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Magnitude (astronomy)
In astronomy, magnitude is a measure of the brightness of an astronomical object, object, usually in a defined passband. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus. Magnitude values do not have a unit. The scale is Logarithmic scale, logarithmic and defined such that a magnitude 1 star is exactly 100 times brighter than a magnitude 6 star. Thus each step of one magnitude is \sqrt[5] \approx 2.512 times brighter than the magnitude 1 higher. The brighter an object appears, the lower the value of its magnitude, with the brightest objects reaching negative values. Astronomers use two different definitions of magnitude: apparent magnitude and absolute magnitude. The ''apparent'' magnitude () is the brightness of an object and depends on an object's intrinsic luminosity, its Cosmic distance ladder, distance, and the Extinction (astronomy), extinction reducing its brightness. The ''absolute'' magnitude () describes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnitude Illustration
Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of magnitude, the class of scale having a fixed value ratio to the preceding class *Scalar (mathematics), a quantity defined only by its magnitude Astronomy * Absolute magnitude, the brightness of a celestial object corrected to a standard luminosity distance *Apparent magnitude, the calibrated apparent brightness of a celestial object * Instrumental magnitude, the uncalibrated apparent magnitude of a celestial object * Limiting magnitude, the faintest apparent magnitude of a celestial body that is detectable or detected by a given instrument. *Magnitude (astronomy), a measure of brightness and brightness differences used in astronomy * Magnitude of eclipse or geometric magnitude, the size of the eclipsed part of the Sun during a solar eclip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker and denser than Earth and any other rocky body in the Solar System. Its atmosphere is composed of mostly carbon dioxide (), with a global sulfuric acid cloud cover and no liquid water. At the mean surface level the atmosphere reaches a temperature of and a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the atmosphere into a supercritical fluid. Venus is the third brightest object in Earth's sky, after the Moon and the Sun, and, like Mercury, appears always relatively close to the Sun, either as a "morning star" or an "evening star", resulting from orbiting closer ( inferior) to the Sun than Earth. The orbits of Venus and Earth make the two planets approach each other in synodic periods of 1.6 years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galileo Galilei
Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a polymath. He was born in the city of Pisa, then part of the Duchy of Florence. Galileo has been called the father of observational astronomy, modern-era classical physics, the scientific method, and modern science. Galileo studied speed and velocity, gravity and free fall, the principle of relativity, inertia, projectile motion and also worked in applied science and technology, describing the properties of the pendulum and "hydrostatic balances". He was one of the earliest Renaissance developers of the thermoscope and the inventor of various sector (instrument), military compasses. With an improved telescope he built, he observed the stars of the Milky Way, the phases of Venus, the Galilean moons, four largest satellites of Jupiter, Saturn's r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minute Of Arc
A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a turn. The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth's circumference is very near . A minute of arc is of a radian. A second of arc, arcsecond (abbreviated as arcsec), or arc second, denoted by the symbol , is a unit of angular measurement equal to of a minute of arc, of a degree, of a turn, and (about ) of a radian. These units originated in Babylonian astronomy as sexagesimal (base 60) subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying, and marksmanship. To express even smaller angles, standard SI prefixes can be employed; the milliar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tycho Brahe
Tycho Brahe ( ; ; born Tyge Ottesen Brahe, ; 14 December 154624 October 1601), generally called Tycho for short, was a Danish astronomer of the Renaissance, known for his comprehensive and unprecedentedly accurate astronomical observations. He was known during his lifetime as an astronomer, astrologer, and alchemist. He was the last major astronomer before the invention of the telescope. Tycho Brahe has also been described as the greatest pre-telescopic astronomer. In 1572, Tycho noticed a completely SN 1572, new star that was brighter than any star or planet. Astonished by the existence of a star that ought not to have been there, he devoted himself to the creation of ever more accurate instruments of measurement over the next fifteen years (1576–1591). Frederick II of Denmark, King Frederick II granted Tycho an estate on the island of Hven and the money to build Uraniborg, the first large observatory in Christian Europe. He later worked underground at Stjerneborg, where he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Keill
John Keill FRS (1 December 1671 – 31 August 1721) was a Scottish mathematician, natural philosopher, and cryptographer who was an important defender of Isaac Newton. Biography Keill was born in Edinburgh, Scotland on 1 December 1671. His father was Robert Keill, an Edinburgh lawyer. His mother was Sarah Cockburn. His brother, James Keill, became a noted physician. Keill studied at Edinburgh University under David Gregory. In 1692, he obtained his bachelor's degree with a distinction in physics and mathematics. Keill then attended Balliol College, Oxford, obtaining an MA on 2 February 1694. After being appointed a lecturer in experimental philosophy at Hart Hall, Keill started giving lectures and performing experiments based on Newton's findings. He instructed his students on the laws of motion, the principles of hydrostatics and optics, and Newtonian propositions on light and colours. In 1698, Keill published ''Examination of Dr. Burnet's Theory of the Earth''. His vo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mizar And Alcor
