Venus is the second planet in distance from the Sun and, apart from the Sun and Moon, the brightest object in the sky. It is
easily observed with the naked eye and its phases (described below), can be seen through a telescope.
Because of its close proximity to the sun, except at greatest elongation (see diagram below), it is not usually visible for more
than three hours before sunrise or three hours after sunset. When visible in the morning, called the morning star, it shines
in the eastern dawn sky and in the evening, the evening star, it shines in the western sky at sunset.
A Venusian day is 243 Earth days, which is longer than its year (Venus orbits
the Sun every 225 days). Venus rotates from east to west, so an observor on the planet would see the Sun rise in the west and
set in the east. Venus has a mass which is 82% that of Earth and no known moons. The planet's dense atmosphere and complete
cloud cover make it impossible to see the surface from Earth. The atmosphere is almost entirely composed of carbon dioxide,
and the clouds are concentrated sulphuric acid, causing a runaway greenhouse effect. This creates a high surface temperature
of 482ºC (900ºF). Sunlight passes through the atmosphere to heat the surface of the planet. Heat is radiated out, but is
trapped by the dense atmosphere and not allowed to escape into space. This makes Venus hotter than Mercury which is closer to
The Pioneer Venus 1 spacecraft (1978) conducted a radar mapping of the surface,
revealing a relatively flat plain surrounding two continent-sized highland areas which have been named Aphrodite Terra and
Ishtar Terra. The Magellan spacecraft (1990-1994) discovered large active volcanoes and lava flows, as well as extensive meteorite
Changing Phase & Apparent Size of Venus
We say that a planet is in conjunction with another planet or object when the two are in line as viewed from Earth. The inner
planets of Venus and Mercury (so called because they revolve around the Sun inside of Earth's orbit), can line up at
superior conjunction when they lie behind the Sun or at inferior conjunction when they lie between the Sun and the Earth.
The outer planets can only line up at superior conjunction as viewed from Earth.
The relative positions of Venus and the Earth are indicated on the diagram,
which has been simplified by keeping the Earth's position fixed. As Venus revolves around the Sun, its sunlit hemisphere is
presented to the Earth in varying amounts showing phases resembling those of the Moon. They can only be seen through a
telescope and were first observed by Galileo in 1610. The full phase is shown at superior conjunction, the quarter phases
at greatest elongations and the new phase at inferior conjunction. Usually a thin crescent remains at the new phase because
the planet crosses a little above or below the Sun.
As Venus passes from superior to inferior conjunction, its distance from the
Earth decreases from 160 million miles to 26 million miles, causing its apparent diameter to increase about six times. As it
approaches the Earth, its apparent brightness increases until the crescent phase is reached. Greatest brilliancy occurs
about five weeks preceding and five weeks following the time of inferior conjunction.
At greatest brilliancy, the sunlit crescent of Venus sends 2.5 times more
light to Earth than the smaller, fully illuminated disk at superior conjunction. At its best, the planet is 15 times
brighter than Sirius, the brightest star.
After passing greatest eastern elongation, Venus appears to move westward
relative to the Sun and passes between the Earth and the Sun at inferior conjunction. It thus changes from an evening star
to a morning star. Inferior conjunction occurs about every 8 years. The last inferior conjunctions were October 31st 2002
and October 28th 2010. The next will be October 26th 2018.
Since Venus does not revolve around the Sun in exactly the same plane as the
Earth, it usually does not pass directly in front of the Sun. Such a passage across the Sun's disk is called a transit. It
is not an eclipse because Venus appears only as a black dot on the solar disk. The last transits of Venus were in 1874,
1882 and 2004 and the next will occur in 2012.
In Roman mythology, Venus was originally a goddess of fields and gardens but later became
identified with the Greek goddess of love and beauty. Venus was the wife of Vulcan but was unfaithful many times. Among her
lovers were the shepherd Adonis and Mars the god of war. She was the daughter of Jupiter and the mother of the god of love,
In terms of astrology, Venus is the planet of pleasure and love governing capacity for love,
ability to appreciate beauty, social grace and friendships. Expressed in the positive form, Venus endows a person with sex
appeal, charm, amiability, an appreciation of the arts and an eye for beauty. These influences are manifested through
romance, art, music, and loving and sharing with others. In the negative form Venus instils decadence, narcissism and
laziness. Being so close to the sun it always lies within two signs of a person's sun sign.