Characteristics.

Physical properties.

Ruthenium, a polyvalent hard white metal, is a member of the platinum group and is in group 8 of the periodic table:  Whereas all other group 8 elements have two electrons in the outermost shell, in ruthenium, the outermost shell has only one electron (the final electron is in a lower shell). This anomaly is observed in the neighboring metals niobium (41), molybdenum (42), and rhodium (45).  Ruthenium has four crystal modifications and does not tarnish at ambient conditions; it oxidizes upon heating to. Ruthenium dissolves in fused alkalis to give ruthenates (), is not attacked by acids (even aqua regia) but is attacked by halogens at high temperatures. Indeed, ruthenium is most readily attacked by oxidizing agents. Small amounts of ruthenium can increase the hardness of platinum and palladium. The corrosion resistance of titanium is increased markedly by the addition of a small amount of ruthenium. The metal can be plated by electroplating and by thermal decomposition. A ruthenium-molybdenum alloy is known to be superconductive at temperatures below 10.6 K. Ruthenium is the last of the 4d transition metals that can assume the group oxidation state +8, and even then it is less stable there than the heavier congener osmium: this is the first group from the left of the table where the second and third-row transition metals display notable differences in chemical behavior. Like iron but unlike osmium, ruthenium can form aqueous cations in its lower oxidation states of +2 and +3.  Ruthenium is the first in a downward trend in the melting and boiling points and atomization enthalpy in the 4d transition metals after the maximum seen at molybdenum, because the 4d subshell is more than half full and the electrons are contributing less to metallic bonding. (Technetium, the previous element, has an exceptionally low value that is off the trend due to its half-filled [Kr]4d5s configuration, though it is not as far off the trend in the 4d series as manganese in the 3d transition series.) Unlike the lighter congener iron, ruthenium is paramagnetic at room temperature, as iron also is above its Curie point.  The reduction potentials in acidic aqueous solution for some common ruthenium ions are shown below:

Isotopes.

Naturally occurring ruthenium is composed of seven stable isotopes. Additionally, 34 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are Ru with a half-life of 373.59 days, Ru with a half-life of 39.26 days and Ru with a half-life of 2.9 days.  Fifteen other radioisotopes have been characterized with atomic weights ranging from 89.93 u (Ru) to 114.928 u (Ru). Most of these have half-lives that are less than five minutes except Ru (half-life: 1.643 hours) and Ru (half-life: 4.44 hours).  The primary decay mode before the most abundant isotope, Ru, is electron capture and the primary mode after is beta emission. The primary decay product before Ru is technetium and the primary decay product after is rhodium.  Ru is a product of fission of a nucleus of uranium or plutonium. High concentrations of detected atmospheric Ru were associated with an alleged undeclared nuclear accident in Russia in 2017.

Occurrence.

As the 74th most abundant element in Earth's crust, ruthenium is relatively rare, found in about 100 parts per trillion. This element is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario, Canada, and in pyroxenite deposits in South Africa. The native form of ruthenium is a very rare mineral (Ir replaces part of Ru in its structure).

Production.

Roughly 30 tonnes of ruthenium are mined each year with world reserves estimated at 5,000 tonnes. The composition of the mined platinum group metal (PGM) mixtures varies widely, depending on the geochemical formation. For example, the PGMs mined in South Africa contain on average 11% ruthenium while the PGMs mined in the former USSR contain only 2% (1992). Ruthenium, osmium, and iridium are considered the minor platinum group metals.  Ruthenium, like the other platinum group metals, is obtained commercially as a by-product from nickel, and copper, and platinum metals ore processing. During electrorefining of copper and nickel, noble metals such as silver, gold, and the platinum group metals precipitate as "anode mud", the feedstock for the extraction. The metals are converted to ionized solutes by any of several methods, depending on the composition of the feedstock. One representative method is fusion with sodium peroxide followed by dissolution in aqua regia, and solution in a mixture of chlorine with hydrochloric acid. Osmium, ruthenium, rhodium, and iridium are insoluble in aqua regia and readily precipitate, leaving the other metals in solution. Rhodium is separated from the residue by treatment with molten sodium bisulfate. The insoluble residue, containing Ru, Os, and Ir is treated with sodium oxide, in which Ir is insoluble, producing dissolved Ru and Os salts. After oxidation to the volatile oxides, is separated from by precipitation of (NH)RuCl with ammonium chloride or by distillation or extraction with organic solvents of the volatile osmium tetroxide. Hydrogen is used to reduce ammonium ruthenium chloride yielding a powder. The product is reduced using hydrogen, yielding the metal as a powder or sponge metal that can be treated with powder metallurgy techniques or argon-arc welding.

Chemical compounds.

The oxidation states of ruthenium range from 0 to +8, and −2. The properties of ruthenium and osmium compounds are often similar. The +2, +3, and +4 states are the most common. The most prevalent precursor is ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically.

Oxides and chalcogenides.

Ruthenium can be oxidized to ruthenium(IV) oxide (RuO, oxidation state +4) which can in turn be oxidized by sodium metaperiodate to the volatile yellow tetrahedral ruthenium tetroxide, RuO, an aggressive, strong oxidizing agent with structure and properties analogous to osmium tetroxide. RuO is mostly used as an intermediate in the purification of ruthenium from ores and radiowastes.  Dipotassium ruthenate (KRuO, +6), and potassium perruthenate (KRuO, +7) are also known. Unlike osmium tetroxide, ruthenium tetroxide is less stable and is strong enough as an oxidising agent to oxidise dilute hydrochloric acid and organic solvents like ethanol at room temperature, and is easily reduced to ruthenate () in aqueous alkaline solutions; it decomposes to form the dioxide above 100 °C. Unlike iron but like osmium, ruthenium does not form oxides in its lower +2 and +3 oxidation states. Ruthenium forms dichalcogenides, which are diamagnetic semiconductors crystallizing in the pyrite structure. Ruthenium sulfide (RuS) occurs naturally as the mineral laurite.  Like iron, ruthenium does not readily form oxoanions, and prefers to achieve high coordination numbers with hydroxide ions instead. Ruthenium tetroxide is reduced by cold dilute potassium hydroxide to form black potassium perruthenate, KRuO, with ruthenium in the +7 oxidation state. Potassium perruthenate can also be produced by oxidising potassium ruthenate, KRuO, with chlorine gas. The perruthenate ion is unstable and is reduced by water to form the orange ruthenate. Potassium ruthenate may be synthesized by reacting ruthenium metal with molten potassium hydroxide and potassium nitrate.  Some mixed oxides are also known, such as MRuO, NaRuO, NaRuO, and MLnRuO.

Halides and oxyhalides.

The highest known ruthenium halide is the hexafluoride, a dark brown solid that melts at 54 °C. It hydrolyzes violently upon contact with water and easily disproportionates to form a mixture of lower ruthenium fluorides, releasing fluorine gas. Ruthenium pentafluoride is a tetrameric dark green solid that is also readily hydrolyzed, melting at 86.5 °C. The yellow ruthenium tetrafluoride is probably also polymeric and can be formed by reducing the pentafluoride with iodine. Among the binary compounds of ruthenium, these high oxidation states are known only in the oxides and fluorides.  Ruthenium trichloride is a well-known compound, existing in a black α-form and a dark brown β-form: the trihydrate is red. Of the known trihalides, trifluoride is dark brown and decomposes above 650 °C, tetrabromide is dark-brown and decomposes above 400 °C, and triiodide is black. Of the dihalides, difluoride is not known, dichloride is brown, dibromide is black, and diiodide is blue. The only known oxyhalide is the pale green ruthenium(VI) oxyfluoride, RuOF.

Coordination and organometallic complexes.

Ruthenium forms a variety of coordination complexes. Examples are the many pentaammine derivatives [Ru(NH)L] that often exist for both Ru(II) and Ru(III). Derivatives of bipyridine and terpyridine are numerous, best known being the luminescent tris(bipyridine)ruthenium(II) chloride.  Ruthenium forms a wide range compounds with carbon-ruthenium bonds. Grubbs' catalyst is used for alkene metathesis. Ruthenocene is analogous to ferrocene structurally, but exhibits distinctive redox properties. The colorless liquid ruthenium pentacarbonyl converts in the absence of CO pressure to the dark red solid triruthenium dodecacarbonyl. Ruthenium trichloride reacts with carbon monoxide to give many derivatives including RuHCl(CO)(PPh) and Ru(CO)(PPh) (Roper's complex). Heating solutions of ruthenium trichloride in alcohols with triphenylphosphine gives tris(triphenylphosphine)ruthenium dichloride (RuCl(PPh)), which converts to the hydride complex chlorohydridotris(triphenylphosphine)ruthenium(II) (RuHCl(PPh)).

