2100 Ra-Shalom

2100 Ra-Shalom (prov. designation: 1978 RA) is an asteroid and near-Earth object of the Aten group on an eccentric orbit in the inner Solar System. It was discovered on 10 September 1978, by American astronomer Eleanor Helin at the Palomar Observatory, California, who named it in commemoration of the Camp David Peace Accords.[3][4] The C-type asteroid (Xc, K) has a rotation period of 19.8 hours and measures approximately 2.7 kilometers (1.7 miles) in diameter.

2100 Ra-Shalom
Shape model of Ra-Shalom from its lightcurve
Discovery [1]
Discovered byE. F. Helin
Discovery sitePalomar Obs.
Discovery date10 September 1978
Designations
(2100) Ra-Shalom
Pronunciation/ˌrɑː ʃəˈloʊm/[2]
Named after
Ra and Shalom
(composed name)[3]
1978 RA · 1975 TB
NEO · Aten [1][4]
Orbital characteristics [1]
Epoch 7 November 2005 (JD 2453681.5)
Uncertainty parameter 0
Observation arc41.07 yr (14,999 days)
Aphelion1.1952 AU
Perihelion0.4688 AU
0.8320 AU
Eccentricity0.4365
0.76 yr (277 days)
104.56°
Inclination15.756°
170.88°
355.98°
Earth MOID0.1496 AU · 58.3 LD
Physical characteristics
Mean diameter
1.98±0.05 km[5]
2.04 km[6]
2.22 km[7]
2.24 km[8]
2.3±0.2 km[9]
2.48 km[10]
2.78 km[11][12]
2.79 km[13]
19.79±0.03 h[14]
19.793±0.001 h[9]
19.797 h[15][lower-alpha 1]
19.79981 h[16]
19.8201±0.00004 h[17]
19.89±0.05[18]
0.080[13]
0.082[11][12]
0.125[10]
0.13±0.03[9][8]
0.14±0.10[19]
0.16[6]
0.177±0.009[5]
C (Tholen)[1] · Xc (SMASS)[1]
C (CALL)[12] · K[9]
B–V = 0.712[1]
U–B = 0.310[1]
15.66±0.1 (R)[lower-alpha 1] · 15.90[10] · 16.05[1][5] · 16.054±0.07[12][20] · 16.06±0.07[14] · 16.06[6] · 16.07[15] · 16.1[7] · 16.11[11]

    Orbit and classification

    Ra-Shalom orbits the Sun at a distance of 0.5–1.2 AU once every 9 months (277 days). Its orbit has an eccentricity of 0.44 and an inclination of 16° with respect to the ecliptic.[1]

    It was the second Aten asteroid to be discovered after 2062 Aten, the family's namesake, also discovered by Helin in 1976. The group of Aten asteroids feature a semi-major axis of less than 1 AU. Of this group, Ra-Shalom has one of the smallest semi-major axes, just 0.832 AU.

    The asteroid has an Earth minimum orbital intersection distance of 0.1496 AU (22,400,000 km) which corresponds to 58.3 lunar distances, far too large to make it a potentially hazardous object.[1] It also comes within 30  gigameter (Gm) of Mars, Venus and Mercury. The closest approaches are to Mercury, to about 0.0784 AU (11.7 Gm).[21]

    Naming

    The minor planet's composed named was chosen by the discoverer to commemorate the Camp David Peace Accords between Egypt and Israel in September 1978, and as a symbol for the universal hope for peace. Ra is the Egyptian Sun-god, who symbolizes enlightenment and life, while Shalom is the traditional Hebrew greeting meaning peace.[3] The official naming citation was published by the Minor Planet Center on 1 November 1978 (M.P.C. 4548).[22]

    Physical characteristics

    Ra-Shalom has been characterized as a C-type and X-type asteroid on the Tholen and SMASS taxonomic scheme, respectively.[1] It has also been characterized as a K-type asteroid.[9] In 1981, the asteroid was detected using radar, revealing a relatively smooth surface at decimeter scales.[23]

