69230 Hermes

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69230 Hermes
Hermes planetoid.jpg
Recovery of Hermes on Oct. 15, 2003.
Discovery [1]
Discovered by Karl Reinmuth
Discovery site Heidelberg Obs.
Discovery date 28 October 1937
MPC designation 69230 Hermes
Named after
1937 UB
Apollo, NEO, PHA
Orbital characteristics[1]
Epoch 27 June 2015 (JD 2457200.5)
Uncertainty parameter 0
Observation arc 77.74 yr (28,396 days)
Aphelion 2.6877 AU
Perihelion 0.6222 AU
1.6550 AU
Eccentricity 0.6240
2.13 yr (777.68 days)
20.70 km/s
Inclination 6.0675°
Earth MOID 0.0043 AU
Physical characteristics
Dimensions 300–450 m[2]
Mass 6.7×1010 kg
13.894 h
13.892±0.006 h[3]
Temperature ~ 216 K[citation needed]

69230 Hermes is an Apollo, Mars- and Venus-crosser binary asteroid[2] that passed Earth at about twice the distance of the Moon on October 30, 1937. It is named after the Greek god Hermes.

At the time, this was the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach (by 4581 Asclepius) observed. At closest approach, Hermes was moving 5° per hour across the sky and reached 8th magnitude.

It was discovered by Karl Reinmuth in images taken at Heidelberg Observatory on October 28, 1937. Only four days of observations could be made before Hermes became too faint to be seen in the telescopes of the day.[4] This was not enough to calculate an orbit, and Hermes was "lost" (see Lost asteroids).[4] It thus did not receive a number, but Reinmuth nevertheless named it after the Greek god Hermes. It was the only unnumbered but named asteroid, having only the provisional designation 1937 UB.

On October 15, 2003, Brian A. Skiff of the LONEOS project 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 orbit is now well known, and Hermes has been assigned sequential number 69230. In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7 Moon distances, without being observed.[5] On October 30, 1937, it passed 0.00494 AU (739,000 km; 459,000 mi) from the Earth and on April 26, 1942, it passed 0.0042415 AU (634,520 km; 394,270 mi) from Earth.[5]

Hermes is an S-type asteroid, a classification first reported by Andy Rivkin and Richard Binzel.[a]

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 radii of 300–450 m (980–1,480 ft),[2] and their orbital separation is only 1,200 metres.

In popular culture[edit]

  • In the 1978 novel The Hermes Fall by John Baxter, the asteroid endangers the Earth in 1980.[6]


  1. ^ a b "JPL Small-Body Database Browser: 69230 Hermes (1937 UB)" (2015-07-24 last obs.). Jet Propulsion Laboratory. Retrieved October 2015. 
  2. ^ a b c "IAUC 8227: C/2003 U1; 1937 UB (HERMES)". IAUC. Retrieved 13 October 2011. 
  3. ^ a b "(69230) Hermes". johnstonsarchive. 20 September 2014. Retrieved August 2015. 
  4. ^ a b Brian G. Marsden (1998-03-29). "How the Asteroid Story Hit: An Astronomer Reveals How a Discovery Spun Out of Control". Minor Planet Center and Boston Globe newspaper. Retrieved 2011-11-14. 
  5. ^ a b "JPL Close-Approach Data: 69230 Hermes (1937 UB)" (2011-08-20 last obs (arc=73.82 years)). Retrieved 2011-11-12. 
  6. ^ Baxter, John (1978). The Hermes Fall. Granada (Panther). ISBN 0-586-04610-0. 


  1. ^ a b Infrared spectroscopic observations of 69230 Hermes (1937 UB): possible unweathered endmember among ordinary chondrite analogs

External links[edit]