Changes

|rotatespeed=6.52 km/h

|rotatespeed=6.52 km/h

|axialtilt=177.36°<ref name=venusfact/>

|axialtilt=177.36°<ref name=venusfact/>

|mass=4.8685 * 10²⁴ kg<ref name=venusfact/>

|mass=4.8685 × 10²⁴ kg<ref name=venusfact/>

|density=5243 kg/m³<ref name=venusfact/>

|density=5243 kg/m³<ref name=venusfact/>

|meanradius=6051.8 km<ref name=venusfact/>

|meanradius=6051.8 km<ref name=venusfact/>

|color=pale yellow

|color=pale yellow

|albedo=0.65<ref name=venusfact/>

|albedo=0.65<ref name=venusfact/>

|pmdm=8 * 10¹⁷ N-m/T<ref name=Luhmann>Luhmann, J. G., and Russell, C. T. "[http://www-spc.igpp.ucla.edu/personnel/russell/papers/venus_mag/ Venus: Magnetic Field and Magnetosphere]." ''Encyclopedia of Planetary Sciences'', J. H. Shirley and R. W. Fainbridge, eds. New York: Chapman and Hall, 1997, pp. 905-907. Accessed May 20, 2008.</ref>

|pmdm=8 × 10¹⁷ N-m/T<ref name=Luhmann>Luhmann, J. G., and Russell, C. T. "[http://www-spc.igpp.ucla.edu/personnel/russell/papers/venus_mag/ Venus: Magnetic Field and Magnetosphere]." ''Encyclopedia of Planetary Sciences'', J. H. Shirley and R. W. Fainbridge, eds. New York: Chapman and Hall, 1997, pp. 905-907. Accessed May 20, 2008.</ref>

|cmdm=1.15 * 10²⁴ N-m/T<ref name=Humphreys>Humphreys, D. R. "[http://www.creationresearch.org/crsq/articles/21/21_3/21_3.html The Creation of Planetary Magnetic Fields]." ''[[Creation Research Society Quarterly]]'' 21(3), December 1984. Accessed April 29, 2008.</ref>

|cmdm=1.15 × 10²⁴ N-m/T<ref name=Humphreys>Humphreys, D. R. "[http://www.creationresearch.org/crsq/articles/21/21_3/21_3.html The Creation of Planetary Magnetic Fields]." ''[[Creation Research Society Quarterly]]'' 21(3), December 1984. Accessed April 29, 2008.</ref>

|mdt=433 a<ref name=calc>Calculated</ref>

|mdt=433 a<ref name=calc>Calculated</ref>

|mhl=300 a<ref name=calc/>

|mhl=300 a<ref name=calc/>

== Orbital characteristics ==

== Orbital characteristics ==

Venus' orbit is more nearly circular than that of any other planet in the [[solar system]].<ref name=Arnett/> It maintains an average distance of 108,210,000&nbsp;km from the sun. Its closeness to both the earth and the sun, and its very high geometric albedo (65%), make it the brightest object in the night sky except for the [[Moon]].

Venus' [[orbit]] is more nearly circular than that of any other planet in the [[solar system]].<ref name=Arnett/> It maintains an average distance of 108,210,000&nbsp;km from the sun. Its closeness to both the earth and the sun, and its very high geometric [[albedo]] (65%), make it the brightest object in the night sky except for the [[Moon]].

The sidereal period of Venus is 224.7 days, and the synodic period is 583.92 days. Remarkably, the Mayans calculated Venus' synodic period at 584 days, a figure accurate to within an incredible three significant digits.<ref name=Kukulcan/> Moreover, the ratio of the synodic year of Venus to the year of Earth is very nearly 13:8, close enough to suggest that Earth and Venus participate in an orbital resonance.

The sidereal period of Venus is 224.7 days, and the synodic period is 583.92 days. Remarkably, the Mayans calculated Venus' synodic period at 584 days, a figure accurate to within an incredible three significant digits.<ref name=Kukulcan/> Moreover, the ratio of the synodic year of Venus to the year of Earth is very nearly 13:8, close enough to suggest that Earth and Venus participate in an orbital resonance.

