367943 Duende
Goldstone radar collage of Duende on 15–16 February 2013
Discovery [1][2]
Discovered byOAM
Discovery siteLa Sagra Obs.
Discovery date23 February 2012
Designations
(367943) Duende
Named after
Duende
(Iberian/Filipino mythology)[1]
2012 DA14
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc364 days
Aphelion0.9916 AU
Perihelion0.8289 AU
0.9103 AU
Eccentricity0.0894
0.87 yr (317 days)
113.74°
1° 8m 5.64s / day
Inclination11.609°
146.96°
195.60°
Earth MOID9.52648×10−5 AU (0.037 LD)
Physical characteristics
Dimensions20 m × 40 m (elongated)[5][6]
Mean diameter
  • 0.20 (assumed)[9]
  • 0.44±0.20[7]
7.2 (2013 peak)[14]

    367943 Duende (provisional designation 2012 DA14) is a micro-asteroid and a near-Earth object of the Aten and Atira group, approximately 30 meters (98 ft) in diameter. It was discovered by astronomers of the Astronomical Observatory of Mallorca at its robotic La Sagra Observatory in 2012, and named for the duende, a goblin-like creature from Iberian and Filipino mythology and folklore.[1] Duende is likely an uncommon L-type asteroid and significantly elongated. For an asteroid of its size, it has a relatively long rotation period of 9.485 hours.[9]

    On 15 February 2013, Duende passed at a record distance of 27,700 km (17,200 mi) or 4.3 Earth radii from Earth's surface.[4] Due to its close passage, its orbit was perturbed significantly enough that it changed from an Apollo asteroid to an Aten asteroid. Duende's passage also coincided with the completely unrelated Chelyabinsk meteor, which entered Earth's atmosphere above Russia just 16 hours earlier.[15][16][17]

    Discovery and past risk assessments

    Duende was discovered on 23 February 2012, seven days after passing 0.0174 AU (2,600,000 km; 1,620,000 mi) from Earth,[18] by the La Sagra Observatory in Granada Province, Spain,[2] using a 0.45-m reflector which was remotely operated by amateur astronomers at the Astronomical Observatory of Mallorca.[19]

    The still relatively imprecise orbit deduced from the short arc of the 2012 observations already made clear that Duende would pass no closer to Earth's surface than 3.2 Earth radii during its 2013 passage.[20] There was at the time, however, a cumulative risk of 0.033% (1 in 3,030) that Duende would impact Earth during one of its 2026 to 2069 approaches.[8]

    2013 passage

    Diagram of Duende passing Earth on 15 February 2013
    Animation of Duende's orbit around Sun
      Duende ·   Sun ·   Earth

    On 9 January 2013, Duende was observed again by Las Campanas Observatory and the observation arc immediately increased from 79 days to 321 days.[1] On 15 February 2013 at 19:25 UT, Duende passed 0.0002276 AU (34,050 km; 21,160 mi) from the center of Earth, with an uncertainty region of about 0.0000001 AU (15 km; 9.3 mi).[18]

    It passed 27,743 kilometers (17,239 mi) above Earth's surface, closer than satellites in geosynchronous orbit. It briefly peaked at an apparent magnitude of roughly 7.2, a factor of a few fainter than would have been visible to the naked eye. The best observation location for the closest approach was Indonesia. Eastern Europe, Asia, and Australia also were well situated to observe Duende during its closest approach.[4]

    Duende was not expected to pass any closer than 1950 km to any satellites.[21] Goldstone Observatory observed Duende with radar from February 16 to February 20.[5][22] Radar observations showed that it is an elongated asteroid with dimensions of 20 by 40 meters (66 by 131 feet).[23] This gives Duende a geometric mean (spherical) diameter equivalent to 28 meters (92 ft).