    Rotation period
    Lightcurve based 3D-model of Ra-Shalom

    In August 2016, a rotational lightcurve of Ra-Shalom was obtained from photometric observations by American astronomer Brian Warner. Lightcurve analysis gave a well-defined rotation period of 19.89 hours with a brightness amplitude of 0.55 magnitude (U=3).[18]

    A large number of previous photometric observations gave a period between 19.79 and 19.8201 hours with a brightness amplitude between 0.3 and 0.41 magnitude.[9][14][15][lower-alpha 1][16][17]

    Diameter and albedo

    According to Spitzer Space Telescope's ExploreNEOs survey, the Japanese Akari satellite, and NASA's Keck Observatory, Ra-Shalom measures between 1.98 and 2.79 kilometers in diameter and its surface has an albedo between 0.080 and 0.177.[5][6][7][8][9][10][11][13] The Collaborative Asteroid Lightcurve Link adopts an albedo of 0.082 and a diameter of 2.78 kilometers with an absolute magnitude of 16.054.[12]

    Notes
    1. Pravec (2003) web: rotation period 19.797 hours with a brightness amplitude of 0.34 in magnitude. Period Identical with Pravec's observation in 1998. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (2100) Ra-Shalom

    References
    1. "JPL Small-Body Database Browser: 2100 Ra-Shalom (1978 RA)" (2016-10-26 last obs.). Jet Propulsion Laboratory. Retrieved 3 July 2017.
    2. "shalom". Dictionary.com Unabridged (Online). n.d.
    3. Schmadel, Lutz D. (2007). "(2100) Ra-Shalom". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 170. doi:10.1007/978-3-540-29925-7_2101. ISBN 978-3-540-00238-3.
    4. "2100 Ra-Shalom (1978 RA)". Minor Planet Center. Retrieved 7 December 2016.
    5. Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
    6. Harris, Alan W. (February 1998). "A Thermal Model for Near-Earth Asteroids". Icarus. 131 (2): 291–301. Bibcode:1998Icar..131..291H. doi:10.1006/icar.1997.5865. Retrieved 11 January 2016.
    7. Trilling, D. E.; Mueller, M.; Hora, J. L.; Harris, A. W.; Bhattacharya, B.; Bottke, W. F.; et al. (September 2010). "ExploreNEOs. I. Description and First Results from the Warm Spitzer Near-Earth Object Survey". The Astronomical Journal. 140 (3): 770–784. Bibcode:2010AJ....140..770T. doi:10.1088/0004-6256/140/3/770. Retrieved 11 January 2016.
    8. Harris, A. W.; Mommert, M.; Hora, J. L.; Mueller, M.; Trilling, D. E.; Bhattacharya, B.; et al. (March 2011). "ExploreNEOs. II. The Accuracy of the Warm Spitzer Near-Earth Object Survey". The Astronomical Journal. 141 (3): 10. Bibcode:2011AJ....141...75H. doi:10.1088/0004-6256/141/3/75. Retrieved 11 January 2016.
    9. Shepard, Michael K.; Clark, Beth Ellen; Nolan, Michael C.; Benner, Lance A. M.; Ostro, Steven J.; Giorgini, Jon D.; et al. (January 2008). "Multi-wavelength observations of Asteroid 2100 Ra-Shalom". Icarus. 193 (1): 20–38. Bibcode:2008Icar..193...20S. CiteSeerX 10.1.1.462.876. doi:10.1016/j.icarus.2007.09.006. Retrieved 11 January 2016.
    10. Harris, Alan W.; Davies, John K.; Green, Simon F. (October 1998). "Thermal Infrared Spectrophotometry of the Near-Earth Asteroids 2100 Ra-Shalom and 1991 EE". Icarus. 135 (2): 441–450. Bibcode:1998Icar..135..441H. doi:10.1006/icar.1998.6002. Retrieved 11 January 2016.
