1036 Ganymed, provisional designation 1924 TD, is a stony asteroid on a highly eccentric orbit, classified as a near-Earth object of the Amor group. It was discovered by German astronomer Walter Baade at the Bergedorf Observatory in Hamburg on 23 October 1924, and named after Ganymede from Greek mythology.[1][2] With a diameter of approximately 35 kilometers (22 miles), Ganymed is the largest of all near-Earth objects but does not cross Earth's orbit. The S-type asteroid has a rotation period of 10.3 hours. In October 2024, it is predicted to approach Earth at a distance of 56,000,000 km; 35,000,000 mi (0.374097 AU).[15]
Orbit of Ganymed (blue), with the inner planets and Jupiter (outermost).
Ganymed is an Amor asteroid, a subgroup of the near-Earth asteroids that approach the orbit of Earth from beyond, but do not cross it. It orbits the Sun at a distance of 1.2–4.1 AU about once every 4 years and 4 months (i.e., 52 months or 1,587 days; semi-major axis of 2.66 AU). Its orbit has a high eccentricity of 0.53 and an inclination of 27° with respect to the ecliptic.[3] The body's observation arc begins at the discovering observatory on 24 October 1924 (99 years ago) (1924-10-24), the night after its official discovery observation.[1]
Close approaches
Earth approach
Ganymed has a minimum orbit intersection distance with Earth of 0.3415 AU (51,000,000 km), or 133 lunar distance. Its next pass of the Earth will be at a distance of 0.374097 AU (56,000,000 km; 34,800,000 mi) on 13 October 2024 (2 months' time) (2024-10-13).[15]
Mars approach
Due to the high eccentricity of its orbit, Ganymed is also a Mars-crosser, intersecting the orbit of the Red Planet at 1.66 AU. On 16 December 2176 (152 years' time) (2176-12-16), it will pass at a distance of 0.02868 AU (4,290,000 km; 2,670,000 mi) from Mars.[15]
Name
The minor planet of Ganymed was named after Ganymede from Greek mythology, using the German spelling ("Ganymed"). Ganymede was a Trojan prince abducted by Zeus to serve as a cup-bearer to the Greek gods. The name had previously also been given to Jupiter's third moon, "Ganymede", which was discovered in 1610 by Italian astronomerGalileo Galilei.[2]
Physical characteristics
Owing to its early discovery date, Ganymed has a rich observational history. A 1931 paper published the absolute magnitude, based on observations to date, as 9.24,[16] slightly brighter than the present value of 9.45.
Ganymed is a stony S-type asteroid, in the Tholen, SMASS and in the S3OS2 taxonomy. This means that it is relatively reflective and composed of iron and magnesium silicates. Spectral measurements put Ganymed in the S (VI) spectral subtype,[13] indicating a surface rich in orthopyroxenes, and possibly metals (although if metals are present they are covered and not readily apparent in the spectra).[13]
The Collaborative Asteroid Lightcurve Link derives an albedo of 0.2809 and a mean-diameter of 31.57 kilometers based on an absolute magnitude of 9.50.[10] Carry published a diameter 34.28±1.38 kilometers in 2012.[17]
An occultation of a star by Ganymed was observed from California on 22 August 1985.[4] Additional observations in 2011 gave an occultation cross-section with a semi-major and minor axis of 39.3 and 18.9 kilometers, respectively.[4]
Rotation and poles
A large number of rotational lightcurves of Ganymed have been obtained from photometric observations since 1985.[18][19][20][14][21][22][23][24][25] Analysis of the best-rated lightcurves obtained by American photometrist Frederick Pilcher at his Organ Mesa Observatory (G50) in New Mexico during 2011 gave a rotation period of 10.297 hours with a consolidated brightness amplitude between 0.28 and 0.31 magnitude ({{{1}}}).[10][11]
Three studies using modeled photometric data from the Uppsala Asteroid Photometric Catalogue, WISE thermal infrared data and other sources, gave a concurring period of 10.313, 10.31284, and 10.31304 hours, respectively. Each modeled lightcurve also determined two spin axes of (214.0°, −73.0°), (190.0°, −78.0°), as well as (198.0°, −79.0°) in ecliptic coordinates (λ, β; L1/B1), respectively.[26][27][28]
In 1998, radar observations of Ganymed by the Arecibo radio telescope produced images of the asteroid, revealing a roughly spherical object.[29] Polarimetric observations conducted by Japanese astronomers concluded that there was a weak correlation between the object's light- and polarimetry curve as a function of rotation angle.[30] Because polarization is dependent on surface terrain and composition, rather than the observed size of the object like the lightcurve, this suggests that the surface features of the asteroid are roughly uniform over its observed surface.[30]
↑ 6.06.16.26.3Usui, 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 Japan63 (5): 1117–1138. doi:10.1093/pasj/63.5.1117. Bibcode: 2011PASJ...63.1117U. (online, AcuA catalog p. 153)
↑ 7.07.1Mainzer, A.; Grav, T.; Bauer, J.; Masiero, J.; McMillan, R. S.; Cutri, R. M. et al. (December 2011). "NEOWISE Observations of Near-Earth Objects: Preliminary Results". The Astrophysical Journal743 (2): 17. doi:10.1088/0004-637X/743/2/156. Bibcode: 2011ApJ...743..156M.