    During the close approach, an observational campaign involving 5 different telescopes in 4 different observatories was carried on in order to get information on the physical properties of this NEO.[7]

    Visible and near-Infrared photometry and visible spectroscopy were obtained at Gran Telescopio Canarias, Telescopio Nazionale Galileo and Calar Alto Observatory and put together. The classification using the M4AST online tool says this is an L-type asteroid. Those peculiar asteroids are characterized by a strongly reddish spectrum shortward of 0.8 μm, and a featureless flat spectrum longward of this, with little or no concave-up curvature related to a 1 μm silicon absorption band. Time-series photometry was also obtained in the Observatorio de La Hita (I95)[2] and Observatorio de Sierra Nevada during two consecutive nights (15–16 February 2013). All of this data were co-phased to build a lightcurve of the object. This lightcurve is double-peak and presents large variations in magnitude, implying a very elongated object, which is compatible with radar observations.[5] The amplitude of the lightcurve yields an axial ratio that, together with the long axis of 40 m inferred from the radar images by Goldstone, results in an equivalent diameter of 18 m, much smaller than the estimations before the close-approach.

    The rotational period was precisely determined from the lightcurve obtaining a value of 8.95±0.08 h.[7] This value is confirmed with an analysis of all the photometry of this objects reported to the Minor Planet Center. Using data pre and post close approach the authors find that the object suffered a spin-up during the event that decreased the rotational period from 9.8±0.1 down to 8.8±0.1 hours, which is compatible with the more accurate value estimated from the light-curve.[9]

    Closest approach of asteroid drawn to scale.

    Orbital shift

    The close approach to Earth reduced the orbital period of Duende from 368 days to 317 days, Its aphelion was reduced from 1.110 to 0.9917 AU, leaving it almost entirely inside Earth's orbit and perturbing it from the Apollo class to the Aten class of near-Earth asteroids.[4][24]

    Its next close approach to Earth will be on 15 February 2046, when it will pass about 0.0148 AU (2,210,000 km; 1,380,000 mi) from Earth. Based on 7 radar observations, the next close approach to Earth similar to the 2013 passage will be on 16 February 2123, when Duende will pass no closer than 0.0002 AU (30,000 km; 19,000 mi) from the center of Earth. For the 2123 passage, the nominal pass will be 0.003 AU (450,000 km; 280,000 mi) from the center of the Moon and then 0.005 AU (750,000 km; 460,000 mi) from the center of Earth.[18]

    Parameter Epoch Aphelion
    (Q)    		 Perihelion
    (q)    		 Semi-major axis
    (a)    		 Eccentricity
    (e)    		 Period
    (p)    		 Inclination
    (i)    		 Longitude ascending node
    (Ω)    		 Mean anomaly
    (M)    		 Argument of perihelion
    (ω)
    Units AU (days) (°)
    Pre-flyby 30 Sep 2012 1.110 0.8935 1.001 0.1081 366.2 10.33° 147.2° 299.9° 271.0°
    Post-flyby 18 Apr 2013 0.9917 0.8289 0.9103 0.0894 317.2 11.60° 146.9° 231.0° 195.5°

    Risks

    Risk assessments calculated before the 2013 passage were based on a diameter of 45 meters and a mass of 130,000 tonnes.[8] It was estimated that, if it were ever to impact Earth, it would enter the atmosphere at a speed of 12.7 km/s, would have a kinetic energy equivalent to 2.4 megatons of TNT,[8] and would produce an air burst with the equivalent of 2.1 megatons of TNT[25] at an altitude of roughly 10.1 kilometers (33,000 ft).[25] The Tunguska event has been estimated at 3–20 megatons.[26] Asteroids of approximately 50 meters in diameter are expected to impact Earth once every 1,200 years or so.[27] Asteroids larger than 35 meters across can pose a threat to a town or city,[28] and the Chelyabinsk meteor which serendipitously occurred on the day of the 2013 passage was due to a 17-meter asteroid. As a result of radar observations, it is now known that Duende is only about 30 meters in diameter.[5]

