By Leander Kahney
In a marriage of science and art, three astronomers have pinpointed the precise time and date of a painting by Dutch painter Vincent Van Gogh based on calculations of the moon’s position in the picture.
Van Gogh’s painting depicts a field of haystacks in Provence, France, with a bright orange orb partially showing over a bluff. The vivid picture was known to have been painted sometime in the summer of 1889, toward the end of the most productive, but troubled, period of the artist’s life.
However, the precise date of its creation has vexed art historians for many years. Even the subject matter was in doubt. For most of the last century the painting was assumed to show the setting sun, not the rising moon. Originally untitled, the painting was known only by its catalog number, F735. It has subsequently been called Rising Moon: Haycocks.
Now, Southwest Texas State University astronomers Russell Doescher and Donald Olson, along with Olson’s wife, Marilyn, an English professor, have determined that Van Gogh was working on the picture at 9:08 p.m. on July 13, 1889.
By coincidence, the exact same scene will be visible on the same date this summer -- which also marks the 150th anniversary of Van Gogh’s birth -- thanks to the lunar cycle.
To establish the painting’s precise date, Doescher and the Olsons traveled to Provence armed with maps, aerial photos, historical weather data and calculations of the moon’s phases.
Thanks to Van Gogh’s letters to his brother, Theo, the three academics knew the picture had been painted sometime between May and September of 1889 while the artist was a patient at a monastery hospital in Saint-Rémy.
However, during the last century Van Gogh scholars have postulated at least six different dates for the painting, one of nearly 300 works produced by the painter during his year’s stay at the hospital. During that year he also painted one of his most famous pieces, Starry Night.
Almost immediately, the scholars were able to determine that Van Gogh painted the scene exactly as he had seen it. The hayfield, the bluff and a farmhouse in the painting are still features of the landscape.
For nearly a week, they camped out in a nearby field, measuring the arc of the rising moon. Using simple trigonometry, the scientists calculated the precise position of the moon in the painting relative to the equator, a point known as the moon’s declination. Using astronomical software, they matched the moon’s declination to two dates in 1889: May 16 and July 13.
The astronomers hoped to eliminate one of the dates by consulting records at the French meteorological office, but reports show clear skies on both days, as depicted in the picture.
However, a bit of simple reasoning clinched the July date. The painting shows stacks of harvested golden wheat. In May, the wheat would still have been green and growing.
During their observations, the astronomers timed the moon’s rise over the bluff, which took less than two minutes. If painted on July 13, the moon depicted by Van Gogh would have been in position at exactly 9:08 p.m.
They used similar astronomical techniques in 2001 to determine the precise timing of another Van Gogh painting, White House at Night, by identifying the twinkling celestial object in the painting as the planet Venus.
A full account of the cosmic sleuthing is printed in the July 2003 issue of Sky & Telescope magazine.
“ If you’re interested in astronomy and you see the moon in pictures or photos, you get interested,” said Stuart Goldman, the magazine’s associate editor.