Venus

Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never far from the Sun, either as morning star or evening star. Aside from the Sun and Moon, Venus is the brightest natural object in Earth's sky, capable of casting visible shadows on Earth at dark conditions and being visible to the naked eye in broad daylight.[19][20]

Venus
Near-global view of Venus in natural colour, taken by the MESSENGER space probe
Designations
Pronunciation/ˈvnəs/ (listen)
Named after
Venus
AdjectivesVenusian /vɪˈnjziən, -ʒən/,[1] rarely Cytherean /sɪθəˈrən/[2] or Venerean / Venerian /vɪˈnɪəriən/[3]
Orbital characteristics[4][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[6]
583.92 days[4]
35.02 km/s
50.115°
Inclination
76.680°[6]
54.884°
SatellitesNone
Physical characteristics
Mean radius
  • 6,051.8±1.0 km[8]
  • 0.9499 Earths
Flattening0[8]
  • 4.6023×108 km2
  • 0.902 Earths
Volume
  • 9.2843×1011 km3
  • 0.857 Earths
Mass
  • 4.8675×1024 kg[9]
  • 0.815 Earths
Mean density
5.243 g/cm3
  • 8.87 m/s2
  • 0.904 g
10.36 km/s (6.44 mi/s)[10]
−116.75 d (retrograde)[11]
1 Venus solar day
−243.0226 d (retrograde)[12]
Equatorial rotation velocity
6.52 km/h (1.81 m/s)
2.64° (for retrograde rotation)
177.36° (to orbit)[4][note 1]
North pole right ascension
  • 18h 11m 2s
  • 272.76°[13]
North pole declination
67.16°
Albedo
Temperature232 K (−41 °C) (blackbody temperature)[16]
Surface temp. min mean max
Kelvin 737 K[4]
Celsius 464 °C
Fahrenheit 867 °F
Surface absorbed dose rate2.1×10−6 μGy/h[17]
Surface equivalent dose rate2.2×10−6 μSv/h
0.092–22 μSv/h at the habitable zone[17]
−4.92 to −2.98[18]
9.7″–66.0″[4]
Atmosphere[4]
Surface pressure
93 bar (9.3 MPa)
92 atm
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°.

Venus is the second largest terrestrial object of the Solar System. It has a surface gravity slightly lower than on Earth and has a weak induced magnetosphere. The atmosphere of Venus consists mainly of carbon dioxide, and, at the planet’s surface, is the densest and hottest of the atmospheres of the four terrestrial planets. With an atmospheric pressure at the planet's surface of about 92 times the sea level pressure of Earth and a mean temperature of 737 K (464 °C; 867 °F), the carbon dioxide gas at Venus's surface is in the supercritical phase of matter. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, making it the planet with the highest albedo in the Solar System. It may have had water oceans in the past,[21][22] but after these evaporated the temperature rose under a runaway greenhouse effect.[23] The possibility of life on Venus has long been a topic of speculation but convincing evidence has yet to be found.

Like Mercury, Venus does not have any moons.[24] Solar days on Venus, with a length of 117 Earth days,[25] are just about half as long as its solar year, orbiting the Sun every 224.7 Earth days.[26] This Venusian daylength is a product of it rotating against its orbital motion, halving its full sidereal rotation period of 243 Earth days, the longest of all the Solar System planets. Venus and Uranus are the only planets with such a retrograde rotation, making the Sun move in their skies from their western horizon to their eastern. The orbit of Venus around the Sun is the closest to Earth's orbit, bringing them closer than any other pair of planets. This occurs during inferior conjunction with a synodic period of 1.6 years. However, Mercury is more frequently the closest to each.

The orbits of Venus and Earth result in the lowest gravitational potential difference and lowest delta-v needed to transfer between them than to any other planet. This has made Venus a prime target for early interplanetary exploration. It was the first planet beyond Earth that spacecraft were sent to, starting with Venera 1 in 1961, and the first planet to be reached, impacted and in 1970 successfully landed on by Venera 7. 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, gaining its mainly used name from the Roman goddess of love and beauty which it is associated with. Furthermore it has been a prime inspiration for writers, poets and scholars. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BCE.[27] Plans for better exploration with rovers or atmospheric missions, potentially crewed, at levels with almost Earth-like conditions have been proposed.


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