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DI Lacertae
DI Lacertae or Nova Lacertae 1910 was a nova in constellation Lacerta which appeared in 1910. It was discovered by Thomas Henry Espinell Compton Espin at Wolsingham Observatory on 30 Dec 1910, at which time it was an 8th magnitude object. Subsequent examination of pre-discovery photographic plates showed that the outburst occurred sometime between 17 November 1910 and 23 November 1910. It reached a peak brightness of magnitude 4.6 on 26 November 1910, making it visible to the naked eye. Before the nova event DI Lacertae was a 14th magnitude star, and by 1950 it had returned to 14th magnitude. DI Lacertae dropped from peak brightness by 3 magnitudes in just 43 days, making it a "fast nova". All novae are binary stars, with a "donor" star orbiting a white dwarf. The two stars are so close to each other that matter is transferred from the donor star to the white dwarf. In the case of DI Lacertae, the oribital period for the binary pair is 13.050 hours, which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving the positions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Luyten in 1922. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red gi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1910 In Science
The year 1910 in science and technology involved some significant events, listed below. Astronomy * May 18 – Earth passes through the tail of Halley's Comet. * Approximate date – The Hertzsprung–Russell diagram is developed by Ejnar Hertzsprung and Henry Norris Russell. Cartography * Behrmann projection introduced. Chemistry * Albert Einstein and Marian Smoluchowski find the Einstein-Smoluchowski formula for the attenuation coefficient due to density fluctuations in a gas. * Umetaro Suzuki isolates the first vitamin complex, aberic acid. * Hoechst AG market Arsphenamine under the trade name '' Salvarsan'', the first organic antisyphilitic, its properties having been discovered the previous fall by bacteriologist Sahachiro Hata during systematic testing in the laboratory of Paul Ehrlich; it rapidly becomes the world's most widely prescribed drug. * George Barger and James Ewens of Wellcome Laboratories in London first synthesize dopamine. Mathematics * Publication of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lacerta
Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for lizard. A small, faint constellation, it was defined in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a "W" shape similar to that of Cassiopeia, and it is thus sometimes referred to as 'Little Cassiopeia'. It is located between Cygnus, Cassiopeia and Andromeda on the northern celestial sphere. The northern part lies on the Milky Way. Notable features Lacerta is typical of Milky Way constellations: no bright galaxies, nor globular clusters, but instead open clusters, for example NGC 7243, the faint planetary nebula IC 5217 and quite a few double stars. It also contains the prototypic blazar BL Lacertae. Lacerta contains no Messier objects. Stars Alpha Lacertae is a blue-white hued main-sequence star of magnitude 3.8, 102 light-years from Earth. It has a spectral type of A1 V and is an optical double star. Beta Lacertae is far ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Novae
A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramatic appearance of a nova vary, depending on the circumstances of the two progenitor stars. All observed novae involve white dwarfs in close binary systems. The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae. They are all considered to be cataclysmic variable stars. Classical nova eruptions are the most common type. They are likely created in a close binary star system consisting of a white dwarf and either a main sequence, subgiant, or red giant star. When the orbital period falls in the range of several days to one day, the white dwarf is close enough to its companion star to start drawing accreted matter onto the surface of the white dwarf, which creates a dense but shallow atmosphere. This atmosp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subdwarf
A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the same spectral type. On a Hertzsprung–Russell diagram subdwarfs appear to lie below the main sequence. The term "subdwarf" was coined by Gerard Kuiper in 1939, to refer to a series of stars with anomalous spectra that were previously labeled as "intermediate white dwarfs". Cool subdwarfs Like ordinary main-sequence stars, cool subdwarfs (of spectral types G to M) produce their energy from hydrogen fusion. The explanation of their underluminosity lies in their low metallicity: these stars are unenriched in elements heavier than helium. The lower metallicity decreases the opacity of their outer layers and decreases the radiation pressure, resulting in a smaller, hotter star for a given mass. This lower opacity also allows them to emit a higher pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Main Sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. Stars on this band are known as main-sequence stars or dwarf stars. These are the most numerous true stars in the universe and include the Sun. After condensation and ignition of a star, it generates thermal energy in its dense core region through nuclear fusion of hydrogen into helium. During this stage of the star's lifetime, it is located on the main sequence at a position determined primarily by its mass but also based on its chemical composition and age. The cores of main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. The strong dependence of the rate of energy ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretion Disk
