Venus

  1. ^ 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°.

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.[13] It has the longest rotation period (243 days) of any planet in the Solar System and rotates in the opposite direction to most other planets (meaning the Sun rises in the west and sets in the east).[14] It does not have any natural satellites. It is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the night sky after the Moon, reaching an apparent magnitude of −4.6 – bright enough to cast shadows at night and, rarely, visible to the naked eye in broad daylight.[15][16] Orbiting within Earth's orbit, Venus is an inferior planet and never appears to venture far from the Sun; its maximum angular distance from the Sun (elongation) is 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, or roughly the pressure found 900 m (3,000 ft) underwater on Earth. Venus is by far the hottest planet in the Solar System, with a mean surface temperature of 735 K (462 °C; 863 °F), 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 water oceans in the past,[17][18] but these would have vaporized as the temperature rose due to a runaway greenhouse effect.[19] The water has probably photodissociated, and the free hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field.[20] Venus's surface is a dry desertscape interspersed with slab-like rocks and is periodically resurfaced by volcanism.

As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the morning star and evening star. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC.[21]

As the planet with the closest approach to Earth, Venus has been a prime target for early interplanetary exploration. It was the first planet beyond Earth visited by a spacecraft (Mariner 2 in 1962), and the first to be successfully landed on (by Venera 7 in 1970). Venus's thick clouds render observation of its surface impossible in visible light, and the first detailed maps did not emerge until the arrival of the Magellan orbiter in 1991. Plans have been proposed for rovers or more complex missions, but they are hindered by Venus's hostile surface conditions.

Venus The Venusian symbol, a circle with a small equal-armed cross beneath it
Venus in approximately true colour, a nearly uniform pale cream, although the image has been processed to bring out details.[1] The planet's disc is about three-quarters illuminated; almost no variation or detail can be seen in the clouds
A real-colour image taken by Mariner 10 processed from two filters, the surface is obscured by thick sulfuric acid clouds
Designations
Pronunciation/ˈviːnəs/ (listen)
AdjectivesVenusian or (rarely) Cytherean, Venerean
Orbital characteristics[3][5]
Epoch J2000
Aphelion
  • 0.728213 AU
  • 108,939,000 km
Perihelion
  • 0.718440 AU
  • 107,477,000 km
  • 0.723332 AU
  • 108,208,000 km
Eccentricity0.006772[2]
583.92 days[3]
35.02 km/s
50.115°
Inclination
76.680°[2]
54.884°
SatellitesNone
Physical characteristics
Mean radius
  • 6,051.8±1.0 km[6]
  • 0.9499 Earths
Flattening0[6]
  • 4.6023×108 km2
  • 0.902 Earths
Volume
  • 9.2843×1011 km3
  • 0.866 Earths
Mass
  • 4.8675×1024 kg[7]
  • 0.815 Earths
Mean density
5.243 g/cm3
  • 8.87 m/s2
  • 0.904 g
10.36 km/s (6.44 mi/s)[8]
−243.025 d (retrograde)[3]
Equatorial rotation velocity
6.52 km/h (1.81 m/s)
2.64° (for retrograde rotation)
177.36° (to orbit)[3][note 1]
North pole right ascension
  •  18h 11m 2s
  • 272.76°[9]
North pole declination
67.16°
Albedo
Surface temp. min mean max
Kelvin 737 K[3]
Celsius 462 °C
Fahrenheit 864 °F (462 °C)
−4.92 to −2.98[12]
9.7″–66.0″[3]
Atmosphere
Surface pressure
92 bar (9.2 MPa)
Composition by volume
  1. ^ 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°.

Physical characteristics

Venus, Earth size comparison
Size comparison with Earth

Venus is one of the four terrestrial planets in the Solar System, meaning that it is a rocky body like Earth. It is similar to Earth in size and mass, and is often described as Earth's "sister" or "twin".[22] The diameter of Venus is 12,103.6 km (7,520.8 mi)—only 638.4 km (396.7 mi) 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 its dense atmosphere is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen.[23]

Geography

The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science in the 20th century. Venera landers in 1975 and 1982 returned images of a surface covered in sediment and relatively angular rocks.[24] The surface was mapped in detail by Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmosphere may indicate that there have been recent eruptions.[25][26]

About 80% of the Venusian surface is covered by smooth, volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth or lobate plains.[27] Two highland "continents" make up the rest of its surface area, one lying in the planet's northern hemisphere and the other just south of the equator. The northern continent is called Ishtar Terra after Ishtar, the Babylonian goddess of love, and is about the size of Australia. Maxwell Montes, the highest mountain on Venus, lies on Ishtar Terra. Its peak is 11 km (7 mi) above the Venusian average surface elevation.[28] The southern continent is called Aphrodite Terra, after the Greek goddess of love, and is the larger of the two highland regions at roughly the size of South America. A network of fractures and faults covers much of this area.[29]

The absence of evidence of lava flow accompanying any of the visible calderas remains an enigma. The planet has few impact craters, demonstrating that the surface is relatively young, approximately 300–600 million years old.[30][31] Venus has some unique surface features in addition to the impact craters, mountains, and valleys commonly found on rocky planets. Among these are flat-topped volcanic features called "farra", which look somewhat like pancakes and range in size from 20 to 50 km (12 to 31 mi) across, and from 100 to 1,000 m (330 to 3,280 ft) high; radial, star-like fracture systems called "novae"; features with both radial and concentric fractures resembling spider webs, known as "arachnoids"; and "coronae", circular rings of fractures sometimes surrounded by a depression. These features are volcanic in origin.[32]

Most Venusian surface features are named after historical and mythological women.[33] Exceptions are Maxwell Montes, named after James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio, and Ovda Regio. The latter three features were named before the current system was adopted by the International Astronomical Union, the body which oversees planetary nomenclature.[34]

The longitudes of physical features on Venus are expressed relative to its prime meridian. The original prime meridian passed through the radar-bright spot at the centre of the oval feature Eve, located south of Alpha Regio.[35] After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne.[36][37]

Surface geology

Maat Mons on Venus
False-colour image of Maat Mons with a vertical exaggeration of 22.5

Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over 100 km (62 mi) across. The only volcanic complex of this size on Earth is the Big Island of Hawaii.[32]:154 This is not because Venus is more volcanically active than Earth, but because its crust is older. Earth's oceanic crust is continually recycled by subduction at the boundaries of tectonic plates, and has an average age of about 100 million years,[38] whereas the Venusian surface is estimated to be 300–600 million years old.[30][32]

Several lines of evidence point to ongoing volcanic activity on Venus. During the Soviet Venera program, the Venera 9 orbiter obtained spectroscopic evidence of lightning on Venus,[39] and the Venera 12 descent probe obtained additional evidence of lightning and thunder.[40][41] The European Space Agency's Venus Express in 2007 detected whistler waves further confirming the occurrence of lightning on Venus.[42][43] One possibility is that ash from a volcanic eruption was generating the lightning. Another piece of evidence comes from measurements of sulfur dioxide concentrations in the atmosphere, which dropped by a factor of 10 between 1978 and 1986, jumped in 2006, and again declined 10-fold.[44] This may mean that levels had been boosted several times by large volcanic eruptions.[45][46]

