June 13, 2004

Venus' Transitory Transit

William Hemmerle of Punta Gorda was especially interested in last Tuesday's transit of Venus - having outlived a prediction that he would never see it.

For those astronomically-challenged, the planet of Venus orbits the Sun a little closer than does the Earth. Periodically Venus and Earth line up on a straight line with the Sun.

This phenomenon could be seen by earthlings for several hours. It was manifested by a tiny silhouette of Venus moving across the Sun disk.

British astronomer Jeremiah Horrocks was first to notice and record it in 1639.

It now is known that the Venusian transit occurs only four times every 243 years. Two are in December, eight years apart. Then, 121 1/2 years later, there are two June transits eight years apart.

After 105 1/2 years, the cycle begins again. The next passage will occur in June 2022. The distances involved are now well known, but the rarity of the brief event is exciting for viewers.

Worldwide Excitement

Astronomers in 1874 were thrilled as the next pair of Venus transits since the 1639 discovery approached.

This time, with cameras and sophisticated measuring devices, they would be able to determine the distance of the Sun from the earth and thus the scale of the solar system.

In the United States, a Venus Transit Commission began well in advance for observations - five by the Naval Observatory, three by the U.S. Geodetic Survey.

When the great event came, the United States launched 8 expeditions, Russia 26, Britain 12, France and Germany six each, Italy three and Holland one.

Nineteenth century astronomy historian Agnes Clerke wrote:

"Every country which had a reputation to keep, or gain, for scientific zeal was forward to cooperate in the great cosmopolitan enterprise of the transit."

New and more equipment was needed. The Naval Observatory asked for funds that included a new telescope.

After some controversy, Congress appropriated $177,000 - a munificent sum at that time -- for the 1874 event. This did not include salaries and the use of Navy facilities and ships.

A Transit of Venus Commission took charge. Plans were ably executed, and a mountain of astronomical data was accumulated. The event was a milestone in astronomical knowledge.

Seaman Thomas

Bill Hemmerle became entranced with Venus transits after inheriting a souvenir album of photographs of the commissioning of the U.S.S. Swatara - a sloop of war -- in May 1874.

His grandfather - William F. Thomas -- was a young able-body seaman on the vessel that was among the first to be fitted with a steam screw as well as masts of sails.

First mission of the ship was to transport and return five Naval Observatory teams of scientists to various sub-Antarctica (46 degrees south latitude) locations. There they would observe the upcoming transit of Venus.

References in the Smithsonian Institution reveal that the Swatara, with its complement of 26 astronomers and photographers, set sail from New York.

The Swarta rounded the Cape of Good Hope --heading east-southeast toward the Crozet Islands where the first observation party was to be landed.

However, high winds and heavy seas precluded a landing. The ship continued on her easterly course towards the Kerguelen group.

Three-Island Harbor was reached Sept. 7. A camp was established at the northern end of Royal Sound. This group was equipped for a long stay to carry out the astronomical observations and also conduct biotic studies of the island.

Then the Swarta headed for Hobart, Tasmania. Astronomer William Harkness and his associates were landed there with equipment and stores.

The group originally intended for Crozet was landed at nearby Campbelltown.

Southland, New Zealand, was reached Oct. 16 and a party of scientists debarked. From there, the Swarta proceeded to Chatham Island east of New Zealand where the final party was established.

Two months after the departure of the Southern parties, the three Northern parties departed from San Francisco to Nagasaki, Japan, by Pacific Mail steamships.

The U.S. Coast Survey party remained in Nagasaki. From there the U.S.S. Kearsarge took science teams to Beijing China and Vladivostok, Russia.

All expeditions were a huge success as solar distances were established and an enlightened view of the cosmos was ushered in.

The Prediction

As the second, nineteenth century transit neared in 1885, Naval Observatory astronomer William Harkness declared:

"We are now on the eve of the second Venus transit of a pair. After this, there will be no other 'til the twenty-first century of our era has dawned upon the Earth, and June flowers are blooming, in 2004.

"When the last transit season occurred, the intellectual world was awakening from the slumber of ages. That wondrous scientific activity -- which has led to our present advanced knowledge -- was just beginning.

"What will be the state of science when the next transit season arrives, God only knows. Not even our children's children will live to take part in the astronomy of that day.

"As for ourselves, we have to do with the present."