History.

Though naturally occurring platinum alloys containing all six platinum-group metals were used for a long time by pre-Columbian Americans and known as a material to European chemists from the mid-16th century, not until the mid-18th century was platinum identified as a pure element. That natural platinum contained palladium, rhodium, osmium and iridium was discovered in the first decade of the 19th century. Platinum in alluvial sands of Russian rivers gave access to raw material for use in plates and medals and for the minting of ruble coins, starting in 1828. Residues from platinum production for coinage were available in the Russian Empire, and therefore most of the research on them was done in Eastern Europe.  It is possible that the Polish chemist Jędrzej Śniadecki isolated element 44 (which he called "vestium" after the asteroid Vesta discovered shortly before) from South American platinum ores in 1807. He published an announcement of his discovery in 1808. His work was never confirmed, however, and he later withdrew his claim of discovery.  Jöns Berzelius and Gottfried Osann nearly discovered ruthenium in 1827. They examined residues that were left after dissolving crude platinum from the Ural Mountains in aqua regia. Berzelius did not find any unusual metals, but Osann thought he found three new metals, which he called pluranium, ruthenium, and polinium. This discrepancy led to a long-standing controversy between Berzelius and Osann about the composition of the residues. As Osann was not able to repeat his isolation of ruthenium, he eventually relinquished his claims. The name "ruthenium" was chosen by Osann because the analysed samples stemmed from the Ural Mountains in Russia. The name itself derives from Ruthenia, the Latin word for Rus', a historical area that included present-day Ukraine, Belarus, western Russia, and parts of Slovakia and Poland.  In 1844, Karl Ernst Claus, a Russian scientist of Baltic German descent, showed that the compounds prepared by Gottfried Osann contained small amounts of ruthenium, which Claus had discovered the same year. Claus isolated ruthenium from the platinum residues of rouble production while he was working in Kazan University, Kazan, the same way its heavier congener osmium had been discovered four decades earlier. Claus showed that ruthenium oxide contained a new metal and obtained 6 grams of ruthenium from the part of crude platinum that is insoluble in aqua regia. Choosing the name for the new element, Claus stated: "I named the new body, in honour of my Motherland, ruthenium. I had every right to call it by this name because Mr. Osann relinquished his ruthenium and the word does not yet exist in chemistry."

Applications.

Approximately 30.9 tonnes of ruthenium were consumed in 2016, 13.8 of them in electrical applications, 7.7 in catalysis, and 4.6 in electrochemistry.  Because it hardens platinum and palladium alloys, ruthenium is used in electrical contacts, where a thin film is sufficient to achieve the desired durability. With similar properties and lower cost than rhodium, electric contacts are a major use of ruthenium. The ruthenium plate is applied to the electrical contact and electrode base metal by electroplating or sputtering.  Ruthenium dioxide with lead and bismuth ruthenates are used in thick-film chip resistors. These two electronic applications account for 50% of the ruthenium consumption.  Ruthenium is seldom alloyed with metals outside the platinum group, where small quantities improve some properties. The added corrosion resistance in titanium alloys led to the development of a special alloy with 0.1% ruthenium. Ruthenium is also used in some advanced high-temperature single-crystal superalloys, with applications that include the turbines in jet engines. Several nickel based superalloy compositions are described, such as EPM-102 (with 3% Ru), TMS-162 (with 6% Ru), TMS-138, and TMS-174, the latter two containing 6% rhenium. Fountain pen nibs are frequently tipped with ruthenium alloy. From 1944 onward, the Parker 51 fountain pen was fitted with the "RU" nib, a 14K gold nib tipped with 96.2% ruthenium and 3.8% iridium.  Ruthenium is a component of mixed-metal oxide (MMO) anodes used for cathodic protection of underground and submerged structures, and for electrolytic cells for such processes as generating chlorine from salt water. The fluorescence of some ruthenium complexes is quenched by oxygen, finding use in optode sensors for oxygen. Ruthenium red, [(NH)Ru-O-Ru(NH)-O-Ru(NH)], is a biological stain used to stain polyanionic molecules such as pectin and nucleic acids for light microscopy and electron microscopy. The beta-decaying isotope 106 of ruthenium is used in radiotherapy of eye tumors, mainly malignant melanomas of the uvea. Ruthenium-centered complexes are being researched for possible anticancer properties. Compared with platinum complexes, those of ruthenium show greater resistance to hydrolysis and more selective action on tumors.  Ruthenium tetroxide exposes latent fingerprints by reacting on contact with fatty oils or fats with sebaceous contaminants and producing brown/black ruthenium dioxide pigment.

Catalysis.

Many ruthenium-containing compounds exhibit useful catalytic properties. The catalysts are conveniently divided into those that are soluble in the reaction medium, homogeneous catalysts, and those that are not, which are called heterogeneous catalysts.  Ruthenium nanoparticles can be formed inside halloysite. This abundant mineral naturally has a structure of rolled nanosheets (nanotubes), which can support both the Ru nanocluster synthesis and its products for subsequent use in industrial catalysis.

Homogeneous catalysis.

Solutions containing ruthenium trichloride are highly active for olefin metathesis. Such catalysts are used commercially for the production of polynorbornene for example. Well defined ruthenium carbene and alkylidene complexes show comparable reactivity and provide mechanistic insights into the industrial processes. The Grubbs' catalysts for example have been employed in the preparation of drugs and advanced materials.  Ruthenium complexes are highly active catalysts for transfer hydrogenations (sometimes referred to as "borrowing hydrogen" reactions). This process is employed for the enantioselective hydrogenation of ketones, aldehydes, and imines. This reaction exploits using chiral ruthenium complexes introduced by Ryoji Noyori. For example, (cymene)Ru(S,S-TsDPEN) catalyzes the hydrogenation of benzil into ("R,R")-hydrobenzoin. In this reaction, formate and water/alcohol serve as the source of H:  A Nobel Prize in Chemistry was awarded in 2001 to Ryōji Noyori for contributions to the field of asymmetric hydrogenation.  In 2012, Masaaki Kitano and associates, working with an organic ruthenium catalyst, demonstrated ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store. Small-scale, intermittent production of ammonia, for local agricultural use, may be a viable substitute for electrical grid attachment as a sink for power generated by wind turbines in isolated rural installations.

Heterogeneous catalysis.

Ruthenium-promoted cobalt catalysts are used in Fischer-Tropsch synthesis.

Emerging applications.

Some ruthenium complexes absorb light throughout the visible spectrum and are being actively researched for solar energy technologies. For example, Ruthenium-based compounds have been used for light absorption in dye-sensitized solar cells, a promising new low-cost solar cell system.  Many ruthenium-based oxides show very unusual properties, such as a quantum critical point behavior, exotic superconductivity (in its strontium ruthenate form), and high-temperature ferromagnetism.

Applications of ruthenium thin films in microelectronics.

