Conjunction (astronomy)
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Conjunction is a term used in positional astronomy and astrology. It means that, as seen from some place (usually the Earth), two celestial bodies appear near one another in the sky.
More generally, in particular in the case of two planets, it means that they merely have the same right ascension (and hence the same hour angle). This is called conjunction in right ascension. However there is also the term conjunction in ecliptical longitude. At such conjunction both objects have the same ecliptical longitude. Conjunction in right ascension and conjunction in ecliptical longitude do normally not take place at the same time, but in most cases nearly at the same time. However at triple conjunctions, it is possible that a conjunction only in right ascension (or ecliptical length) occur. At the time of conjunction - it does not matter if in right ascension or in ecliptical longitude - the involved planets are close together upon the celestial sphere. In the vast majority of such cases, one of the planets will appear to pass north or south of the other.
However, if the two celestial bodies attain the same declination at the time of a conjunction at right ascension (or the same ecliptical largitude at a conjunction in ecliptical longitude), the one closest to the Earth will pass in front of the other. In such a case an occultation tooks place, or if the moon passes in front of the sun a solar eclipse, if Mercury passes in front of the sun a transit of Mercury or if Venus passes in front of the sun a transit of Venus. Occultations, especially such in which the eclipsing body is not the sun or the moon are very rarely. More frequent, however, is an occultation of a planet by the Moon, which will generally occur every few years on average (and is often visible only from certain locations and not everywhere the two objects are above the horizon at the time, as in the case of a lunar eclipse). Solar eclipses are globally considered not rare events (every year occur at least two), but for a certain location, especially total or annular solar eclipses are rarely.
It is often believed that the Star of Bethlehem was a triple conjunction between Jupiter and Saturn in the year 6BC. However the angle distance between Jupiter and Saturn was at this event approximately 1 degree, this is twice the diametre of the moon in the sky. Occultations of Saturn by Jupiter did not occur in historic times and will not occur before the year 7541.
As seen from a planet that is superior, if an inferior planet is on the opposite side of the Sun, it is in superior conjunction with the Sun. An inferior conjunction occurs when the two planets lie in a line on the same side of the Sun. In an inferior conjunction, the superior planet is "in opposition" to the Sun as seen from the inferior planet.
The terms "inferior conjunction" and "superior conjunction" are used in particular for the planets Mercury and Venus, which are inferior planets as seen from the Earth. However, this definition can be applied to any pair of planets, as seen from the one further from the Sun.
A planet (or asteroid or comet) is simply said to be in conjunction, when it is in conjunction with the Sun, as seen from the Earth. The Moon is in conjunction with the Sun at New Moon (or rather Dark Moon).
"Quasi-conjunctions" are also possible; in this scenario, a planet in retrograde motion — always either Mercury or Venus — will "drop back" in right ascension until it almost allows another planet to overtake it, but then the former planet will resume its forward motion and thereafter appear to draw away from it again. This will occur in the morning sky, before dawn; or the reverse may happen in the evening sky after dusk, with Mercury or Venus entering retrograde motion just as it is about to overtake another planet (often Mercury and Venus are both of the planets involved, and when this situation arises they may remain in very close visual proximity for several days or even longer). The quasi-conjunction is reckoned as occurring at the time the distance in right ascension between the two planets is smallest, even though, when declination is taken into account, they may appear closer together shortly before or after this.
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Grand Conjunctions
2007
A very remarkable planetary/galactic configuration occurs on 23rd and 24th December 2007. The 23/12 configuration — Mars, Earth, Sun, Mercury, Jupiter, Galactic Centre, is shown in the graphic simulation (link) below; it becomes even more remarkable in that it will be joined/triggered by the full moon (conjunct mars) at about 2am on December 24th when a simultaneous Venus square Neptune occurs. It's even more remarkable in that the Pluto/sun conjunction appears exactly on the Winter Solstice... just past conjunction with the Galactic Centre.
Link below is the view from Mars toward the Jupiter, Mars, Earth, Mercury, Pluto alignment toward the Galactic Centre on 23rd of Dec 2007 which occurs just after the Pluto/Jupiter (Heliocentric) conjunction on 23rd Nov 2007. NASA Solar System Simulator for 23rd Dec 2007 (http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=5&vbody=4&month=12&day=23¢ury=20&decade=0&year=7&hour=00&minute=0&fovmul=1&rfov=30&bfov=30&porbs=1&brite=1)
2002
In late April of 2002, a rare grand conjunction occurred; in which Saturn, Jupiter, Mars, Venus and Mercury were all visible concomitantly in the west-northwest sky, shortly after sundown; this will happen again in early July of 2060, except that on that occasion the quintet will be bunched in the east-northeast sky, shortly before dawn.
2000
In May of 2000, the five brightest planets aligned within 20° of the Sun, as seen from the Earth. This could not be observed since they were too close to the Sun.
1987
On August 24, 1987, the five objects closest to Earth — the Sun, Moon, Mercury, Venus and Mars — were within approximately 5° of one another, the Sun setting first, followed by Mars, Venus, Mercury and the Moon, in that order, within 20 minutes. As in the 2000 conjunction above, this event was unobservable due to the Sun being part of the line-up.