Venus's orbit is inclined 3.39 degrees from the ecliptic. For this reason, Venus usually passes north or south of the sun in its conjunctions with earth. However, every century or so, Venus makes a pair of transits across the Sun, eight years apart. Indeed, the transit of Venus in 1769 allowed astronomers to determine the length of the astronomical unit.<ref name=Hornsby>Hornsby, T. "[http://gallica.bnf.fr/ark:/12148/bpt6k55866b/f617.chemindefer The quantity of the Sun's parallax, as deduced from the observations of the transit of Venus on June 3, 1769]." ''Phil. Trans. R. Soc.'' 61:574-579, December 19, 1771. {{doi|10.1098/rstl.1771.0054}} Accessed May 22, 2008.</ref>

Venus's orbit is inclined 3.39 degrees from the [[ecliptic]]. For this reason, Venus usually passes north or south of the sun in its conjunctions with earth. However, every century or so, Venus makes a pair of transits across the Sun, eight years apart. Indeed, the transit of Venus in 1769 allowed astronomers to determine the length of the astronomical unit.<ref name=Hornsby>Hornsby, T. "[http://gallica.bnf.fr/ark:/12148/bpt6k55866b/f617.chemindefer The quantity of the Sun's parallax, as deduced from the observations of the transit of Venus on June 3, 1769]." ''Phil. Trans. R. Soc.'' 61:574-579, December 19, 1771. {{doi|10.1098/rstl.1771.0054}} Accessed May 22, 2008.</ref>

Venus made such a transit on June 8, 2004, and will make another on June 6, 2012. After that, astronomers do not expect another transit until the year 2117.<ref name=transit>Bueter, Chuck. ''[http://www.transitofvenus.org/ Transit of Venus]''. 2003-2008. Accessed May 20, 2008.</ref>

Venus made such a transit on June 8, 2004 and another on June 6, 2012.<ref>[https://www.nasa.gov/mission_pages/sunearth/multimedia/venus-transit-2012.html 2012 Transit of Venus] from nasa.gov</ref> Astronomers do not expect another transit until the year 2117.<ref name=transit>Bueter, Chuck. ''[http://www.transitofvenus.org/ Transit of Venus]''. 2003-2008. Accessed May 20, 2008.</ref>

=== Phases of Venus ===

=== Phases of Venus ===

Like the Moon, Venus does show phases. [[Galileo Galilei]] was the first to observe the phases of Venus. If Venus's motion were confined to a Ptolemaic epicycle in an orbit between the Moon and the Sun, Venus would never show any phase but a crescent&mdash;but Galileo observed a full range of phases, from waxing crescent to "first quarter" to waxing gibbous to full to waning gibbous to "last quarter" to waning crescent to "new." Such phases proved inexplicable by the Ptolemaic model and constituted the strongest evidence in favor of [[Nicolaus Copernicus]]'s model of [[heliocentricity]].<ref name=utk1>"[http://csep10.phys.utk.edu/astr161/lect/history/galileo.html Galileo, the Telescope, and the Laws of Dynamics]." ''Astronomy 161: The Solar System''. Department of Physics and Astronomy, University of Tennessee, Knoxville, TN. Accessed May 20, 2008.</ref>

Like the Moon, Venus does show phases. [[Galileo Galilei]] was the first to observe the phases of Venus. If Venus's motion were confined to a Ptolemaic epicycle in an orbit between the Moon and the Sun, Venus would never show any phase but a crescent&mdash;but Galileo observed a full range of phases, from waxing crescent to "first quarter" to waxing gibbous to full to waning gibbous to "last quarter" to waning crescent to "new." Such phases proved inexplicable by the Ptolemaic model and constituted the strongest evidence in favor of [[Nicolaus Copernicus]]'s model of [[heliocentric theory|heliocentricity]].<ref name=utk1>"[http://csep10.phys.utk.edu/astr161/lect/history/galileo.html Galileo, the Telescope, and the Laws of Dynamics]." ''Astronomy 161: The Solar System''. Department of Physics and Astronomy, University of Tennessee, Knoxville, TN. Accessed May 20, 2008.</ref>

Venus's waxing phases are on its left side, whereas the Moon's waxing phases are on its right side. This shows that Venus moves about the Sun in the same direction that the Moon moves around the earth.