Mizar and Alcor are two stars forming a naked eye double in the handle of the Big Dipper (or Plough) asterism in the constellation of Ursa Major. Their magnitudes are 2.2 and 3.9, and the pair can easily be seen without the aid of a telescope. Mizar and its fainter companion Alcor are actually a four-star binary system consisting of two pairs of double stars that are gravitationally bound to each other. The traditional name Mizar derives from the Arabic المئزر or miʼzar, meaning "apron; wrapper, covering, cover". Alcor was originally the Arabic سها or Suhā/Sohā, meaning either the "forgotten" or "neglected" one. The ancient Persians and the Bedouins used distinguishing Mizar and Alcor as a test of vision. Mizar, also designated Zeta Ursae Majoris (ζ Ursae Majoris, abbreviated Zeta UMa, ζ UMa), is itself a quadruple system and Alcor, also designated 80 Ursae Majoris (80 UMa), is a binary, the pair together forming a sextuple system. In fact, Mizar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arcturus
, - bgcolor="#FFFAFA" , Note (category: variability): , , H and K emission vary. Arcturus is a red giant star in the Northern celestial hemisphere, northern constellation of Boötes, and the brightest star in the constellation. It has the Bayer designation α Boötis, which is Latinisation of names, Latinized to Alpha Boötis and abbreviated Alf Boo or α Boo. With an apparent visual magnitude of −0.05, it is the List of brightest stars, fourth-brightest star in the night sky and the brightest in the northern celestial hemisphere. Arcturus forms one corner of the Spring Triangle Asterism (astronomy), asterism. Located relatively close at 36.7 light-years from the Sun, Arcturus is a red giant of Stellar classification, spectral type K1.5III—an aging star around 7.1 billion years old that has used up its Stellar core, core hydrogen and stellar evolution, evolved off the main sequence. It is about the same mass Solar mass, as the Sun, but has expanded to 25 times Sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnitude
Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of magnitude, the class of scale having a fixed value ratio to the preceding class *Scalar (mathematics), a quantity defined only by its magnitude Astronomy * Absolute magnitude, the brightness of a celestial object corrected to a standard luminosity distance *Apparent magnitude, the calibrated apparent brightness of a celestial object * Instrumental magnitude, the uncalibrated apparent magnitude of a celestial object * Limiting magnitude, the faintest apparent magnitude of a celestial body that is detectable or detected by a given instrument. *Magnitude (astronomy), a measure of brightness and brightness differences used in astronomy * Magnitude of eclipse or geometric magnitude, the size of the eclipsed part of the Sun during a solar eclip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ptolemy
Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzantine, Islamic science, Islamic, and Science in the Renaissance, Western European science. The first was his astronomical treatise now known as the ''Almagest'', originally entitled ' (, ', ). The second is the ''Geography (Ptolemy), Geography'', which is a thorough discussion on maps and the geographic knowledge of the Greco-Roman world. The third is the astrological treatise in which he attempted to adapt horoscopic astrology to the Aristotelian physics, Aristotelian natural philosophy of his day. This is sometimes known as the ' (, 'On the Effects') but more commonly known as the ' (from the Koine Greek meaning 'four books'; ). The Catholic Church promoted his work, which included the only mathematically sound geocentric model of the Sola ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iridium Flare 2008 08 11
Iridium is a chemical element; it has the symbol Ir and atomic number 77. This very hard, brittle, silvery-white transition metal of the platinum group, is considered the second-densest naturally occurring metal (after osmium) with a density of as defined by experimental X-ray crystallography. 191Ir and 193Ir are the only two naturally occurring isotopes of iridium, as well as the only stable isotopes; the latter is the more abundant. It is one of the most corrosion-resistant metals, even at temperatures as high as . Iridium was discovered in 1803 in the acid-insoluble residues of platinum ores by the English chemist Smithson Tennant. The name ''iridium'', derived from the Greek word ''iris'' (rainbow), refers to the various colors of its compounds. Iridium is one of the rarest elements in Earth's crust, with an estimated annual production of only in 2023. The dominant uses of iridium are the metal itself and its alloys, as in high-performance spark plugs, crucibles for rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Illuminance
In photometry (optics), photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception.International Electrotechnical Commission (IEC): ''International Electrotechnical Vocabulary.'ref. 845-21-060, illuminance/ref> Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance. In SI derived units, SI units illuminance is measured in lux (lx), or equivalently in lumen (unit), lumens per square metre (Lumen (unit), lm·meter, m−2). Luminous exitance is measured in lm·m−2 only, not lux. International Electrotechnical Commission (IEC): ''International Electrotechnical Vocabulary.'ref. 845-21-081, luminous exitance/ref> In the CGS system, the unit of illuminance is the phot, which is equal to . The foot-candle is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