An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other forces induce instabilities causing orbiting material in the disk to spiral inward towards the central body. Gravitational and frictional forces compress and raise the temperature of the material, causing the emission of electromagnetic radiation. The frequency range of that radiation depends on the central object's mass. Accretion disks of young stars and protostars radiate in the infrared; those around neutron stars and black holes in the X-ray part of the spectrum. The study of oscillation modes in accretion disks is referred to as diskoseismology. Manifestations Accretion disks are a ubiquitous phenomenon in astrophysics; active galactic nuclei, protoplanetary disks, and gamma ray bursts all involve accretion disks. These disks ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Ultraviolet Explorer
International Ultraviolet Explorer (IUE or Explorer 57, formerly SAS-D), was the first space observatory primarily designed to take ultraviolet (UV) electromagnetic spectrum. The satellite was a collaborative project between NASA, the United Kingdom's Science and Engineering Research Council (SERC, formerly UKSRC) and the European Space Agency (ESA), formerly European Space Research Organisation (ESRO). The mission was first proposed in early 1964, by a group of scientists in the United Kingdom, and was launched on 26 January 1978 aboard a NASA Thor-Delta 2914 launch vehicle. The mission lifetime was initially set for 3 years, but in the end it lasted 18 years, with the satellite being shut down in 1996. The switch-off occurred for financial reasons, while the telescope was still functioning at near original efficiency. It was the first space observatory to be operated in real time by astronomers who visited the groundstations in the United States and Europe. Astronomers made ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Far Ultraviolet Spectroscopic Explorer
Far Ultraviolet Spectroscopic Explorer (FUSE, Explorer 77, and MIDEX-0) represented the next generation, high-orbit, ultraviolet space observatory covering the wavelength range of 90.5–119.5 nanometre (nm) of the NASA operated by the Johns Hopkins University Applied Physics Laboratory. FUSE was launched on a Delta II launch vehicle on 24 June 1999, at 15:44:00 UTC, as a part of NASA's Origins Program. FUSE detected light in the far ultraviolet portion of the electromagnetic spectrum, which is mostly unobservable by other telescopes. Its primary mission was to characterize universal deuterium in an effort to learn about the stellar processing times of deuterium left over from the Big Bang. FUSE resides in a low Earth orbit, approximately in altitude, with an inclination of 24.98° and a 99.80 minutes orbital period. Its Explorer program designation is Explorer 77. Mission The primary objective of FUSE was to use high-resolution spectroscopy at far ultraviolet waveleng ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photographic Plate
Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinner than common window glass. History Glass plates were far superior to film for research-quality imaging because they were stable and less likely to bend or distort, especially in large-format frames for wide-field imaging. Early plates used the wet collodion process. The wet plate process was replaced late in the 19th century by gelatin dry plates. A view camera nicknamed "The Mammoth" weighing was built by George R. Lawrence in 1899, specifically to photograph "The Alton Limited" train owned by the Chicago & Alton Railway. It took photographs on glass plates measuring × . Glass plate photographic material largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Celestial Reference System
The International Celestial Reference System (ICRS) is the current standard celestial reference system adopted by the International Astronomical Union (IAU). Its origin is at the barycenter of the Solar System, with axes that are intended to "show no global rotation with respect to a set of distant extragalactic objects". This fixed reference system differs from previous reference systems, which had been based on Catalogues of Fundamental Stars that had published the positions of stars based on direct "observations of heir equatorial coordinates, right ascension and declination" and had adopted as "privileged axes ... the mean equator and the dynamical equinox" at a particular date and time. The International Celestial Reference Frame (ICRF) is a realization of the International Celestial Reference System using reference celestial sources observed at radio wavelengths. In the context of the ICRS, a reference ''frame'' (RF) is the physical realization of a reference ''syste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