Relatively recently, ruthenium has been suggested as a material that could beneficially replace other metals and silicides in microelectronics components. Ruthenium tetroxide (RuO) is highly volatile, as is ruthenium trioxide (RuO). By oxidizing ruthenium (for example with an oxygen plasma) into the volatile oxides, ruthenium can be easily patterned. The properties of the common ruthenium oxides make ruthenium a metal compatible with the semiconductor processing techniques needed to manufacture microelectronics.  To continue miniaturization of microelectronics, new materials are needed as dimensions change. There are three main applications for thin ruthenium films in microelectronics. The first is using thin films of ruthenium as electrodes on both sides of tantalum pentoxide (TaO) or barium strontium titanate ((Ba, Sr)TiO, also known as BST) in the next generation of three-dimensional dynamic random access memories (DRAMs). Ruthenium thin-film electrodes could also be deposited on top of lead zirconate titanate (Pb(ZrTi)O, also known as PZT) in another kind of RAM, ferroelectric random access memory (FRAM). Platinum has been used as the electrodes in RAMs in laboratory settings, but it is difficult to pattern. Ruthenium is chemically similar to platinum, preserving the function of the RAMs, but in contrast to Pt patterns easily. The second is using thin ruthenium films as metal gates in p-doped metal-oxide-semiconductor field effect transistors (p-MOSFETs). When replacing silicide gates with metal gates in MOSFETs, a key property of the metal is its work function. The work function needs to match the surrounding materials. For p-MOSFETs, the ruthenium work function is the best materials property match with surrounding materials such as HfO, HfSiO, HfNO, and HfSiNO, to achieve the desired electrical properties. The third large-scale application for ruthenium films is as a combination adhesion promoter and electroplating seed layer between TaN and Cu in the copper dual damascene process. Copper can be directly electroplated onto ruthenium, in contrast to tantalum nitride. Copper also adheres poorly to TaN, but well to Ru. By depositing a layer of ruthenium on the TaN barrier layer, copper adhesion would be improved and deposition of a copper seed layer would not be necessary.  There are also other suggested uses. In 1990, IBM scientists discovered that a thin layer of ruthenium atoms created a strong anti-parallel coupling between adjacent ferromagnetic layers, stronger than any other nonmagnetic spacer-layer element. Such a ruthenium layer was used in the first giant magnetoresistive read element for hard disk drives. In 2001, IBM announced a three-atom-thick layer of the element ruthenium, informally referred to as "pixie dust", which would allow a quadrupling of the data density of current hard disk drive media.

Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemicals. Russian-born scientist of Baltic-German ancestry Karl Ernst Claus discovered the element in 1844 at Kazan State University and named ruthenium in honor of Russia (Ruthenia is the Latin name of Rus). Ruthenium is usually found as a minor component of platinum ores; the annual production has risen from about 19 tonnes in 2009 to some 35.5 tonnes in 2017. Most ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum alloys and as a chemistry catalyst. A new application of ruthenium is as the capping layer for extreme ultraviolet photomasks. Ruthenium is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario and in pyroxenite deposits in South Africa.

<unk>()是一种化学元素,化学符号为Ru,原子序为44,是在元素周期表中铂族的稀有过渡金属。<unk>与铂族的其他金属一样,对大多数其他化学物质都是惰性的。1844年,俄籍的波罗的海德意志科学家卡尔·恩斯特·克劳斯(Karl Ernst Claus)在喀山国立大学发现了该元素,随后以鲁塞尼亚(Ruthenia)做为此元素的拉丁名称,以此纪念这个被发现于俄罗斯的元素。一般而言,<unk>是在铂矿石的次要成分中被发现,年产量从2009年的约19吨上升到2017年的约35.5吨。生产出的<unk>大部分用于制造耐磨电接头和厚膜电阻,其次是用于铂合金和当成化学反应催化剂,另有一项新用途则是当作极紫外光光罩的覆盖层。<unk>通常和其他铂族金属同时蕴藏在乌拉尔山脉、北美洲和南美洲的矿石中。加拿大安大略省大萨德伯里的镍黄铁矿以及南非辉石岩矿床中,也发现了稀少但有商业重要性的存量。


Name.

The term "Romance" comes from the Vulgar Latin adverb, "in Roman", derived from : for instance, in the expression, "to speak in Roman" (that is, the Latin vernacular), contrasted with, "to speak in Latin"

Samples.

Lexical and grammatical similarities among the Romance languages, and between Latin and each of them, are apparent from the following examples having the same meaning in various Romance lects:  English: She always closes the window before she dines / before dining.  Romance-based creoles and pidgins  Some of the divergence comes from semantic change: where the same root words have developed different meanings. For example, the Portuguese word is descended from Latin "window" (and is thus cognate to French, Italian, Romanian and so on), but now means "skylight" and "slit". Cognates may exist but have become rare, such as in Spanish, or dropped out of use entirely. The Spanish and Portuguese terms meaning "to throw through a window" and

Classification and related languages.

The classification of the Romance languages is inherently difficult, because most of the linguistic area is a dialect continuum, and in some cases political biases can come into play. Along with Latin (which is not included among the Romance languages) and a few extinct languages of ancient Italy, they make up the Italic branch of the Indo-European family.

Proposed divisions.

There are various schemes used to subdivide the Romance languages. Three of the most common schemes are as follows:

Italo-Western vs. Eastern vs. Sardinian.

The main subfamilies that have been proposed by Ethnologue within the various classification schemes for Romance languages are:  This three-way division is made primarily based on the outcome of Vulgar Latin (Proto-Romance) vowels: Italo-Western is in turn split along the so-called "La Spezia–Rimini Line" in northern Italy, which divides the central and southern Italian languages from the so-called Western Romance languages to the north and west. The primary characteristics dividing the two are:  The reality is somewhat more complex. All of the "southeast" characteristics apply to all languages southeast of the line, and all of the "northwest" characteristics apply to all languages in France and (most of) Spain. However, the Gallo-Italic languages are somewhere in between. All of these languages do have the "northwest" characteristics of

Gallo-Romance languages.

Gallo-Romance can be divided into the following subgroups: The following groups are also sometimes considered part of Gallo-Romance:  The Gallo-Romance languages are generally considered the most innovative (least conservative) among the Romance languages. Characteristic Gallo-Romance features generally developed earliest and appear in their most extreme manifestation in the Langue d'oïl, gradually spreading out along riverways and transalpine roads.  In some ways, however, the Gallo-Romance languages are conservative. The older stages of many of the languages preserved a two-case system consisting of nominative and oblique, fully marked on nouns, adjectives and determiners, inherited almost directly from the Latin nominative and accusative and preserving a number of different declensional classes and irregular forms. The languages closest to the oïl epicenter preserve the case system the best, while languages at the periphery lose it early.  Notable characteristics of the Gallo-Romance languages are:

Pidgins, creoles, and mixed languages.

Some Romance languages have developed varieties which seem dramatically restructured as to their grammars or to be mixtures with other languages. It is not always clear whether they should be classified as Romance, pidgins, creole languages,

Auxiliary and constructed languages.

Latin and the Romance languages have also served as the inspiration and basis of numerous auxiliary and constructed languages, so-called "neo-romantic languages".  The concept was first developed in 1903 by Italian mathematician Giuseppe Peano, under the title Latino sine flexione. He wanted to create a "naturalistic" international language, as opposed to an autonomous constructed language like Esperanto or Volapuk which were designed for maximal simplicity of lexicon and derivation of words. Peano used Latin as the base of

Modern status.

The Romance language most widely spoken natively today is Spanish, followed by Portuguese, French, Italian and Romanian, which together cover a vast territory in Europe and beyond, and work as official and national languages in dozens of countries.  French, Italian, Portuguese, Spanish, and Romanian are also official languages of the European Union. Spanish, Portuguese, French, Italian, Romanian, and Catalan were the official languages of the defunct Latin Union; and French and Spanish are two of the six official languages of the United Nations. Outside Europe, French, Portuguese and Spanish are spoken and enjoy official status in various countries that emerged from the respective colonial empires.  Spanish is an official language in Spain and in nine countries of South America, home to about half that continent's population; in six countries of Central America (all except Belize); and in Mexico. In the Caribbean, it is official in Cuba, the Dominican Republic, and Puerto Rico. In all these countries, Latin American Spanish is the vernacular language of the majority of the population, giving Spanish the most native speakers of any Romance language. In Africa it is an official language of Equatorial Guinea.  Portuguese, in its original homeland, Portugal, is spoken by virtually the entire population of 10 million. As the official language of Brazil, it is spoken by more than 200 million people in that country, as well as by neighboring residents of eastern Paraguay and northern Uruguay, accounting for a little more than half the population of South America, thus making Portuguese the most spoken official Romance language in a single country. It is the official language of six African countries (Angola, Cape Verde, Guinea-Bissau, Mozambique, Equatorial Guinea, and São Tomé and Príncipe), and is spoken as a first language by perhaps 30 million residents of that continent. In Asia, Portuguese is co-official with other languages in East Timor and Macau, while most Portuguese-speakers in Asia—some 400,000—are in Japan due to return immigration of Japanese Brazilians. In North America 1,000,000 people speak Portuguese as their home language. In Oceania, Portuguese is the second most spoken Romance language, after French, due mainly to the number of speakers in East Timor. Its closest relative, Galician, has official status in the autonomous community of Galicia in Spain, together with Spanish.  Outside Europe, French is spoken natively most in the Canadian province of Quebec, and in parts of New Brunswick and Ontario.

