(69230) Hermes

 
The recovery image of asteroid Hermes by Brian Skiff using the LONEOS 59-cm Schmidt telescope on October 15, 2003. 
Credit: Brian A. Skiff, Lowell Observatory

Asteroid (69230) Hermes was discovered by German astronomer Karl Reinmuth (1892–1979) at Heidelberg Observatory on October 28, 1937. Only four days of observations could be made before the asteroid became too faint to be seen in the telescopes. This was not enough to calculate an orbit, and Hermes became a lost asteroid. It thus did not receive a number — only the provisional designation 1937 UB — but Reinmuth nevertheless named it after the Greek god Hermes. On October 15, 2003, Brian A. Skiff of the LONEOS project in Lowell Observatory in Flagstaff, Arizona, made an asteroid observation that, when the orbit was calculated backwards in time (by Timothy B. Spahr, Steven Chesley and Paul Chodas), turned out to be a rediscovery of Hermes. The asteroid has been assigned sequential number 69230.

   Hermes has an eccentric orbit (e = 0.624) with a perihelion 0.623 au, an aphelion 2.688 au, and an orbital period of 778 days (2.13 years). It is a potentially hazardous asteroid and near-Earth object of the Apollo group, a subgroup of asteroids that cross the orbit of Earth. Hermes has an Earth minimum orbital intersection distance of 0.0041 au (610,000 km). The asteroid is also a Mars- and Venus-crosser. Hermes passed Earth on October 30, 1937 at a distance of 739,000 km. For decades it was the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach (by 4581 Asclepius) observed. Hermes came even closer to the Earth (but unobserved) on April 26, 1942, at a distance of 634,520 km.

   Hermes is a stony S-type asteroid. Radar observations led by Jean-Luc Margot at Arecibo Observatory and Goldstone in October and November 2003 showed Hermes to be a binary asteroid. The primary and secondary components have nearly identical diameters of approximately 630 ± 120 meters and 540 ± 120 meters, respectively, and their orbital separation is only 1,200 metres. The two components are in double synchronous rotation with a period of 13.89 hours.
 
The orbit of the asteroid (69230) Hermes. Credit: NASA Solar System Dynamics
 
 
Karl Wilhelm Reinmuth, discoverer of 395 minor planets, including Hermes

   Karl Wilhelm Reinmuth (4 April 1892 – 6 May 1979) was a German astronomer and discoverer of 395 minor planets, made between 1914–1957 at the Heidelberg-Königstuhl State Observatory. Among his most notable discoveries are two near-Earth objects: (1862) Apollo and (69230) Hermes, several large Jupiter trojans (including 911 Agamemnon, 1143 Odysseus, 1172 Äneas, 1173 Anchises, 1208 Troilus, 1404 Ajax, 1437 Diomedes and 1749 Telamon), and two periodic comets – 30P/Reinmuth and 44P/Reinmuth.


© 2025, Andrew Mirecki


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