Astronomical transit

A passage or passage is an astronomical event:

• In general, the coincidence of two astronomical objects, such as the perihelion - the point in time between two perihelion passages, or the passage of the moon through the meridian plane.

Especially as a transit following passages are referred to:

• The meridian passage: An object crosses the meridian ( the south direction at the location of the observer ). At constant declination it does not reach the greatest height above the horizon, in the other case. For more information, see the culmination and astronomical position determination.
• The Transit of two celestial bodies or partial coverage, which are specifically addressed in this article.
• The passage of a star through the reticle of a measuring telescope, see Stern passage.

Transit of two celestial bodies

Taking a seemingly smaller celestial body in front of another over and covered him thereby partially, so this passage is called a transit. The size ratio is determined by the apparent size. In the opposite case - in a possibly complete coverage of a seemingly smaller celestial body - this is called occultation.

The Transit is a special case of the conjunction.

The following configurations are possible:

• When a planet through one of the lower planets (Mercury or Venus) is passing from the sun.

• A moon ( satellite ) of a planet moves in front of the planet over
• An asteroid or comet draws from the sun past (see: asteroid passage)
• An artificial satellite (such as the International Space Station ) is passing in front of the sun or the moon
• A double star passage ( eclipsing variable stars ) and the passage of an exoplanet in front of its host star

For passage of a lower planet from the sun, it is necessary that the inferior conjunction ( planet between the Sun and Earth ) coincides with the node (intersection of the orbital plane with the ecliptic ).

Time and duration of the passage are always dependent on the viewing position.

Passages of artificial satellites

Even artificial earth satellites can fall into the line of sight between an observer on the earth and the sun or the moon. However, such events are difficult to observe because of the visibility strip is only a few kilometers wide. However, for example, transits of the International Space Station have been frequently observed and photographed against the sun and moon. The satellite travels mostly over for 0.5-2 seconds before the sun. As with a planetary passage is no subjective visual brightness decrease to register.