391 Ingeborg (prov. designation:A894 VBor1894 BE) is an asteroid and second-largest Mars-crosser on an eccentric orbit from the asteroid belt. It was discovered by German astronomer Max Wolf on 1 November 1894, at the Heidelberg Observatory in southwest Germany. When discovered, it was observed for a couple of weeks, and follow-up observations were made in 1901 and 1904.[3][4]
According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Ingeborg measures between 15.75 and 18.15 kilometers in diameter and its surface has an albedo between 0.282 and 0.495.[6][7][8] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.20 and calculates a diameter of 19.63 kilometers based on an absolute magnitude of 10.9.[5] Other large Mars crossing minor planets include 132 Aethra (43 km), 323 Brucia (36 km), and 2204 Lyyli (25 km).
^ abcdeNugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117.
^ abcdUsui, 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)
^ abWisniewski, W. Z.; Michalowski, T. M.; Harris, A. W.; McMillan, R. S. (March 1995). "Photoelectric Observations of 125 Asteroids". Abstracts of the Lunar and Planetary Science Conference. 26: 1511. Bibcode:1995LPI....26.1511W.
^Koff, R. A.; Brincat, S. M.; Stephens, R. D.; Pravec, P. (September 2001). "Lightcurve Photometry of Asteroid 391 Ingeborg". The Minor Planet Bulletin. 28: 46–48. Bibcode:2001MPBu...28...46K.
^Hanus, J.; Broz, M.; Durech, J.; Warner, B. D.; Brinsfield, J.; Durkee, R.; et al. (November 2013). "An anisotropic distribution of spin vectors in asteroid families". Astronomy and Astrophysics. 559: 19. arXiv:1309.4296. Bibcode:2013A&A...559A.134H. doi:10.1051/0004-6361/201321993.
^Hanus, J.; Durech, J.; Oszkiewicz, D. A.; Behrend, R.; Carry, B.; Delbo, M.; et al. (February 2016). "New and updated convex shape models of asteroids based on optical data from a large collaboration network". Astronomy and Astrophysics. 586: 24. arXiv:1510.07422. Bibcode:2016A&A...586A.108H. doi:10.1051/0004-6361/201527441.
^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.
^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.
^Schmadel, Lutz D. (2007). "Appendix 11 – Minor Planet Names with Unknown Meaning". Dictionary of Minor Planet Names – Fifth Revised and Enlarged revision. Springer Berlin Heidelberg. pp. 927–929. ISBN978-3-540-00238-3.