Venus's waxing phases are on its left side, whereas the Moon's waxing phases are on its right side. This shows that Venus moves about the Sun in the same direction that the Moon moves around the earth.

== Rotational characteristics ==

== Rotational characteristics ==

Venus rotates retrograde, or east to west, with a sidereal day of 5832.5 hours, or 243.686 Earth sidereal days. Venus' ''solar'' day is considerably shorter, at 2802.0 hours (117 sidereal days). This means that on Venus, it's day is longer than its year.Oddly enough, the solar day of Venus is almost exactly one-fifth its synodic year with respect to the earth, with the result that at each inferior conjunction (closest approach) of Earth and Venus, the same (night) side of Venus faces the Earth. This has led some astronomers to speculate that Earth and Venus are in some kind of [[tidal lock]]. However, at least two authorities stated that and Earth-Venus gravitational interaction would not produce such a lock unless the sun itself were producing a "tide" in Venus's atmosphere.<ref name=Gold>Gold, Thomas, and Soter, Steven. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4731C9M-CY&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=8edbfeb87ffb38474d3984472bf1ebdd Atmospheric tides and the resonant rotation of Venus]." ''Icarus'' 11(3):356-366, November 1969. {{doi|10.1016/0019-1035(69)90068-2}} Accessed May 21, 2008.</ref>

Venus rotates retrograde, or east to west, with a sidereal day of 5832.5 hours, or 243.686 Earth sidereal days. Venus' ''solar'' day is considerably shorter, at 2802.0 hours (117 sidereal days). This means that on Venus, it's day is longer than its year. Oddly enough, the solar day of Venus is almost exactly one-fifth its synodic year with respect to the earth, with the result that at each inferior conjunction (closest approach) of Earth and Venus, the same (night) side of Venus faces the Earth. This has led some astronomers to speculate that Earth and Venus are in some kind of [[tidal lock]]. However, at least two authorities stated that and Earth-Venus gravitational interaction would not produce such a lock unless the sun itself were producing a "tide" in Venus's atmosphere.<ref name=Gold>Gold, Thomas, and Soter, Steven. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4731C9M-CY&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=8edbfeb87ffb38474d3984472bf1ebdd Atmospheric tides and the resonant rotation of Venus]." ''Icarus'' 11(3):356-366, November 1969. {{doi|10.1016/0019-1035(69)90068-2}} Accessed May 21, 2008.</ref>

== Physical characteristics ==

== Physical characteristics ==

Venus's mass is 4.8685 * 10²⁴ kg, or about 81.5% that of earth.<ref name=venusfact/> Its radius is 6051.8&nbsp;km. Perhaps on account of Venus' very long sidereal day, Venus is an almost perfect sphere.

Venus's mass is 4.8685 × 10²⁴ kg, or about 81.5% that of earth.<ref name=venusfact/> Its radius is 6051.8&nbsp;km. Perhaps on account of Venus' very long sidereal day, Venus is an almost perfect sphere.

=== Atmosphere ===

=== Atmosphere ===

=== Magnetosphere ===

=== Magnetosphere ===

Venus's magnetosphere is far too weak to protect it from the radiation of the solar wind. Its magnetic dipole moment cannot be more than 8 * 10¹⁷ N-m/T, or about 10⁻⁵ times that of the earth. Given its mass, it should have had a magnetic dipole moment at creation of 1.15 * 10²⁴ N-m/T. Thus its decay time is very short (433 Julian years) and its half-life even shorter (300 Julian years). The conventional explanation is that the very slow rotation of Venus precludes any dynamo effect. [[Russell Humphreys]], however, suggests that Venus simply has a small and relatively non-conductive core and was thus less able to maintain its magnetic field since creation as well as Earth has.