In 2008 and 2009, the first direct evidence for ongoing volcanism was observed by Venus Express, in the form of four transient localized infrared hot spots within the rift zone Ganis Chasma,[47][n 1] near the shield volcano Maat Mons. Three of the spots were observed in more than one successive orbit. These spots are thought to represent lava freshly released by volcanic eruptions.[48][49] The actual temperatures are not known, because the size of the hot spots could not be measured, but are likely to have been in the 800–1,100 K (527–827 °C; 980–1,520 °F) range, relative to a normal temperature of 740 K (467 °C; 872 °F).[50]

PIA00103 Venus - 3-D Perspective View of Lavinia Planitia
Impact craters on the surface of Venus (false-colour image reconstructed from radar data)

Almost a thousand impact craters on Venus are evenly distributed across its surface. On other cratered bodies, such as Earth and the Moon, craters show a range of states of degradation. On the Moon, degradation is caused by subsequent impacts, whereas on Earth it is caused by wind and rain erosion. On Venus, about 85% of the craters are in pristine condition. The number of craters, together with their well-preserved condition, indicates the planet underwent a global resurfacing event about 300–600 million years ago,[30][31] followed by a decay in volcanism.[51] Whereas Earth's crust is in continuous motion, Venus is thought to be unable to sustain such a process. Without plate tectonics to dissipate heat from its mantle, Venus instead undergoes a cyclical process in which mantle temperatures rise until they reach a critical level that weakens the crust. Then, over a period of about 100 million years, subduction occurs on an enormous scale, completely recycling the crust.[32]

Venusian craters range from 3 to 280 km (2 to 174 mi) in diameter. No craters are smaller than 3 km, because of the effects of the dense atmosphere on incoming objects. Objects with less than a certain kinetic energy are slowed down so much by the atmosphere that they do not create an impact crater.[52] Incoming projectiles less than 50 m (160 ft) in diameter will fragment and burn up in the atmosphere before reaching the ground.[53]

Internal structure

Venus structure
The internal structure of Venus – the crust (outer layer), the mantle (middle layer) and the core (yellow inner layer)

Without seismic data or knowledge of its moment of inertia, little direct information is available about the internal structure and geochemistry of Venus.[54] The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is at least partially liquid because the two planets have been cooling at about the same rate.[55] The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth's.[56] The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong to subduct without water to make it less viscous. This results in reduced heat loss from the planet, preventing it from cooling and providing a likely explanation for its lack of an internally generated magnetic field.[57] Instead, Venus may lose its internal heat in periodic major resurfacing events.[30]

Atmosphere and climate

Venuspioneeruv
Cloud structure in the Venusian atmosphere in 1979, revealed by observations in the ultraviolet band by Pioneer Venus Orbiter
Venus globe
Global radar view of Venus (without the clouds) from Magellan between 1990 and 1994

Venus has an extremely dense atmosphere composed of 96.5% carbon dioxide, 3.5% nitrogen, and traces of other gases, most notably sulfur dioxide.[58] The mass of its atmosphere is 93 times that of Earth's, whereas the pressure at its surface is about 92 times that at Earth's—a pressure equivalent to that at a depth of nearly 1 kilometre (0.62 mi) under Earth's oceans. The density at the surface is 65 kg/m3, 6.5% that of water or 50 times as dense as Earth's atmosphere at 293 K (20 °C; 68 °F) at sea level. The CO
2
-rich atmosphere generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 735 K (462 °C; 864 °F).[13][59] This makes Venus's surface hotter than Mercury's, which has a minimum surface temperature of 53 K (−220 °C; −364 °F) and maximum surface temperature of 700 K (427 °C; 801 °F),[60][61] even though Venus is nearly twice Mercury's distance from the Sun and thus receives only 25% of Mercury's solar irradiance. This temperature is higher than that used for sterilization.

Studies have suggested that billions of years ago Venus's atmosphere was much more like Earth's than it is now, and that there may have been substantial quantities of liquid water on the surface, but after a period of 600 million to several billion years,[62] a runaway greenhouse effect was caused by the evaporation of that original water, which generated a critical level of greenhouse gases in its atmosphere.[63] Although the surface conditions on Venus are no longer hospitable to any Earth-like life that may have formed before this event, there is speculation on the possibility that life exists in the upper cloud layers of Venus, 50 km (31 mi) up from the surface, where the temperature ranges between 303 and 353 K (30 and 80 °C; 86 and 176 °F) but the environment is acidic.[64][65][66]

Thermal inertia and the transfer of heat by winds in the lower atmosphere mean that the temperature of Venus's surface does not vary significantly between the night and day sides, despite Venus's extremely slow rotation. Winds at the surface are slow, moving at a few kilometres per hour, but because of the high density of the atmosphere at the surface, they exert a significant amount of force against obstructions, and transport dust and small stones across the surface. This alone would make it difficult for a human to walk through, even if the heat, pressure, and lack of oxygen were not a problem.[67]

Above the dense CO
2
layer are thick clouds consisting mainly of sulfuric acid, which is formed by sulfur dioxide and water through a chemical reaction resulting in sulfuric acid hydrate. Additionally, the atmosphere consists of approximately 1% ferric chloride.[68][69] Other possible constituents of the cloud particles are ferric sulfate, aluminium chloride and phosphoric anhydride. Clouds at different levels have different compositions and particle size distributions.[68] These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of Venus's surface. The permanent cloud cover means that although Venus is closer than Earth to the Sun, it receives less sunlight on the ground. Strong 300 km/h (185 mph) winds at the cloud tops go around Venus about every four to five Earth days.[70] Winds on Venus move at up to 60 times the speed of its rotation, whereas Earth's fastest winds are only 10–20% rotation speed.[71]

The surface of Venus is effectively isothermal; it retains a constant temperature not only between day and night sides but between the equator and the poles.[3][72] Venus's minute axial tilt—less than 3°, compared to 23° on Earth—also minimises seasonal temperature variation.[73] The only appreciable variation in temperature occurs with altitude. The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about 655 K (380 °C; 715 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).[74][75] In 1995, the Magellan spacecraft imaged a highly reflective substance at the tops of the highest mountain peaks that bore a strong resemblance to terrestrial snow. This substance likely formed from a similar process to snow, albeit at a far higher temperature. Too volatile to condense on the surface, it rose in gaseous form to higher elevations, where it is cooler and could precipitate. The identity of this substance is not known with certainty, but speculation has ranged from elemental tellurium to lead sulfide (galena).[76]

The clouds of Venus may be capable of producing lightning.[77] The existence of lightning in the atmosphere of Venus has been controversial since the first suspected bursts were detected by the Soviet Venera probes. In 2006–07, Venus Express clearly detected whistler mode waves, the signatures of lightning. Their intermittent appearance indicates a pattern associated with weather activity. According to these measurements, the lightning rate is at least half of that on Earth.[42] In 2007, Venus Express discovered that a huge double atmospheric vortex exists at the south pole.[78][79]

Venus Express also discovered, in 2011, that an ozone layer exists high in the atmosphere of Venus.[80] On 29 January 2013, ESA scientists reported that the ionosphere of Venus streams outwards in a manner similar to "the ion tail seen streaming from a comet under similar conditions."[81][82]

In December 2015 and to a lesser extent in April and May 2016, researchers working on Japan's Akatsuki mission observed bow shapes in the atmosphere of Venus. This was considered direct evidence of the existence of perhaps the largest stationary gravity waves in the solar system.[83][84][85]

Synthetic atmosphere absorption spectrum
Absorption spectrum of a simple gas mixture corresponding to Earth's atmosphere
Synthetic Venus atmosphere absorption spectrum
The composition of the atmosphere of Venus based on HITRAN data[86] created using HITRAN on the Web system.[87]

Magnetic field and core

In 1967, Venera 4 found Venus's magnetic field to be much weaker than that of Earth. This magnetic field is induced by an interaction between the ionosphere and the solar wind,[88][89] rather than by an internal dynamo as in the Earth's core. Venus's small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation.

