Mercury transit

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The transit of Mercury on November 8, 2006

A Mercury transit (from Latin transitus 'passage', 'passing'), also Mercury passage or Mercury passage , is a passing of the planet Mercury in front of the sun . Mercury moves as a tiny black point over the solar disk within several hours. In total, there is a transit of Mercury 13 or 14 times per century. Because of the planet's small apparent size, a transit of Mercury cannot be seen with the naked eye. Pierre Gassendi was the first person to observe a passage through Mercury on November 7, 1631, after Johannes Kepler had calculated such a passage for the first time in 1629.

Celestial mechanics basics

Inclination of Mercury's orbit against the orbit of the earth

During a Mercury transit, the sun, Mercury and earth are almost exactly in line. The principle of this rare planetary constellation is similar to that of a solar eclipse , in which the moon moves in front of the sun and darkens it. In contrast to a solar eclipse, however, a transit of Mercury does not cause an eclipse on Earth, since Mercury only covers a maximum of 0.004 percent of the sun's surface. In contrast, during solar eclipses the moon can cover the entire sun. During the transit, Mercury can be seen from Earth as a tiny point (magnified as a small disk) that wanders from east to west (left to right) over the solar disk within several hours.

The constellation in which a transit can occur is called the lower conjunction . Since Mercury rotates around the sun much faster than the earth with a sidereal orbit period of approx. 88 days, it happens about every 108 to 130 days that Mercury overtakes the earth on its orbit further inside the solar system. However, a conjunction does not lead to a transit every time, since Mercury does not run exactly in the plane of the earth's orbit (ecliptic) around the sun, but its orbit is inclined by 7 ° to the ecliptic. As a result, the planet usually passes above or below the solar disk when there is a conjunction. Mercury's orbit only intersects the earth's orbit in the two orbit nodes . In order for Mercury to pass in front of the Sun, a lower conjunction must take place in the immediate vicinity of one of the two nodes.

A Mercury transit can be 3½, 7, 9½ or 13 years apart from the previous transit; very rarely (November 1993 to November 1999) it is 6 years. A cycle of Mercury transits is repeated approximately every 46 years. During this time there have been 46 orbits of the earth and 191 orbits of Mercury around the sun. After that, Mercury is again in exactly the same position as seen from Earth; the deviation from this cycle is only 0.34 days.

The two nodes of Mercury's orbit are at about 46 ° and 226 ° ecliptical longitude , where the Earth is located on November 10th and May 7th. Transits at the ascending node therefore take place in November, those at the descending node in May. A clear difference can be observed between the frequency of transits at the two nodes. While around two thirds of all Mercury transits occur at the ascending node in November, only one third occurs in May and thus on the descending node. This is also due to the high eccentricity of Mercury's orbit. When passing through in November, Mercury is further away from Earth than when passing through in May. As a result, a passage is still possible with a greater distance between Mercury and the orbit node during a lower conjunction than with a lower conjunction in May. Since the orbital nodes of the planet Mercury slowly shift to larger values ​​of the ecliptical longitude, the dates for the Mercury transits also shift to later and later calendar dates over the centuries. From the year 3426, Mercury transits will not take place until June and December.

In addition, transits in May take longer than November transits, since Mercury is almost at the point of its orbit furthest from the sun, the aphelion , during May transits and thus has almost its lowest possible speed. In contrast, during November transits, Mercury is only a few days before perihelion , the point of its orbit closest to the sun, and thus has almost its highest possible orbital speed. The high eccentricity also plays a role here, since with a higher eccentricity as a result of Kepler's second law, the path speed fluctuates more strongly in the course of a revolution. In perihelion the orbital speed of the planet is 59 km / s, more than 50% higher than in aphelion with 38.9 km / s.

The Mercury transit of November 8, 2006 was only fully visible from Oceania and the west coast of North America. In Europe, the time of transit fell during the night and could therefore not be observed there. The passage through Mercury on May 7, 2003 could be fully followed from Europe; it lasted about 5 hours 20 minutes. The transit on May 9, 2016 was fully visible in Europe.

Sequence of a Mercury transit

Scheme of the four contacts of a transit

In the transit of Mercury a distinction is made - as in every planetary transit in front of the sun - four contacts:

The first contact represents the first contact of the small planetary disk with the sun and thus the beginning of the transit. Only a few seconds later, if the exact position on the sun's edge is known, the corresponding indentation can be recognized. The second contact is the point in time when the Mercury disc is completely in front of the sun for the first time and separates from the sun's edge. The phase between the first and the second contact is called entry , it only lasts between one and four minutes in a Mercury transit. Then the planet appears to be moving in front of the sun. The third and fourth contact represent a reversal of the first two contacts. The exit begins at the third contact , which ends with the fourth contact, which also ends the entire transit.