    • The uncertainty region of Duende during planetary encounters is now well determined through 2123.[18]
    • Duende was therefore removed from the Sentry Risk Table on 16 February 2013.[29]
    • It is estimated that there are more than a million near-Earth asteroids smaller than 100 meters.[30]
    Airburst estimates for a stony asteroid with a diameter ranging from 30 to 85 meters[25]
    Diameter Kinetic energy at atmospheric entry Airburst energy Airburst altitude Average frequency
    30 m (98 ft)708 kt530 kt16.1 km (53,000 ft)185 years
    50 m (160 ft)3.3 Mt2.9 Mt8.5 km (28,000 ft)764 years
    70 m (230 ft)9 Mt8.5 Mt3.4 km (11,000 ft)1900 years
    85 m (279 ft)16.1 Mt15.6 Mt0.435 km (1,430 ft)3300 years

    The table above uses Sentry's stony asteroid density of 2600 kg/m3, Sentry's atmospheric entry velocity (Vimpact) of 12.7 km/s,[8] and an angle of 45 degrees.

    For kinetic energy at atmospheric entry, 3.3 Mt is equivalent to DF-4, 9 Mt is equivalent to Ivy Mike and 15.6 Mt is equivalent to Castle Bravo. For air burst energy, 530 kt is equivalent to W88 and 2.9 Mt is equivalent to R-12 Dvina.

    Naming

    This minor planet was named after the duende, fairy- or goblin-like mythological creatures from Iberian, Latin American and Filipino folklore.[1] The approved naming citation was published by the Minor Planet Center 17 November 2013 (M.P.C. 85916).[31]

    See also

    Notes

    1. ↑ rotation period of at least 8 hours (lower limit). Radiometric observations from 16 February 2013. No Quality Code given. Summary figures for (367943) Duende at LCDB
    2. ↑ Lightcurve plot of 2012 DA14 (367943 Duende), Bruce L. Gary, Hereford Arizona Observatory, (2013). Period of 9.1±0.5 hours, and a high brightness amplitude of 1.37±0.03. Quality Code of 3-. Summary figures at LCDB

