:: wikimiki.org ::
| Elongation |
Elongation
Elongation is an astronomical term that refers to the angle between the Sun and a planet, as viewed from Earth.
When an inferior planet is visible after sunset, it is near its greatest eastern elongation. When an inferior planet is visible before sunrise, it is near its greatest western elongation. The value of the greatest elongation (west or east), for Mercury, is between 18° and 28°; and for Venus between 45° and 47°.
Unfortunately for observers in the Northern hemishere, the largest elongations of Mercury take place when the ecliptic has a low inclination toward the horizon, so it is in areas northwards approximately 40° not to see Mercury at its greatest elongations with the naked eye.
See also
- Astronomical conjunction
Category:Spherical astronomy
Category:Celestial mechanics
Astronomical:This article is about the science branch. For information about the magazine, see Astronomy (magazine).
Astronomy (magazine) as they circled the Moon in 1969. Located near the center of the far side of Earth's Moon, its diameter is about 58 miles (93 km).]]
Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, "law of the stars") is the science of celestial objects and phenomena that originate outside the Earth's atmosphere, such as stars, planets, comets, galaxies, and the cosmic background radiation. It is concerned with the formation and development of the universe, the evolution and physical and chemical properties of celestial objects and the calculation of their motions. Astronomical observations are not only relevant for astronomy as such, but provide essential information for the verification of fundamental theories in physics, such as general relativity theory. Complementary to observational astronomy, theoretical astrophysics seeks to explain astronomical phenomena.
Astronomy is one of the oldest sciences, with a scientific methodology existing at the time of Ancient Greece and advanced observation techniques possibly much earlier (see archaeoastronomy). Historically, amateurs have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena.
Astronomy is not to be confused with astrology, which assumes that people's destiny and human affairs in general are correlated to the apparent positions of astronomical objects in the sky -- although the two fields share a common origin, they are quite different; astronomers embrace the scientific method, while astrologers do not.
In other words, there is no proof that the stars predict our future, but there is proof
that our planet is 93 million miles from the sun.
Divisions
In ancient Greece and other early civilizations, astronomy consisted largely of astrometry, measuring positions of stars and planets in the sky. Later, the work of Kepler and Newton, whose work led to the development of celestial mechanics, mathematically predicting the motions of celestial bodies interacting under gravity, and solar system objects in particular. Much of the effort in these two areas, once done largely by hand, is highly automated nowadays, to the extent that they are rarely considered as independent disciplines anymore. Motions and positions of objects are now more easily determined, and modern astronomy is more concerned with observing and understanding the actual physical nature of celestial objects.
Since the twentieth century, the field of professional astronomy has split into observational astronomy and theoretical astrophysics. Although most astronomers incorporate elements of both into their research, because of the different skills involved, most professional astronomers tend to specialize in one or the other. Observational astronomy is concerned mostly with acquiring data, which involves building and maintaining instruments and processing the results; this branch is at times referred to as "astrometry" or simply as "astronomy". Theoretical astrophysics is concerned mainly with ascertaining the observational implications of different models, and involves working with computer or analytic models.
The fields of study can also be categorized in other ways. Categorization by the region of space under study (for example, Galactic astronomy, Planetary Sciences); by subject, such as star formation or cosmology; or by the method used for obtaining information.
By subject or problem addressed
theoretical astrophysics. Photographed by Mars Global Surveyor, the long dark streak is formed by a moving swirling column of Martian atmosphere (with similarities to a terrestrial tornado). The dust devil itself (the black spot) is climbing the crater wall. The streaks on the right are sand dunes on the crater floor.]]
- Astrometry: the study of the position of objects in the sky and their changes of position. Defines the system of coordinates used and the kinematics of objects in our galaxy.
- Astrophysics: the study of physics of the universe, including the physical properties (luminosity, density, temperature, chemical composition) of astronomical objects.
- Cosmology: the study of the origin of the universe and its evolution. The study of cosmology is theoretical astrophysics at its largest scale.
- Galaxy formation and evolution: the study of the formation of the galaxies, and their evolution.
- Galactic astronomy: the study of the structure and components of our galaxy and of other galaxies.
- Extragalactic astronomy: the study of objects (mainly galaxies) outside our galaxy.
