Star that seemed to vanish more than 130 years ago is found again

A star that was spotted in 1892 by one of the most gifted astronomical observers of all time but then apparently disappeared has been found again – right where he lost it.

Edward Emerson Barnard was an accomplished astronomer famous for his discovery in 1892 fifth moon of Jupiter Amaltheaalmost three centuries later Galileo Galilei I saw the first four. But a few weeks earlier, he had made a puzzling observation that continued to bother him. The short article he published about this in a magazine in 1906 was entitled “Unexplained sighting“.

He thought he saw a star close to Venus One morning he pointed his telescope at this planet, hoping to discover satellites.

He rated its brightness as magnitude 7 on a scale used by astronomers, where fainter objects receive a higher number. On a dark night, a person with good eyesight can see stars around 6th magnitude at most.

Barnard looked for the star in the only all-sky catalog at that time, Bonner Durchmusterung. It listed all stars that were magnitude 9.5 or brighter, so his 7th magnitude star should have been there, but it wasn't. And watching again later, it seemed to disappear. The only star he could find near this location was an 11th magnitude star, about a hundred times less luminous.

Could it be a large asteroid? “Not Ceres, Pallas, Juno and Vesta, which were elsewhere,” he later wrote. Some believed that the 11th magnitude star he later saw in a similar position, or another nearby star, may have been temporarily brighter. Others suggested that Barnard was deceived by a “ghost” – a random reflection of Venus in his telescope. But the mystery remained—until a group of astronomers decided to get to the bottom of it in December 2024.

“In a Zoom meeting I do once a week called the Asteroid Lunch, I happened to mention it,” says Tim Hunter.

Soon Hunter, an amateur astronomer from Arizona and co-founder of the International Dark-Sky Association, is now DarkSky International – was part of a group of amateur and professional astronomers who studied all the proposed explanations. They found good reasons to reject each of them.

They were about to give up when a member of the group Roger Seraggiolian optical engineer at the University of Arizona, decided to test the ghost theory again by looking at Venus at dawn, as Barnard had done. He did this using a telescope with an antique eyepiece similar to the one Barnard may have used. A surprise awaited him.

Although Venus was not in the same position in the sky as Barnard observed it in 1892, “immediately in the field I saw a star,” says Ceraggioli. He reasoned that it must be quite bright to be visible at dawn. But the star map on his computer told him it was actually only 8th magnitude—relatively faint.

The group concluded that Barnard had experienced something similar. This suggests that the 7th magnitude star he thought he saw was in fact an 11th magnitude star subsequently documented at the site, which appeared brighter than it actually was in the morning light. Barnard was relatively new to the 36-inch telescope Lick Observatory on Mount Hamilton in California, through which he saw a star near Venus, and he had no other stars of known brightness with which to compare it.

Barnard's mistake is forgivable, Ceraggioli notes, given that determining the brightness of a star by eye was a specialized skill in Barnard's time, developed only by astronomers studying variable stars, which he never did.

Hunter, too, believes the astronomer's reputation is still “pretty perfect. We're all big fans of Barnard. It's a pretty minor mistake.”

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