Immediately after the second and just before the third contact at a Mercury passage which can drop phenomenon (black dropEffect) are observed.

The observation of the transits of Mercury in 1999 and 2003 acquired significance in terms of the history of science. Three American astronomers attempted to prove the drop phenomenon on these occasions. They used the TRACE space telescope for this . They succeeded in demonstrating the drop phenomenon even though Mercury has no atmosphere. In doing so, they refuted the previous view, gained on the occasion of the Venus transits , that this phenomenon is caused by a planetary atmosphere. Today it is known that the drop phenomenon is caused by the limited optical resolution of the telescopes used.

Historical Mercury Passages

Mercury crossed a group of sunspots on May 9, 1970. Analog photography at an altitude of 1700 m on the Etna volcano, Sicily

Since a transit of Mercury cannot be observed with the naked eye without magnification using optical aids, no observations of Mercury transits are known from the time before the invention of the telescope at the beginning of the 17th century. The Moroccan astronomer Alpetragius , who lived in the 12th century, believed that Mercury was transparent because it was never seen to pass in front of the sun. However, there were also previous observations that were incorrectly interpreted as Mercury transit; For example, Einhard reported in the Anglo-Saxon Chronicles that in March 807 Mercury was said to have passed the solar disk for eight days. In reality, he must have witnessed an exceptionally large sunspot that was visible to the naked eye.

The German astronomer Johannes Kepler succeeded in making the first exact calculation of a Mercury transit in 1629 with the help of the Rudolfinian tables , completed in 1627 , in which he predicted the planetary positions much more precisely than they were given in the tables previously used. With the help of the tablets he predicted a passage through Mercury on November 7, 1631, when his calculations only deviated from the actual transit by about five hours. However, Kepler died in November 1630 and was therefore no longer able to observe the transit of Mercury himself. On November 7, 1631, the Frenchman Pierre Gassendi (at the same time as two other people in other places) observed the passage of Mercury from Paris. He determined the diameter of Mercury to be around 20 arc seconds, which was well below the value of 130 arc seconds previously determined by Tycho Brahe . During the transit of Mercury in 1661, Johannes Hevelius measured an even smaller diameter than Gassendi. He also saw the occurrence of the transit on the day on which the tables calculated on the basis of elliptical orbits had predicted it as proof of the correctness of Kepler's first law , according to which planets move on elliptical orbits around the sun.

On November 7, 1677, the British astronomer Edmond Halley succeeded in taking exact measurements of the transit of Mercury taking place at that time. At that time he was on the Atlantic island of St. Helena to compile a catalog of the stars of the southern sky . He also noticed during this passage that such a device is suitable for calculating the length of the astronomical unit (the distance between the sun and the earth). However, he found that the Mercury disk is too small to get exact results and that a Venus transit would be more suitable for such a project. This was later confirmed by French astronomers who observed the passes of Mercury in 1723 and 1753 and also achieved only very imprecise results.

Thus, later transits focused on observing the small disk of Mercury itself. Above all, they investigated whether the planet had a moon , looked for evidence of an atmosphere and tried to determine other phenomena during a transit. The search for a moon was in vain.

Until the Mariner 10 space probe became the first space probe to reach Mercury in March 1974 and found that the planet had no atmosphere, the search for evidence of an atmosphere on the planet was one of the most important scientific objectives when observing a transit of Mercury. During the passage of Mercury in 1736, a French observer noticed a shiny ring around the black disk. This observation was confirmed by several observers in 1799 (including the German Johann Hieronymus Schroeter ); also in 1832, when a ring with a purple hue was reported, and in 1868, when William Huggins believed he saw an envelope of light about half the width of the planet's apparent diameter. These phenomena have not yet been finally clarified, but no atmosphere can be held responsible for them. It is believed that these observations are either due to diffraction or can be explained by the inaccuracy of the observation instruments that also caused the drop phenomenon .

During the Mercury transit of 1832, Bessel was able to show that Mercury - similar to the Venus transits - shows a change in shape at the edge of the sun, which is now referred to as the drop phenomenon , whereby an atmospheric cause is excluded for the atmosphere-free Mercury. The observations carried out simultaneously with Argelander on two instruments also showed that the effect is instrument-dependent.

