The Discovery of the Perseid Meteors
Prior to 1837, nobody realized the Perseids were an annual event.
But young Edward did not go to Yale. He did not go to college. His parents felt that his chronic eyelid inflammation would keep him from succeeding in higher education. So in 1827, at the age of 16, Edward became a clerk in a bookstore that served Yale students and faculty and was also the college's publishing house.
Everyone in New Haven with intellectual interests stopped by the bookstore, and Herrick reveled in conversations with professors such as astronomer Denison Olmsted and chemist Benjamin Silliman. The young clerk worked hard, and by age 24 he had become one of the bookstore's owners. Unfortunately, business stalled over the next three years and left Herrick broke.
American astronomers in 1837 were still gripped by the excitement of the epic meteor deluge that had taken place four years earlier. On the night of November 12-13, 1833, more than a thousand shooting stars per minute had been seen radiating from the constellation Leo (Sky & Telescope: November 1995, page 24). Astronomers had been taken completely by surprise; it was the first time that most of them had paid attention to meteors at all. They were especially startled by Olmsted's demonstration that the shower's meteors must have been flying together in parallel from a distant region of space. Most astronomers had believed that meteors were mere atmospheric phenomena, to be ignored like clouds and weather.
Now astronomers were searching historical records and turning up accounts of previous mid-November meteor showers. But to observe abundant meteors in August? That seemed odd.
A Second Annual Meteor Shower?
Following Olmsted's example, Herrick wrote an article for the January 1838 issue of Silliman's American Journal of Science and Arts in which he proposed the existence of a second annual meteor shower. He listed his evidence and asked for information from anyone else who had seen the display.
While his first article was being published, Herrick turned up four more accounts from other years of meteors plummeting through the skies on August 9th or 10th. He was convinced.
"There generally occurs on or about the 9th of August in every year," he wrote, "a remarkably large number of shooting stars."
In a second article Herrick drew further correct conclusions:
Herrick discarded notions that meteors were meteorological, like lightning or rainbows, or debris falling back to Earth after the eruption of a volcano. "Shooting stars are without doubt cosmical or celestial bodies," he wrote, "and not of atmospheric or terrestrial origin." What could that source be?
The August meteors remain near their peak for about three days, and off-peak meteors span perhaps two weeks.
Like those of November, the August meteors have a "starting point," a spot in the sky from which they seem to radiate. Herrick could not yet fix its position among the stars; the meteors were not abundant enough to make their radiant obvious.
The August meteors are more numerous than those of November almost every year, except on rare, overwhelming occasions when the November meteors pour down in torrents.
In addition to November and August, there was probably a third annual meteor shower around April 30th (now called the Lyrids). Herrick found only three cases of it in 1095, 1122, and 1803 but mighty storms of meteors had come in late April of those years.
"It is not impossible," Herrick wrote, "that these meteoric showers are derived from nebulous or cometary bodies which, at stated times, the earth falls in." Here was another correct insight, one that Olmsted had broached. The hypothesis that meteors have a cometary origin was confirmed 28 years after Herrick's article, when the connection between meteor and comet orbits was demonstrated.
Pleased with his achievement, Herrick wrote up the new evidence for his annual August shower, included his theories about of meteors, and gave the paper to Silliman for publication in his journal. Less than two weeks later Herrick received crushing news. He was not the shower's discoverer after all.