional spherical shell of space surrounding stars where the surface temperatures of any planets present might maintain liquid water in which life could potentially survive. In 1959, physicists Philip Morrison and Giuseppe Cocconi described the zone in a SETI research paper. In 1961, Frank Drake popularized the concept in his Drake equation. The CHZ of a particular star is "centered" on a distance determined by the equation:

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Habitable zone, Habitable zone - The Circumstellar habitable zone, Habitable zone - The Galactic habitable zone

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The main contents of the outer solar system are probably very numerous small bodies akin to comets from one or another population, and the place where the Solar Wind meets the Interstellar Medium. Of the bodies that orbit the Sun, major constituents include the Kuiper Belt, or scattered disk objects, trans-Neptunian objects(aka TNO's), and, the unconfirmed Oort Cloud. Work by Michael E. Brown's team has brought many recent discoveries in this area. From whichever population source, Comets frequently originate within the area, their po ...

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Outer solar system, Outer solar system - Contents and Structure, Outer solar system - Influence and Evolution, Outer solar system - Scale

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The key instrument of nearly all modern observational astronomy is the telescope. This serves the dual purposes of gathering more light so that very faint objects can be observed, and magnifying the image so that small and distant objects can be observed. The optics used in a telescope have very exacting requirements which require great precision in their construction. Typical requirements for grinding and polishing a curved mirror, for example, require the surface to be within a f ...

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Observational astronomy, Observational astronomy - Unaided eye, Observational astronomy - Telescopes, Observational astronomy - Optical telescopes, Observational astronomy - Other instruments, Observational astronomy - Observation tools, Observational astronomy - Observing, Observational astronomy - Related lists

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His work was continuously disputed for many years by the senior scientist in space physics, the British-American geophysicist Sydney Chapman. Alfvén had trouble with the peer review system. He did not in any circumstance benefit without volition the acceptance generally afforded senior scientists in scientific journals. Alfvén once submitted a paper on the theory of magnetic storms and auroras to the leading American journal Terrestrial Magnetism and Atmospheric Electricity and the paper was rejected on the ground that it did not agree wit ...

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Hannes Alfvén, Hannes Alfvén - Introduction, Hannes Alfvén - Education, Hannes Alfvén - Early years, Hannes Alfvén - Research awards and contributions, Hannes Alfvén - Awards, Hannes Alfvén - Memberships, Hannes Alfvén - Developed and researched, Hannes Alfvén - Alfvén versus the Big Bang, Hannes Alfvén - Later years, Hannes Alfvén - Personal life

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To perform an orbital spaceflight, a spacecraft must go higher and faster than for a sub-orbital spaceflight. A spacecraft has not made orbit until it is circling the Earth at a sufficiently great speed such that the weight of the spacecraft is exactly equal to the centripetal acceleration required to keep it in a circular orbit (see circular motion). It must not only rise above the atmosphere, but must also achieve a sufficient orbital speed (angular velocity). For a low Earth orbit, this is about 7.9 km/s (18,000 mph). Robert God ...

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Outer space, Outer space - Milestones on the way to space, Outer space - Regions of outer space, Outer space - Space does not equal orbit

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As Friedrich Wilhelm Herschel in Hanover, Germany, one of ten children (of which four died very young). In 1755 the Hanoverian Guards regiment in whose band William and his brother Jacob were engaged was ordered to England. At the time, the crowns of England and Hanover were united under George II. He learned English quickly and, at age nineteen, he changed his name to Frederick William Herschel. He became a successful music teacher and bandleader, played the organ and the oboe, and composed numerous musical works, most ...

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William Herschel, William Herschel - Biography, William Herschel - Other astronomical work, William Herschel - Discovery of infrared radiation, William Herschel - Named after Herschel

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The most striking feature of most planetaria is their large dome shaped projection screens onto which scenes of stars, planets and other celestial objects can be made to appear and move realistically to simulate the complex 'motions of the heavens'. These domes can be anything from 3 to 30 m in diameter, accommodating from 1 to 500 people. Traditionally, planetaria domes were mounted horizontally, matching the natural horizon of the real night sky. However, because that configuration requires highly inclined chairs for comfortable vie ...

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Planetarium, Planetarium - Overview, Planetarium - History, Planetarium - Notable planetariums, Planetarium - Planetarium computer software

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The current system of provisional designation of asteroids has been in place since 1925, and superseded several previous conventions, each of which was rendered obsolete by the increasing numbers of asteroid discoveries. Provisional designation in astronomy - Historical designations. The first four asteroids were discovered in the early 19th century, after which there was a lengthy gap before the discovery of the fifth. Astronomers initially had no reason to believe that there would be countless thousands ...

