In the fourth canto of Childe Harold’s Pilgrimage, the poem that made Lord Byron famous, the poet describes a remarkable twilight that he observed while cruising along the Brenta Canal in Italy. “The Moon is up,” he writes. “A Single Star is at her side, and reigns/With her o’er half the lovely heaven.” But as Samantha Mathewson reports for Space.com, an astronomer's recent analysis of the work suggests that the brilliant star that captured Byron's attention may actually be the planet Jupiter.
Donald Olson, an astronomer and physics professor at Texas State University, began his investigation by poring through Byron’s personal letters and manuscripts. In a first edition of Childe Harold’s Pilgrimage, Byron scribbled a note stating that the poem was no mere figment of his imagination. "The above description may seem fantastical or exaggerated to those who have never seen an Oriental or an Italian sky—yet it is but a literal,” he wrote, according to a Texas State University press release.
The diary of John Cam Hobhouse, a close friend of Byron who accompanied the poet on his travels, provided the date for the arresting twilight. “Wednesday August 20th 1817: Ride with Byron,” Hobhouse recorded. “Riding home, remarked the moon reigning on the right of us and the Alps still blushing with the gaze of the sunset. The Brenta came down upon us all purple—a delightful scene, which Byron has put in three stanzas of his Childe Harold.”
Olson then used astronomical software to reconstruct the sky as it would have appeared in that location on the evening of August 20, nearly 200 years ago. Jupiter, he found, was aligned with the moon that day, and would have shone brightly above Byron as he rode along the Brenta's banks. The results of this modeling, along with Byron's and Hobhouse's descriptions, led Olson to conclude that Jupiter is the “single star” that hovers next to the moon in the famous poem.
Additional lines may provide further clues about the scene that greeted Byron that evening. Childe Harold describes, for example, “meek Dian’s crest.” It is a reference to Diana, the Roman goddess associated with the moon, who was often depicted with a diadem (or “crest”) resting on her forehead. According to Olson’s astronomical model, the moon on August 20, 1817 would have been in what's known as the waxing gibbous phase—when more than half of the orb is light, but it is capped with a crescent of darkness.
Then there is Byron’s mention of Iris, goddess of the rainbow in Greek mythology. “Heaven is free/From clouds, but of all colours seems to be/Melted to one vast Iris of the West,” the poet writes. Olsen speculates that the source of this spectacular, technicolor sky was the 1815 eruption of Mount Tambora, a volcano in Indonesia. For years after the explosion, people around the world reported seeing vibrantly colored sunsets, the result of gas, dust and aerosols flung into the air during the eruption.
“It is likely that Byron observed a ‘Tambora Twilight’ as the backdrop for his observation of the moon and Jupiter that August evening in 1817,” according to the press release.
The results of Olson’s investigation recently appeared in the latest issue of Sky & Telescope magazine but have not been published in a scientific journal. It may be impossible to know for certain what Byron was looking at when he was inspired to pen the last canto of Childe Harold. But modern skywatchers may soon get a glimpse of similar skies: Jupiter is due to align with the moon on several occasions in late July and August. So don't forget to look up and catch the celestial scene that perhaps dazzled the beloved poet.