In 1868, Huggins observed a glowing point on the Mercury disk next to the light envelope. This observation has also been passed down several times in the course of history. Such a point on the disk of Mercury was mentioned for the first time by the German Johann von Wurzelbau in 1697. During the passage of Mercury in 1799, Schroeter and his assistant Karl Ludwig Harding observed greyish points on the planet's disk, and similar observations were made by other astronomers on later passes. However, no such observation has been reported since the late 19th century, so that it is probably also due to imprecise optics.

Special forms of Mercury transit

Central transit

Very rare, almost central passage through Mercury from November 10, 1973. Photographed in Switzerland.

If one calculates the mean of all previous transits since 1600, the transit line of the Mercury disk had an average minimum distance of a good 500  arc seconds (8 ′ 20 ″) from the center of the solar disk. That is about 45 times the apparent size of the planet in front of the sun (11 ″) and about a quarter of the apparent size of the sun (32 ′) itself. Mercury thus moves at its average minimum distance about halfway between the center and the Edge of the sun over.

In the last four centuries there have been a total of five transits of Mercury, the minimum distance between them being less than 100 arc seconds (1 ′ 40 ″) past the center of the Sun. The closest to the center was the transit of November 10, 1973, which had a minimum distance of only 26.4 arc seconds to the center and thus came very close to a central transit. A transit in which the small disk of the planet crosses the exact center of the sun is theoretically possible, but statistically very unlikely due to the small size of Mercury.

On November 11, 2019, Mercury approached the center up to 75.9 ″. The transit on November 12, 2190, with a minimum distance of 9.1 arc seconds to the center, will be the closest transit of this millennium to a central one. The last transit of Mercury with an even shorter distance (7.2 arc seconds) took place on April 21, 1056.

Grazing transit

In principle, it is also possible that Mercury moves exactly along the edge of the sun. Such a transit is known as a grazing transit. A total of 2.8% of all Mercury transits are grazing, calculated over a period of half a million years.

During the grazing passage of Mercury on November 15, 1999, Mercury moved completely past the sun for some areas of the earth, and only partially for others. The penultimate such transit took place on October 22, 1559. The next Mercury transit, during which Mercury only partially steps in front of the sun for observers in some areas, but completely in others, will not take place again until May 11, 2391. Grazing transits of this type make up about 1.1 percent of all passes through Mercury.

In addition, it is possible that a passage through Mercury is visible as a partial passage from some areas of the earth, while the planet passes by the edge of the sun for observers in other parts of the world and is therefore not observable. Such a transit last occurred on May 11, 1937. The penultimate event of this kind was on October 21, 1342. The next passage through Mercury, which observers will see as a partial passage in some parts of the world, while in other parts of the world Mercury just passes the sun, will not be until December 13. Enter May 2608. Over half a million years, grazing transits of this type occur slightly more frequently than those of the other type, accounting for 1.7% of all Mercury transits.

Simultaneous transits

Simultaneous transits of Mercury
and solar eclipses
up to 16000
date Type
July 5th, 6757 partially
4th August 9361 annular
4th February 9622 annular
August 11, 9966 total
August 20, 10663 total
August 25, 11268 total
February 28, 11575 annular
April 20, 15790 annular

Since Venus and Mercury have different node lengths, a simultaneous occurrence of Mercury and Venus transit is not possible in our epoch. Currently, the orbital nodes of Mercury and Venus are about 28 degrees apart. However, the orbit lines of Mercury and Venus do not move at the same speed. Mercury's orbit line moves a little faster at a change of 1.2 degrees per century than that of Venus, which moves about 0.9 degrees per century. In the course of the next centuries, the nodes of Mercury's orbit will come closer and closer to those of Venus' orbit, so that a double transit would be possible in about 10,000 years. The astronomers Jean Meeus from Belgium and Aldo Vitagliano from the University of Naples Federico II in Italy calculated that the next simultaneous transit of Mercury and Venus will not occur until 69.163. The next one will not take place until 224,508. In similar calculations based on the past millennia, they also found that there was no simultaneous passage of the planets in front of the sun in the last 280,000 years.

The simultaneous occurrence of a solar eclipse and a passage through Mercury is theoretically possible earlier due to the faster moving lunar nodes . However, due to the rarity of both events, such an event is extremely rare; it will not occur until July 5, 6757 and be seen in the south of the Pacific . This solar eclipse is only a partial one. On July 20, 8059, however, a transit of Mercury will occur simultaneously with a ring-shaped eclipse. The next transit of Mercury, which occurs simultaneously with a total solar eclipse, will not take place until August 11, 9966.

observation

General information

Mercury transit of November 8, 2006 (Mercury top right, a sunspot below )

Observation of the sun or a planetary transit with the naked eye or with self-made filters can cause permanent damage to the eye and even blindness. In the case of self-made filters made from untested materials, there is no guarantee that harmful but invisible ultraviolet and infrared components of sunlight will be filtered out. In particular, you should never look into the sun with binoculars or telescopes without optical sun filters, as the optical bundling of sunlight can lead directly to severe eye injuries.