The lack of an intrinsic magnetic field at Venus was surprising, given that it is similar to Earth in size and was expected also to contain a dynamo at its core. A dynamo requires three things: a conducting liquid, rotation, and convection. The core is thought to be electrically conductive and, although its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo.[90][91] This implies that the dynamo is missing because of a lack of convection in Venus's core. On Earth, convection occurs in the liquid outer layer of the core because the bottom of the liquid layer is much hotter than the top. On Venus, a global resurfacing event may have shut down plate tectonics and led to a reduced heat flux through the crust. This caused the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, no internal geodynamo is available to drive a magnetic field. Instead, the heat from the core is being used to reheat the crust.[92]

One possibility is that Venus has no solid inner core,[93] or that its core is not cooling, so that the entire liquid part of the core is at approximately the same temperature. Another possibility is that its core has already completely solidified. The state of the core is highly dependent on the concentration of sulfur, which is unknown at present.[92]

The weak magnetosphere around Venus means that the solar wind is interacting directly with its outer atmosphere. Here, ions of hydrogen and oxygen are being created by the dissociation of neutral molecules from ultraviolet radiation. The solar wind then supplies energy that gives some of these ions sufficient velocity to escape Venus's gravity field. This erosion process results in a steady loss of low-mass hydrogen, helium, and oxygen ions, whereas higher-mass molecules, such as carbon dioxide, are more likely to be retained. Atmospheric erosion by the solar wind probably led to the loss of most of Venus's water during the first billion years after it formed.[94] The erosion has increased the ratio of higher-mass deuterium to lower-mass hydrogen in the atmosphere 100 times compared to the rest of the solar system.[95]

Orbit and rotation

Venusorbitsolarsystem
Venus orbits the Sun at an average distance of about 108 million kilometres (about 0.7 AU) and completes an orbit every 224.7 days. Venus is the second planet from the Sun and orbits the Sun approximately 1.6 times (yellow trail) in Earth's 365 days (blue trail)

Venus orbits the Sun at an average distance of about 0.72 AU (108 million km; 67 million mi), and completes an orbit every 224.7 days. Although all planetary orbits are elliptical, Venus's orbit is the closest to circular, with an eccentricity of less than 0.01.[3] When Venus lies between Earth and the Sun in inferior conjunction, it makes the closest approach to Earth of any planet at an average distance of 41 million km (25 million mi).[3] The planet reaches inferior conjunction every 584 days, on average.[3] Because of the decreasing eccentricity of Earth's orbit, the minimum distances will become greater over tens of thousands of years. From the year 1 to 5383, there are 526 approaches less than 40 million km; then there are none for about 60,158 years.[96]

All the planets in the Solar System orbit the Sun in a anticlockwise direction as viewed from above Earth's north pole. Most planets also rotate on their axes in an anti-clockwise direction, but Venus rotates clockwise in retrograde rotation once every 243 Earth days—the slowest rotation of any planet. Because its rotation is so slow, Venus is very close to spherical.[97] A Venusian sidereal day thus lasts longer than a Venusian year (243 versus 224.7 Earth days). Venus's equator rotates at 6.52 km/h (4.05 mph), whereas Earth's rotates at 1,669.8 km/h (1,037.6 mph).[98] Venus's rotation has slowed down in the 16 years between the Magellan spacecraft and Venus Express visits; each Venusian sidereal day has increased by 6.5 minutes in that time span.[99] Because of the retrograde rotation, the length of a solar day on Venus is significantly shorter than the sidereal day, at 116.75 Earth days (making the Venusian solar day shorter than Mercury's 176 Earth days).[100] One Venusian year is about 1.92 Venusian solar days.[101] To an observer on the surface of Venus, the Sun would rise in the west and set in the east,[101] although Venus's opaque clouds prevent observing the Sun from the planet's surface.[102]

Venus may have formed from the solar nebula with a different rotation period and obliquity, reaching its current state because of chaotic spin changes caused by planetary perturbations and tidal effects on its dense atmosphere, a change that would have occurred over the course of billions of years. The rotation period of Venus may represent an equilibrium state between tidal locking to the Sun's gravitation, which tends to slow rotation, and an atmospheric tide created by solar heating of the thick Venusian atmosphere.[103][104] The 584-day average interval between successive close approaches to Earth is almost exactly equal to 5 Venusian solar days,[105] but the hypothesis of a spin–orbit resonance with Earth has been discounted.[106]

Venus has no natural satellites.[107] It has several trojan asteroids: the quasi-satellite 2002 VE68[108][109] and two other temporary trojans, 2001 CK32 and 2012 XE133.[110] In the 17th century, Giovanni Cassini reported a moon orbiting Venus, which was named Neith and numerous sightings were reported over the following 200 years, but most were determined to be stars in the vicinity. Alex Alemi's and David Stevenson's 2006 study of models of the early Solar System at the California Institute of Technology shows Venus likely had at least one moon created by a huge impact event billions of years ago.[111] About 10 million years later, according to the study, another impact reversed the planet's spin direction and caused the Venusian moon gradually to spiral inward until it collided with Venus.[112] If later impacts created moons, these were removed in the same way. An alternative explanation for the lack of satellites is the effect of strong solar tides, which can destabilize large satellites orbiting the inner terrestrial planets.[107]

Observation

Venus-pacific-levelled
Venus is always brighter than all other planets or stars (except the Sun) as seen from Earth. The second brightest object on the image is Jupiter.

To the naked eye, Venus appears as a white point of light brighter than any other planet or star (apart from the Sun).[113] The planet's mean apparent magnitude is -4.14 with a standard deviation of 0.31.[12] The brightest magnitude occurs during crescent phase about one month before or after inferior conjunction. Venus fades to about magnitude −3 when it is backlit by the Sun.[114] The planet is bright enough to be seen in a clear midday sky[115] and is more easily visible when the Sun is low on the horizon or setting. As an inferior planet, it always lies within about 47° of the Sun.[116]

Venus "overtakes" Earth every 584 days as it orbits the Sun.[3] As it does so, it changes from the "Evening Star", visible after sunset, to the "Morning Star", visible before sunrise. Although Mercury, the other inferior planet, reaches a maximum elongation of only 28° and is often difficult to discern in twilight, Venus is hard to miss when it is at its brightest. Its greater maximum elongation means it is visible in dark skies long after sunset. As the brightest point-like object in the sky, Venus is a commonly misreported "unidentified flying object".