- Stellar astronomy: the study of the stars.
- Stellar evolution: the study of the evolution of stars from their formation to their end as a stellar remnant.
- Star formation: the study of the condition and processes that led to the formation of stars in the interior of gas clouds, and the process of formation itself.
- Planetary Sciences: the study of the planets of the Solar System.
- Astrobiology: the study of the advent and evolution of biological systems in the Universe.
Other disciplines that may be considered part of astronomy:
- Archaeoastronomy
- Astrochemistry
- Astrosociobiology
- Astrophilosophy
See the list of astronomical topics for a more exhaustive list of astronomy-related pages.
Ways of obtaining information
list of astronomical topics
:Main article: Observational astronomy.
In astronomy, information is mainly received from the detection and analysis of light and other forms of electromagnetic radiation. Other cosmic rays are also observed, and several experiments are designed to detect gravitational waves in the near future.
A traditional division of astronomy is given by the region of the electromagnetic spectrum observed:
- Optical astronomy is the part of astronomy that uses optical components (mirrors, lenses, CCD detectors and photographic films) to observe light from near infrared to near ultraviolet wavelengths. Visible light astronomy (using wavelengths that can be detected with the eyes, about 400 - 700 nm) falls in the middle of this range. The most common tool is the telescope, with electronic imagers and spectrographs.
- Infrared astronomy deals with the detection and analysis of infrared radiation (wavelengths longer than red light). The most common tool is the telescope but using a detector which is sensitive to the infrared. Space telescopes are also used to avoid atmospheric thermal emission, atmospheric opacity, and the effects of astronomical seeing at infrared and other wavelengths.
- Radio astronomy detects radiation of millimetre to dekametre wavelength. The receivers are similar to those used in radio broadcast transmission but much more sensitive. See also Radio telescopes.
- High-energy astronomy includes X-ray astronomy, gamma-ray astronomy, and extreme UV (ultraviolet) astronomy, as well as studies of neutrinos and cosmic rays.
Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere is transparent at the wavelengths being detected. Infrared light is heavily absorbed by water vapor, so infrared observatories have to be located in high, dry places or in space.
The atmosphere is opaque at the wavelengths of X-ray astronomy, gamma-ray astronomy, UV astronomy and (except for a few wavelength "windows") Far infrared astronomy, so observations
must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however be detected by the large air showers they produce, and the study of cosmic rays can also be regarded as a branch of astronomy.
History of astronomy
cosmic ray
:Main article: History of astronomy.
In early times, astronomy only comprised the observation and predictions of the motions of the naked-eye objects. Aristotle said that the Earth was the center of the Universe and everything rotated around it in orbits that were perfect circles. Aristotle had to be right because people thought that Earth had to be in the center with everything rotating around it because the wind would not scatter leaves, and birds would only fly in one direction. For a long time, people thought that Aristotle was right, but it is probable that Aristotle accidentally did more to hinder our knowledge than help it.
The Rigveda refers to the 27 constellations associated with the motions of the sun and also the 12 zodiacal divisions of the sky. The ancient Greeks made important contributions to astronomy, among them the definition of the magnitude system. The Bible contains a number of statements on the position of the earth in the universe and the nature of the stars and planets, most of which are poetic rather than literal; see Biblical cosmology. In 500 AD, Aryabhata presented a mathematical system that described the earth as spinning on its axis and considered the motions of the planets with respect to the sun.
Observational astronomy was mostly stagnant in medieval Europe, but flourished in the Iranian world and other parts of Islamic realm. The late 9th century Persian astronomer al-Farghani wrote extensively on the motion of celestial bodies. His work was translated into Latin in the 12th century. In the late 10th century, a huge observatory was built near Tehran, Persia (now Iran), by the Persian astronomer al-Khujandi, who observed a series of meridian transits of the Sun, which allowed him to calculate the obliquity of the ecliptic. Also in Persia, Omar Khayyám performed a reformation of the calendar that was more accurate than the Julian and came close to the Gregorian. Abraham Zacuto was responsible in the 15th century for the adaptations of astronomical theory for the practical needs of Portuguese caravel expeditions.
