| 单词 | enceladus |
| 释义 | EnceladusenUKEn·cel·a·dusE0124100 (ĕn-sĕl′ə-dəs)Enceladus(ɛnˈsɛlədəs)EnceladusEnceladusenUKEnceladus(ĕnsĕl`ədəs), in astronomy, one of the named moons, or natural satellites, of SaturnSaturn,in astronomy, 6th planet from the sun. Astronomical and Physical Characteristics of Saturn Saturn's orbit lies between those of Jupiter and Uranus; its mean distance from the sun is c.886 million mi (1. ..... Click the link for more information. . Also known as Saturn II (or S2), Enceladus is 310 mi (500 km) in diameter, orbits Saturn at a mean distance of 147,900 mi (238,020 km), and has equal orbital and rotational periods of 1.37 earth days. It was discovered in 1789 by the English astronomer Sir William HerschelHerschel , family of distinguished English astronomers. Sir William Herschel Sir William Herschel, 1738–1822, born Friedrich Wilhelm Herschel, was a great pioneer in astronomy. ..... Click the link for more information. . Enceladus has the highest reflectivity (almost 100%) of any body in the solar system. Its surface, apparently dominated by fresh, clean ice, is marked by few craters, smooth plains, and extensive fissures and ridges. Observations indicate that Enceladus has had five distinct geologic periods. The fresh surface suggests relatively recent cryovolcanism, caused perhaps by tidal forces exerted by Saturn and the moon DioneDione , in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn IV (or S4), Dione is 695 mi (1,120 km) in diameter, orbits Saturn at a mean distance of 234,500 mi (377,400 km), and has an orbital period of 2. ..... Click the link for more information. , with which Enceladus forms a satellite pair (that is, they interact gravitationally). In 2005 the space probe Cassini discovered Enceladus has an atmosphere, albeit one that must be replenished by a source on the moon, because its gravity is too weak to permanently retain an atmosphere. The probe also discovered (2006 and subsequent flybys) geyserlike eruptions on the moon. These eruptions contribute material to the replenishment of Saturn's E ring, and are fed by a global saltwater ocean beneath the surface ice. The ocean has a nutrient content that would support microbial life as well as organic compounds that are necessary precursors for life. Enceladus(en-sell -ă-dŭs) A satellite of Saturn, discovered in 1789 by William Herschel, that is one of the innermost moons of the planet, orbiting it at a distance of 238 100 km. It has been found to have a varied surface of ancient and youthful geological developments. Its diameter is only 500 km and its density 1.6 g cm–3. Enceladus is the most highly reflective large object in the Solar System with an albedo approaching 1.0. The surface shows evidence of highly cratered regions (5–35 km diameter), smooth plains, and ridged plains. The valleys and ridges indicate crustal movements that may have been associated with faulting and the extrusion of fluids. Tidal effects from the nearby and larger satellite Dione may account for the production of the surface faulting and may have allowed the warmer fluid from the interior to resurface portions of the satellite. This situation also occurs on the Jovian satellite Io, so it is possible that Enceladus is still geologically active. During flybys in February and March 2005, the Cassini/Huygens spacecraft founded evidence of a significant atmosphere of ionized water vapor, due perhaps to volcanism, the eruption of geysers, or the escape of gases from the surface or the interior of Enceladus. The E ring of Saturn shows a pronounced peak of brightness in the orbit of Enceladus and may consist of particles that have escaped from the satellite. See also Table 2, backmatter.Enceladusa satellite of Saturn, approximately 500 km in diameter and located at a mean distance of 237,900 km from the center of Saturn. It was discovered in 1789 by W. Herschel. Enceladus[‚en·se′lä·du̇s]Enceladus |
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