Phases

Phases Venus
The phases of Venus and evolution of its apparent diameter

As it orbits the Sun, Venus displays phases like those of the Moon in a telescopic view. The planet appears as a small and "full" disc when it is on the opposite side of the Sun (at superior conjunction). Venus shows a larger disc and "quarter phase" at its maximum elongations from the Sun, and appears its brightest in the night sky. The planet presents a much larger thin "crescent" in telescopic views as it passes along the near side between Earth and the Sun. Venus displays its largest size and "new phase" when it is between Earth and the Sun (at inferior conjunction). Its atmosphere is visible through telescopes by the halo of sunlight refracted around it.[116]

Transits

The Venusian orbit is slightly inclined relative to Earth's orbit; thus, when the planet passes between Earth and the Sun, it usually does not cross the face of the Sun. Transits of Venus occur when the planet's inferior conjunction coincides with its presence in the plane of Earth's orbit. Transits of Venus occur in cycles of 243 years with the current pattern of transits being pairs of transits separated by eight years, at intervals of about 105.5 years or 121.5 years—a pattern first discovered in 1639 by the English astronomer Jeremiah Horrocks.[117]

The latest pair was June 8, 2004 and June 5–6, 2012. The transit could be watched live from many online outlets or observed locally with the right equipment and conditions.[118]

The preceding pair of transits occurred in December 1874 and December 1882; the following pair will occur in December 2117 and December 2125.[119] The oldest film known is the 1874 Passage de Venus, showing the 1874 Venus transit of the sun. Historically, transits of Venus were important, because they allowed astronomers to determine the size of the astronomical unit, and hence the size of the Solar System as shown by Horrocks in 1639.[120] Captain Cook's exploration of the east coast of Australia came after he had sailed to Tahiti in 1768 to observe a transit of Venus.[121][122]

Pentagram of Venus

Venus geocentric orbit curve simplified Line (pentagram)
The pentagram of Venus. Earth is positioned at the centre of the diagram, and the curve represents the direction and distance of Venus as a function of time.

The pentagram of Venus is the path that Venus makes as observed from Earth. Successive inferior conjunctions of Venus repeat very near a 13:8 orbital resonance (Earth orbits 8 times for every 13 orbits of Venus), shifting 144° upon sequential inferior conjunctions. The resonance 13:8 ratio is approximate. 8/13 is approximately 0.615385 while Venus orbits the Sun in 0.615187 years.[123]

Daylight apparitions

Naked eye observations of Venus during daylight hours exist in several anecdotes and records. Astronomer Edmund Halley calculated its maximum naked eye brightness in 1716, when many Londoners were alarmed by its appearance in the daytime. French emperor Napoleon Bonaparte once witnessed a daytime apparition of the planet while at a reception in Luxembourg.[124] Another historical daytime observation of the planet took place during the inauguration of the American president Abraham Lincoln in Washington, D.C., on 4 March 1865.[125] Although naked eye visibility of Venus's phases is disputed, records exist of observations of its crescent.[126]

Ashen light

A long-standing mystery of Venus observations is the so-called ashen light—an apparent weak illumination of its dark side, seen when the planet is in the crescent phase. The first claimed observation of ashen light was made in 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated it may result from electrical activity in the Venusian atmosphere, but it could be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.[127][40]

Studies

Early studies

Venus Drawing
The "black drop effect" as recorded during the 1769 transit

Though some ancient civilizations referred to Venus both as the "morning star" and as the "evening star", names that reflect the assumption that these were two separate objects, the earliest recorded observations of Venus by the ancient Sumerians show that they recognized Venus as a single object,[128] and associated it with the goddess Inanna.[128][129][130] Inanna's movements in several of her myths, including Inanna and Shukaletuda and Inanna's Descent into the Underworld appear to parallel the motion of the planet Venus.[128] The Venus tablet of Ammisaduqa, believed to have been compiled around the mid-seventeenth century BCE,[131] shows the Babylonians understood the two were a single object, referred to in the tablet as the "bright queen of the sky", and could support this view with detailed observations.[132]

The Chinese historically referred to the morning Venus as "the Great White" (Tài-bái 太白) or "the Opener (Starter) of Brightness" (Qǐ-míng 啟明), and the evening Venus as "the Excellent West One" (Cháng-gēng 長庚).[133]

The ancient Greeks also initially believed Venus to be two separate stars: Phosphorus, the morning star, and Hesperus, the evening star. Pliny the Elder credited the realization that they were a single object to Pythagoras in the sixth century BCE,[134] while Diogenes Laërtius argued that Parmenides was probably responsible for this rediscovery.[135] Though they recognized Venus as a single object, the ancient Romans continued to designate the morning aspect of Venus as Lucifer, literally "Light-Bringer", and the evening aspect as Vesper, both of which are literal translations of their traditional Greek names.

In the second century, in his astronomical treatise Almagest, Ptolemy theorized that both Mercury and Venus are located between the Sun and the Earth. The 11th century Persian astronomer Avicenna claimed to have observed the transit of Venus,[136] which later astronomers took as confirmation of Ptolemy's theory.[137] In the 12th century, the Andalusian astronomer Ibn Bajjah observed "two planets as black spots on the face of the Sun"; these were later identified as the transits of Venus and Mercury by the Maragha astronomer Qotb al-Din Shirazi in the 13th century, though this identification cannot be true as there were no Venus transits in Ibn Bajjah's lifetime.[138][n 2]

Phases-of-Venus
Galileo's discovery that Venus showed phases (although remaining near the Sun in Earth's sky) proved that it orbits the Sun and not Earth

When the Italian physicist Galileo Galilei first observed the planet in the early 17th century, he found it showed phases like the Moon, varying from crescent to gibbous to full and vice versa. When Venus is furthest from the Sun in the sky, it shows a half-lit phase, and when it is closest to the Sun in the sky, it shows as a crescent or full phase. This could be possible only if Venus orbited the Sun, and this was among the first observations to clearly contradict the Ptolemaic geocentric model that the Solar System was concentric and centred on Earth.[141][142]

The 1639 transit of Venus was accurately predicted by Jeremiah Horrocks and observed by him and his friend, William Crabtree, at each of their respective homes, on 4 December 1639 (24 November under the Julian calendar in use at that time).[143]

The atmosphere of Venus was discovered in 1761 by Russian polymath Mikhail Lomonosov.[144][145] Venus's atmosphere was observed in 1790 by German astronomer Johann Schröter. Schröter found when the planet was a thin crescent, the cusps extended through more than 180°. He correctly surmised this was due to scattering of sunlight in a dense atmosphere. Later, American astronomer Chester Smith Lyman observed a complete ring around the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.[146] The atmosphere complicated efforts to determine a rotation period for the planet, and observers such as Italian-born astronomer Giovanni Cassini and Schröter incorrectly estimated periods of about 24 h from the motions of markings on the planet's apparent surface.[147]

Ground-based research

Vénus télescope
Modern telescopic view of Venus from Earth's surface

Little more was discovered about Venus until the 20th century. Its almost featureless disc gave no hint what its surface might be like, and it was only with the development of spectroscopic, radar and ultraviolet observations that more of its secrets were revealed. The first ultraviolet observations were carried out in the 1920s, when Frank E. Ross found that ultraviolet photographs revealed considerable detail that was absent in visible and infrared radiation. He suggested this was due to a dense, yellow lower atmosphere with high cirrus clouds above it.[148]