During the Renaissance, Copernicus proposed a heliocentric model of the Solar System. His work was defended, expanded upon, and corrected by Galileo Galilei and Johannes Kepler. Galileo added the innovation of using telescopes to enhance his observations. Kepler was the first to devise a system that described correctly the details of the motion of the planets with the Sun at the center. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was left to Newton's invention of celestial dynamics and his law of gravitation to finally explain the motions of the planets. Newton also developed the reflecting telescope.
Stars were found to be faraway objects. With the advent of spectroscopy it was proved that they were similar to our own sun, but with a wide range of temperatures, masses, and sizes. The existence of our galaxy, the Milky Way, as a separate group of stars was only proven in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe, seen in the recession of most galaxies from us. Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as black holes and neutron stars. Physical cosmology made huge advances during the 20th century, with the model of the Big Bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's Law, and cosmological abundances of elements.
Timelines in astronomy
cosmological abundances of elements
- Artificial satellites and space probes
- Astronomical maps, catalogs, and surveys
- Big Bang
- Black hole physics
- Cosmic microwave background astronomy
- Cosmology
- Galaxies, clusters of galaxies, and large scale structure
- Interstellar medium and intergalactic medium
- Natural satellites
- Other background radiation fields
- Solar astronomy
- Solar system astronomy
- Stellar astronomy
- Telescopes, observatories, and observing technology
- White dwarfs, neutron stars, and supernovae
See also
- List of astronomical topics
- Astronomers and Astrophysicists
- Astronomical cycles
- Astronomical naming conventions
- Astronomical object
- Astronomical observatories
- Astronomy organizations
- Astronomical symbols
- Space science
- Celestial navigation
Astronomy tools
- Binoculars
- Telescope
- Computers
- Calculator
- Observatory
- Space observatory
- Maksutov telescope
External Links
- [http://www.space.com/ Space.com]
- [http://www.Astronomy.com/ Astronomy.com]
- [http://www.AbsoluteAstronomy.com/ AbsoluteAstronomy.com]
- [http://www.badastronomy.com/ Bad Astronomy]
- [http://www.nasa.gov/ Nasa]
- [http://www.run4space.com Run4Space Forum]
- [http://antwrp.gsfc.nasa.gov/apod/astropix.html/ Astronomy Picture of the Day]
ko:천문학
ms:Astronomi
ja:天文学
simple:Astronomy
th:ดาราศาสตร์
Astronomical conjunctionConjunction is a term used in positional astronomy and astrology. It means that, as seen from some place (usually the Earth), two celestial bodies appear near one another in the sky.
Passing close
More generally, in the particular case of two planets, it means that they merely have the same right ascension (and hence the same hour angle). This is called conjunction in right ascension. However there is also the term conjunction in ecliptical longitude. At such conjunction both objects have the same ecliptical longitude. Conjunction in right ascension and conjunction in ecliptical longitude do not normally take place at the same time, but in most cases nearly at the same time. However at triple conjunctions, it is possible that a conjunction only in right ascension (or ecliptical length) occur. At the time of conjunction - it does not matter if in right ascension or in ecliptical longitude - the involved planets are close together upon the celestial sphere. In the vast majority of such cases, one of the planets will appear to pass north or south of the other.
Passing closer
However, if two celestial bodies attain the same declination at the time of a conjunction in right ascension (or the same ecliptical latitude at a conjunction in ecliptical longitude), the one closest to the Earth will pass in front of the other. In such a case, a syzygy takes place. If one object moves into the shadow of another, the event is an eclipse. For example, if the moon passes in front of the sun, this event is called a solar eclipse. If the visible disk of the nearer object is considerably smaller than that of the farther object, the event is called a transit. When Mercury passes in front of the sun, it is a transit of Mercury, and when Venus passes in front of the sun, it is a transit of Venus. When the nearer object is larger than the farther one, it will completely obscure its smaller companion; this is an occultation. Occultations in which the larger body is neither the sun nor the moon are very rare. More frequent, however, is an occultation of a planet by the Moon, which will generally occur every few years.
One famous event
It is often believed that the Star of Bethlehem was a triple conjunction between Jupiter and Saturn in the year 6BC. However the angle distance between Jupiter and Saturn was at this event approximately 1 degree, this is twice the diametre of the moon in the sky. Occultations of Saturn by Jupiter did not occur in historic times and will not occur before the year 7541.