History.

Romance languages are the continuation of Vulgar Latin, the popular and colloquial sociolect of Latin spoken by soldiers, settlers, and merchants of the Roman Empire, as distinguished from the classical form of the language spoken by the Roman upper classes, the form in which the language was generally written. Between 350 BC and 150 AD, the expansion of the Empire, together with its administrative and educational policies, made Latin the dominant native language in continental Western Europe. Latin also exerted a strong influence in southeastern Britain, the Roman province of Africa, western Germany, Pannonia and the whole Balkans.  During the Empire's decline, and after its fragmentation and the collapse of Western half in the fifth and sixth centuries, the spoken varieties of Latin became more isolated from each other, with the western dialects coming under heavy Germanic influence (the Goths and Franks in particular) and the eastern dialects coming under Slavic influence. The dialects diverged from classical Latin at an accelerated rate and eventually evolved into a continuum of recognizably different typologies. The colonial empires established by Portugal, Spain, and France from the fifteenth century onward spread their languages to the other continents to such an extent that about two-thirds of all Romance language speakers today live outside Europe.  Despite other influences (e.g. "substratum" from pre-Roman languages, especially Continental Celtic languages; and "superstratum" from later Germanic or Slavic invasions), the phonology, morphology, and lexicon of all Romance languages consist mainly of evolved forms of Vulgar Latin. However, some notable differences occur between today's Romance languages and their Roman ancestor. With only one or two exceptions, Romance languages have lost the declension system of Latin and, as a result, have SVO sentence structure and make extensive use of prepositions.

Vulgar Latin.

Documentary evidence is limited about Vulgar Latin for the purposes of comprehensive research, and the literature is often hard to interpret or generalize. Many of its speakers were soldiers, slaves, displaced peoples, and forced resettlers, more likely to be natives of conquered lands than natives of Rome. In Western Europe, Latin gradually replaced Celtic and other Italic languages, which were related to it by a shared Indo-European origin. Commonalities in syntax and vocabulary facilitated the adoption of Latin.  Vulgar Latin is believed to have already had most of the features shared by all Romance languages, which distinguish them from Classical Latin, such as the almost complete loss of the Latin grammatical case system and its replacement by prepositions; the loss of the neuter grammatical gender and comparative inflections; replacement of some verb paradigms by innovations (e.g. the synthetic future gave way to an originally analytic strategy now typically formed by infinitive +

Fall of the Western Roman Empire.

During the political decline of the Western Roman Empire in the fifth century, there were large-scale migrations into the empire, and the Latin-speaking world was fragmented into several independent states. Central Europe and the Balkans were occupied by Germanic and Slavic tribes, as well as by Huns. These incursions isolated the Vlachs from the rest of Romance-speaking Europe.  British and African Romance—the forms

Fall of the Eastern Roman empire.

Meanwhile, large-scale migrations into the Eastern Roman Empire started with the Goths and continued with Huns, Avars, Bulgars, Slavs, Pechenegs, Hungarians and Cumans. The invasions of Slavs were the most thoroughgoing, and they partially reduced the Romanic element in the Balkans. The invasion of the

Early Romance.

Over the course of the fourth to eighth centuries, local changes in phonology, morphology, syntax and lexicon accumulated to the point that the speech of any locale was noticeably different from another. In principle, differences between any two lects increased the more they were separated geographically, reducing easy mutual intelligibility between speakers of distant communities. Clear evidence of some levels of change is found in the "Reichenau Glosses", an eighth-century compilation of about 1,200 words from the fourth-century Vulgate of Jerome that had changed in phonological form or were no longer normally used, along with their eighth-century equivalents in proto-Franco-Provençal. The following are some examples with reflexes in several modern Romance languages for comparison: In all of the above examples, the words appearing in the fourth century Vulgate are the same words as would have been used in Classical Latin of c. 50 BC. It is likely that some of these words had already disappeared from casual speech by the time of the "Glosses"; but if so, they may well have been still widely understood, as there is no recorded evidence that the common people of the time had difficulty understanding the language.  By the 8th

Recognition of the vernaculars.

Between the 10th and 13th centuries, some local vernaculars developed a written form and began to supplant Latin in many of its roles. In some countries, such as Portugal, this transition was expedited by force of

Uniformization and standardization.

The invention of the printing press brought a tendency towards greater uniformity of standard languages within political boundaries, at the expense of

Sound changes.

Consonants.

Significant sound changes affected the consonants of the Romance languages.

Apocope.

There was a tendency to eliminate final consonants in Vulgar Latin, either by dropping them (apocope) or adding a vowel after them (epenthesis).  Many final consonants were rare, occurring only in certain prepositions (e.g. "ad" "towards", "apud" "at, near (a person)"), conjunctions ("sed" "but"), demonstratives (e.g. "illud" "that (over there)", "hoc" "this"), and nominative singular noun forms, especially of neuter nouns (e.g. "lac" "milk", "mel" "honey", "cor" "heart"). Many of these prepositions and conjunctions were replaced by others, while the nouns were regularized into forms based on their oblique stems that avoided the

Palatalization.

Palatalization was one of the most important processes affecting consonants in Vulgar Latin. This eventually resulted in a whole series of "" and consonants in most Romance languages, e.g. Italian.  The following historical stages occurred:  Note how the environments become progressively less "palatal", and the languages affected become progressively fewer.  The outcomes of palatalization depended on the historical stage, the consonants involved, and the languages involved. The primary division is between the Western Romance languages, with resulting from palatalization of, and the remaining languages (Italo-Dalmatian and Eastern Romance), with resulting. It is often suggested that was the original result in all languages, with > a later innovation in the Western Romance languages. Evidence of this is the fact that Italian has both and as outcomes of palatalization in different environments, while Western Romance has only. Even more suggestive is the fact

Lenition.

Stop consonants shifted by lenition in Vulgar Latin in some areas.  The voiced labial consonants and (represented by and, respectively) both developed a fricative as an intervocalic allophone. This is clear from the orthography; in medieval times, the spelling of a consonantal is often used for what had been a in Classical Latin, or the two spellings were used interchangeably. In many Romance languages (Italian, French, Portuguese, Romanian, etc.), this fricative later developed into a ; but in others (Spanish, Galician, some

Vowel prosthesis.

In Late Latin a prosthetic vowel /i/ (lowered to /e/ in most languages) was inserted at the beginning of any word that began with (referred to as "s impura") and a voiceless consonant (#sC- > isC-): Prosthetic /i/ ~ /e/ in Romance languages may have been influenced by Continental Celtic languages, although the phenomenon exists or existed in some areas where Celtic was never present (e.g. Sardinia, southern Italy). While Western Romance words undergo prothesis, cognates in Balkan Romance and southern Italo-Romance do not, e.g. Italian "scrivere", "spada", "spirito",

Stressed vowels.

Loss of vowel length, reorientation.

One profound change that affected Vulgar Latin was the reorganisation of its vowel system. Classical Latin had five short vowels, "ă, ĕ, ĭ, ŏ, ŭ", and five long vowels, "ā, ē, ī, ō, ū", each of which was an individual phoneme (see the table in the right, for their likely pronunciation in IPA), and four diphthongs, "ae", "oe", "au" and "eu" (five according to some authors, including "ui"). There were also long and short versions of "y", representing the rounded vowel in Greek borrowings, which however probably came to be pronounced even before Romance vowel changes started.  There is evidence that in the imperial period all the short vowels except "a" differed by quality as well as by length from their long counterparts. So, for example "ē" was pronounced close-mid while "ĕ" was pronounced open-mid, and "ī" was pronounced close while "ĭ" was pronounced near-close.  During the Proto-Romance period, phonemic length distinctions were lost. Vowels

Latin diphthongs.

