transitsfasen

Transitsfasen refers to the different stages an object undergoes as it passes in front of another celestial body, typically observed from Earth. This phenomenon is most commonly associated with the transit of planets like Venus or Mercury across the face of the Sun. During a transit, the transiting object appears as a small dark dot moving across the brighter disk of the Sun.

The transit begins with the ingress, when the transiting object first touches the limb of the Sun. This is followed by the phase of transit, where the object is fully visible on the Sun's disk. The transit concludes with the egress, when the object reaches the opposite limb of the Sun and begins to disappear. If the transiting object is a planet, there are often two distinct points of contact during ingress and egress, sometimes referred to as "first contact" and "second contact" for ingress, and "third contact" and "fourth contact" for egress. These contacts mark the precise moments when the limb of the transiting body touches the limb of the Sun.

The duration of a transit varies depending on the celestial bodies involved and their orbital positions. Transits of Venus are rare, occurring in pairs separated by 8 years, with the pairs themselves occurring roughly every 105 or 121 years. Transits of Mercury are more frequent, happening around 13 or 14 times a century. Observing these transits allows astronomers to gather valuable data about the transiting objects and the Sun, and historically, they played a significant role in determining the size of the solar system and the astronomical unit.