Superior and inferior
As seen from a planet that is superior, if an inferior planet is on the opposite side of the Sun, it is in superior conjunction with the Sun. An inferior conjunction occurs when the two planets lie in a line on the same side of the Sun. In an inferior conjunction, the superior planet is "in opposition" to the Sun as seen from the inferior planet.
The terms "inferior conjunction" and "superior conjunction" are used in particular for the planets Mercury and Venus, which are inferior planets as seen from the Earth. However, this definition can be applied to any pair of planets, as seen from the one further from the Sun.
A planet (or asteroid or comet) is simply said to be in conjunction, when it is in conjunction with the Sun, as seen from the Earth. The Moon is in conjunction with the Sun at New Moon (or rather Dark Moon).
"Quasi-conjunctions" are also possible; in this scenario, a planet in retrograde motion — always either Mercury or Venus — will "drop back" in right ascension until it almost allows another planet to overtake it, but then the former planet will resume its forward motion and thereafter appear to draw away from it again. This will occur in the morning sky, before dawn; or the reverse may happen in the evening sky after dusk, with Mercury or Venus entering retrograde motion just as it is about to overtake another planet (often Mercury and Venus are both of the planets involved, and when this situation arises they may remain in very close visual proximity for several days or even longer). The quasi-conjunction is reckoned as occurring at the time the distance in right ascension between the two planets is smallest, even though, when declination is taken into account, they may appear closer together shortly before or after this.
Grand conjunctions
2007
A very remarkable planetary/galactic configuration occurs on 23rd and 24 December 2007. The 23/12 configuration — Mars, Earth, Sun, Mercury, Jupiter, Galactic Centre, is shown in the graphic simulation (link) below; it becomes even more remarkable in that it will be joined/triggered by the full moon (conjunct mars) at about 2am on December 24 when a simultaneous Venus square Neptune occurs. It is even more remarkable in that the Pluto/sun conjunction appears exactly on the Winter Solstice... just past conjunction with the Galactic Centre.
Link below is the view from Mars toward the Jupiter, Mars, Earth, Mercury,
Pluto alignment toward the Galactic Centre on 23 December 2007 which occurs just after
the Pluto/Jupiter (Heliocentric) conjunction on 23 November 2007.
[http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=5&vbody=4&month=12&day=23¢ury=20&decade=0&year=7&hour=00&minute=0&fovmul=1&rfov=30&bfov=30&porbs=1&brite=1 NASA Solar System Simulator for 23rd Dec 2007]
2002
In late April of 2002, a rare grand conjunction occurred; in which Saturn, Jupiter, Mars, Venus and Mercury were all visible concomitantly in the west-northwest sky, shortly after sundown; this will happen again in early July of 2060, except that on that occasion the quintet will be bunched in the east-northeast sky, shortly before dawn.
2000
In May of 2000, the five brightest planets aligned within 20° of the Sun, as seen from the Earth. This could not be observed since they were too close to the Sun.
1987
On August 24, 1987, the five objects closest to Earth — the Sun, Moon, Mercury, Venus and Mars — were within approximately 5° of one another, the Sun setting first, followed by Mars, Venus, Mercury and the Moon, in that order, within 20 minutes. As in the 2000 conjunction above, this event was unobservable due to the Sun being part of the line-up.
Conjunctions of planets in right ascension 2005-2020
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
See also
- Astrological aspects
- Astronomical opposition
- Elongation
- Great Conjunction
- Greatest Conjunction
- Transit of Venus
- Triple Conjunction
External links
- [http://www.marco-peuschel.de/JUPITEROCCULTSATURN.pdf Occultations of Saturn by Jupiter]
Category:Astrometry
Category:Celestial mechanics
Celestial mechanics is an application of physics, particularly Newtonian mechanics, to astronomical objects such as stars and planets.
Category:Classical mechanics
Category:Astronomy
ko:분류:천체역학
Körnerwarze
Die Körnerwarze (Carabus cancellatus) ist eine Art aus der Familie der Laufkäfer.
