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Transits of the Inner Planets Mercury and Venus Are Possible 2004 Transit of Venus by Fred Espenak Printable version by JP GODARD Fred Espenak e-mail: mailto:[email protected] Planetary Systems Branch - Code 693 NASA's Goddard Space Flight Center, Greenbelt, Maryland 20771 USA Permission is freely granted to reproduce this data when accompanied by an acknowledgment: "Transit Predictions by Fred Espenak, NASA/GSFC" All calculations and diagrams presented in this section are those of the author and he assumes full responsibility for their accuracy. "Transit Predictions by Fred Espenak, NASA/GSFC" 1/39 Table of contents PLANETARY TRANSITS ACROSS THE SUN 3 2004 TRANSIT OF VENUS 6 OBSERVING THE TRANSIT 8 FREQUENCY OF TRANSITS 8 HISTORY OF TRANSITS 9 AN IMAGE OF ONE OF THE 1700 PLATES TAKEN WORLDWIDE DURING THE 1882 TRANSIT, SHOWING VENUS CROSSING THE DISK OF THE SUN. 10 COMMEMORATIVE STAMP OF THE 1769 COOK’S EXPEDITION TO TAHITI 10 PREDICTIONS FOR THE 2004 TRANSIT OF VENUS 11 INTRODUCTION 11 TRANSIT CONTACT TIMES FOR CITIES AROUND THE WORLD 12 CIRCUMSTANCES FOR EUROPE 13 WORLD VISIBILITY OF 2004 TRANSIT OF VENUS 21 2004 AND 2012 TRANSITS OF VENUS 24 INTRODUCTION 24 GEOGRAPHIC VISIBILITY OF 2004 JUNE 08 25 GEOGRAPHIC VISIBILITY OF 2012 JUNE 06 25 FREQUENCY OF TRANSITS 25 ADDITIONAL COMMENTS 26 KEY TO CATALOGS OF TRANSITS OF VENUS 32 FOOTNOTES 34 VENUS FACT SHEET 35 ACKNOWLEDGMENTS 37 REFERENCES (TRANSIT PREDICTIONS) 38 REFERENCES (HISTORY OF TRANSITS) 38 LINKS ON TRANSITS 39 All calculations and diagrams presented in this section are those of the author and he assumes full responsibility for their accuracy. "Transit Predictions by Fred Espenak, NASA/GSFC" 2/39 Planetary Transits Across the Sun Transit of Mercury on 1973 Nov 10. The transit or passage of a planet across the disk of the Sun may be thought of as a special kind of eclipse. As seen from Earth, only transits of the inner planets Mercury and Venus are possible. Planetary transits are far more rare than eclipses of the Sun by the Moon. On the average, there are 13 transits of Mercury each century. In comparison, transits of Venus usually occur in pairs with eight years separating the two events. However, more than a century elapses between each transit pair. The first transit ever observed was of the planet Mercury in 1631 by the French astronomer Gassendi. A transit of Venus occurred just one month later but Gassendi's attempt to observe it failed because the transit was not visible from Europe. In 1639, Jerimiah Horrocks and William Crabtree became the first to witness a transit of Venus. At the present time, all transits of Mercury fall within several days of May 08 and November 10. Since Mercury's orbit is inclined seven degrees to Earth's, it intersects the ecliptic at two points or nodes which cross the Sun each year on those dates. If Mercury passes through inferior conjunction at that time, a transit will occur. During November transits, Mercury is near perihelion and exhibits a disk only 10 arc-seconds in diameter. By comparison, the planet is near aphelion during May transits and appears 12 arc-seconds across. However, the probability of a May transit is smaller by a factor of almost two. Mercury's slower orbital motion at aphelion makes it less likely to cross the node during the critical period. November transits recur at intervals of 7, 13, or 33 years while May transits recur only over the latter two intervals. The following table lists all transits of Mercury from 1924 through 2050. All calculations and diagrams presented in this section are those of the author and he assumes full responsibility for their accuracy. "Transit Predictions by Fred Espenak, NASA/GSFC" 3/39 Transits of Mercury: 1901-2050 Date Universal Separation* Time (Sun and Mercury) 1924 May 08 01:41 85" 1927 Nov 10 05:44 129" 1937 May 11 09:00 955" 1940 Nov 11 23:20 368" 1953 Nov 14 16:54 862" 1957 May 06 01:14 907" 1960 Nov 07 16:53 528" 1970 May 09 08:16 114" 1973 Nov 10 10:32 26" 1986 Nov 13 04:07 471" 1993 Nov 06 03:57 927" 1999 Nov 15 21:41 963" (graze) 2003 May 07 07:52 708" 2006 Nov 08 21:41 423" 2016 May 09 14:57 319" 2019 Nov 11 15:20 76" 2032 Nov 13 08:54 572" 2039 Nov 07 08:46 822" 2049 May 07 14:24 512" • distance (arc-seconds) between the centers of the Sun and Mercury To determine whether a transit of Mercury is visible from a specific geographic location, it is simply a matter of calculating the Sun's altitude and azimuth during each phase of the transit using information tabulated in the Seven Century Catalog of Mercury Transit. For the relevant equations and a sample calculation , see Transit Visibility. This web page also has links to several Excel files which perform the calculations automatically when the user inputs the latitude and longitude of any location. In 1716, Edmond Halley published a paper describing exactly how transits could be used to measure the Sun's distance, thereby establishing the absolute scale of the solar system from Kepler's third law. Unfortunately, his method proved somewhat impractical since contact timings of the required accuracy are difficult to make. Nevertheless, the 1761 and 1769 expeditions to observe the transits of Venus gave astronomers their first good value for the Sun's distance. Photograph of the Transit of Venus on 1882 Dec 06. Taken by students at Vassar College (Sky & Telescope Feb. 1961). All calculations and diagrams presented in this section are those of the author and he assumes full responsibility for their accuracy. "Transit Predictions by Fred Espenak, NASA/GSFC" 4/39 Because Venus's orbit is considerably larger than Mercury's orbit, transits of Venus are much rarer. Indeed, only six such events have occurred since the invention of the telescope (1631,1639, 1761,1769, 1874 and 1882). Transits of Venus are only possible during early December and June when Venus's orbital nodes pass across the Sun. Transits of Venus show a clear pattern of recurrence at intervals of 8, 121.5, 8 and 105.5 years. The following table lists all transits of Venus during the 800 year period from 1601 through 2400. Transits of Venus: 1601-2400 Date Universal Separation Time (Sun and Venus) 1631 Dec 07 05:19 940" 1639 Dec 04 18:25 522" 1761 Jun 06 05:19 573" 1769 Jun 03 22:25 608" 1874 Dec 09 04:05 832" 1882 Dec 06 17:06 634" 2004 Jun 08 08:19 627" 2012 Jun 06 01:28 553" 2117 Dec 11 02:48 724" 2125 Dec 08 16:01 733" 2247 Jun 11 11:30 693" 2255 Jun 09 04:36 492" 2360 Dec 13 01:40 628" 2368 Dec 10 14:43 835" To determine whether a transit of Venus is visible from a specific geographic location, it is simply a matter of calculating the Sun's altitude and azimuth during each phase of the transit using information tabulated in the Six Millennium Catalog of Venus Transits. For the relevant equations and a sample calculation , see Transit Visibility. This web page also has links to several Excel files which perform the calculations automatically when the user inputs the latitude and longitude of any location. The 2004 transit of Venus will be best seen from Europe,Africa and Asia. However, the final stages of the event will also be visible from the eastern USA and Canada. Since Venus will subtend 61 arc- seconds, it should be visible to the naked eye using suitable filtration. The first transit of Venus in 121 years is most eagerly anticipated. All calculations and diagrams presented in this section are those of the author and he assumes full responsibility for their accuracy. "Transit Predictions by Fred Espenak, NASA/GSFC" 5/39 2004 Transit of Venus Published in Observer's Handbook 2004, Royal Astronomical Society of Canada The transit or passage of a planet across the face of the Sun is a relatively rare occurrence. As seen from Earth, only transits of Mercury and Venus are possible. On average, there are 13 transits of Mercury each century. In contrast, transits of Venus occur in pairs with more than a century separating each pair. No living person has seen a transit of Venus because the most recent one occurred in 1882. This situation is about to change since Venus will transit the Sun on Tuesday, 2004 June 08. The entire event will be widely visible from the Europe, Africa and Asia as shown in the map in Figure 1. Japan, Indonesia, the Philippines and Australia will witness the beginning of the transit but the Sun will set before the event ends. Similarly, observers in western Africa, eastern North America, the Caribbean and most of South America will see the end of the event since the transit will already be in progress at sunrise from those locations. All calculations and diagrams presented in this section are those of the author and he assumes full responsibility for their accuracy. "Transit Predictions by Fred Espenak, NASA/GSFC" 6/39 The principal events occurring during a transit are conveniently characterized by contacts, analogous to the contacts of an annular solar eclipse. The transit begins with contact I, the instant the planet's disk is externally tangent with the Sun. Shortly after contact I, the planet can be seen as a small notch along the solar limb. The entire disk of the planet is first seen at contact II when the planet is internally tangent with the Sun.
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