The Latin diphthongs "ae" and "oe", pronounced and in earlier Latin, were early on monophthongized.  "ae" became by the 1st century at the latest. Although this sound was still distinct from all existing vowels, the neutralization of Latin vowel length eventually caused its merger with < short "e": e.g. "caelum" "sky" > French "ciel", Spanish/Italian "cielo", Portuguese "céu", with the same vowel as in "mele" "honey" > French/Spanish "miel", Italian "miele", Portuguese "mel". Some words show an early merger of "ae" with, as in "praeda" "booty" > *"prēda" > French "proie" (vs. expected **"priée"), Italian "preda" (not **"prieda") "prey"; or "faenum" "hay" > *"fēnum" > Spanish "heno", French "foin" (but Italian "fieno" /fjɛno/).  "oe" generally merged with : "poenam" "punishment" > Romance * > Spanish/Italian "pena", French "peine"; "foedus" "ugly" > Romance * > Spanish "feo", Portuguese "feio". There are relatively few such outcomes, since "oe" was rare in Classical Latin (most original instances had become Classical "ū", as in Old Latin "oinos" "one" > Classical

Further developments.

Front-rounded vowels.

Characteristic of the Gallo-Romance languages and Rhaeto-Romance languages are the front rounded vowels. All of these languages show an unconditional change /u/ > /y/, e.g. "lūnam" > French "lune", Occitan. Many of the languages in Switzerland and Italy show the further change /y/ > /i/. Also very common is some variation of the French development (lengthened in open syllables) > >, with mid back vowels diphthongizing in some circumstances and then re-monophthongizing into mid-front rounded vowels. (French has both and, with developing from in certain circumstances.)

Unstressed vowels.

There was more variability in the result of the unstressed vowels. Originally in Proto-Romance, the same nine vowels developed in unstressed as stressed syllables, and in Sardinian, they coalesced into the same five vowels in the same way.  In Italo-Western Romance, however, vowels in unstressed syllables were significantly different from stressed vowels, with yet a third outcome for final unstressed syllables. In non-final unstressed syllables, the seven-vowel system of stressed syllables developed, but then the low-mid vowels merged into the high-mid vowels. This system is still preserved, largely or completely, in all of the conservative Romance languages

Intertonic vowels.

The so-called "intertonic vowels" are word-internal unstressed vowels, i.e. not in the initial, final, or "tonic" (i.e. stressed) syllable, hence intertonic. Intertonic vowels were the most subject to loss or modification. Already in Vulgar Latin intertonic vowels between a single consonant and a following /r/ or /l/ tended to drop: "vétulum" "old" > "veclum" > Dalmatian "vieklo", Sicilian "vecchiu", Portuguese "velho". But many languages ultimately dropped almost all intertonic vowels.  Generally, those languages south

Writing systems.

The Romance languages for the most part have kept the writing system of Latin, adapting it to their evolution. One exception was Romanian before the nineteenth century, where, after the Roman retreat, literacy was reintroduced through the Romanian Cyrillic alphabet, a Slavic influence. A Cyrillic alphabet was also used for Romanian (Moldovan) in the USSR. The non-Christian populations of Spain also used the scripts of their religions (Arabic and Hebrew) to write Romance languages such as Ladino and Mozarabic in "aljamiado".

Letters.

The Romance languages are written with the classical Latin alphabet of 23 letters – "A", "B", "C", "D", "E", "F", "G", "H", "I", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "V", "X", "Y", "Z" – subsequently modified and augmented in various ways. In particular, the single Latin letter "V" split into "V" (consonant) and "U" (vowel), and the letter "I" split into "I" and "J". The Latin letter "K" and the new letter "W", which came to be widely used in Germanic languages, are seldom used in most Romance languages – mostly for unassimilated foreign names and words. Indeed, in Italian prose is properly. Catalan eschews importation of "foreign" letters more than most languages. Thus Wikipedia is in Catalan but in Spanish.  While most of the 23

Digraphs and trigraphs.

Since most Romance languages have more sounds than can be accommodated in the Roman Latin alphabet they all resort to the use of digraphs and trigraphs – combinations of two or three letters with a single phonemic value. The concept (but not the actual combinations) is derived from Classical Latin, which used, for example, "TH", "PH", and "CH" when transliterating the Greek letters "θ", "φ" (later "φ"), and "χ". These were once aspirated sounds in Greek before changing to corresponding fricatives, and the "H" represented what sounded to the Romans like an following,, and respectively. Some of the digraphs used in modern scripts are:  While the digraphs "CH", "PH", "RH" and "TH" were at one time used in many words of Greek origin, most languages have now replaced them with "C/QU", "F", "R" and "T". Only French has kept these etymological spellings, which now represent or,, and, respectively.

Double consonants.

Gemination, in the languages where it occurs, is usually indicated by doubling the consonant, except when it does not contrast phonemically with the corresponding short consonant, in which case gemination is not indicated. In Jèrriais, long consonants are marked with an apostrophe: is a long, is a long, and is a long. The phonemic contrast between geminate and single consonants is widespread in Italian, and normally indicated in the traditional orthography: 'done' vs. 'fate, destiny';'s/he, it fell' vs.'s/he, it falls'. The double consonants in French orthography, however, are merely etymological. In Catalan, the gemination of is marked by a ("flying point"):.

Diacritics.

Romance languages also introduced various marks (diacritics) that may be attached to some letters, for various purposes. In some cases, diacritics are used as an alternative to digraphs and trigraphs; namely to represent a larger number of sounds than would be possible with the basic alphabet, or to distinguish between sounds that

Upper and lower case.

Most languages are written with a mixture of two distinct but phonetically identical variants or "cases" of the alphabet: majuscule ("uppercase" or "capital letters"), derived from Roman stone-carved letter shapes, and minuscule ("lowercase"), derived from Carolingian writing and Medieval quill pen handwriting which were later adapted by printers in the fifteenth and sixteenth centuries.  In particular, all Romance languages capitalize (use

Vocabulary comparison.

The tables below provide a vocabulary comparison that illustrates a number of examples of sound shifts that have occurred between Latin and Romance languages.

References.

Overviews:  Phonology:  Lexicon:  French:  Portuguese:  Spanish:  Italian:  Rhaeto-Romance:

The Romance languages (nowadays rarely Latin languages, or Neo-Latin languages) are the modern languages that evolved from Vulgar Latin between the third and eighth centuries. They are a subgroup of the Italic languages in the Indo-European language family.

罗马语族(又称罗曼语族、拉丁语族),属于印欧语系,是从意大利语族衍生出来的现代语族,主要包括从拉丁语演化而来的现代诸语言。操罗马语族语言的人主要包括传统意义上的“欧洲拉丁人”。罗马帝国瓦解之后,原本统一的拉丁语也随地域的不同而产生各类方言。这些方言就是今日罗马诸语言的雏形。


History.

The weaving industry survived until most of Europe's textile industry was devastated by Asian imports. Some textile distribution centres are still left in the town. Former weaving mills can still be found in the city area, now used as offices for the computer industry. This is due to the takeover of Hollerith by IBM which used the punched card technology from the weaving mills.

Geography.

Neighbouring towns and cities: Böblingen (contiguous), Stuttgart (15 km), Leonberg. The highest point is 531 meters above sea level and to the north is the Glemswald (Nature reserve).

Culture.

Sindelfingen has an annual International Street Fair which features ethnic food and performances from the partner cities, as well as from various local ethnic clubs.

Demography.

The resident counts below are either estimates, based upon census (*) or official records of respective statistical offices. All figures after 1871 are taken from the statistical office of Baden-Württemberg.

Mercedes-Benz factory.

