69230 Hermes

69230 Hermes is a sub-kilometer sized asteroid and binary system on an eccentric orbit,[10] 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.[3] It is famous for having been the last remaining named lost asteroid, rediscovered in 2003. The S-type asteroid has a rotation period of 13.9 hours.[7] Its synchronous companion was discovered in 2003. The primary and secondary are similar in size; they measure approximately 810 meters (2,700 ft) and 540 meters (1,800 ft) in diameter, respectively.[5]

69230 Hermes
Recovery of Hermes on 15 October 2003
Discovery [1]
Discovered byK. Reinmuth
Discovery siteHeidelberg Obs.
Discovery date28 October 1937
Designations
(69230) Hermes
Pronunciation/ˈhɜːrmiːz/[2]
Named after
Hermes (Greek mythology)[3]
1937 UB
NEO · PHA · Apollo [1][4]
Mars- and Venus-crosser
AdjectivesHermian, Hermean /ˈhɜːrmiən, hərˈmiːən/
Orbital characteristics [4]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 0
Observation arc80.94 yr (29,565 d)
Aphelion2.6878 AU
Perihelion0.6226 AU
1.6552 AU
Eccentricity0.6239
2.13 yr (778 d)
73.583°
0° 27m 46.08s / day
Inclination6.0670°
34.217°
92.746°
Known satellites1[5]
(P:13.892±0.006 h)[6][7]
(D: 0.54 km,[8] 0.56 km[9])
Earth MOID0.0043 AU (1.6752 LD)
Physical characteristics
Mean diameter
0.8±0.1 km[6]
0.81 km (derived)[5]
0.85 km[7][10]
Mean density
1.6 g/cm3 (assumed)[5]
13.894 h[11][12][lower-alpha 1]
0.25±0.12[5][11]
0.265±0.099[6]
S [13][lower-alpha 2] · Sq [7][14]
17.48[6]
17.5[1][4]
17.55[15]
17.57[7][11][16]

    Discovery

    Hermes was discovered by German astronomer Karl Reinmuth in images taken at Heidelberg Observatory on 28 October 1937.[1] Only four days of observations could be made before it became too faint to be seen in the telescopes of the day.[17] This was not enough to calculate an orbit, and Hermes became a lost asteroid.[17] 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 others long lost were (1862) Apollo, discovered in 1932 and numbered 1973, and (2101) Adonis, discovered in 1936 and numbered 1977.[18]

    On 15 October 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. Additional precovery observations were published by the Minor Planet Center, the earliest being found by an amateur astronomer on images taken serendipitously by the MPG/ESO 2.2-m La Silla telescope on 16 September 2000.

    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.[3] The official naming citation was published by the Minor Planet Center on 9 November 2003 (M.P.C. 50255).[19]

    Orbit and classification

    Hermes is an Apollo asteroid, a subgroup of near-Earth asteroids that cross the orbit of Earth. It orbits the Sun at a distance of 0.6–2.7 AU once every 2 years and 2 months (778 days; semi-major axis of 1.66 AU). Its orbit has an eccentricity of 0.62 and an inclination of 6° with respect to the ecliptic.[4] 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.[20]

    Close approaches
    Animation of 69230 Hermes's orbit - close approach in 1942
       Sun ·    Earth ·   69230 Hermes

    The asteroid has an Earth minimum orbital intersection distance of 0.0041 AU (610,000 km) which translates into 1.6 LD.[4] On 30 October 1937, Hermes passed 0.00494 AU (739,000 km) from Earth, and on 26 April 1942, 0.0042415 AU (634,520 km) from Earth.[21] In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7 lunar distances; the second pass was unobserved at the height of the Second World War.[21] 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.