Spectroscopic observations in the 1900s gave the first clues about the Venusian rotation. Vesto Slipher tried to measure the Doppler shift of light from Venus, but found he could not detect any rotation. He surmised the planet must have a much longer rotation period than had previously been thought.[149] Later work in the 1950s showed the rotation was retrograde. Radar observations of Venus were first carried out in the 1960s, and provided the first measurements of the rotation period, which were close to the modern value.[150]

Radar observations in the 1970s revealed details of the Venusian surface for the first time. Pulses of radio waves were beamed at the planet using the 300 m (980 ft) radio telescope at Arecibo Observatory, and the echoes revealed two highly reflective regions, designated the Alpha and Beta regions. The observations also revealed a bright region attributed to mountains, which was called Maxwell Montes.[151] These three features are now the only ones on Venus that do not have female names.[34]

Exploration

Mariner 2
Artist's impression of Mariner 2, launched in 1962, a skeletal, bottle-shaped spacecraft with a large radio dish on top

The first robotic space probe mission to Venus, and the first to any planet, began with the Soviet Venera program in 1961.[152] The United States' exploration of Venus had its first success with the Mariner 2 mission on 14 December 1962, becoming the world's first successful interplanetary mission, passing 34,833 km (21,644 mi) above the surface of Venus, and gathering data on the planet's atmosphere.[153][154]

On 18 October 1967, the Soviet Venera 4 successfully entered the atmosphere and deployed science experiments. Venera 4 showed the surface temperature was hotter than Mariner 2 had calculated, at almost 500 °C (932 °F), determined that the atmosphere is 95% carbon dioxide (CO
2
), and discovered that Venus's atmosphere was considerably denser than Venera 4's designers had anticipated.[155] The joint Venera 4Mariner 5 data were analysed by a combined Soviet–American science team in a series of colloquia over the following year,[156] in an early example of space cooperation.[157]

In 1974, Mariner 10 swung by Venus on its way to Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speeds in the Venusian atmosphere.

Venus as captured by Mariner 10
Global view of Venus in ultraviolet light done by Mariner 10.

In 1975, the Soviet Venera 9 and 10 landers transmitted the first images from the surface of Venus, which were in black and white. In 1982 the first colour images of the surface were obtained with the Soviet Venera 13 and 14 landers.

NASA obtained additional data in 1978 with the Pioneer Venus project that consisted of two separate missions:[158] Pioneer Venus Orbiter and Pioneer Venus Multiprobe.[159] The successful Soviet Venera program came to a close in October 1983, when Venera 15 and 16 were placed in orbit to conduct detailed mapping of 25% of Venus's terrain (from the north pole to 30°N latitude)[160]

Several other Venus flybys took place in the 1980s and 1990s that increased the understanding of Venus, including Vega 1 (1985), Vega 2 (1985), Galileo (1990), Magellan (1994), Cassini–Huygens (1998), and MESSENGER (2006). Then, Venus Express by the European Space Agency (ESA) entered orbit around Venus in April 2006. Equipped with seven scientific instruments, Venus Express provided unprecedented long-term observation of Venus's atmosphere. ESA concluded that mission in December 2014.

As of 2016, Japan's Akatsuki is in a highly elliptical orbit around Venus since 7 December 2015, and there are several probing proposals under study by Roscosmos, NASA, and India's ISRO.

In 2016, NASA announced that it was planning a rover, the Automaton Rover for Extreme Environments, designed to survive for an extended time in Venus's environmental conditions. It would be controlled by a mechanical computer and driven by wind power.[161]

In culture

Van Gogh - Starry Night - Google Art Project
Venus is portrayed just to the right of the large cypress tree in Vincent van Gogh's 1889 painting The Starry Night.[162][163]

Venus is a primary feature of the night sky, and so has been of remarkable importance in mythology, astrology and fiction throughout history and in different cultures. Classical poets such as Homer, Sappho, Ovid and Virgil spoke of the star and its light.[164] Romantic poets such as William Blake, Robert Frost, Alfred Lord Tennyson and William Wordsworth wrote odes to it.[165]

Because the movements of Venus appear to be discontinuous (it disappears due to its proximity to the sun, for many days at a time, and then reappears on the other horizon), some cultures did not recognize Venus as single entity; instead, they assumed it to be two separate stars on each horizon: the morning and evening star. Nonetheless, a cylinder seal from the Jemdet Nasr period indicates that the ancient Sumerians already knew that the morning and evening stars were the same celestial object. The Sumerians associated the planet with the goddess Inanna (known as Ishtar by the later Akkadians and Babylonians), and their myths of Inanna are often allegories for the apparent motions and cycles of the planet.[128] In the Old Babylonian period, the planet Venus was known as Ninsi'anna, and later as Dilbat.[166] The name "Ninsi'anna" translates to "divine lady, illumination of heaven", which refers to Venus as the brightest visible "star". Earlier spellings of the name were written with the cuneiform sign si4 (= SU, meaning "to be red"), and the original meaning may have been "divine lady of the redness of heaven", in reference to the color of the morning and evening sky.[167] Venus is described in Babylonian cuneiform texts such as the Venus tablet of Ammisaduqa, which relates observations that possibly date from 1600 BC.[168]

In Chinese the planet is called Jīn-xīng (金星), the golden planet of the metal element. In India Shukra Graha ("the planet Shukra") which is named after a powerful saint Shukra. Shukra which is used in Indian Vedic astrology[169] means "clear, pure" or "brightness, clearness" in Sanskrit. One of the nine Navagraha, it is held to affect wealth, pleasure and reproduction; it was the son of Bhrgu, preceptor of the Daityas, and guru of the Asuras.[170] The word Shukra is also associated with semen, or generation. Venus is known as Kejora in Indonesian and Malay. Modern Chinese, Japanese and Korean cultures refer to the planet literally as the "metal star" (金星), based on the Five elements.[171][172][173]

The Ancient Egyptians and Greeks believed Venus to be two separate bodies, a morning star and an evening star. The Egyptians knew the morning star as Tioumoutiri and the evening star as Ouaiti.[174] The Greeks used the names Phosphoros (meaning "light-bringer"; alternately Heosphoros, meaning "dawn-bringer") for the morning star, and Hesperus (meaning "Western one") for the evening star.[175] Though by the Roman era they were recognized as one celestial object, known as "the star of Venus", the traditional two Greek names continued to be used, though usually translated to Latin as Lucifer and Hesperus.[175][176]

Venus was considered the most important celestial body observed by the Maya, who called it Chac ek,[177] or Noh Ek', "the Great Star".[178]

Modern fiction

With the invention of the telescope, the idea that Venus was a physical world and possible destination began to take form.

The impenetrable Venusian cloud cover gave science fiction writers free rein to speculate on conditions at its surface; all the more so when early observations showed that not only was it similar in size to Earth, it possessed a substantial atmosphere. Closer to the Sun than Earth, the planet was frequently depicted as warmer, but still habitable by humans.[179] The genre reached its peak between the 1930s and 1950s, at a time when science had revealed some aspects of Venus, but not yet the harsh reality of its surface conditions. Findings from the first missions to Venus showed the reality to be quite different, and brought this particular genre to an end.[180] As scientific knowledge of Venus advanced, so science fiction authors tried to keep pace, particularly by conjecturing human attempts to terraform Venus.[181]

Symbol

The astronomical symbol for Venus is the same as that used in biology for the female sex: a circle with a small cross beneath.[182] The Venus symbol also represents femininity, and in Western alchemy stood for the metal copper.[182] Polished copper has been used for mirrors from antiquity, and the symbol for Venus has sometimes been understood to stand for the mirror of the goddess.[182]

Habitability

The speculation of the existence of life on Venus decreased significantly since the early 1960s, when spacecraft began studying Venus and it became clear that the conditions on Venus are extreme compared to those on Earth.

