69230 Hermes

69230 Hermes
Recovery of Hermes on 15 October 2003
Discovery [1]
Discovered by Karl Reinmuth
Discovery site Heidelberg Obs.
Discovery date 28 October 1937
Designations
MPC designation (69230) Hermes
Named after
 Hermes (Greek mythology)[2]
1937 UB
NEO · PHA · Apollo [1][3]
Mars- and Venus-crosser
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 77.74 yr (28,396 days)
Aphelion 2.6873 AU
Perihelion 0.6224 AU
1.6549 AU
Eccentricity 0.6239
2.13 yr (778 days)
20.70 km/s
155.83°
0° 27m 46.8s / day
Inclination 6.0678°
34.221°
92.747°
Known satellites 1 (R:13.892±0.006 h)[4][5][6]
(D: 0.54 km,[7] 0.56 km[8])
Earth MOID 0.0041 AU · 1.6 LD
Physical characteristics
Dimensions 0.6±0.12 km
0.63 km[8]
0.6–0.9 km[9]
0.85 km (effective system)[6][9]
0.8±0.1 km[5]
Mean density
 1.6 g/cm3[4]
13.892 h[10]
13.894±0.004 h[11][lower-alpha 1]
13.894±0.007 h[12]
13.894±0.004[7]
0.23 (derived)[6]
0.25±0.12[4][11]
0.265±0.099[5]
S [13][lower-alpha 2] · Sq [6][14]
17.48±0.1[5] · 17.5[1] · 17.55[10] · 17.57[6][11] · 17.57±0.12[15]

    69230 Hermes, provisional designation 1937 UB, is a sub-kilometer sized asteroid and binary system on an eccentric orbit,[9] classified as a potentially hazardous asteroid and near-Earth object of the Apollo group, that passed Earth at approximately twice the distance of the Moon on 30 October 1937. The asteroid was named after Hermes from Greek mythology.[2] It is famous for being the last remaining lost asteroid, rediscovered in 2003.

    Discovery

    Hermes was discovered by German astronomer Karl Reinmuth in images taken at Heidelberg Observatory on 28 October 1937.[3] Only four days of observations could be made before it became too faint to be seen in the telescopes of the day.[16] This was not enough to calculate an orbit, and Hermes became a lost asteroid.[16] It thus did not receive a number, but Reinmuth nevertheless named it after the Greek god Hermes. It was the third unnumbered but named asteroid, having only the provisional designation 1937 UB. The two other long lost were (1862) Apollo, discovered 1932 and numbered 1973, and (2101) Adonis, discovered 1936 and numbered 1977.[17]

    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. It has been assigned sequential number 69230.

    Orbit and classification

    Hermes orbits the Sun at a distance of 0.6–2.7 AU once every 2 years and 2 months (778 days). Its orbit has an eccentricity of 0.62 and an inclination of 6° with respect to the ecliptic.[1] Due to its eccentricity, Hermes is also a Mars- and Venus-crosser. Frequent close approaches to both Earth and Venus make it unusually challenging to forecast its orbit more than a century in advance, though there is no known impact risk within that timeframe.[18]

    Close approaches

    The asteroid has an Earth minimum orbital intersection distance of 0.0041 AU (610,000 km) which translates into 1.6 LD.[1]

    On 30 October 1937, Hermes passed 0.00494 AU (739,000 km) from the Earth and on 26 April 1942, it passed 0.0042415 AU (634,520 km) from Earth.[19] In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7 lunar distances, without being observed.[19]

    For decades, Hermes was known to have made 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.

    Physical characteristics

    Spectral type

    Hermes is a stony S-type asteroid, as reported by Andy Rivkin and Richard Binzel.[13][lower-alpha 2] It has been characterized as a Sq-subtype using the SpeX instrument at NASA Infrared Telescope Facility. Sq-types transition to the Q-type asteroid.[14]

    Lightcurves

    Three rotational lightcurves of Hermes were obtained from photometric observations in October 2003. Lightcurve analysis gave a well-defined rotation period between 13.892 and 13.894 hours with a brightness variation between and 0.06 and 0.08 magnitude, which indicates that the body has a nearly spherical shape (U=3/3/3).[10][11][12] [lower-alpha 1]

    Satellite

    Arecibo radar image from 19 October 2003, showing the relative motion of the components.[8]

    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 315 m (1,033 ft) and 280 m (920 ft), respectively,[8] and their orbital separation is only 1,200 metres,[9] much smaller than the Hill radius of 35 km.[7]

    The two components are in double synchronous rotation (similar to the Trans-Neptunian system Pluto and Charon).[8] Hermes is one of only three systems of that kind known in the near-Earth object population. The other two are 1994 CJ1 and (190166) 2005 UP156.[20]

    Naming

    This minor planet was named after the Greek god Hermes, who is the messenger of the gods and son of Zeus and Maia (also see 5731 and 66). Recovered and numbered in autumn 2003, Hermes was originally named by the Astronomical Calculation Institute as early as 1937.[2] The official naming citation was published by the Minor Planet Center on 9 November 2003 (M.P.C. 50255).[21]

    In the 1978 novel The Hermes Fall by John Baxter, the asteroid endangers the Earth in 1980.[22]