The factory was founded in 1915 by Daimler Motoren Gesellschaft to produce aircraft engines, hence why the plant initially had a runway located onsite. Post-World War I the first passenger car was manufactured, following the merger with Benz & Cie. founded by Karl Benz. In 1926, the entire body shop of the new Daimler-Benz group was relocated to the Sindelfingen plant, allowing plant manager Wilhelm Friedle to introduce assembly line production the following year, and in 1929 the first press shop was opened. By 1938 the plant employed about 6,500 people, and in the lead-in to World War II most production was aligned to military contracts, mainly trucks such as the LC 3000; passenger car production ceased by 1942. Initially replacing male workers with local women, Mercedes then took forced labour, including prisoners of war. Western European prisoners were initially housed in near-by boarding houses, but with the start of the Eastern front the local Nazi administration formed the co-located Riedmühle concentration camp, which from 1942 loaned workers to the company in return for payment to the Nazi Government in Berlin. By 1944, almost half of Daimler Benz's 63,610 Daimler Benz employees were civilian forced labourers. Post-WW2, Daimler-Benz admitted its links with the Nazi regime, and became involved in the German Industry Foundation's initiative "Remembrance, Responsibility and Future". With heavy Allied bombing, the town and plant were not suitably reconstructed until late 1946, with resumed production of the Mercedes-Benz W136. Two-shift production was introduced from 1950, with the relocation of final car assembly to the plant, meaning that by 1955 80,500 cars were manufactured. The Mercedes-Benz W116 was first produced in 1972, the first model of the Mercedes-Benz S-Class, which the plant still produces today as the current model Mercedes-Benz W222. Until 2015, the plant was the top-producing Daimler AG plant, when with 319,000 vehicles manufactured it was overtaken by the Bremen plant with 324,000.  Today, covering 2,955,944 m2 with a production area 1,305,557 m2, the 37,000 people employed (April 2016 - around 10,000 are research and development), the plant still produces over 300,000 vehicles per year, around 15% of total Daimler Group vehicle production. Second in production scale to Bremen in the Daimler Group, it is the third largest vehicle manufacturing plant in Germany, behind Volkswagen's Wolfsburg plant and the Audi plant at Ingolstadt.

Transportation.

Sindelfingen can be reached through the A8 and A81 motorways, and through the S-Bahn connections to Stuttgart or Herrenberg; the nearest airport is in Stuttgart.

Twin towns.

Sindelfingen is twinned with:

Sindelfingen is a southern German town in Baden-Württemberg. Near Stuttgart, it lies at the headwaters of the Schwippe (a tributary of the river Würm), and is home to a Mercedes-Benz assembly plant.

辛德尔芬根(Sindelfingen)是位于德国巴登-符腾堡州的一个城市。位于斯图加特西南15公里处。当地的主要经济产业是汽车业和纺织业。首见记载于1155年。


Physical characteristics.

Saturn is a gas giant because it is predominantly composed of hydrogen and helium. It lacks a definite surface, though it may have a solid core. Saturn's rotation causes it to have the shape of an oblate spheroid; that is, it is flattened at the poles and bulges at its equator. Its equatorial and polar radii differ by almost 10%: 60,268 km versus 54,364 km. Jupiter, Uranus, and Neptune, the other giant planets in the Solar System, are also oblate but to a lesser extent. The combination of the bulge and rotation rate means that the effective surface gravity along the equator,, is 74% that at the poles and is lower than the surface gravity of Earth. However, the equatorial escape velocity of nearly is much higher than that for Earth.  Saturn is the only planet of the Solar System that is less dense than water—about 30% less. Although Saturn's core is considerably denser than water, the average specific density of the planet is due to the atmosphere. Jupiter has 318 times Earth's mass, and Saturn is 95 times Earth's mass. Together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System.

Internal structure.

Despite consisting mostly of hydrogen and helium, most of Saturn's mass is not in the gas phase, because hydrogen becomes a non-ideal liquid when the density is above, which is reached at a radius containing 99.9% of Saturn's mass. The temperature, pressure, and density inside Saturn all rise steadily toward the core, which causes hydrogen to be a metal in the deeper layers.  Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium, with trace amounts of various volatiles. This core is similar in composition to Earth, but is more dense. The examination of Saturn's gravitational moment, in combination with physical models of the interior, has allowed constraints to be placed on the mass of Saturn's core. In 2004, scientists estimated that the core must be 9–22 times the mass of Earth, which corresponds to a diameter of about 25,000 km. This is surrounded by a thicker liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions to a gas with increasing altitude. The outermost layer spans 1,000 km and consists of gas.  Saturn has a hot interior, reaching 11,700 °C at its core, and it radiates 2.5 times more energy into space than it receives from the Sun. Jupiter's thermal energy is generated by the Kelvin–Helmholtz mechanism of slow gravitational compression, but such a process alone may not be sufficient to explain heat production for Saturn, because it is less massive. An alternative or additional mechanism may be generation of heat through the "raining out" of droplets of helium deep in Saturn's interior. As the droplets descend through the lower-density hydrogen, the process releases heat by friction and leaves Saturn's outer layers depleted of helium. These descending droplets may have accumulated into a helium shell surrounding the core. Rainfalls of diamonds have been suggested to occur within Saturn, as well as in Jupiter and ice giants Uranus and Neptune.

Atmosphere.

The outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium by volume. The proportion of helium is significantly deficient compared to the abundance of this element in the Sun. The quantity of elements heavier than helium (metallicity) is not known precisely, but the proportions are assumed to match the primordial abundances from the formation of the Solar System. The total mass of these heavier elements is estimated to be 19–31 times the mass of the Earth, with a significant fraction located in Saturn's core region.  Trace amounts of ammonia, acetylene, ethane, propane, phosphine, and methane have been detected in Saturn's atmosphere. The upper clouds are composed of ammonia crystals, while the lower level clouds appear to consist of either ammonium hydrosulfide () or water. Ultraviolet radiation from the Sun causes methane photolysis in the upper atmosphere, leading to a series of hydrocarbon chemical reactions with the resulting products being carried downward by eddies and diffusion. This photochemical cycle is modulated by Saturn's annual seasonal cycle.

Cloud layers.

Saturn's atmosphere exhibits a banded pattern similar to Jupiter's, but Saturn's bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn's finer cloud patterns were not observed until the flybys of the "Voyager" spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made.  The composition of the clouds varies with depth and increasing pressure. In the upper cloud layers, with the temperature in the range 100–160 K and pressures extending between 0.5–2 bar, the clouds consist of ammonia ice. Water ice clouds begin at a level where the pressure is about 2.5 bar and extend down to 9.5 bar, where temperatures range from 185–270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure range 3–6 bar with temperatures of 190–235 K. Finally, the lower layers, where pressures are between 10–20 bar and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution.  Saturn's usually bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter. In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the "Voyager" encounters, and in 1994 another smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice. Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020.  The winds on Saturn are the second fastest among the Solar System's planets, after Neptune's. "Voyager" data indicate peak easterly winds of. In images from the "Cassini" spacecraft during 2007, Saturn's northern hemisphere displayed a bright blue hue, similar to Uranus. The color was most likely caused by Rayleigh scattering. Thermography has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, suspected to be the warmest spot on Saturn.

North pole hexagonal cloud pattern.

A persisting hexagonal wave pattern around the north polar vortex in the atmosphere at about 78°N was first noted in the "Voyager" images. The sides of the hexagon are each about long, which is longer than the diameter of the Earth. The entire structure rotates with a period of (the same period as that of the planet's radio emissions) which is assumed to be equal to the period of rotation of Saturn's interior. The hexagonal feature does not shift in longitude like the other clouds in the visible atmosphere. The pattern's origin is a matter of much speculation. Most scientists think it is a standing wave pattern in the atmosphere. Polygonal shapes have been replicated in the laboratory through differential rotation of fluids.

South pole vortex.

HST imaging of the south polar region indicates the presence of a jet stream, but no strong polar vortex nor any hexagonal standing wave. NASA reported in November 2006 that "Cassini" had observed a "hurricane-like" storm locked to the south pole that had a clearly defined eyewall. Eyewall clouds had not previously been seen on any planet other than Earth. For example, images from the "Galileo" spacecraft did not show an eyewall in the Great Red Spot of Jupiter.  The south pole storm may have been present for billions of years. This vortex is comparable to the size of Earth, and it has winds of 550 km/h.

Other features.

"Cassini" observed a series of cloud features nicknamed "String of Pearls" found in northern latitudes. These features are cloud clearings that reside in deeper cloud layers.

Magnetosphere.

Saturn has an intrinsic magnetic field that has a simple, symmetric shape – a magnetic dipole. Its strength at the equator – 0.2 gauss (20 μT) – is approximately one twentieth of that of the field around Jupiter and slightly weaker than Earth's magnetic field. As a result, Saturn's magnetosphere is much smaller than Jupiter's. When "Voyager 2" entered the magnetosphere, the solar wind pressure was high and the magnetosphere extended only 19 Saturn radii, or 1.1 million km (712,000 mi), although it enlarged within several hours, and remained so for about three days. Most probably, the magnetic field is generated similarly to that of Jupiter – by currents in the liquid metallic-hydrogen layer called a metallic-hydrogen dynamo. This magnetosphere is efficient at deflecting the solar wind particles from the Sun. The moon Titan orbits within the outer part of Saturn's magnetosphere and contributes plasma from the ionized particles in Titan's outer atmosphere. Saturn's magnetosphere, like Earth's, produces aurorae.

