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| perihelion = | semimajor = | eccentricity = 0.006772 〔 | period = | synodic_period = 583.92 days〔 | avg_speed = 35.02 km/s | inclination = | asc_node = 76.680° 〔 | arg_peri = 54.884° | mean_anomaly = 50.115° | satellites = None | allsatellites=yes | physical_characteristics = yes | mean_radius = | flattening = 0〔 | surface_area = | volume = | mass = | density = | surface_grav = | escape_velocity = | sidereal_day = (retrograde)〔 | rot_velocity = | axial_tilt = 2.64° (for retrograde rotation) 177.36° (to orbit)〔〔Defining the rotation as retrograde, as done by NASA space missions and the USGS, puts Ishtar Terra in the northern hemisphere and makes the axial tilt 2.64°. Following the right-hand rule for prograde rotation puts Ishtar Terra in the southern hemisphere and makes the axial tilt 177.36°.〕 | right_asc_north_pole = | declination = 67.16° | albedo = | magnitude = | angular_size = 〔 | temperatures = yes | temp_name1 = Kelvin | mean_temp_1 = 737 K〔 | temp_name2 = Celsius | mean_temp_2 = 462 °C | mean_name3 = Fahrenheit | mean_temp_3 = | pronounced = | adjectives = Venusian or (rarely) Cytherean, Venerean | atmosphere = yes | surface_pressure = 92 bar (9.2 MPa) | atmosphere_composition = }} Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.〔 It has no natural satellite. It is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, mass, proximity to the Sun and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of , Venus is by far the hottest planet in the Solar System, even though Mercury is closer to the Sun. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It may have had oceans in the past,〔David Shiga (Did Venus's ancient oceans incubate life? ), New Scientist, 10 October 2007〕 but these would have vaporized as the temperature rose due to a runaway greenhouse effect.〔B.M. Jakosky, "Atmospheres of the Terrestrial Planets", in Beatty, Petersen and Chaikin (eds,), ''The New Solar System,'' 4th edition 1999, Sky Publishing Company (Boston) and Cambridge University Press (Cambridge), pp. 175–200〕 The water has most probably photodissociated, and, because of the lack of a planetary magnetic field, the free hydrogen has been swept into interplanetary space by the solar wind. Venus's surface is a dry desertscape interspersed with slab-like rocks and periodically refreshed by volcanism. == Physical characteristics == Venus is one of the four terrestrial planets in the Solar System, meaning that, like Earth, it is a rocky body. In size and mass, it is similar to Earth, and is often described as Earth's "sister" or "twin". The diameter of Venus is 12,092 km (only 650 km less than Earth's) and its mass is 81.5% of Earth's. Conditions on the Venusian surface differ radically from those on Earth because of its dense carbon dioxide atmosphere. The mass of the atmosphere of Venus is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen.〔(【引用サイトリンク】title=Atmosphere of Venus )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Venus」の詳細全文を読む スポンサード リンク
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