Venus's magnetosphere is far too weak to protect it from the radiation of the solar wind. Its magnetic dipole moment cannot be more than 8 × 10¹⁷ N-m/T, or about 10⁻⁵ times that of the earth. Given its mass, it should have had a magnetic dipole moment at creation of 1.15 × 10²⁴ N-m/T. Thus its decay time is very short (433 Julian years) and its half-life even shorter (300 Julian years). The conventional explanation is that the very slow rotation of Venus precludes any dynamo effect. [[Russell Humphreys]], however, suggests that Venus simply has a small and relatively non-conductive core and was thus less able to maintain its [[magnetic field]] since creation as well as Earth has.

== Satellites ==

== Satellites ==

The [[United States]] and the [[Union of Soviet Socialist Republics]] both sent multiple rocket probes to Venus. The Soviet Union holds the present record for attempted missions (successful or failed) to Venus, including [[Project Sputnik]] and the highly prolific [[Project Venera]]. The first several Venera landers were crushed by the 92-bar atmosphere before they could even reach the surface. But eventually the Soviets did succeed in launching probes that descended to Venus's surface by parachute and transmitted data and even images.

The [[United States]] and the [[Union of Soviet Socialist Republics]] both sent multiple rocket probes to Venus. The Soviet Union holds the present record for attempted missions (successful or failed) to Venus, including [[Project Sputnik]] and the highly prolific [[Project Venera]]. The first several Venera landers were crushed by the 92-bar atmosphere before they could even reach the surface. But eventually the Soviets did succeed in launching probes that descended to Venus's surface by parachute and transmitted data and even images.

The American [[Project Mariner]] achieved some success, mainly with orbiters that either traveled to Venus directly or (in the case of [[Mariner 10]]) made brief rendez-vous with Venus on the way to Mercury. The USA also launched the [[Pioneer Venus]] series of missions, including one orbiter and a total of five atmospheric descenders.<ref name=timeline>Williams, David R. "[http://nssdc.gsfc.nasa.gov/planetary/chronology_venus.html Chronology of Venus Exploration]." National Space Science Data Center, [[National Aeronautics and Space Administration|NASA]], November 20, 2007. Accessed May 22, 2008.</ref>

The American [[Project Mariner]] achieved some success, mainly with orbiters that either travelled to Venus directly or (in the case of [[Mariner 10]]) made brief rendez-vous with Venus on the way to Mercury. The USA also launched the [[Pioneer Venus]] series of missions, including one orbiter and a total of five atmospheric descenders.<ref name=timeline>Williams, David R. "[http://nssdc.gsfc.nasa.gov/planetary/chronology_venus.html Chronology of Venus Exploration]." National Space Science Data Center, [[National Aeronautics and Space Administration|NASA]], November 20, 2007. Accessed May 22, 2008.</ref>

In 1967, a NASA contractor developed plans for sending an [[Project Apollo|Apollo]]-style rocket with a three-man crew to make rendez-vous with Venus in 1974 and also fly close to Mercury and the Sun. The mission was projected to last a year by carrying an extra life-support module, using the spent S-IVB stage as expanded living quarters, and mounting a solar cell array system on the S-IVB.<ref name=Feldman>Feldman, M. S., ''et al.'' ''[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790072165_1979072165.pdf Manned Venus Flyby].'' Bellcomm, Inc., Contract No. NASw-417, February 1, 1967. Accessed May 22, 2008.</ref>

In 1967, a NASA contractor developed plans for sending an [[Project Apollo|Apollo]]-style rocket with a three-man crew to make rendez-vous with Venus in 1974 and also fly close to Mercury and the Sun. The mission was projected to last a year by carrying an extra life-support module, using the spent S-IVB stage as expanded living quarters, and mounting a solar cell array system on the S-IVB.<ref name=Feldman>Feldman, M. S., ''et al.'' ''[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790072165_1979072165.pdf Manned Venus Flyby].'' Bellcomm, Inc., Contract No. NASw-417, February 1, 1967. Accessed May 22, 2008.</ref>