Orbit and rotation.

The average distance between Saturn and the Sun is over 1.4 billion kilometers (9 AU). With an average orbital speed of 9.68 km/s, it takes Saturn 10,759 Earth days (or about years) to finish one revolution around the Sun. As a consequence, it forms a near 5:2 mean-motion resonance with Jupiter. The elliptical orbit of Saturn is inclined 2.48° relative to the orbital plane of the Earth. The perihelion and aphelion distances are, respectively, 9.195 and 9.957 AU, on average. The visible features on Saturn rotate at different rates depending on latitude and multiple rotation periods have been assigned to various regions (as in Jupiter's case).  Astronomers use three different systems for specifying the rotation rate of Saturn. "System I" has a period of (844.3°/d) and encompasses the Equatorial Zone, the South Equatorial Belt, and the North Equatorial Belt. The polar regions are considered to have rotation rates similar to "System I". All other Saturnian latitudes, excluding the north and south polar regions, are indicated as "System II" and have been assigned a rotation period of (810.76°/d). "System III" refers to Saturn's internal rotation rate. Based on radio emissions from the planet detected by "Voyager 1" and "Voyager 2", System III has a rotation period of (810.8°/d). System III has largely superseded System II.  A precise value for the rotation period of the interior remains elusive. While approaching Saturn in 2004, "Cassini" found that the radio rotation period of Saturn had increased appreciably, to approximately. The latest estimate of Saturn's rotation (as an indicated rotation rate for Saturn as a whole) based on a compilation of various measurements from the "Cassini", "Voyager" and "Pioneer" probes was reported in September 2007 is.  In March 2007, it was found that the variation of radio emissions from the planet did not match Saturn's rotation rate. This variance may be caused by geyser activity on Saturn's moon Enceladus. The water vapor emitted into Saturn's orbit by this activity becomes charged and creates a drag upon Saturn's magnetic field, slowing its rotation slightly relative to the rotation of the planet.  An apparent oddity for Saturn is that it does not have any known trojan asteroids. These are minor planets that orbit the Sun at the stable Lagrangian points, designated L and L, located at 60° angles to the planet along its orbit. Trojan asteroids have been discovered for Mars, Jupiter, Uranus, and Neptune. Orbital resonance mechanisms, including secular resonance, are believed to be the cause of the missing Saturnian trojans.

Natural satellites.

Saturn has 82 known moons, 53 of which have formal names. In addition, there is evidence of dozens to hundreds of moonlets with diameters of 40–500 meters in Saturn's rings, which are not considered to be true moons. Titan, the largest moon, comprises more than 90% of the mass in orbit around Saturn, including the rings. Saturn's second-largest moon, Rhea, may have a tenuous ring system of its own, along with a tenuous atmosphere. Many of the other moons are small: 34 are less than 10 km in diameter and another 14 between 10 and 50 km in diameter. Traditionally, most of Saturn's moons have been named after Titans of Greek mythology. Titan is the only satellite in the Solar System with a major atmosphere, in which a complex organic chemistry occurs. It is the only satellite with hydrocarbon lakes.  On 6 June 2013, scientists at the IAA-CSIC reported the detection of polycyclic aromatic hydrocarbons in the upper atmosphere of Titan, a possible precursor for life. On 23 June 2014, NASA claimed to have strong evidence that nitrogen in the atmosphere of Titan came from materials in the Oort cloud, associated with comets, and not from the materials that formed Saturn in earlier times.  Saturn's moon Enceladus, which seems similar in chemical makeup to comets, has often been regarded as a potential habitat for microbial life. Evidence of this possibility includes the satellite's salt-rich particles having an "ocean-like" composition that indicates most of Enceladus's expelled ice comes from the evaporation of liquid salt water. A 2015 flyby by "Cassini" through a plume on Enceladus found most of the ingredients to sustain life forms that live by methanogenesis.  In April 2014, NASA scientists reported the possible beginning of a new moon within the A Ring, which was imaged by "Cassini" on 15 April 2013.

Planetary rings.

Saturn is probably best known for the system of planetary rings that makes it visually unique. The rings extend from outward from Saturn's equator and average approximately in thickness. They are composed predominantly of water ice with trace amounts of tholin impurities, and a peppered coating of approximately 7% amorphous carbon. The particles that make up the rings range in size from specks of dust up to 10 m. While the other gas giants also have ring systems, Saturn's is the largest and most visible.  There are two main hypotheses regarding the origin of the rings. One hypothesis is that the rings are remnants of a destroyed moon of Saturn. The second hypothesis is that the rings are left over from the original nebular material from which Saturn was formed. Some ice in the E ring comes from the moon Enceladus's geysers. The water abundance of the rings varies radially, with the outermost ring A being the most pure in ice water. This abundance variance may be explained by meteor bombardment.  Beyond the main rings at a distance of 12 million km from the planet is the sparse Phoebe ring, which is tilted at an angle of 27° to the other rings and, like Phoebe, orbits in retrograde fashion.  Some of the moons of Saturn, including Pandora and Prometheus, act as shepherd moons to confine the rings and prevent them from spreading out. Pan and Atlas cause weak, linear density waves in Saturn's rings that have yielded more reliable calculations of their masses.

History of observation and exploration.

The observation and exploration of Saturn can be divided into three main phases. The first era was ancient observations (such as with the naked eye), before the invention of the modern telescopes. Starting in the 17th century, progressively more advanced telescopic observations from Earth have been made. The third phase is visitation by space probes, by either orbiting or flyby. In the 21st century, observations continue from Earth (including Earth-orbiting observatories like the Hubble Space Telescope) and, until its 2017 retirement, from the "Cassini" orbiter around Saturn.

Ancient observations.

Saturn has been known since prehistoric times, and in early recorded history it was a major character in various mythologies. Babylonian astronomers systematically observed and recorded the movements of Saturn. In ancient Greek, the planet was known as Phainon, and in Roman times it was known as the "star of Saturn". In ancient Roman mythology, the planet Phainon was sacred to this agricultural god, from which the planet takes its modern name. The Romans considered the god Saturnus the equivalent of the Greek god Cronus; in modern Greek, the planet retains the name "Cronus"—: "Kronos".  The Greek scientist Ptolemy based his calculations of Saturn's orbit on observations he made while it was in opposition. In Hindu astrology, there are nine astrological objects, known as Navagrahas. Saturn is known as "Shani" and judges everyone based on the good and bad deeds performed in life. Ancient Chinese and Japanese culture designated the planet Saturn as the "earth star" (). This was based on Five Elements which were traditionally used to classify natural elements.  In ancient Hebrew, Saturn is called 'Shabbathai'. Its angel is Cassiel. Its intelligence or beneficial spirit is 'Agȋȇl (), and its darker spirit (demon) is Zȃzȇl (). Zazel has been described as a great angel, invoked in Solomonic magic, who is "effective in love conjurations". In Ottoman Turkish, Urdu and Malay, the name of Zazel is 'Zuhal', derived from the Arabic language ().

European observations (17th–19th centuries).

Saturn's rings require at least a 15-mm-diameter telescope to resolve and thus were not known to exist until Christiaan Huygens saw them in 1659. Galileo, with his primitive telescope in 1610, incorrectly thought of Saturn's appearing not quite round as two moons on Saturn's sides. It was not until Huygens used greater telescopic magnification that this notion was refuted, and the rings were truly seen for the first time. Huygens also discovered Saturn's moon Titan; Giovanni Domenico Cassini later discovered four other moons: Iapetus, Rhea, Tethys and Dione. In 1675, Cassini discovered the gap now known as the Cassini Division.  No further discoveries of significance were made until 1789 when William Herschel discovered two further moons, Mimas and Enceladus. The irregularly shaped satellite Hyperion, which has a resonance with Titan, was discovered in 1848 by a British team.  In 1899 William Henry Pickering discovered Phoebe, a highly irregular satellite that does not rotate synchronously with Saturn as the larger moons do. Phoebe was the first such satellite found and it takes more than a year to orbit Saturn in a retrograde orbit. During the early 20th century, research on Titan led to the confirmation in 1944 that it had a thick atmosphere – a feature unique among the Solar System's moons.