The fact that Venus is located closer to the Sun than Earth, raising temperatures on the surface to nearly 735 K (462 °C; 863 °F), the atmospheric pressure is ninety times that of Earth, and the extreme impact of the greenhouse effect, make water-based life as currently known unlikely. A few scientists have speculated that thermoacidophilic extremophile microorganisms might exist in the lower-temperature, acidic upper layers of the Venusian atmosphere.[183][184][185] The atmospheric pressure and temperature fifty kilometres above the surface are similar to those at Earth's surface. This has led to proposals to use aerostats (lighter-than-air balloons) for initial exploration and ultimately for permanent "floating cities" in the Venusian atmosphere.[186] Among the many engineering challenges are the dangerous amounts of sulfuric acid at these heights.[186]

See also

Notes

  1. ^ Misstated as "Ganiki Chasma" in the press release and scientific publication.[48]
  2. ^ Several claims of transit observations made by medieval Islamic astronomers have been shown to be sunspots.[139] Avicenna did not record the date of his observation. There was a transit of Venus within his lifetime, on 24 May 1032, although it is questionable whether it would have been visible from his location.[140]

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External links

Cartographic resources

2000 Wimbledon Championships – Women's Singles

Lindsay Davenport was the defending champion, but lost in the final to Venus Williams.

Venus Williams won her first Grand Slam title, defeating Lindsay Davenport in the final, 6–3, 7–6(7-3).

3rd millennium

In contemporary history, the third millennium is a period of time that began on January 1, 2001, and will end on December 31, 3000 of the Gregorian calendar. It is distinct from the millennium known as the 2000s which began on January 1, 2000 and will end on December 31, 2999.

Aphrodite

Aphrodite is an ancient Greek goddess associated with love, beauty, pleasure, passion and procreation. She is identified with the planet Venus, which is named after the Roman goddess Venus, with whom Aphrodite was extensively syncretized. Aphrodite's major symbols include myrtles, roses, doves, sparrows, and swans.

The cult of Aphrodite was largely derived from that of the Phoenician goddess Astarte, a cognate of the East Semitic goddess Ishtar, whose cult was based on the Sumerian cult of Inanna. Aphrodite's main cult centers were Cythera, Cyprus, Corinth, and Athens. Her main festival was the Aphrodisia, which was celebrated annually in midsummer. In Laconia, Aphrodite was worshipped as a warrior goddess. She was also the patron goddess of prostitutes, an association which led early scholars to propose the concept of "sacred prostitution", an idea which is now generally seen as erroneous.

In Hesiod's Theogony, Aphrodite is born off the coast of Cythera from the foam (aphros) produced by Uranus's genitals, which his son Cronus has severed and thrown into the sea. In Homer's Iliad, however, she is the daughter of Zeus and Dione. Plato, in his Symposium 180e, asserts that these two origins actually belong to separate entities: Aphrodite Ourania (a transcendent, "Heavenly" Aphrodite) and Aphrodite Pandemos (Aphrodite common to "all the people"). Aphrodite had many other epithets, each emphasizing a different aspect of the same goddess, or used by a different local cult. Thus she was also known as Cytherea (Lady of Cythera) and Cypris (Lady of Cyprus), due to the fact that both locations claimed to be the place of her birth.

In Greek mythology, Aphrodite was married to Hephaestus, the god of blacksmiths and metalworking. Despite this, Aphrodite was frequently unfaithful to him and had many lovers; in the Odyssey, she is caught in the act of adultery with Ares, the god of war. In the First Homeric Hymn to Aphrodite, she seduces the mortal shepherd Anchises. Aphrodite was also the surrogate mother and lover of the mortal shepherd Adonis, who was killed by a wild boar. Along with Athena and Hera, Aphrodite was one of the three goddesses whose feud resulted in the beginning of the Trojan War and she plays a major role throughout the Iliad. Aphrodite has been featured in western art as a symbol of female beauty and has appeared in numerous works of western literature. She is a major deity in modern Neopagan religions, including the Church of Aphrodite, Wicca, and Hellenismos.

Lucifer

Lucifer ( LEW-si-fər; "light-bringer") was a Latin name for the planet Venus as the morning star in the ancient Roman era, and is often used for mythological and religious figures associated with the planet. Due to the unique movements and discontinuous appearances of Venus in the sky, mythology surrounding these figures often involved a fall from the heavens to earth or the underworld. Interpretations of a similar term in the Hebrew Bible, translated in the King James Version as "Lucifer", led to a Christian tradition of applying the name Lucifer and its associated stories of a fall from heaven to Satan. Most modern scholarship regards these interpretations as questionable, and translates the term in the relevant Bible passage (Isaiah 14:12) as "morning star" or "shining one" rather than as a proper name, "Lucifer".As a name for the devil, the more common meaning in English, "Lucifer" is the rendering of the Hebrew word הֵילֵל‎ in Isaiah (Isaiah 14:12) given in the King James Version of the Bible. The translators of this version took the word from the Latin Vulgate, which translated הֵילֵל by the Latin word lucifer (uncapitalized), meaning "the morning star, the planet Venus", or, as an adjective, "light-bringing".As a name for the morning star, "Lucifer" is a proper name and is capitalized in English. In Greco-Roman civilization the morning star was often personified and considered a god and in some versions considered a son of Aurora (the Dawn).

Magellan (spacecraft)

The Magellan spacecraft, also referred to as the Venus Radar Mapper, was a 1,035-kilogram (2,282 lb) robotic space probe launched by NASA of the United States, on May 4, 1989, to map the surface of Venus by using synthetic aperture radar and to measure the planetary gravitational field.

The Magellan probe was the first interplanetary mission to be launched from the Space Shuttle, the first one to use the Inertial Upper Stage booster for launching, and the first spacecraft to test aerobraking as a method for circularizing its orbit. Magellan was the fifth successful NASA mission to Venus, and it ended an eleven-year gap in U.S. interplanetary probe launches.

Mons pubis

In human anatomy, and in mammals in general, the mons pubis (pubic mound, also known simply as the mons, and known specifically in females as the mons Venus or mons veneris), is a rounded mass of fatty tissue found over the pubic symphysis of the pubic bones.

Observations and explorations of Venus

Observations of the planet Venus include those in antiquity, telescopic observations, and from visiting spacecraft. Spacecraft have performed various flybys, orbits, and landings on Venus, including balloon probes that floated in the atmosphere of Venus. Study of the planet is aided by its relatively close proximity to the Earth, compared to other planets, but the surface of Venus is obscured by an atmosphere opaque to visible light.

Planet

A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Five planets in the Solar System are visible to the naked eye. These were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union (IAU) officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of planetary mass based on where or what they orbit. Although eight of the planetary bodies discovered before 1950 remain "planets" under the modern definition, some celestial bodies, such as Ceres, Pallas, Juno and Vesta (each an object in the solar asteroid belt), and Pluto (the first trans-Neptunian object discovered), that were once considered planets by the scientific community, are no longer viewed as such.