    11. Delbó, Marco; Harris, Alan W.; Binzel, Richard P.; Pravec, Petr; Davies, John K. (November 2003). "Keck observations of near-Earth asteroids in the thermal infrared". Icarus. 166 (1): 116–130. Bibcode:2003Icar..166..116D. doi:10.1016/j.icarus.2003.07.002. Retrieved 11 January 2016.
    12. "LCDB Data for (2100) Ra-Shalom". Asteroid Lightcurve Database (LCDB). Retrieved 7 December 2016.
    13. Delbo, Marco; Walsh, Kevin; Mueller, Michael; Harris, Alan W.; Howell, Ellen S. (March 2011). "The cool surfaces of binary near-Earth asteroids". Icarus. 212 (1): 138–148. Bibcode:2011Icar..212..138D. doi:10.1016/j.icarus.2010.12.011. Retrieved 11 January 2016.
    14. Harris, A. W.; Young, J. W.; Dockweiler, Thor; Gibson, J.; Poutanen, M.; Bowell, E. (January 1992). "Asteroid lightcurve observations from 1981". Icarus. 95 (1): 115–147.ResearchsupportedbyLowellObservatoryEndowmentandNASA. Bibcode:1992Icar...95..115H. doi:10.1016/0019-1035(92)90195-D. ISSN 0019-1035. Retrieved 11 January 2016.
    15. Pravec, Petr; Wolf, Marek; Sarounová, Lenka (November 1998). "Lightcurves of 26 Near-Earth Asteroids". Icarus. 136 (1): 124–153. Bibcode:1998Icar..136..124P. doi:10.1006/icar.1998.5993. Retrieved 11 January 2016.
    16. Kaasalainen, Mikko; Pravec, Petr; Krugly, Yurij N.; Sarounová, Lenka; Torppa, Johanna; Virtanen, Jenni; et al. (January 2004). "Photometry and models of eight near-Earth asteroids". Icarus. 167 (1): 178–196. Bibcode:2004Icar..167..178K. doi:10.1016/j.icarus.2003.09.012. Retrieved 11 January 2016.
    17. Durech, J.; Vokrouhlický, D.; Baransky, A. R.; Breiter, S.; Burkhonov, O. A.; Cooney, W.; et al. (November 2012). "Analysis of the rotation period of asteroids (1865) Cerberus, (2100) Ra-Shalom, and (3103) Eger - search for the YORP effect". Astronomy and Astrophysics. 547: 9. arXiv:1210.2219. Bibcode:2012A&A...547A..10D. doi:10.1051/0004-6361/201219396. Retrieved 11 January 2016.
    18. Warner, Brian D. (January 2017). "Near-Earth Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2016 July-September". The Minor Planet Bulletin. 44 (1): 22–36. Bibcode:2017MPBu...44...22W. ISSN 1052-8091. Retrieved 11 June 2017.
    19. Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; et al. (September 2011). "ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population". The Astronomical Journal. 142 (3): 12. Bibcode:2011AJ....142...85T. doi:10.1088/0004-6256/142/3/85. Retrieved 11 January 2016.
    20. 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 7 December 2016.
    21. "JPL Close-Approach Data: 2100 Ra-Shalom (1978 RA)" (2013-10-25 last obs). Retrieved 5 May 2009.
    22. Schmadel, Lutz D. "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7.
    23. Ostro, S. J.; Harris, A. W.; Campbell, D. B.; Shapiro, I. I.; Young, J. W. (November 1984). "Radar and photoelectric observations of asteroid 2100 Ra-Shalom". Icarus. 60 (2): 391–403. Bibcode:1984Icar...60..391O. doi:10.1016/0019-1035(84)90198-2. ISSN 0019-1035. Retrieved 11 January 2016.
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