Modern NASA and ESA probes.

"Pioneer 11" flyby.

"Pioneer 11" made the first flyby of Saturn in September 1979, when it passed within 20,000 km of the planet's cloud tops. Images were taken of the planet and a few of its moons, although their resolution was too low to discern surface detail. The spacecraft also studied Saturn's rings, revealing the thin F-ring and the fact that dark gaps in the rings are bright when viewed at high phase angle (towards the Sun), meaning that they contain fine light-scattering material. In addition, "Pioneer 11" measured the temperature of Titan.

Voyager flybys.

In November 1980, the "Voyager 1" probe visited the Saturn system. It sent back the first high-resolution images of the planet, its rings and satellites. Surface features of various moons were seen for the first time. "Voyager 1" performed a close flyby of Titan, increasing knowledge of the atmosphere of the moon. It proved that Titan's atmosphere is impenetrable in visible wavelengths; therefore no surface details were seen. The flyby changed the spacecraft's trajectory out from the plane of the Solar System.  Almost a year later, in August 1981, "Voyager 2" continued the study of the Saturn system. More close-up images of Saturn's moons were acquired, as well as evidence of changes in the atmosphere and the rings. Unfortunately, during the flyby, the probe's turnable camera platform stuck for a couple of days and some planned imaging was lost. Saturn's gravity was used to direct the spacecraft's trajectory towards Uranus.  The probes discovered and confirmed several new satellites orbiting near or within the planet's rings, as well as the small Maxwell Gap (a gap within the C Ring) and Keeler gap (a 42 km-wide gap in the A Ring).

"Cassini–Huygens" spacecraft.

The "Cassini–Huygens" space probe entered orbit around Saturn on 1 July 2004. In June 2004, it conducted a close flyby of Phoebe, sending back high-resolution images and data. "Cassini" flyby of Saturn's largest moon, Titan, captured radar images of large lakes and their coastlines with numerous islands and mountains. The orbiter completed two Titan flybys before releasing the "Huygens" probe on 25 December 2004. "Huygens" descended onto the surface of Titan on 14 January 2005.  Starting in early 2005, scientists used "Cassini" to track lightning on Saturn. The power of the lightning is approximately 1,000 times that of lightning on Earth. In 2006, NASA reported that "Cassini" had found evidence of liquid water reservoirs no more than tens of meters below the surface that erupt in geysers on Saturn's moon Enceladus. These jets of icy particles are emitted into orbit around Saturn from vents in the moon's south polar region. Over 100 geysers have been identified on Enceladus. In May 2011, NASA scientists reported that Enceladus "is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it".  "Cassini" photographs have revealed a previously undiscovered planetary ring, outside the brighter main rings of Saturn and inside the G and E rings. The source of this ring is hypothesized to be the crashing of a meteoroid off Janus and Epimetheus. In July 2006, images were returned of hydrocarbon lakes near Titan's north pole, the presence of which were confirmed in January 2007. In March 2007, hydrocarbon seas were found near the North pole, the largest of which is almost the size of the Caspian Sea. In October 2006, the probe detected an 8,000 km diameter cyclone-like storm with an eyewall at Saturn's south pole.  From 2004 to 2 November 2009, the probe discovered and confirmed eight new satellites. In April 2013 "Cassini" sent back images of a hurricane at the planet's north pole 20 times larger than those found on Earth, with winds faster than. On 15 September 2017, the "Cassini-Huygens" spacecraft performed the "Grand Finale" of its mission: a number of passes through gaps between Saturn and Saturn's inner rings. The atmospheric entry of "Cassini" ended the mission.

Possible future missions.

The continued exploration of Saturn is still considered to be a viable option for NASA as part of their ongoing New Frontiers program of missions. NASA previously requested for plans to be put forward for a mission to Saturn that included the Saturn Atmospheric Entry Probe, and possible investigations into the habitability and possible discovery of life on Saturn's moons Titan and Enceladus by "Dragonfly".

Observation.

Saturn is the most distant of the five planets easily visible to the naked eye from Earth, the other four being Mercury, Venus, Mars and Jupiter. (Uranus, and occasionally 4 Vesta, are visible to the naked eye in dark skies.) Saturn appears to the naked eye in the night sky as a bright, yellowish point of light. The mean apparent magnitude of Saturn is 0.46 with a standard deviation of 0.34. Most of the magnitude variation is due to the inclination of the ring system relative to the Sun and Earth. The brightest magnitude, −0.55, occurs near in time to when the plane of the rings is inclined most highly, and the faintest magnitude, 1.17, occurs around the time when they are least inclined. It takes approximately 29.5 years for the planet to complete an entire circuit of the ecliptic against the background constellations of the zodiac. Most people will require an optical aid (very large binoculars or a small telescope) that magnifies at least 30 times to achieve an image of Saturn's rings, in which clear resolution is present. When Earth passes through the ring plane, which occurs twice every Saturnian year (roughly every 15 Earth years), the rings briefly disappear from view because they are so thin. Such a "disappearance" will next occur in 2025, but Saturn will be too close to the Sun for observations.  Saturn and its rings are best seen when the planet is at, or near, opposition, the configuration of a planet when it is at an elongation of 180°, and thus appears opposite the Sun in the sky. A Saturnian opposition occurs every year—approximately every 378 days—and results in the planet appearing at its brightest. Both the Earth and Saturn orbit the Sun on eccentric orbits, which means their distances from the Sun vary over time, and therefore so do their distances from each other, hence varying the brightness of Saturn from one opposition to the next. Saturn also appears brighter when the rings are angled such that they are more visible. For example, during the opposition of 17 December 2002, Saturn appeared at its brightest due to a favorable relative to the Earth, even though Saturn was closer to the Earth and Sun in late 2003. From time to time, Saturn is occulted by the Moon (that is, the Moon covers up Saturn in the sky). As with all the planets in the Solar System, occultations of Saturn occur in "seasons". Saturnian occultations will take place monthly for about a 12-month period, followed by about a five-year period in which no such activity is registered. The Moon's orbit is inclined by several degrees relative to Saturn's, so occultations will only occur when Saturn is near one of the points in the sky where the two planes intersect (both the length of Saturn's year and the 18.6-Earth year nodal precession period of the Moon's orbit influence the periodicity).

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine times that of Earth. It only has one-eighth the average density of Earth; however, with its larger volume, Saturn is over 95 times more massive. Saturn is named after the Roman god of wealth and agriculture; its astronomical symbol (♄) represents the god's sickle.

土星,为太阳系八大行星之一,至太阳距离(由近到远)位于第六、体积则仅次于木星。并与木星同属气体(类木)巨星。古代中国亦称之为镇星(常写作填星)。土星是中国古代人根据五行学说结合肉眼观测到的土星的颜色(黄色)来命名的(按照五行学说即木青、金白、火赤、水黑、土黄)。而其他语言中土星的名称基本上来自希腊/罗马神话传说,例如在欧美各主要语言(英语、法语、西班牙语、俄语、葡萄牙语、德语、意大利语等)中土星的名称来自于罗马神话中的农业之神萨图尔努斯(拉丁文:),其他的还有希腊神话中的克洛诺斯(泰坦族,宙斯的父亲,一说其在罗马神话中即萨图尔努斯)、巴比伦神话中的尼努尔塔和印度神话中的沙尼。土星的天文学符号是代表农神萨图尔努斯的镰刀(Unicode: )。土星主要由氢组成,还有少量的氦与微痕元素,内部的核心包括岩石和冰,外围由数层金属氢和气体包覆着。最外层的大气层在外观上通常情况下都是平淡的,虽然有时会有长时间存在的特征出现。土星的风速高达1,800公里/时,风速明显比木星快。土星的行星磁场强度介于地球和更强的木星之间。土星有一个显著的环系统,主要的成分是冰的微粒和较少数的岩石残骸以及尘土。已经确认的土星的卫星有82颗,是八大行星中最多。其中,土卫六是土星系统中最大和太阳系中第二大的卫星(半径2575KM,太阳系最大的衞星是木星的木卫三,半径2634KM),比行星中的水星还要大;并且土卫六是唯一拥有明显大气层的卫星。还有,土星距离地球13亿千米;地球一天等于23小时56分4.1秒,土星一天等于10小时42分0秒,是地球一天的大约九分之四。