    Notes

    1. 1 2 Lightcurve plot of (69230) Hermes, Palmer Divide Observatory, Brian D. Warner (2003). Summary figures at LCDB
    2. 1 2 Infrared spectroscopic observations of 69230 Hermes (1937 UB): possible unweathered endmember among ordinary chondrite analogs

    References

    1. 1 2 3 4 5 6 "JPL Small-Body Database Browser: 69230 Hermes (1937 UB)" (2015-07-24 last obs.). Jet Propulsion Laboratory. Retrieved 28 June 2017.
    2. 1 2 3 Schmadel, Lutz D. (2006). Dictionary of Minor Planet Names – (69230) Hermes, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 226. ISBN 978-3-540-34361-5. Retrieved 12 March 2017.
    3. 1 2 "69230 Hermes (1937 UB)". Minor Planet Center. Retrieved 12 March 2017.
    4. 1 2 3 Johnston, Robert (20 September 2014). "(69230) Hermes". johnstonsarchive.net. Retrieved 28 June 2017.
    5. 1 2 3 4 Marchis, F.; Enriquez, J. E.; Emery, J. P.; Mueller, M.; Baek, M.; Pollock, J.; et al. (November 2012). "Multiple asteroid systems: Dimensions and thermal properties from Spitzer Space Telescope and ground-based observations". Icarus. 221 (2): 1130–1161. arXiv:1604.05384. Bibcode:2012Icar..221.1130M. doi:10.1016/j.icarus.2012.09.013. Retrieved 28 June 2017.
    6. 1 2 3 4 5 "LCDB Data for (69230) Hermes". Asteroid Lightcurve Database (LCDB). Retrieved 28 June 2017.
    7. 1 2 3 "(69230) Hermes". Asteroids with Satellites Database – Johnston's Archive. Retrieved 13 September 2017.
    8. 1 2 3 4 5 "Radar observations of long-lost asteroid 1937 UB (Hermes)". Cornell University, Arecibo Observatory. Retrieved 13 September 2017.
    9. 1 2 3 4 Margot, J. L.; Nolan, M. C.; Negron, V.; Hine, A. A.; Campbell, D. B.; Howell, E. S.; et al. (October 2003). "1937 UB (Hermes)". IAU Circ. (8227). Bibcode:2003IAUC.8227....2M. Retrieved 28 June 2017.
    10. 1 2 3 Pravec, P.; Kusnirak, P.; Warner, B.; Behrend, R.; Harris, A. W.; Oksanen, A.; et al. (October 2003). "1937 UB (Hermes)". IAU Circ. (8233). Bibcode:2003IAUC.8233....3P. Retrieved 28 June 2017.
    11. 1 2 3 4 Pravec, P.; Scheirich, P.; Kusnirák, P.; Sarounová, L.; Mottola, S.; Hahn, G.; et al. (March 2006). "Photometric survey of binary near-Earth asteroids". Icarus. 181 (1): 63–93. Bibcode:2006Icar..181...63P. doi:10.1016/j.icarus.2005.10.014. Retrieved 28 June 2017.
    12. 1 2 Behrend, Raoul. "Asteroids and comets rotation curves – (69230) Hermes". Geneva Observatory. Retrieved 28 June 2017.
    13. 1 2 Rivkin, A. S.; Binzel, R. P.; Sunshine, J.; Bus, S. J.; Burbine, T. H.; Saxena, A. (December 2004). "Infrared spectroscopic observations of 69230 Hermes (1937 UB): possible unweathered endmember among ordinary chondrite analogs". Icarus. 172 (2): 408–414. Bibcode:2004Icar..172..408R. doi:10.1016/j.icarus.2004.07.006. Retrieved 28 June 2017.
    14. 1 2 Thomas, Cristina A.; Emery, Joshua P.; Trilling, David E.; Delbó, Marco; Hora, Joseph L.; Mueller, Michael (January 2014). "Physical characterization of Warm Spitzer-observed near-Earth objects". Icarus. 228: 217–246. arXiv:1310.2000. Bibcode:2014Icar..228..217T. doi:10.1016/j.icarus.2013.10.004. Retrieved 28 June 2017.
    15. ↑ Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026. Retrieved 28 June 2017.
    16. 1 2 Brian G. Marsden (29 March 1998). "How the Asteroid Story Hit: An Astronomer Reveals How a Discovery Spun Out of Control". Minor Planet Center and Boston Globe newspaper. Retrieved 30 November 2017.
    17. ↑ D. Schmadel, Dictionary of Minor Planet Names
    18. ↑ https://science.nasa.gov/science-news/science-at-nasa/2003/31oct_hermes "The Curious Tale of Asteroid Hermes." Retrieved 27/12/2017.
    19. 1 2 "JPL Close-Approach Data: 69230 Hermes (1937 UB)" (2011-08-20 last obs (arc=73.82 years)). Retrieved 2011-11-12.
    20. ↑ "Goldstone Radar Observations Planning: 2001 QP153 and 2005 UP156". Goldstone observatory. Retrieved 13 September 2017.
    21. ↑ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 28 June 2017.
    22. ↑ Baxter, John (1978). The Hermes Fall. Granada (Panther). ISBN 0-586-04610-0.
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