Conjunctions in Right Ascension in 2005-2007
Date | Time UTC | Planet | Angle distance | Planet | Elongation to sun |
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January 14th, 2005 | 00:40:51 | Mercury | 21' south of | Venus | 18,5° West |
February 8th, 2005 | 01:29:22 | Mercury | 2°04' south of | Neptune | 4,2° West |
February 14th, 2005 | 19:15:10 | Venus | 58' south of | Neptune | 10,7° West |
February 20th, 2005 | 00:46:34 | Mercury | 1°00' south of | Uranus | 4,9° Ost |
March 4th, 2005 | 03:31:36 | Venus | 41' south of | Uranus | 6,6° West |
March 28th, 2005 | 22:31:53 | Mercury | 4°49' north of | Venus | 1,5° West |
April 13th, 2005 | 00:26:23 | Mars | 1°15' south of | Neptune | 66,0° West |
May 14th, 2005 | 20:24:10 | Mars | 1°11' south of | Uranus | 73,8° West |
June 25th, 2005 | 21:22:52 | Venus | 1°18' north of | Saturn | 22,8° East |
June 26th, 2005 | 06:13:43 | Mercury | 1°25' north of | Saturn | 22,5° East |
June 27th, 2005 | 20:18:55 | Mercury | 5' south of | Venus | 23,3° East |
July 7th, 2005 | 08:21:22 | Mercury | 1°38' south of | Venus | 25,8° East |
September 2nd, 2005 | 12:05:52 | Venus | 1°22' south of | Jupiter | 38,7° East |
October 6th, 2005 | 07:01:37 | Mercury | 1°28' south of | Jupiter | 12,6° East |
January 17th, 2006 | 02:23:03 | Mercury | 7°53'south of | Venus | 6,5° West |
February 1st, 2006 | 12:13:51 | Mercury | 1°57' north of | Neptune | 4,5° East |
February 14th, 2006 | 15:40:57 | Mercury | 2' north of | Uranus | 14,1° East |
March 26th, 2006 | 21:02:41 | Venus | 1°52' north of | Neptune | 46,5° West |
April 18th, 2006 | 12:27:31 | Venus | 19' north of | Uranus | 45,0° West |
June 17th, 2006 | 22:50:40 | Mars | 35' north of | Saturn | 42,0° East |
August 20th, 2006 | 22:40:10 | Mercury | 31' north of | Saturn | 11,2° West |
August 26th, 2006 | 23:09:47 | Venus | 4' north of | Saturn | 16,3° West |
September 15th, 2006 | 20:32:28 | Mercury | 10' south of | Mars | 12,1° East |
October 24th, 2006 | 19:44:11 | Venus | 43' north of | Mars | 0,6° West |
October 25th, 2006 | 21:42:16 | Mercury | 3°56' south of | Jupiter | 21,2° East |
October 28th, 2006 | 16:32:15 | Mercury | 3°43' south of | Jupiter | 19,1° East |
November 7th, 2006 | 13:36:58 | Mercury | 1°14' south of | Venus | 2,8° East |
November 11th, 2006 | 17:51:38 | Mercury | 39' north of | Mars | 6,2° West |
November 15th, 2006 | 22:52:15 | Venus | 27' south of | Jupiter | 4,8° East |
December 9th, 2006 | 20:17:18 | Mercury | 1°02' north of | Mars | 15,1° West |
December 11th, 2006 | 23:34:02 | Mars | 49' south of | Jupiter | 15,7° West |
January 18th, 2007 | 18:10:50 | Venus | 1°25' south of | Neptune | 20,1° Ost |
January 26th, 2007 | 06:46:07 | Mercury | 1°28' south of | Neptune | 12,7° Ost |
February 7th, 2007 | 13:13:57 | Venus | 44' south of | Uranus | 24,6° Ost |
March 25th, 2007 | 07:23:59 | Mars | 1°00' south of | Neptune | 43,2° West |
April 1st, 2007 | 06:59:14 | Mercury | 1°37' south of | Uranus | 25,0° West |
April 28th, 2007 | 18:57:38 | Mars | 44' south of | Uranus | 50,6° West |
July 2nd, 2007 | 00:44:38 | Venus | 46' south of | Saturn | 42,6° Ost |
August 9th, 2007 | 08:46:28 | Venus | 8°29' south of | Saturn | 10,6° Ost |
August 15th, 2007 | 22:59:23 | Mercury | 10°04' north of | Venus | 1,8° Ost |
August 18th, 2007 | 11:30:22 | Mercury | 30' north of | Saturn | 3,2° Ost |
October 15th, 2007 | 14:05:43 | Venus | 2°56' south of | Saturn | 45,8° West |
December 20th, 2007 | 21:46:21 | Mercury | 1°48' south of | Jupiter | 1,9° Ost |
See also
- Astrological aspects
- Astronomical opposition
- Elongation
- Triple Conjunction
- Great Conjunction
- Greatest Conjunction
- Transit of Venus
Weblinks
- Occultations of Saturn by Jupiter (http://www.marco-peuschel.de/JUPITEROCCULTSATURN.pdf)cs:Konjunkce (astronomie)