The planets were thought by Ptolemy to orbit Earth in deferent and epicycle motions. Although the idea that the planets orbited the Sun had been suggested many times, it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations, performed by Galileo Galilei. About the same time, by careful analysis of pre-telescopic observational data collected by Tycho Brahe, Johannes Kepler found the planets' orbits were elliptical rather than circular. As observational tools improved, astronomers saw that, like Earth, each of the planets rotated around an axis tilted with respect to its orbital pole, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics, and even hydrology.

Planets are generally divided into two main types: large low-density giant planets, and smaller rocky terrestrials. There are eight planets in the Solar System. In order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites.

Several thousands of planets around other stars ("extrasolar planets" or "exoplanets") have been discovered in the Milky Way. As of 1 March 2019, 3,999 known extrasolar planets in 2,987 planetary systems (including 654 multiple planetary systems), ranging in size from just above the size of the Moon to gas giants about twice as large as Jupiter have been discovered, out of which more than 100 planets are the same size as Earth, nine of which are at the same relative distance from their star as Earth from the Sun, i.e. in the circumstellar habitable zone. On December 20, 2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A 2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way.

Around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone.

Serena Williams

Serena Jameka Williams (born September 26, 1981) is an American professional tennis player. The Women's Tennis Association (WTA) ranked her world No. 1 in singles on eight separate occasions between 2002 and 2017. She reached the No. 1 ranking for the first time on July 8, 2002. On her sixth occasion, she held the ranking for 186 consecutive weeks, tying the record set by Steffi Graf. In total, she has been No. 1 for 319 weeks, which ranks third in the "Open Era" among female players behind Graf and Martina Navratilova.

Williams holds the most Grand Slam titles in singles, doubles, and mixed doubles combined among active players. Her 39 major titles puts her joint-third on the all-time list and second in the Open Era: 23 in singles, 14 in women's doubles, and two in mixed doubles. She is the most recent female player to have held all four Grand Slam singles titles simultaneously (2002–03 and 2014–15) and the third player to achieve this twice, after Rod Laver and Graf. She is also the most recent player to have won a Grand Slam title on each surface (hard, clay and grass) in one calendar year. She is also, together with her sister Venus, the most recent player to have held all four Grand Slam women's doubles titles simultaneously (2009–10).

Her total of 23 Grand Slam singles titles marks the record for the most Grand Slam tournament wins in the Open Era, and is second on the all-time list behind Margaret Court (24). She has won an all-time record of 13 Grand Slam singles titles on hard court. Williams holds the Open Era record for most titles won at the Australian Open (7) and shares the Open Era record for most titles won at the US Open with Chris Evert (6). She also holds the all-time record for the most women's singles matches won at majors with 335 matches.

Williams has won 14 Grand Slam doubles titles, all with her sister Venus, and the pair are unbeaten in Grand Slam doubles finals. As a team, she and Venus have the third most women's doubles Grand Slam titles, behind the 18 titles of Natasha Zvereva (14 with Gigi Fernández) and the record 20 titles won by Martina Navratilova and Pam Shriver. Williams is also a five-time winner of the WTA Tour Championships in the singles division. She has also won four Olympic gold medals, one in women's singles and three in women's doubles—an all-time record shared with her sister, Venus. The arrival of the Williams sisters has been credited with ushering in a new era of power and athleticism on the women's professional tennis tour. She is currently ranked at No.10 in the world by the WTA.Earning almost $29 million in prize money and endorsements, Williams was the highest paid female athlete in 2016. She repeated this feat in 2017 when she was the only woman on Forbes' list of the 100 highest paid athletes with $27 million in prize money and endorsements. She has won the 'Laureus Sportswoman of the Year' award four times (2003, 2010, 2016, 2018), and in December 2015, she was named Sportsperson of the Year by Sports Illustrated magazine.

Solar System

The Solar System is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury.The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are ice giants, being composed mostly of substances with relatively high melting points compared with hydrogen and helium, called volatiles, such as water, ammonia and methane. All eight planets have almost circular orbits that lie within a nearly flat disc called the ecliptic.

The Solar System also contains smaller objects. The asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, and beyond them a newly discovered population of sednoids. Within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets. Identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to these two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds, freely travel between regions. Six of the planets, at least four of the dwarf planets, and many of the smaller bodies are orbited by natural satellites, usually termed "moons" after the Moon. Each of the outer planets is encircled by planetary rings of dust and other small objects.

The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region in the interstellar medium known as the heliosphere. The heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium; it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, may also exist at a distance roughly a thousand times further than the heliosphere. The Solar System is located in the Orion Arm, 26,000 light-years from the center of the Milky Way galaxy.

Taurus (astrology)

Taurus (Greek for Ταύρος (Tavros) (Latin for "The Bull") is the second astrological sign in the present zodiac. It spans from 30° to 60° of the zodiac. This sign belongs to the Earth element or triplicity, and therefore has a feminine or negative polarity. It has a Fixed modality, quality or quadruplicity. It is a Venus-ruled sign just like Libra. It is the sign where the Moon has its exaltation at exactly 3°. The Sun transits in the sign of Taurus from approximately April 21 until May 21 in western astrology. People born between these dates, depending on which system of astrology they subscribe to, may be called Taureans.

The Birth of Venus

The Birth of Venus (Italian: Nascita di Venere [ˈnaʃʃita di ˈvɛːnere]) is a painting by the Italian artist Sandro Botticelli probably made in the mid 1480s. It depicts the goddess Venus arriving at the shore after her birth, when she had emerged from the sea fully-grown (called Venus Anadyomene and often depicted in art). The painting is in the Uffizi Gallery in Florence, Italy.

Although the two are not a pair, the painting is inevitably discussed with Botticelli's other very large mythological painting, the Primavera, also in the Uffizi. They are among the most famous paintings in the world, and icons of the Italian Renaissance; of the two, the Birth is even better known than the Primavera. As depictions of subjects from classical mythology on a very large scale they were virtually unprecedented in Western art since classical antiquity, as was the size and prominence of a nude female figure in the Birth. It used to be thought that they were both commissioned by the same member of the Medici family, but this is now uncertain.

They have been endlessly analysed by art historians, with the main themes being: the emulation of ancient painters and the context of wedding celebrations (generally agreed), the influence of Renaissance Neo-Platonism (somewhat controversial), and the identity of the commissioners (not agreed). Most art historians agree, however, that the Birth does not require complex analysis to decode its meaning, in the way that the Primavera probably does. While there are subtleties in the painting, its main meaning is a straightforward, if individual, treatment of a traditional scene from Greek mythology, and its appeal is sensory and very accessible, hence its enormous popularity.

Transit of Venus

A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus can be seen from Earth as a small black dot moving across the face of the Sun. The duration of such transits is usually several hours (the transit of 2012 lasted 6 hours and 40 minutes). A transit is similar to a solar eclipse by the Moon. While the diameter of Venus is more than three times that of the Moon, Venus appears smaller, and travels more slowly across the face of the Sun, because it is much farther away from Earth.

