A star spotted by astronomer Edward Emerson Barnard near Venus in 1892 seemed to disappear, puzzling experts for over a century. Recent investigations by a team of astronomers have resolved the enigma, attributing it to an optical illusion in morning light. The discovery reaffirms Barnard's observational skills while clarifying the event.
In 1892, Edward Emerson Barnard, renowned for discovering Jupiter's fifth moon Amalthea that same year, observed a bright star near Venus while using the 36-inch telescope at Lick Observatory on Mount Hamilton in California. He estimated its brightness at 7th magnitude, visible on a dark night to those with good eyesight. However, the star was absent from the Bonner Durchmusterung catalogue, which included all stars up to 9.5 magnitude, and subsequent observations revealed only an 11th magnitude star—about 100 times dimmer—in the same position.
Barnard documented his perplexing sighting in a 1906 journal article titled 'An unexplained observation.' Theories abounded: it might have been a large asteroid like Ceres or Vesta, but those were elsewhere; perhaps a nearby star temporarily brightened or a 'ghost' reflection from Venus fooled the telescope. None fully satisfied, leaving the mystery intact for decades.
In December 2024, during a weekly Zoom meeting called Asteroid Lunch, amateur astronomer Tim Hunter from Arizona—co-founder of DarkSky International—raised the topic. A collaborative group of amateurs and professionals, including optical engineer Roger Ceragioli from the University of Arizona, systematically dismissed prior explanations.
Ceragioli tested the ghost theory by observing Venus at dawn with a vintage eyepiece similar to Barnard's. Though Venus was not in the 1892 position, he immediately spotted a star in the field of view, which his star map identified as 8th magnitude—relatively dim yet appearing brighter in morning light. The team concluded that Barnard's 7th magnitude sighting was actually the documented 11th magnitude star, enhanced by dawn conditions. As a newcomer to the Lick telescope without nearby comparison stars, Barnard's estimation was understandable, especially since visual brightness assessment was a specialized skill for variable star experts, which he was not.
Hunter praised Barnard, saying, 'We are all very big Barnard fans. It’s a fairly minor error.' Ceragioli noted, 'Immediately in the field, I saw a star.' The findings appear in the Journal of Astronomical History and Heritage (DOI: 10.3724/SP.J.1440-2807.2025.03.05).