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Provisional designation in astronomy, Provisional designation in astronomy - Asteroids, Provisional designation in astronomy - Historical designations, Provisional designation in astronomy - Genesis of the current system, Provisional designation in astronomy - Later refinements, Provisional designation in astronomy - Examples, Provisional designation in astronomy - Comets, Provisional designation in astronomy - Satellites of planets, Provisional designation in astronomy - Asteroid moons

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In ancient Greece and other early civilizations, astronomy consisted largely of astrometry, measuring positions of stars and planets in the sky. Later, with the work of astronomers Kepler and Newton, whose work led to the development of celestial mechanics, the mathematical prediction of the motions of celestial bodies interacting gravitationally became the focus of astronomy. This was applied to solar system objects in particular. Motions and positions of objects are now more easily determined, and modern astronomy is more concerned with observing and understanding the actua ...

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Astronomy, Astronomy - Divisions, Astronomy - By subject or problem addressed, Astronomy - Ways of obtaining information, Astronomy - History of astronomy, Astronomy - Timelines in astronomy, Astronomy - Astronomy tools

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Until the rise of space travel in the twentieth century, there was little distinction between astrodynamics and celestial mechanics. The fundamental techniques, such as those used to solve the Keplerian problem, are therefore the same in both fields. Furthermore, the history of the fields is essentially identical. Astrodynamics - Kepler's equation. Kepler was the first to successfully model ...

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Astrodynamics, Astrodynamics - Laws of astrodynamics, Astrodynamics - Formulae for ellipse, Astrodynamics - Historical approaches, Astrodynamics - Kepler's equation, Astrodynamics - Perturbation theory, Astrodynamics - Modern techniques, Astrodynamics - Conic orbits, Astrodynamics - Transfer orbits, Astrodynamics - The patched conic approximation, Astrodynamics - The universal variable formulation, Astrodynamics - Perturbations, Astrodynamics - Non-ideal orbits, Astrodynamics - Interplanetary superhighway and fuzzy orbits, Astrodynamics - Reference

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The concept for an ultraviolet spectographic astronomnical satellite was first proposed to ESRO, the fore-runner to ESA, by a group of British scientists in 1964. The proposal at the time was beyond the technological capability of ESA and so the concept was offered by Robert Wilson to NASA, who took up the idea and developed it as SAS-D (Small Astronomy Satellite-D). SERC joined the resulting project and provided the Vidicon cameras for the spectrographs as well as software for the scientific instruments. ESA provided the solar arrays to pow ...

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International Ultraviolet Explorer, International Ultraviolet Explorer - Project History, International Ultraviolet Explorer - Scientific Firsts and Discoveries

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Astronomical spectroscopy began with Isaac Newton's initial observations of the light of the Sun, dispersed by a prism. He saw a rainbow of colour, and may even have seen absorption lines. These dark bands which appear throughout the solar spectrum were first described in detail by Joseph von Fraunhofer. Most stellar spectra share these two dominant features of the Sun's spectrum: emission at all wavelengths across the optical spectrum (the continuum) with ...

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Astronomical spectroscopy, Astronomical spectroscopy - Stars, Astronomical spectroscopy - Nebulae, Astronomical spectroscopy - Galaxies, Astronomical spectroscopy - Quasars, Astronomical spectroscopy - Planets and asteroids, Astronomical spectroscopy - Comets

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Astrophysical maser - Discrete Transition Energy. Like a laser, the emission from a maser is stimulated (or seeded) and monochromatic, having the frequency corresponding to the energy difference between two quantum-mechanical energy levels of the species in the gain medium which have been pumped into a non-thermal population distribution. However, naturally occurring masers lack the resonant cavity engineered for terrestrial laboratory masers. Indeed, the emission from an astrophysical maser is due to a single pass through the gain medium and th ...

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Astrophysical maser, Astrophysical maser - Background, Astrophysical maser - Discrete Transition Energy, Astrophysical maser - Nomenclature, Astrophysical maser - Astrophysical conditions, Astrophysical maser - Discovery, Astrophysical maser - Historical background, Astrophysical maser - Anti-pumped absorption, Astrophysical maser - Known Interstellar Species, Astrophysical maser - Maser environments, Astrophysical maser - Comets and planetary Atmospheres, Astrophysical maser - Stellar atmospheres, Astrophysical maser - Star-forming regions, Astrophysical maser - Supernova remnants, Astrophysical maser - Extragalactic sources, Astrophysical maser - Ongoing research, Astrophysical maser - Variability, Astrophysical maser - Open questions

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