Conjunction (astronomy)

The conjunction is the aspect in which a celestial body with another heavenly body has the same value in right ascension (conjunction in right ascension ) or in ecliptic longitude (conjunction in length).

Contact is the aspect in which the objects have the same azimuthal position, the apparent coincidence of two celestial bodies.

Contact designates the same facts, in particular but also special moments with touches of objects.

  • 5.1 Special forms of the conjunction
  • 5.2 Other aspects of

Time points

Conjunction in right ascension, declination and touch are generally apart in time. It is possible that two celestial bodies come into conjunction in ecliptic longitude (but not in right ascension ), and vice versa. Falls below the angular separation of two celestial bodies, the sum of the apparent radii, there is contact. Depending on whether the larger or the smaller body is closer to the observer, ie which of the two "front " position, this is referred to transit and occultation.

While the conjunctions take place every synodic period touches are relatively rare.

When visually larger objects then is called four selected time points as 1st - 4th Contact:

  • The first and fourth contact is the moment in which touch the edges of the heavenly bodies, the center of the smaller body but yet, or is already outside of the disc of the larger ones.
  • The second and third contacts, the timing of the edge of contact in which the passage has to take place.

See also Solar Eclipse, solar limb, Roaming coverage.

All three phenomena are generally exclusively related to an observer on the Earth, but could also be defined by analogy to any other points of view ( topozentrisches problem). Then find these events at other times instead.

Special conjunctions

Conjunctions between the planets among themselves, the planets and bright stars, the moon and planets, and the moon and bright stars often give off an interesting sight. They are therefore listed in astronomical almanacs.

Particularly spectacular is the meeting of Jupiter and Saturn in the sky, which is called the Great Conjunction, in a special case as Largest conjunction.

Conjunctions of minor planets, or the faint planets Uranus and Neptune with bright planets or fixed stars also allow ungeübteren observers visit these objects, since the bright planet or star may serve as a guiding star.

Interesting conjunctions arise from passages of satellites, but require very precise statement and special observation.

Planetary conjunctions

Triple Conjunction and loop

If two celestial bodies at almost the same time in opposition to the Sun, so there may be three conjunctions within a few months because of the apparent loop orbits of celestial bodies involved. This is known as a triple conjunction. Such events are very rare among the planets. The last such triple conjunction between Mars and Jupiter place in 1980, between Jupiter and Saturn in 1981 and between Mars and Saturn 1945/46, instead, the next such events occur again until 2123 ( triple conjunction of Mars - Jupiter), 2238/39 ( triple conjunction Jupiter - Saturn) and 2148 ( triple conjunction of Mars - Saturn) a. Triple conjunctions between Jupiter and Uranus and Jupiter and Neptune are more common.

Upper and lower Conjunction

For the inferior planets Mercury and Venus in conjunction with conjunctions with the sun is the term upper and lower Conjunction Conjunction used. Are Mercury and Venus - as seen from the Earth - behind the sun, so they are in superior conjunction, they stand between the sun and Earth, so they are in inferior conjunction. The two planets have at superior conjunction of the largest Erdabstand, at inferior conjunction, they have the smallest Erdabstand, but only in exceptional cases ( Mercury and Venus during a passage or Venus at great northern or southern sun distance ) visible.

For the upper planet, there is only one type of conjunction with the sun ( behind this, they can not stand between the earth and sun). If an upper Planet in conjunction, so he has the maximum Erdabstand and is invisible from the Earth. The upper planets reach their best visibility at the time of opposition.

Conjunctions of the moon

If the Moon is in conjunction with the Sun, so we have a new moon. Like Mercury, Venus and the moon attracts mostly north or south of the sun and then, only when the moon is near its orbit node, it attracts observers in some areas of the planet from the sun over. In these areas, a solar eclipse takes place.