Körnerwarzen werden bis zu 3,2 Zentimeter lang. Der Chitin-Panzer glänzt in einer Mischung aus braun, rot und grün. Auf den Flügeldecken befinden sich deutliche Längsrillen, in denen „körnige“ Erhebungen sind. Die Fühler sind lang und fadenförmig. Auch die Beine sind recht lang.
Körnerwarzen sind in Europa sehr häufig. Die Tiere sind auf Wiesen und Feldern sowie in Gärten anzufinden.
Die vor allem nachtaktiven Tiere jagen am Boden Insekten, darunter auch den Kartoffelkäfer, weshalb die Art sehr wichtig für die Landwirtschaft ist. Tagsüber verstecken sich die Tiere meist unter Steinen, manchmal sind sie jedoch auch bei Tageslicht unterwegs. Sie überwintern im Boden. Bei Bedrohung können die Käfer bis zu 25 Zentimeter weit ihren Magensaft verspritzen. In Deutschland steht die Körnerwanze unter Naturschutz.
Die Weibchen legen etwa 45 Eier, aus denen die Larven schlüpfen. Sie haben eine ähnliche Lebensweise wie die erwachsenen Tiere. Nachdem sich die Larven verpuppt haben, schlüpft im Herbst der fertige Käfer.
Kategorie:Käfer
dating ads site Granada accommodation Kwiaciarnia d online casinos tablice
|
|
|
| :: RELATED NEWS :: |
Göt
Göt, block av stål (eller annan metall) avsett för vidare bearbetning genom ex. valsning eller smidning. Göten framställs från flytande metall genom gjutning i kokiller, och kan väga från några kilo upp till tiotals ton. Numera ersätts ofta göten av stränggjutna ämnen
|
Ostkaka
Ostkaka tillverkas genom att mjölk ystas med ostlöpe och ostkakans speciella konsistens uppstår när kaseinet i mjölken koagulerar. En förenklad variant av ostkaka kan hemma tillagas av färskost, ägg, socker, hackad mandel och grädde som rörs ihop och gräddas i ugn vid 175 grader. Det rekommenderas att äta ostkakan avsvalnad men ljummen. Olika sorters sylt passar bra till.
Ostkaka har föreslagits som officiell nationalrätt för Sverige.
Read More... |
|
Kulturkampen i Preussen
Den så kallade kulturkampen, d v s striden mellan den ultramontana katolicismen och staten, var en viktig tilldragelse i Preussens inrikespolitik under 1870-talet.
Genom ofelbarhetsdogmen och genom förlusten av Kyrkostaten hade katolska kyrkan 1870 fått en helt ny ställning. Tysklands katoliker ville förmå det nya kejsarriket att återge påven hans världsliga makt, vilket regeringen
|
Prinsen av Wales
Prince of Wales, Prins av Wales, Charles' av Storbritannien, nuvarande brittiske tronföljarens officiella titel utanför Skottland, den 21:e i ordningen, sedan 26 juli 1958. Titeln tillfalles inte per automatik, men
|
Självreduktion
Självreduktion (även autoreduktion), politisk taktik som innebär att en person bekämpar kapitalismen genom att reducera sitt eget bidrag till detta samhällssystem. Termen självreduktion används främst av autonomister, även om samma taktik tillämpats av många andra, exempelvis den kooperativa rörelsen och de så kallade politisk taktik som innebär att en person bekämpar kapitalismen genom att reducera sitt eget bidrag till detta samhällssystem. Termen självreduktion används främst av autonomister, även om samma taktik tillämpats av många andra, exempelvis den kooperativa rörelsen och de så kallade politisk riktning som uppstod under 1970-talet i Italien. Autonomismen var ursprungligen en mycket militant riktning med terroristiska inslag. Dagens autonomism är dock betydligt mer återhållsam och agerar främst genom civil olydnad, självreduktion och aktioner för självvalö
|
Folksjäl
Begreppet folksjäl avser en överindividuell entitet som utgörs av ett folks kollektiva medvetande. Folksjälen representerar en enhetligt etnisk folkgrupp. Föreställningen om en folksjäl är vanligt förekommande inom nationalismen; många andra menar att det är en konstruktion som inte finner någon motsvarighet
|
|
