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Kappa Draconis
Kappa Draconis, Latinisation of names, Latinized from κ Draconis, is a blue giant star located in the northern circumpolar constellation of Draco (constellation), Draco. At an apparent magnitude of 3.88, it is barely visible to the naked eye when artificial lighting from cities is present. Nevertheless, it is a powerful star, approximately five time as massive as the Sun. It is about 460 light-years away, and is 1,400 times brighter than the Sun. The star is currently located at declination (right ascension ), but due to the effects of precession, Kappa Draconis was the nearest star to the north celestial pole visible to the naked eye from 1793 BC to approximately 1000 BC, though it was 6° removed from perfect alignment, making it only an approximate pole star, similar to the roughly 7° variance from perfect alignment of the much brighter (magnitude 2.08) star Beta Ursae Minoris, Kochab, at the same time during Earth's precession. Properties Kappa Draconis is a clas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Draco (constellation)
Draco is a constellation in the far northern sky. Its name is Latin for dragon. It was one of the 48 Lists of constellations, constellations listed by the 2nd century Greek astronomer Ptolemy, and remains one of the 88 modern constellations today. The north pole of the ecliptic is in Draco. Draco is circumpolar star, circumpolar from northern latitudes, meaning that it never sets and can be seen at any time of year. Features Stars Thuban (α Draconis) was the northern pole star from 3942 BC, when it moved farther north than Theta Boötis, until 1793 BC. The Egyptian Pyramids were designed to have one side facing north, with an entrance passage geometrically aligned so that Thuban would be visible at night. Due to the effects of Axial precession (astronomy), precession, it will again be the pole star around the year AD 21000. It is a blue-white giant star of magnitude 3.7, 309 light-years from Earth. The traditional name of Alpha Draconis, Thuban, means "head of the serpe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Spectrum
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects. A stellar spectrum can reveal many properties of stars, such as their chemical composition, temperature, density, mass, distance and luminosity. Spectroscopy can show the velocity of motion towards or away from the observer by measuring the Doppler shift. Spectroscopy is also used to study the physical properties of many other types of celestial objects such as planets, nebulae, galaxies, and active galactic nuclei. Background Astronomical spectroscopy is used to measure three major bands of radiation in the electromagnetic spectrum: visible light, radio waves, and X-rays. While all spectroscopy looks at specific bands of the spectrum, different methods are required to acquire the signal depending on the freque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda Draconis
Lambda Draconis (λ Draconis, abbreviated Lam Dra, λ Dra), also named Giausar ( ), is a solitary, orange-red star in the northern circumpolar constellation of Draco. It is visible to the naked eye with an apparent visual magnitude of +3.85. Based upon an annual parallax shift of 9.79 mas as seen from the Earth, the star is located around 333 light years from the Sun. This is an evolved red giant star on the asymptotic giant branch with a stellar classification of M0III-IIIa Ca1. It is a suspected slow irregular variable with a periodicity of roughly 1,100 days. It has an estimated 1.53 times the mass of the Sun and a measured radius of 70 times the radius of the Sun. It is radiating 884 times the solar luminosity from its photosphere at an effective temperature of 3,761 K. Nomenclature λ Draconis ( Latinised to ''Lambda Draconis'') is the star's Bayer designation. It bore the traditional name ''Giausar'' (also written as ''Gianfar, Giansar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Draconis
Thuban (), with Bayer designation Alpha Draconis or α Draconis, is a binary star system in the northern constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star from the 4th to 2nd millennium BC. Johann Bayer gave Thuban the designation Alpha and placed it as the only member of his ''secundae'' magnitude class in Draco, although its current apparent magnitude of 3.65 means it is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis (Eltanin), which Bayer placed in his ''tertiae'' magnitude class although its current apparent magnitude is 2.24. Nomenclature ''α Draconis'' ( Latinised to ''Alpha Draconis'') is the star's Bayer designation. The traditional name ''Thuban'' is derived from the Arabic word ' ('large snake' (e.g. a python or a legendary draconian serpent)). It is sometimes known as the ''Dragon's Tail'' and as ''Adib'' . ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purple Forbidden Enclosure
The Purple Forbidden enclosure ( Zǐ wēi yuán) is one of the San Yuan ( Sān yuán) or Three Enclosures. Stars and constellations of this group lie near the north celestial pole and are visible all year from temperate latitudes in the Northern Hemisphere. Asterisms The asterisms are: See also * Twenty-Eight Mansions The Twenty-Eight Mansions (), also called or , are part of the Chinese constellations system. They can be considered as the equivalent to the Zodiac, zodiacal constellations in Western astronomy, though the Twenty-eight Mansions reflect the move ... References Chinese constellations Chinese astrology Purple {{china-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Astronomy
Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The Ancient China, ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categorized in the twenty-eight mansions have been found on oracle bones unearthed at Anyang, dating back to the mid-Shang dynasty. The core of the "mansion" (宿 ''xiù'') system also took shape around this period, by the time of King Wu Ding (1250–1192 BCE). Detailed records of astronomical observations began during the Warring States period (fourth century BCE). They flourished during the Han period (202 BCE – 220 CE) and subsequent dynasties with the publication of star catalogues. Chinese astronomy was equatorial, centered on close observation of circumpolar stars, and was based on different principles from those in traditional Western astronomy, where heliacal risings and settings of zodiac constellations formed the basic ecliptic framew ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kappa Draconis
Kappa Draconis, Latinisation of names, Latinized from κ Draconis, is a blue giant star located in the northern circumpolar constellation of Draco (constellation), Draco. At an apparent magnitude of 3.88, it is barely visible to the naked eye when artificial lighting from cities is present. Nevertheless, it is a powerful star, approximately five time as massive as the Sun. It is about 460 light-years away, and is 1,400 times brighter than the Sun. The star is currently located at declination (right ascension ), but due to the effects of precession, Kappa Draconis was the nearest star to the north celestial pole visible to the naked eye from 1793 BC to approximately 1000 BC, though it was 6° removed from perfect alignment, making it only an approximate pole star, similar to the roughly 7° variance from perfect alignment of the much brighter (magnitude 2.08) star Beta Ursae Minoris, Kochab, at the same time during Earth's precession. Properties Kappa Draconis is a clas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: * ''Intrinsic variables'', whose luminosity actually changes periodically; for example, because the star swells and shrinks. * ''Extrinsic variables'', whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Many, possibly most, stars exhibit at least some oscillation in luminosity: the energy output of the Sun, for example, varies by about 0.1% over an 11-year solar cycle. Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Irregular Variable
An irregular variable is a type of variable star in which variations in brightness show no regular periodicity. There are two main sub-types of irregular variable: eruptive and pulsating. Eruptive irregular variables are divided into three categories: * Group I variables are split into subgroups IA (spectral types O to A) and IB (spectral types F through M). * Orion variables, GCVS type IN (irregular and nebulous), indigenous to star-forming regions, may vary by several magnitudes with rapid changes of up to 1 magnitude in 1 to 10 days, are similarly divided by spectral type into subgroups INA and INB, but with the addition of another subgroup, INT, for T Tauri stars, or INT(YY) for YY Orionis stars. * The third category of eruptive irregulars are the IS stars, which show rapid variations of 0.5 to 1 magnitude in a few hours or days; again, these come in subgroups ISA and ISB. Pulsating irregular giants or supergiants, called slow irregular variable A slow irregular variable (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Catalogue Of Variable Stars
The General Catalogue of Variable Stars (GCVS) is a list of variable stars in the Milky Way Galaxy. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR, edited by and Pavel Parenago. Second and third editions were published in 1958 and 1968. The fourth edition, containing 28,435 stars, was published in three volumes in 1985–1987. Later, two more volumes were published: the fourth volume containing reference tables and the fifth volume containing extragalactic variable stars. The first release of the fifth edition (GCVS 5.1), which is periodically updated, currently contains 58,035 variable stars; it is available at the GCVS website and at the VizieR A vizier (; ; ) is a high-ranking political advisor or Minister (government), minister in the Near East. The Abbasids, Abbasid caliphs gave the title ''wazir'' to a minister formerly called ''katib'' (secretary), who was at first merely a help ... astronomical catalogue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectroscopic Binary
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars using a telescope, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough, they can gravitationally distort each other's outer stellar atmospheres. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Core
A stellar core is the extremely hot, dense region at the center of a star. For an ordinary main sequence star, the core region is the volume where the temperature and pressure conditions allow for energy production through thermonuclear fusion of hydrogen into helium. This energy in turn counterbalances the mass of the star pressing inward; a process that self-maintains the conditions in Thermal equilibrium, thermal and hydrostatic equilibrium. The minimum temperature required for stellar hydrogen fusion exceeds 107 Kelvin, K (), while the density at the core of the Sun is over . The core is surrounded by the stellar envelope, which transports energy from the core to the stellar atmosphere where it is radiated away into space. Main sequence Main sequence stars are distinguished by the primary energy-generating mechanism in their central region, which joins four hydrogen nuclei to form a single helium atom through thermonuclear fusion. The Sun is an example of this class of star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