Transits of Venus are among the rarest of predictable astronomical phenomena. They occur in a pattern that generally repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years. The periodicity is a reflection of the fact that the orbital periods of Earth and Venus are close to 8:13 and 243:395 commensurabilities.The last transit of Venus was on 5 and 6 June 2012, and was the last Venus transit of the 21st century; the prior transit took place on 8 June 2004. The previous pair of transits were in December 1874 and December 1882. The next transits of Venus will take place on 10–11 December 2117, and 8 December 2125.Venus transits are historically of great scientific importance as they were used to gain the first realistic estimates of the size of the Solar System. Observations of the 1639 transit, combined with the principle of parallax, provided an estimate of the distance between the Sun and the Earth that was more accurate than any other up to that time. The 2012 transit provided scientists with a number of other research opportunities, particularly in the refinement of techniques to be used in the search for exoplanets.

Venus (Marvel Comics)

Venus is the name of two fictional characters appearing in American comic books published by Marvel Comics. The first, originally based on the goddess Venus (Aphrodite) from Roman and Greek mythology, was retconned to actually be a siren that only resembles the goddess. The second is stated to be the true goddess, who now wishes only to be referred to by her Greek name, Aphrodite. The similarities between the two characters are a point of conflict in the comics.

Venus (mythology)

Venus (, Classical Latin: ) is a Roman goddess, whose functions encompassed love, beauty, desire, sex, fertility, prosperity and victory. In Roman mythology, she was the mother of the Roman people through her son,who was the father of her child. Aeneas, who survived the fall of Troy and fled to Italy. Julius Caesar claimed her as his ancestor. Venus was central to many religious festivals, and was revered in Roman religion under numerous cult titles.

The Romans adapted the myths and iconography of her Greek counterpart Aphrodite for Roman art and Latin literature. In the later classical tradition of the West, Venus became one of the most widely referenced deities of Greco-Roman mythology as the embodiment of love and sexuality.

Venus Williams

Venus Ebony Starr Williams (born June 17, 1980) is an American professional tennis player who is currently ranked world No. 36 in the WTA singles rankings. She is generally regarded as one of the all-time greats of women's tennis and, along with younger sister Serena Williams, is credited with ushering in a new era of power and athleticism on the women's professional tennis tour.Williams has been ranked world No. 1 by the Women's Tennis Association on three occasions, for a total of 11 weeks. She first reached the No. 1 ranking on February 25, 2002, the first African American woman to do so in the Open Era, and the second all time since Althea Gibson. Williams' seven Grand Slam singles titles are tied for 12th on the all-time list, and 8th on the Open Era list, more than any other active female player except Serena. She has reached 16 Grand Slam finals, most recently at Wimbledon in 2017. She has also won 14 Grand Slam Women's doubles titles, all with Serena; the pair is unbeaten in Grand Slam doubles finals.[19] Williams also has two Mixed Doubles titles. Her five Wimbledon singles titles tie her with two other women for eighth place on the all-time list, but gives her sole possession of No. 4 on the Open Era List, trailing only the nine titles of Martina Navratilova and the seven of Serena and Steffi Graf. From the 2000 Wimbledon Championships to the 2001 US Open, Williams won four of the six Grand Slam singles tournaments in that span. At the 2018 US Open, Williams extended her record as the all-time leader, male or female, in Grand Slams played, with 80. With her run to the 2017 Wimbledon singles final, she broke the record for longest time between first and most recent grand slam singles finals appearances.

Williams has won four Olympic gold medals, one in singles and three in women's doubles, along with a silver medal in mixed doubles, pulling even with Kathleen McKane Godfree for the most Olympic medals won by a male or female tennis player. She is the only tennis player to have won a medal at four Olympic Games. At the 2000 Sydney Olympics, Williams became only the second player to win Olympic gold medals in both singles and doubles at the same Olympic Games, after Helen Wills Moody in 1924.

With 49 singles titles, Williams trails only Serena among active players on the WTA Tour with most singles titles. Her 35-match winning streak from the 2000 Wimbledon Championships to the 2000 Generali Ladies Linz tournament final is the longest since January 1, 2000. She is also one of only three active WTA players to have reached the finals of all four Grand Slams, along with Serena and Maria Sharapova.

Venus de Milo

The Aphrodite of Milos (Greek: Αφροδίτη της Μήλου, Aphroditi tis Milou), generally known as the Venus de Milo, is an ancient Greek statue and one of the most famous works of ancient Greek sculpture. Initially it was attributed to the sculptor Praxiteles, however from an inscription that was on its plinth, the statue is thought to be the work of Alexandros of Antioch. Created sometime between 130 and 100 BC, the statue is believed to depict Aphrodite, the Greek goddess of love and beauty; however, some scholars claim it is the sea-goddess Amphitrite, venerated on Milos. It is a marble sculpture, slightly larger than life size at 203 cm (6 ft 8 in) high. Part of an arm and the original plinth were lost following its discovery. It is currently on permanent display at the Louvre Museum in Paris. The statue is named after the Greek island of Milos, where it was discovered.

Venus figurines

A Venus figurine is any Upper Paleolithic statuette portraying a woman, with fewer sculptures depicting men or figures of uncertain sex, and those in relief or engraved on rock or stones are often discussed together. Most have been unearthed in Europe, but others have been found as far away as Siberia, extending their distribution across much of Eurasia, although with many gaps, such as the Mediterranean outside Italy.Most of them date from the Gravettian period (26,000–21,000 years ago), but examples exist as early as the Venus of Hohle Fels, which dates back at least 35,000 years to the Aurignacian, and as late as the Venus of Monruz, from about 11,000 years ago in the Magdalenian. These figurines were carved from soft stone (such as steatite, calcite or limestone), bone or ivory, or formed of clay and fired. The latter are among the oldest ceramics known. In total, some 144 such figurines are known; virtually all of modest size, between 3 cm and 40 cm or more in height. They are some of the earliest works of prehistoric art.

Most of them have small heads, wide hips, and legs that taper to a point. Various figurines exaggerate the abdomen, hips, breasts, thighs, or vulva, although many do not, and the concentration in popular accounts on those that do reflects modern preoccupations rather than the range of actual artefacts. In contrast, arms and feet are often absent, and the head is usually small and faceless. Depictions of hairstyles can be detailed, and especially in Siberian examples, clothing or tattoos may be indicated.The original cultural meaning and purpose of these artifacts is not known. It has frequently been suggested that they may have served a ritual or symbolic function. There are widely varying and speculative interpretations of their use or meaning: they have been seen as religious figures, as erotic art or sex aids, grandmother goddesses or as self-depictions by female artists.

Venus flytrap

The Venus flytrap (Dionaea muscipula) is a carnivorous plant native to subtropical wetlands on the East Coast of the United States in North Carolina and South Carolina. It catches its prey—chiefly insects and arachnids—with a trapping structure formed by the terminal portion of each of the plant's leaves, which is triggered by tiny hairs (called "trigger hairs" or "sensitive hairs") on their inner surfaces.

When an insect or spider crawling along the leaves contacts a hair, the trap prepares to close, snapping shut only if another contact occurs within approximately twenty seconds of the first strike. Triggers may occur if one-tenth of the insect is within contact. The requirement of redundant triggering in this mechanism serves as a safeguard against wasting energy by trapping objects with no nutritional value, and the plant will only begin digestion after five more stimuli to ensure it has caught a live bug worthy of consumption.

Dionaea is a monotypic genus closely related to the waterwheel plant (Aldrovanda vesiculosa) and sundews (Drosera), all of which belong to the family Droseraceae.

Venus
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