A transit of Mercury cannot be observed with eclipse glasses or the like without optical magnification , since Mercury, with an apparent size of an average of 11 arc seconds (about 175 times smaller than the apparent diameter of the sun), is too small to be recognized without magnification. The NASA therefore recommends a telescope with a 50- to 100-fold magnification. However, this telescope must be equipped with a special solar filter that is attached in front of the lens , but not behind the eyepiece , as the heat would be too great there. The easiest way to observe the sun is to use the eyepiece projection of the sun image onto white paper. The telescope is aimed at the sun using its shadow and a sheet of paper is held 10–30 cm behind the eyepiece. The sun appears as a bright circular area and is brought into focus by turning the eyepiece. Mercury then moves as a small, dark disc over the surface over the course of hours. Eyepieces with non-cemented lenses should be used, as the high power density of the bundled sun rays can heat the cement to such an extent that the eyepiece is damaged.

The last passages of Mercury were also broadcast by webcam from several websites , including the European Southern Observatory in 2003 .

Mercury transit dates from 1950 to 2100

The ratio of the orbital periods around the sun between Earth and Mercury is approximately 54:13, in a somewhat poorer approximation 137:33 and in a good approximation 191:46, see Mercury positions . This means that after 13, 33 or 46 years the constellation is roughly the same again and therefore May and November transits are often repeated after such a number of years, where 46 is of course the sum of 13 and 33. A very imprecise approximation is the ratio 29: 7, an even worse one is 25: 6.

There are often 13 years between two consecutive of the more frequent November transits, but it can also be 7 years and, in individual cases (1993–1999), only 6 years. There are always 13 or 33 years between two neighboring, rarer May transits, in the rare case (1937 to 1957) it is 20 years.

Mercury transits

Middle transit date		 Time ( UTC ) Years since the last /
penultimate / third last transit
Beginning center The End total May Nov
November 14, 1953 15:37 16:54 18:11
May 6, 1957 23:59 01:14 02:30 3.5 20/33/66
November 7, 1960 14:34 16:53 19:12 3.5 7th
May 9, 1970 04:19 08:16 12:13 9.5 13/33/46
November 10, 1973 07:47 10:32 13:17 3.5 13/20
November 13, 1986 01:43 04:07 06:31 13 13/26/33
November 6, 1993 03:06 03:57 04:47 7th 7/20/33
November 15, 1999 21:15 21:41 22:07 6th 6/13/26
May 7, 2003 05:13 07:52 10:32 3.5 33/46/79
November 8, 2006 19:12 21:41 00:10 3.5 7/13/20
May 9, 2016 11:12 14:57 18:42 9.5 13/46/59
November 11, 2019 12:35 15:20 18:04 3.5 13/20/26
November 13, 2032 06:41 8:54 am 11:07 13 13/26/33
November 7, 2039 07:17 08:46 10:15 7th 7/20/33
May 7, 2049 11:04 14:24 17:45 9.5 33/46/79
November 9, 2052 23:53 02:29 05:06 3.5 13/26/33
May 10, 2062 18:16 21:36 00:57 9.5 13/46/59
November 11, 2065 17:24 20:06 22:48 3.5 13/26/33
November 14, 2078 11:42 13:41 15:39 13 13/26/39
November 7, 2085 11:42 13:34 15:26 7th 7/20/33
May 8, 2095 17:20 21:05 00:50 9.5 33/46/59
November 10, 2098 04:35 07:16 09:57 3.5 13/20/33

Periodicity over longer time intervals

If one takes out the partial Venus transit of May 1937, then from 1924 through 1957, 1970, 2003, 2016, 2049, 2062, 2095, 2108, 2141, 2154 to 2187, the Mercury transits always alternate in May after 13 and then after 33 years; only the transit to be expected according to this scheme in May 2200 does not take place, while one takes place again in 2220. Looking in the other direction, a transit was missed in 1911, but a May transit had previously taken place in 1891.

In the November transits, such series are found in significantly longer periods, for example from 1743 through 1776, 1789, 1822, 1835, 1868, 1881, 1914, 1927, 1960, 1973, 2006, 2019, 2052, 2065, 2098, 2111, 2144, 2157 , 2190, 2203, 2236, 2249, 2282, 2295, 2328, 2341, 2374, 2387 to 2420. This series cannot be continued because in the years 1730 and 2433 transits were / are missed.

