1627 Ivar

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1627 Ivar
1627Ivar (Lightcurve Inversion).png
Light-curve-based 3D-model of Ivar
Discovered byE. Hertzsprung
Discovery siteJohannesburg Obs.
(Leiden Southern Station)
Discovery date25 September 1929
(1627) Ivar
Named after
Ivar Hertzsprung
(discoverer's brother)[2]
1929 SH · 1957 NA
1957 XA
NEO · Amor[1][3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc87.62 yr (32,002 days)
Aphelion2.6015 AU
Perihelion1.1240 AU
1.8628 AU
2.54 yr (929 days)
0° 23m 15.72s / day
Earth MOID0.1117 AU · 43.5 LD
Physical characteristics
Dimensions8.370±0.075 km[4]
9.12 km[5]
9.9±2.8 km[6]
10.2 km[7]
4.795 h[8]
4.795±0.002 h[9]
4.795170 h[10]

4.79517±0.00005 h[11]

4.7954±0.006 h[12]
4.796 h[13]
4.7961±0.0001 h[14]
4.797 h[15]
4.798 h[16][17]
4.80 h[18]
0.151 (taken)[21]
S (Tholen)[1] · S (SMASS)[1]
Srw[22] · S[21][23][24]
B–V = 0.872[1]
U–B = 0.459[1]
12.87±0.1[6] · 12.87[5][21] · 12.90[7] · 12.99±0.25[23] · 13.00[24] · 13.17[8] · 13.2[1][4] · 13.22±0.23[14] · 13.24[15]

1627 Ivar, provisional designation 1929 SH, is an elongated stony asteroid and near-Earth object of the Amor group, approximately 15×6×6 km.[25] It was discovered on 25 September 1929, by Danish astronomer Ejnar Hertzsprung at Leiden Southern Station, annex to the Johannesburg Observatory in South Africa.[3] It was named after Ivar Hertzsprung, brother of the discoverer.[2] 1627 Ivar was the first asteroid to be imaged by radar, in July 1985 by the Arecibo Observatory.[26]

Classification and orbit[edit]

Ivar orbits the Sun at a distance of 1.1–2.6 AU once every 2 years and 6 months (929 days). Its orbit has an eccentricity of 0.40 and an inclination of 8° with respect to the ecliptic.[1] Ivar's observation arc begins with its official discovery observation in 1929, as no precoveries were taken, and no prior identifications were made.[3]

It has an Earth minimum orbit intersection distance of 0.1117 AU (16,700,000 km) which corresponds to 43.5 lunar distances. The eccentric Amor asteroid is also a Mars-crosser. In August 2074, it will pass Earth at 0.141 AU, closer than it actually approached Mars in July 1975 (0.150 AU).[1]

Physical characteristics[edit]

In the SMASS and Tholen taxonomic scheme, Ivar is characterized as a common stony S-type asteroid.[1]

Rotation period[edit]

A large number of rotational lightcurves of Ivar have been obtained from photometric observations since 1985 (see infobox). They give a well-defined rotation period between 4.795 and 4.80 hours with a brightness variation between 0.27 and 1.40 magnitude, indicative of its non-spheroidal shape (also see 3D-model image).[14][15][27] New radar and visual observations refined the period to 4.7951689 ± 0.0000026 hours.[25] Future photometric observations will show whether the YORP effect will slowly change the body's spin rate (as seen with 1862 Apollo).[9]

In 1985, the body was observed with radar from the Arecibo Observatory in Puerto Rico at a distance of 0.20 AU. The measured radar cross-section was 7.5 square kilometers.[28] It was the first asteroid to be imaged by radar.[26] Radar observations have been performed again in June & July 2013 and July 2018.

Diameter and albedo[edit]

According to the EXPLORENEOs survey carried out by the Spitzer Space Telescope, thermal infrared observations by the Keck Observatory, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, and thermal modeling by Alan Harris, Ivar measures between 8.37 and 10.2 kilometers in diameter, and it surface has an albedo between 0.09 and 0.15.[4][5][6][7] The Collaborative Asteroid Lightcurve Link adopts an albedo of 0.151 and a diameter of 9.12 kilometers with an absolute magnitude of 12.87.[21] According to model based on radar and photometric observations Ivar is an elongated asteroid with maximum extensions along the three body-fixed coordinates being 15.15 × 6.25 × 5.66 km ± 10%.[25]


This minor planet was named by the discoverer in honor of his late brother Ivar Hertzsprung.[2] The official naming citation was published by the Minor Planet Center in February 1959 (M.P.C. 1860).[29]


  1. ^ a b c d e f g h i j k "JPL Small-Body Database Browser: 1627 Ivar (1929 SH)" (2017-05-08 last obs.). Jet Propulsion Laboratory. Retrieved 4 June 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1627) Ivar". Dictionary of Minor Planet Names – (1627) Ivar. Springer Berlin Heidelberg. p. 129. doi:10.1007/978-3-540-29925-7_1628. ISBN 978-3-540-00238-3.
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  8. ^ a b Pravec, Petr; Sarounová, Lenka; Wolf, Marek (December 1996). "Lightcurves of 7 Near-Earth Asteroids". Icarus. 124 (2): 471–482. Bibcode:1996Icar..124..471P. doi:10.1006/icar.1996.0223.
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  13. ^ Harris, A. W.; Young, J. W. (June 1985). "Photometric Results for Earth Approaching Asteroids". Bulletin of the American Astronomical Society. 17: 726. Bibcode:1985BAAS...17R.726H.
  14. ^ a b c Warner, Brian D. (January 2014). "Near-Earth Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2013 June–September". The Minor Planet Bulletin. 41 (1): 41–47. Bibcode:2014MPBu...41...41W. ISSN 1052-8091.
  15. ^ a b c Hahn, G.; Magnusson, P.; Harris, A. W.; Young, J. W.; Belkora, L. A.; Fico, N. J.; et al. (April 1989). "Physical studies of Apollo-Amor asteroids – UBVRI photometry of 1036 Ganymed and 1627 Ivar". Icarus. 78 (2): 363–381. Bibcode:1989Icar...78..363H. doi:10.1016/0019-1035(89)90184-X. ISSN 0019-1035.
  16. ^ Lupishko, D. F.; Velichko, F. P.; Shevchenko, V. G. (October 1986). "The asteroid 1627 Ivar – UBV photometry, period, and sense of rotation". Kinematika I Fizika Nebesnykh Tel. 2: 39–43. Bibcode:1986KFNT....2...39L. ISSN 0233-7665.
  17. ^ Kiss, L. L.; Szabó, Gy.; Sárneczky, K. (November 1999). "CCD photometry and new models of 5 minor planets". Astronomy and Astrophysics Supplement. 140: 21–28. arXiv:astro-ph/9909159. Bibcode:1999A&AS..140...21K. doi:10.1051/aas:1999115.
  18. ^ Szabo, Gyula; Kiss, Laszlo L. (February 2001). "CCD photometric investigations of small bodies in the solar system" (PDF). Publications of the Astronomy Department of the Eötvös University. 11 (11): 119. Bibcode:2001PADEU..11..119S. Archived from the original (PDF) on 26 October 2003. Retrieved 28 December 2016.
  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.
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  22. ^ 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.
  23. ^ a b Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 – Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007.
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  26. ^ a b To See the Unseen, A History of Planetary Radar Astronomy - chapter 9, Andrew J. Butrica, The NASA History Series
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External links[edit]