C/1925 F1 (Shajn–Comas Solá)

Comet Shajn–Comas Solá, formal designation C/1925 F1, is a non-periodic comet co-discovered by Grigory Shajn and Josep Comas Solá in 1925. At the time, it was the comet with the most distant known perihelion distance (until the discovery of 29P/Schwassmann–Wachmann two years later), which enabled astronomers to continue observing it until March 1927.

Observational history

Discovery

The comet was first spotted by accident from the Simeis Observatory in Crimea by Soviet astronomer, Grigory Shajn, on 22 March 1925. Having just recently transferred from the Pulkovo Observatory, Shajn was not used to operating the telescope at Simeis at the time, hence pointing the instrument to the wrong direction in his first trial run. He noticed a diffuse 11th-magnitude object in an erroneous photographic plate where he recognized it as a comet. In a letter he wrote to George van Biesbroeck, he later recalled:

"Had I not made the mistake in guiding, the trail of the comet would have had nearly the same length as the star trails, and I doubt that I would have distinguished it from a star."

Shortly afterwards, the comet was independently discovered by Spanish astronomer, Josep Comas Solá, from the Fabra Observatory in Barcelona, Spain on 23 March 1925, but was unable to confirm his discovery until March 25th.

Orbit

At the time of discovery, the comet was located within the constellation of Virgo. It was also three days before its closest approach with Earth and almost five months before perihelion. Due to its very slow motion across the sky, the comet's orbit was initially difficult to determine.

Howard B. Kaster and Katherine Prescott determined a perihelion date of 17 September 1925 and a perihelion distance of 4.14 AU (619 million km).