AstroCruises (TM) Venus Transit Page

Venus transit map courtesy of Fred Espenak, NASA/Goddard Space Flight Center. For more information on planetary transits across the sun, see Fred Espenak's Planetary Transit Page sunearth.gsfc.nasa.gov/eclipse/transit/transit.html.

2004 Venus Transit

For about six hours on Tuesday, June 8, 2004, the planet Venus passes directly between Earth and the sun. At that time some places on Earth will be able to see Venus transit, or move, across the face of the sun. No living person has witnessed this celestial event, which last happened in 1882. Transits of Venus occur four times during a 243-year repeating cycle at intervals of eight, 105.5, eight and 121.5 years.

AstroCruises (TM) specializes in programs that view naked-eye astronomical phenomena aboard cruise ships, but this event warrants an exception to our usual criteria for an astronomy cruise. The apparent width of Venus is about three percent of the diameter of the sun so, while the transit should be visible to the naked eye with a CE certified solar filter, it can better be seen as a magnified image with a telescope using a solar filter or with solar projectors such as the Sun Gun or Sunspotter solar viewers. A ship that is in port at the time of the transit will allow a telescope or solar projector to be set up on a steady platform, not possible if the ship were at sea at the time. The transit takes place at 5:13 to 11:25 a.m. UTC (GMT), so the entire transit of Venus will be visible from the Indian Ocean, Black Sea and Mediterranean, with the clearest skies expected in the Mediterranean.

Are your eyes sharp enough to spot Venus against the face of the sun with these solar viewers?
To the naked eye the sun appears the size of a quarter held about 8 feet 8 inches (2.65 meters) away,
with Venus only one-third of the height of one of the numbers on the quarter's date.

There are other astronomical events of interest during the period a transit cruise would take place. Comet Q4 (NEAT) is expected to be easily visible to the naked eye at the time, above the horizon most of the night and predicted as brighter than the dimmest Big Dipper star until June 2 and brighter than the dimmest Little Dipper star until June 25 (the Harvard-Smithsonian Astrophysical Observatory publishes predictions for the daily brightness of the comet). Comet T7 (LINEAR) is also expected to be visible in the evening sky, predicted as brighter than Big Dipper stars through June 3 and brighter than Little Dipper stars through June 14. The moon is waning between the full moon of June 3 and the new moon of June 17, so this is the time of month when early evening is darkest and best for stargazing. The monthly last and first appearances of the crescent moon take place shortly before and after June 17, and the crescent moon with earthshine will be visible for several more days around that date. Solar projection equipment can also show daily sunspot activity during the cruise.

The next transit of Venus occurs on June 6, 2012, and then it will be more than a century before the next pair of transits comes around in 2117 and 2125. More details about the 2004 Venus transit can be found on Web pages by Fred Espenak, Chuck Bueter, Juergen Giesen and Paper Plate Education.

Venus transit illustration courtesy of Fred Espenak, NASA/Goddard Space Flight Center.

Venus Transit Trivia

Only six Venus transits have occurred since the invention of the telescope, those in 1631,1639, 1761,1769, 1874, and 1882. In late 1631 French astronomer Pierre Gassendi became the first to observe a transit of Mercury. The next month Gassendi tried to observe the transit of Venus, but clouds hid the fact that the transit was not visible from Europe -- no one is known to have witnessed it. British astronomer Jeremiah Horrocks and his friend William Crabtree were apparently the only ones to observe the transit of Venus on December 4, 1639.

In 1769 England's Royal Society and Royal Greenwich Observatory outfitted Captain Cook's First Voyage, which went to Tahiti to observe the Venus transit (comet calculator Edmond Halley had determined that if the transit of Venus were observed from a number of different locations on Earth, the distances to Venus and the sun could be accurately calculated). The 2004 Venus transit will not be visible from Tahiti, but the 2012 transit will be.

John Philip Sousa wrote Transit of Venus March to honor American physicist Joseph Henry, the first Secretary of the Smithsonian Institution and a member of the U.S. Transit of Venus Commission. Henry's statue stands in front of the Smithsonian Institution's "Castle" on the Mall in Washington, D.C., a short distance from the Smithsonian National Air and Space Museum.

Mercury Transits

Mercury, the only other planet that comes between Earth and the sun, transits 14 times in the 21st century. Never a naked-eye event, transits of Mercury need a telescope that magnifies 50x to 100x. The next Mercury transit occurs November 8, 2006, and the one after that in 2016.