Comet Ryves

Lore & Background

The comet was discovered by amateur astronomer Percy Mayow Ryves on 10 August 1931 using a small telescope in Zaragoza, Spain. He noted that the comet was faintly visible with the naked eye. George van Biesbroeck observed it on 14 August 1931, reporting a tail one degree long and an apparent magnitude of 4. It appeared as a ball of hot gas traveling at one hundred miles per second from the Naval Observatory. Soon after, the comet became unobservable as it passed between the Sun and Earth. It passed within 0.075 AU of the Sun on 25 August, and it is estimated that it became as bright as Venus, but it was too close to the Sun and the horizon to be observed. It then moved towards the far side of the Sun.

Ryves's Comet was recovered in early October, and its brightness was estimated to be of ninth magnitude by 9 October 1931, no longer observable with the naked eye. Astronomers at the Yerkes Observatory waited until just prior to dawn to observe and photograph it. Yerkes Observatory director Edwin B. Frost determined that the comet was two hours east of the Sun and seven degrees removed from it. In October it was one hundred times fainter than when first observed in August. Its coma had an estimated diameter of 3–4 arcminutes, and its tail was estimated photographically to be three quarters of a degree long and facing towards the Sun. Its orbit indicates that it approached Jupiter down to 0.15 AU, resulting in a hyperbolic orbit before perihelion.

Reader's Guide

Comet Ryves holds significance as a bright comet discovered by an amateur astronomer using modest equipment, demonstrating the continued role of amateurs in astronomical discovery. Its close perihelion of 0.075 AU brought it extremely near the Sun, and it is estimated to have reached the brightness of Venus, though it was unobservable at that peak due to its proximity to the Sun and horizon. The comet's recovery in October at ninth magnitude, one hundred times fainter than in August, illustrates the rapid fading typical of sungrazing comets. Observations from Yerkes Observatory and the University of California Leuschner Observatory, along with George van Biesbroeck's early measurements, provided data on its tail length and magnitude. The comet's orbit, which brought it within 0.15 AU of Jupiter, resulted in a hyperbolic trajectory before perihelion, highlighting gravitational perturbations. Its legacy lies in the detailed record of its brief visibility and the challenges of observing a comet so close to the Sun.

Did You Know?

• It passed within 0.075 AU of the Sun on 25 August 1931, and is estimated to have become as bright as Venus, though it was too close to the Sun to be observed.
• George van Biesbroeck observed the comet on 14 August 1931 and noted a tail one degree long and an apparent magnitude of 4.