Venus

Venus is the second planet from the Sun. It is a rocky planet, has an atmosphere, which is by far the thickest of all rocky Solar System bodies, and it is the only rocky Solar System body almost as large and massive as Earth. Orbiting inferiorly (inside of Earth's orbit), it appears in Earth's sky always close to the Sun, as either a "morning star" or "evening star". While this is also true for Mercury, Venus appears as such much more prominently, since it is the third brightest object in Earth's sky, after the Moon and the Sun,[20][21] appearing brighter than any other star-like classical planet, and any fixed star of Earth's sky. With such prominent appearances in Earth's sky, Venus has been a common and important object for humans, in both their cultures and astronomy.

Quick facts: Designations, Pronunciation, Named after, Adj... ▼

Venus

Near-global view of Venus in natural colour, taken by the MESSENGER space probe
Designations
Pronunciation	/ˈviːnəs/ (listen)
Named after	Roman goddess of love (see goddess Venus)
Adjectives	Venusian /vɪˈnjuːziən, -ʒən/,[1] rarely Cytherean /sɪθəˈriːən/[2] or Venerean / Venerian /vɪˈnɪəriən/[3]
Symbol
Orbital characteristics[4][5]
Epoch J2000
Aphelion	0.728213 AU 108,939,000 km
Perihelion	0.718440 AU 107,477,000 km
Semi-major axis	0.723332 AU 108,208,000 km
Eccentricity	0.006772[6]
Orbital period (sidereal)	224.701 d[4] 0.615198 yr 1.92 Venus solar day
Orbital period (synodic)	583.92 days[4]
Average orbital speed	35.02 km/s
Mean anomaly	50.115°
Inclination	3.39458° to ecliptic 3.86° to Sun's equator 2.15° to invariable plane[7]
Longitude of ascending node	76.680°[6]
Argument of perihelion	54.884°
Satellites	None
Physical characteristics
Mean radius	6,051.8±1.0 km[8] 0.9499 Earths
Flattening	0[8]
Surface area	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
Surface gravity	8.87 m/s2 0.904 g
Escape velocity	10.36 km/s (6.44 mi/s)[10]
Synodic rotation period	−116.75 d (retrograde)[11] 1 Venus solar day
Sidereal rotation period	−243.0226 d (retrograde)[12]
Equatorial rotation velocity	6.52 km/h (1.81 m/s)
Axial tilt	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	0.689 (geometric)[14] 0.76 (Bond)[15]
Temperature	232 K (−41 °C) (blackbody temperature)[16]
Surface temp. min mean max Kelvin 737 K[4] Celsius 464 °C Fahrenheit 867 °F
Surface absorbed dose rate	2.1×10−6 μGy/h[17]
Surface equivalent dose rate	2.2×10−6 μSv/h 0.092–22 μSv/h at cloud level[17]
Apparent magnitude	−4.92 to −2.98[18]
Absolute magnitude (H)	−4.4[19]
Angular diameter	9.7″–66.0″[4]
Atmosphere[4]
Surface pressure	93 bar (9.3 MPa) 92 atm
Composition by volume	96.5% carbon dioxide 3.5% nitrogen 0.015% sulfur dioxide 0.0070% argon 0.0020% water vapour 0.0017% carbon monoxide 0.0012% helium 0.0007% neon Trace carbonyl sulfide Trace hydrogen chloride Trace hydrogen fluoride
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 negative hemisphere and makes the axial tilt 177.36°.

Venus retains, despite having only a weak induced magnetosphere, an especially thick atmosphere of mainly carbon dioxide, creating an extreme greenhouse effect together with its global sulfuric acid cloud cover. Because of this, the atmosphere reaches at its bottom a mean temperature of 737 K (464 °C; 867 °F) and a crushing pressure of 92 times that of Earth's at sea level, turning the air into a supercritical fluid, though at cloudy altitudes of 50 km (30 mi) Earth like levels are found. Conditions possibly favourable for life on Venus have been identified at its cloud layers, while recent research has found indicative, but not convincing evidence. Early in Venus' history water might have been abundant enough to form oceans, before it probably evaporated when greenhouse effects cascaded and then was taken away into space by the solar wind.[22][23][24] Internally Venus is thought to consist of a core, mantle, and crust, the latter releasing internal heat through its active volcanism, shaping the surface with large resurfacing instead of plate tectonics.

Venus has no moon (like Mercury).[25] It rotates retrograde (like Uranus), against its orbital direction. Having been slowed by the strong currents and drag of the atmosphere it completes a sidereal rotation, relative to the stars, in 243 Earth days. Therefore it rotates slower than it is orbiting, having a solar year of 224.7 Earth days,[26] this results together with the retrograde rotation in having a solar day of 117 Earth days.[27] Venus and Earth approach each other in synodic periods of 1.6 years. While coming closer to each other at inferior conjunction than any other pair of planets, since they have the closest two planetary orbits, they still on average stay closer to Mercury than to any other planet, due to its most central orbit.[28] That said Venus and Earth have between them the lowest difference in gravitational potential than between any other planet from them. This has allowed Venus to be the most accessible destination and attractive gravity assist waypoint for interplanetary flights.

In 1961, Venus became the target of the first interplanetary flight in human history, followed by many essential interplanetary firsts, confirming in 1970 Venus' inhospitable surface conditions with the first soft landing on another planet. Venus as a place for humans to be was a popular topic in early science fiction. Actual proposals have suggested to send crews particularly on flybys, used as gravity assists for crewed missions to Mars, or to enter the atmosphere and stay afloat at altitudes with conditions most comparable to Earth's surface, including radiation and gravitation, than anywhere in the Solar System. Currently robotic probes are studying and will be sent to study Venus, having been providing crucial knowledge particularly about greenhouse effects, informing predictions about global warming on Earth.[29][30]