In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth. The astronomical symbol for conjunction is ☌ and handwritten . The conjunction symbol is not used in modern astronomy. It continues to be used in astrology.
Twilight on Earth is the illumination of the lower atmosphere when the Sun itself is not directly visible because it is below the horizon. Twilight is produced by sunlight scattering in the upper atmosphere, illuminating the lower atmosphere so that Earth's surface is neither completely lit nor completely dark. The word twilight is also used to denote the periods of time when this illumination occurs.
In classical antiquity, the seven classical planets are the seven non-fixed astronomical objects in the sky visible to the naked eye: Mars, Jupiter, Venus, Saturn, Mercury, the Sun, and the Moon. The word planet comes from two related Greek words, πλάνης planēs and πλανήτης planētēs, both with the original meaning of "wanderer", expressing the fact that these objects move across the celestial sphere relative to the fixed stars. Greek astronomers such as Geminus and Ptolemy often divided the seven planets into the Sun, the Moon, and the five planets.
In astronomy, an extraterrestrial sky is a view of outer space from the surface of an astronomical body other than Earth.
A triple conjunction is an astronomical event, where two planets or a planet and a star meet each other three times in a short period either in opposition or at the time of inferior conjunction, if an inferior planet is involved. The visible movement of the planet or the planets in the sky is therefore normally prograde at the first conjunction, retrograde at the second conjunction and again prograde at the third conjunction.
In many cases astronomical phenomena viewed from the planet Mars are the same or similar to those seen from Earth but sometimes they can be quite different. For example, because the atmosphere of Mars does not contain an ozone layer, it is also possible to make UV observations from the surface of Mars.
Spherical astronomy or positional astronomy is the branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on Earth. It relies on the mathematical methods of spherical geometry and the measurements of astrometry.
The phases of Venus are the variations of lighting seen on the planet's surface, similar to lunar phases. The first recorded observations of them were telescopic observations by Galileo Galilei in 1610. Although the extreme crescent phase of Venus has been observed with the naked eye, there are no indisputable historical pre-telescopic records of it being observed.
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.
Astrological transits are one of the main means used in horoscopic astrology to forecast future trends and developments. As its name implies, astrological transits involve a method of interpreting the ongoing movement of the planets as they transit the horoscope. This is most often done for the birth or Natal Chart of a particular individual. Particular attention is paid to changes of sign, or house, and to the aspects or angles the transiting planets make with the natal chart.
Greek astronomy is astronomy written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras. It is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the language of scholarship throughout the Hellenistic world following the conquests of Alexander. This phase of Greek astronomy is also known as Hellenistic astronomy, while the pre-Hellenistic phase is known as Classical Greek astronomy. During the Hellenistic and Roman periods, much of the Greek and non-Greek astronomers working in the Greek tradition studied at the Musaeum and the Library of Alexandria in Ptolemaic Egypt.
In astronomy a phase curve describes the brightness of a reflecting body as a function of its phase angle. The brightness usually refers the object's absolute magnitude, which, in turn, is its apparent magnitude at a distance of one astronomical unit from the Earth and Sun. The phase angle equals the arc subtended by the observer and the sun as measured at the body.
Planets in astrology have a meaning different from the modern astronomical understanding of what a planet is. Before the age of telescopes, the night sky was thought to consist of two very similar components: fixed stars, which remained motionless in relation to each other, and "wandering stars", which moved relative to the fixed stars over the course of the year.
Venus, as one of the brightest objects in the sky, has been known since prehistoric times and has been a major fixture in human culture for as long as records have existed. As such, it has a prominent position in human culture, religion, and myth. 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.
