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 it was faintly visible with the naked eye. Later observations from Yerkes Observatory and the University of California Leuschner Observatory followed. George van Biesbroeck observed it on 14 August 1931, noting 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 the comet became unobservable as it passed between the Sun and Earth. It passed within 0.075 AU of the Sun on 25 August. 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 Comet was recovered in early October, and its brightness was estimated at ninth magnitude by 9 October 1931, no longer visible to the naked eye. Astronomers at Yerkes Observatory waited until just before 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 then 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 is significant primarily for its extremely close approach to the Sun—0.075 AU—which placed it among the sungrazing comets of its era. Its discovery by an amateur astronomer using a small telescope underscores the role of non-professional observers in early 20th-century astronomy. The comet's brightness, estimated to have rivaled Venus at perihelion, was unfortunately unobservable due to its proximity to the Sun. The recovery of the comet in October, when it had faded to ninth magnitude, allowed continued study, including observations by Yerkes Observatory and director Edwin B. Frost. The comet's hyperbolic orbit, influenced by a close approach to Jupiter of 0.15 AU, is a key orbital detail. The comet's tail, observed pointing toward the Sun in October, is an unusual feature noted in the photographic record. The comet's legacy lies in its well-documented observational history across multiple observatories and its demonstration of how a bright sungrazing comet can become temporarily invisible at peak brightness.

Did You Know?

• It passed within 0.075 AU (11.2 million km) of the Sun on 25 August 1931.
• At its brightest, it was estimated to be as bright as Venus, but was too close to the Sun to be observed.
• Its orbit approached Jupiter to within 0.15 AU, resulting in a hyperbolic orbit before perihelion.