    References

    1. 1 2 3 4 5 6 "367943 Duende (2012 DA14)". Minor Planet Center. Retrieved 20 February 2018.
    2. 1 2 3 "MPEC 2012-D51 : 2012 DA14". IAU Minor Planet Center. 24 February 2012. Retrieved 20 February 2018.
    3. 1 2 3 "JPL Small-Body Database Browser: 367943 Duende (2012 DA14)" (2013-02-21 last obs.). Jet Propulsion Laboratory. Retrieved 20 February 2018.
    4. 1 2 3 4 Paul Chodas & Don Yeomans (1 February 2013). "Asteroid 2012 DA14 To Pass Very Close to the Earth on February 15, 2013". NASA/JPL Near-Earth Object Program Office. Retrieved 1 February 2013.
    5. 1 2 3 4 5 Dr. Lance A. M. Benner (13 January 2013). "2012 DA14 Goldstone Radar Observations Planning". NASA/JPL Asteroid Radar Research. Retrieved 15 January 2013.
    6. ↑ "L. Johnson 2012 DA14 Update: radar images showing elongated object ~20x40m". Minor Planet Center.
    7. 1 2 3 4 5 6 7 de León, J.; Ortiz, J. L.; Pinilla-Alonso, N.; Cabrera-Lavers, A.; Alvarez-Candal, A.; Morales, N.; et al. (July 2013). "Visible and near-infrared observations of asteroid 2012 DA14 during its closest approach of February 15, 2013". Astronomy and Astrophysics. 555: 5. arXiv:1303.0554. Bibcode:2013A&A...555L...2D. doi:10.1051/0004-6361/201321373. S2CID 55096537.
    8. 1 2 3 4 5 6 "2012 DA14 Impact Risk". NASA Near-Earth Object Program. 25 August 2012. Archived from the original on 25 August 2012. Retrieved 10 January 2013.
    9. 1 2 3 4 5 6 "LCDB Data for (367943) Duende". Asteroid Lightcurve Database (LCDB). Retrieved 20 February 2018.
    10. ↑ Gary, Bruce L. (July 2013). "Asteroid 2012 DA14 Rotation Light Curve". The Minor Planet Bulletin. 40 (3): 122–124. Bibcode:2013MPBu...40..122G. ISSN 1052-8091.
    11. ↑ Elenin, Leonid; Molotov, Igor (October 2013). "Lightcurve Analysis of Extremely Close Near-Earth Asteroid - 2012 DA14". The Minor Planet Bulletin. 40 (4): 187–188. Bibcode:2013MPBu...40..187E. ISSN 1052-8091.
    12. 1 2 Terai, Tsuyoshi; Urakawa, Seitaro; Takahashi, Jun; Yoshida, Fumi; Oshima, Goichi; Aratani, Kenta; et al. (November 2013). "Time-series photometry of Earth flyby asteroid 2012 DA14". Astronomy and Astrophysics. 559: 4. arXiv:1310.0577. Bibcode:2013A&A...559A.106T. doi:10.1051/0004-6361/201322158. S2CID 118658921.
    13. ↑ Urakawa, Seitaro; Fujii, Mitsugu; Hanayama, Hidekazu; Takahashi, Jun; Terai, Tsuyoshi; Ohshima, Osamu (August 2013). "Visible Spectroscopic Observations of a Near-Earth Object, 2012 DA14". Publications of the Astronomical Society of Japan. 65 (4): 3. arXiv:1306.2111. Bibcode:2013PASJ...65L...9U. doi:10.1093/pasj/65.4.L9.
    14. ↑ "2012 DA14 Ephemerides for 15 February 2013". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 10 January 2013.
    15. ↑ Don Yeomans & Paul Chodas (1 March 2013). "Additional Details on the Large Fireball Event over Russia on Feb. 15, 2013". NASA/JPL Near-Earth Object Program Office. Archived from the original on 6 March 2013. Retrieved 2 March 2013.
    16. ↑ "Russia Meteor Not Linked to Asteroid Flyby". NASA. Retrieved 15 February 2013.
    17. ↑ "Russian Asteroid Strike". ESA.int. Retrieved 16 February 2013.
    18. 1 2 3 4 "JPL Close-Approach Data: (2012 DA14)" (2013-02-19 last obs (arc=362 days (Radar=7 obs); Uncertainty=0)). Retrieved 19 February 2013.
    19. ↑ "Earth remains safe for now—but what about next asteroid?". tri-cityherald. Archived from the original on 2 April 2015. Retrieved 2 March 2015.
    20. ↑ Paul Chodas; Jon Giorgini & Don Yeomans (6 March 2012). "Near-Earth Asteroid 2012 DA14 to Miss Earth on February 15, 2013". NASA/JPL Near-Earth Object Program Office. Archived from the original on 24 December 2013. Retrieved 6 March 2012.
    21. ↑ "Closest approaches of 2012 DA14 to known satellites – no encounter is closer than ~2000 km". Jonathan's Space Report No. 674. 10 February 2013. Retrieved 11 February 2013.
    22. ↑ SPACE DAILY
    23. ↑ Phil Plait (19 February 2013). "An Asteroid's Parting Shot". Bad Astronomy blog. Retrieved 19 February 2013.
    24. ↑ Horizons output. "Horizon Online Ephemeris System". Retrieved 10 January 2013. ("Ephemeris Type: Elements" PR value)
    25. 1 2 3 Robert Marcus; H. Jay Melosh & Gareth Collins (2010). "Earth Impact Effects Program". Imperial College London / Purdue University. Retrieved 9 February 2013. (solution using 45 meters, 2600 kg/m3, 12.7 km/s, 45 degrees)
    26. ↑ "Sandia supercomputers offer new explanation of Tunguska disaster". Sandia National Laboratories. 17 December 2007. Archived from the original on 18 January 2008. Retrieved 22 December 2007.
    27. ↑ "Record Setting Asteroid Flyby". NASA Science. 28 January 2013. Retrieved 29 January 2013.
    28. ↑ Will Ferguson (22 January 2013). "Asteroid Hunter Gives an Update on the Threat of Near-Earth Objects". Scientific American. Retrieved 23 January 2013.
    29. ↑ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 16 February 2013.
    30. ↑ "WISE Revises Numbers of Asteroids Near Earth". NASA/JPL. 29 September 2011. Retrieved 6 March 2012.
    31. ↑ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 20 February 2018.
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