Scientists eye new data expected from Venus transit

by Peter Duveen



Archivist Randall Rosenfeld helps elucidate obscure details about the upcoming transit of Venus at a recent conference in Toronto, Canada.

PETER'S NEW YORK, Sunday, June 3, 2012--The University of Toronto will highlight a relatively rare astronomical event on Tuesday with a multimedia presentation at its Varsity Stadium. Not only will the Transit of Venus be projected onto a large viewing screen, but special disposable eye gear fitted with specially treated plastic filters will be distributed to the crowd to prevent anyone from having their vision impaired due to the damage that often results from directly viewing the sun. The planet Venus will show up as a round black dot during a six-hour pilgrimage across the sun. During the transit, there will also be a performance in the stadium of part of an opera, the plot of which is based on the true story of a man who sacrificed practically everything of value in his life to view the event.

Transits have been observed at least since 1639, when knowledge of astronomy reached a stage advanced enough to predict precisely when the planet Venus would post itself between the earth and the sun, thus enabling earthlings to see the silhouette of the planet against the disk of our nearest star. This happens two times within the space of about eight years, after which more than a century passes before the next transit. After Tuesday, more than a hundred years will pass before the cycle recurs.

At one time, hopes were high that accurate measurements of the event from different vantage points on earth could be used to gage the distance of the earth from the sun. In fact, measures obtained from the observation of the 1639 transit by Jeremiah Horrocks, an English astronomer in his early 20s, did yield an improved calculation of this distance. But transits have not been employed for this purpose since the late 19th Century, when astronomers developed more accurate means for measuring the diameter of the earth's orbit.

Yet those who have been emphasizing the transit have found fresh reasons for scrutinizing it. During the last event in 2004, it seems that, just before the planet began its journey in front of the sun, its atmosphere lit up in the form of a bright halo surrounding its surface. This appears to have been the first time the Venusian atmosphere was observed from earth-based telescopes.


Close to a hundred participants are engaged by, from left to right, Paul Greenham, Erich Weidenhammer and Ari Gross and Erich Weidenhammer, who have worked to established a budding museum consisting of scientific equipment gleaned from various departments at the University of Toronto.

At a recent conference (April 28) hosted by the University of Toronto's Institute for the History and Philosophy of Science and Technology, Dr. Jay M. Pasachoff, director of the observatory at Williams College in Williamstown, Mass., explained to a gathering of about 100 participants that more accurate observations of what he called "atmosphere scattering" would be made during the Tuesday event.

An additional reason for paying close attention to the transit, according to another presenter, Dr. James Graham of the Dunlap Institute of Astronomy and Physics, will be to take measurements of exactly how much the sun dims when Venus obscures ever so slightly the output of light and heat put out by our closest star. These observations, Dr. Graham explained, can be used to interpret similar dimmings of far-away stars, thus enabling astronomers to formulate ideas about the size of planets that may be orbiting them.


Professor Jay M. Pasachoff of the Hopkins Observatory at Williams College in Williamstown, Mass., remarks on observations of the Venusian atmosphere.

The day-long conference featured a diverse roster of speakers, each addressing a particular facet of the transit. Department head and renowned historian of physics and mathematics Dr. Craig Fraser offered a general introduction, followed by Randall Rosenfeld, archivist for the Royal Astronomical Society of Canada, who treated the conference to a rendition of a complicated baroque musical piece on a rustic hand-made flute. Rosenfeld was followed by Dr. Bernard Lightman of York University, who led the audience through the complicated debate between two 19th Century astronomers who failed to see eye-to-eye on exactly how observations of the transit should be made.

Midway through the day, Paul Greenham, Ari Gross and Erich Weidenhammer of the Institute took participants on a tour of what is shaping up to become a museum for astronomical instruments whose historical value has superseded their practical utility. Among these was a telescope used for viewing the transit of 1882, about which so much hullabaloo occurred regarding the expensive expeditions sent around the world to observe it. Included in the featured instruments of the museum was an electron microscope, ads for which the writer remembers seeing in Scientific American magazine when he was a preteen.


A telescope used to view the 1882 transit of Venus is one of the exhibits in a fledgling museum on the premises of the University of Toronto.

Composer Victor Davies played prerecorded excerpts of his opera, Transit of Venus, while projecting scenes from the opera on a viewing screen. The work's elaborate plot line, based on a play by Maureen Hunter, would have made Puccini's librettists blush. Dr. Michael Reid and Mubdi Rahman of the Dunlap Institute discussed ways in which the transit could be used as a teaching opportunity for high school students. Dr. Ralph Chou of the University of Waterloo suggested ideas for viewing the transit safely, and documented the type of eye damage experienced by careless observers in past years. Others assisting in the production of the conference included Rebecca Michaels, John Percy and Teresa Branch Smith.


Composer Victor Davies reviews the story line of the opera he completed on the theme of the transit.

All presenters emphasized that observations of the transit should be conducted cautiously, with attention paid to observing it without injuring the eyes. The image of the sun can be projected from a telescope, or even through a pinhole in cardboard, onto a screen where it may be viewed without danger. Various types of treated glass and plastic are used for the purpose of viewing the image of the sun directly without damaging the eyes. Even better, one may travel to the University of Toronto, where the event can be viewed live at Varsity Stadium on screens that will provide perhaps the best images possible for the enjoyment of the educated layman.

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