Another series of this kind, half of which corresponds to the latter in the common time interval, is found from 1960 through 1993, 2006, 2039, 2052, 2085, 2098, 2131, 2144, 2177, 2190, 2223, 2236, 2269, 2282, 2315, 2328 , 2361, 2374, 2407, 2420, 2453, 2466, 2499, 2512, 2545, 2558, 2591, 2604 up to the year 2637. It cannot be continued either, since in 1947 and 2650 no transit took place or will take place!

If you pull both series together, you discover that from 1960 to 2420 there are always November transits at intervals of 13, 20 and 13 years.

In addition to this series, in the table above we find November transits in the years 1953, 1986, 1999, 2032 and 2078. Apart from the absence of a transit in 2045, these are also at intervals of alternately 33 and 13 years. It will end permanently in the 21st century, as there will be no transit in 2091 either. On the other hand, it can be traced back to 1940, 1907, 1894, 1861, 1848, 1815, 1802, 1769, 1756, 1723, 1710, 1677, 1664, 1631, 1618, 1585, 1572, 1539, 1526, 1493, 1480, 1447, 1434 , 1401, 1388, 1355, 1342 (partially) traced back to exactly 1309, since a transit is not missed until 1296. However, in the late Middle Ages it was still October transits.

See also

literature

Web links

Commons : Mercury Transit  - collection of images, videos and audio files
Wiktionary: Mercury transit  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c d e Fred Espenak: Transits of Mercury. In: NASA / Goddard SFC: Eclipse Home Page (English).
  2. ↑ Loomis, p. 217.
  3. ^ HM Nautical Almanac Office: 2006 Transit of Mercury.
  4. ^ HM Nautical Almanac Office: 2003 Transit of Mercury.
  5. ^ American Astronomical Society : Explanation of the Black-Drop Effect at Transits of Mercury and the Forthcoming Transit of Venus. ( Memento of November 3, 2007 in the Internet Archive ) January 2004.
  6. ↑ Maunder, p. 23.
  7. ^ Lynn, WT: Eclipses mentioned in the Anglo-Saxon Chronicle. bibcode : 1892Obs .... 15..224L
  8. ↑ Linton, p. 228.
  9. ↑ a b Maunder, p. 25.
  10. ↑ Maunder, p. 26.
  11. ^ FW Bessel: passage of mercury through the sun. In: Astronomical News. Volume X (1832), No. 228, col. 185-196, here: col. 187-188. ( Dig ).
  12. ↑ Maunder, p. 27.
  13. ^ A b Transits of Mercury on Earth: Half million years catalog. ( Memento of the original from January 1, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. At: transit.savage-garden.org. @1@ 2Template: Webachiv / IABot / transit.savage-garden.org
  14. ↑ Marco Peuschel: Conjunctions, coverings and transits - The small almanac of the planets. Self-published by Engelsdorfer Verlag, Leipzig 2006, ISBN 3-939144-66-5 .
  15. ↑ a b c Hans Zekl: Double Transits - When can Venus and Mercury be seen in front of the Sun at the same time? At: astronomie.de. Retrieved January 4, 2012. See Jean Meeus; Aldo Vitagliano: Simultaneous transits. In: The Journal of the British Astronomical Association 114 (2004), no.3.
  16. ↑ Simultaneous occurrence of solar eclipse and transit of Mercury: 6757 July 05. ( Memento of the original from March 31, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. At: transit.savage-garden.org. @1@ 2Template: Webachiv / IABot / transit.savage-garden.org
  17. ↑ Simultaneous occurrence of solar eclipse and transit of Mercury: 8059 Jul 20. ( Memento of the original from March 31, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. At: transit.savage-garden.org. @1@ 2Template: Webachiv / IABot / transit.savage-garden.org
  18. ↑ Fred Espenak: 2006 Transit of Mercury. At: nasa.gov.
  19. ↑ European Southern Observatory: Webcam of the Mercury passage from 2003.
  20. ^ NASA - Catalog of Transits of Mercury. For entries after 2050. Retrieved November 11, 2019 .
  21. ↑ Mercury transit on May 9, 2016. In: Sternwarte-Peterberg.de. Association of Amateur Astronomers of Saarland eV, April 17, 2016, accessed on April 17, 2016 .
Passages in our solar system
Venus earth Mars Jupiter Saturn Uranus Neptune
Mercury Mercury Mercury Mercury Mercury Mercury Mercury
  Venus Venus Venus Venus Venus Venus
    earth earth earth earth earth
      Mars Mars Mars Mars
        Jupiter Jupiter Jupiter
  moon Deimos     Saturn Saturn
    Phobos       Uranus