    History of close approaches of large near-Earth objects since 1908 (A)
    PHA Date Approach distance (lunar dist.) Abs.
    mag
    (H)    		 Diameter (C)
    (m)    		 Ref (D)
    Nomi-
    nal(B)    		 Mini-
    mum    		 Maxi-
    mum
    (33342) 1998 WT241908-12-163.5423.5373.54717.9556–1795data
    (458732) 2011 MD51918-09-170.9110.9090.91317.9556–1795data
    (7482) 1994 PC11933-01-172.9272.9272.92816.8749–1357data
    69230 Hermes1937-10-301.9261.9261.92717.5668–2158data
    69230 Hermes1942-04-261.6511.6511.65117.5668–2158data
    (137108) 1999 AN101946-08-072.4322.4292.43517.9556–1795data
    (33342) 1998 WT241956-12-163.5233.5233.52317.9556–1795data
    (163243) 2002 FB31961-04-124.9034.9004.90616.41669–1695data
    (192642) 1999 RD321969-08-273.6273.6253.63016.31161–3750data
    (143651) 2003 QO1041981-05-182.7612.7602.76116.01333–4306data
    2017 CH11992-06-054.6913.3916.03717.9556–1795data
    (170086) 2002 XR141995-06-244.2594.2594.26018.0531–1714data
    (33342) 1998 WT242001-12-164.8594.8594.85917.9556–1795data
    4179 Toutatis2004-09-294.0314.0314.03115.302440–2450data
    2014 JO252017-04-194.5734.5734.57317.8582–1879data
    (137108) 1999 AN102027-08-071.0141.0101.01917.9556–1795data
    (35396) 1997 XF112028-10-262.4172.4172.41816.9881–2845data
    (154276) 2002 SY502071-10-303.4153.4123.41817.6714–1406data
    (164121) 2003 YT12073-04-294.4094.4094.40916.21167–2267data
    (385343) 2002 LV2076-08-044.1844.1834.18516.61011–3266data
    (52768) 1998 OR22079-04-164.6114.6114.61215.81462–4721data
    (33342) 1998 WT242099-12-184.9194.9194.91917.9556–1795data
    (85182) 1991 AQ2130-01-274.1404.1394.14117.11100data
    314082 Dryope2186-07-163.7092.9964.78617.5668–2158data
    (137126) 1999 CF92192-08-214.9704.9674.97318.0531–1714data
    (290772) 2005 VC2198-05-051.9511.7912.13417.6638–2061data
    (A) List includes near-Earth approaches of less than 5 lunar distances (LD) of objects with H brighter than 18.
    (B) Nominal geocentric distance from the Earth's center to the object's center (earth radius≈6400 km).
    (C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.
    (D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)
    (E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches

    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).[15][11][12] [lower-alpha 1]

    Satellite
    Arecibo radar image from 19 October 2003, showing the relative motion of the components.[9]

    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,[9] and their orbital separation is only 1,200 metres,[10] much smaller than the Hill radius of 35 km.[8]

    The two components are in double synchronous rotation (similar to the Trans-Neptunian system Pluto and Charon).[9] Hermes is one of only four systems of that kind known in the near-Earth object population. The other three are 1994 CJ1, (190166) 2005 UP156, and 2017 YE5.[22]

    In the 1978 novel The Hermes Fall by John Baxter, the asteroid endangers the Earth in 1980.[23]

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

    References
    1. "69230 Hermes (1937 UB)". Minor Planet Center. Retrieved 12 March 2017.
    2. "Hermes". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
    3. Schmadel, Lutz D. (2006). "(69230) Hermes [1.65, 0.62, 6.1]". Dictionary of Minor Planet Names – (69230) Hermes, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 226. doi:10.1007/978-3-540-34361-5_2696. ISBN 978-3-540-34361-5.
    4. "JPL Small-Body Database Browser: 69230 Hermes (1937 UB)" (2018-10-05 last obs.). Jet Propulsion Laboratory. Retrieved 30 October 2018.
    5. Johnston, Robert (20 September 2014). "(69230) Hermes". johnstonsarchive.net. Retrieved 28 June 2017.
    6. 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.
    7. "LCDB Data for (69230) Hermes". Asteroid Lightcurve Database (LCDB). Retrieved 28 June 2017.
    8. "(69230) Hermes". Asteroids with Satellites Database – Johnston's Archive. Retrieved 13 September 2017.
    9. "Radar observations of long-lost asteroid 1937 UB (Hermes)". Cornell University, Arecibo Observatory. Retrieved 13 September 2017.
    10. 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 (8227): 2. Bibcode:2003IAUC.8227....2M. Retrieved 28 June 2017.
    11. 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. Behrend, Raoul. "Asteroids and comets rotation curves – (69230) Hermes". Geneva Observatory. Retrieved 28 June 2017.
    13. 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. 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, P.; Kusnirak, P.; Warner, B.; Behrend, R.; Harris, A. W.; Oksanen, A.; et al. (October 2003). "1937 UB (Hermes)". IAU Circ. 8233 (8233): 3. Bibcode:2003IAUC.8233....3P. Retrieved 28 June 2017.
    16. 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.
    17. 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.
    18. D. Schmadel, Dictionary of Minor Planet Names
    19. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 28 June 2017.
    20. https://science.nasa.gov/science-news/science-at-nasa/2003/31oct_hermes "The Curious Tale of Asteroid Hermes." Retrieved 27/12/2017.
    21. "JPL Close-Approach Data: 69230 Hermes (1937 UB)" (2011-08-20 last obs (arc=73.82 years)). Retrieved 12 November 2011.
    22. "Goldstone Radar Observations Planning: 2001 QP153 and 2005 UP156". Goldstone observatory. Retrieved 13 September 2017.
    23. Baxter, John (1978). The Hermes Fall. Granada (Panther). ISBN 978-0-586-04610-4.

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