↑Harris, A. W.; Young, J. W. (June 1985). "Photometric Results for Earth Approaching Asteroids.". Bulletin of the American Astronomical Society17: 726. Bibcode: 1985BAAS...17R.726H.
↑Lupishko, D. F.; Velichko, F. P.; Kazakov, V. V.; Shevchenko, V. G. (February 1987). "The asteroid 1036 Ganymede - Light curves, period, and sense of rotation". Kinematika I Fizika Nebesnykh Tel3: 92. ISSN0233-7665. Bibcode: 1987KFNT....3...92L.
↑Lupishko, D. F.; Velichko, F. P.; Shevchenko, V. G. (June 1988). "Photometry of the AMOR type asteroids 1036 Ganymede and 1139 Atami". Astronomicheskii Vestnik22: 167–173.InRussian. ISSN0320-930X. Bibcode: 1988AVest..22..167L.
↑Skiff, Brian A.; Bowell, Edward; Koehn, Bruce W.; Sanborn, Jason J.; McLelland, Kyle P.; Warner, Brian D. (July 2012). "Lowell Observatory Near-Earth Asteroid Photometric Survey (NEAPS) - 2008 May through 2008 December". The Minor Planet Bulletin39 (3): 111–130. ISSN1052-8091. Bibcode: 2012MPBu...39..111S.
↑Velichko, F. P.; Magnusson, P. (March 2012). "Photometry and Polarimetry of the Largest NEA 1036 Ganymed". Astronomicheskii Tsirkulyar1575: 1–2. Bibcode: 2012ATsir1575....1V.
↑Hanus, J.; Delbo', M.; Durech, J.; Alí-Lagoa, V. (August 2015). "Thermophysical modeling of asteroids from WISE thermal infrared data - Significance of the shape model and the pole orientation uncertainties". Icarus256: 101–116. doi:10.1016/j.icarus.2015.04.014. Bibcode: 2015Icar..256..101H.
↑Viikinkoski, M.; Hanus, J.; Kaasalainen, M.; Marchis, F.; Durech, J. (November 2017). "Adaptive optics and lightcurve data of asteroids: twenty shape models and information content analysis". Astronomy and Astrophysics607: 14. doi:10.1051/0004-6361/201731456. Bibcode: 2017A&A...607A.117V.
↑ 30.030.1Nakayama, Hiroyuki; Fujii, Yasumasa; Ishiguro, Masateru; Nakamura, Ryosuke; Yokogawa, Sozo; Yoshida, Fumi et al. (July 2000). "Observations of Polarization and Brightness Variations with the Rotation for Asteroids 9 Metis, 52 Europa, and 1036 Ganymed". Icarus146 (1): 220–231. doi:10.1006/icar.2000.6396. Bibcode: 2000Icar..146..220N.
Further reading
Fevig, Ronald A.; Fink, U (May 2007). "Spectral observations of 19 weathered and 23 fresh NEAs and their correlations with orbital parameters". Icarus188 (1): 175–188. doi:10.1016/j.icarus.2006.11.023. Bibcode: 2007Icar..188..175F.
External links
Radar Images of 1036 Ganymed, Arecibo Observatory project R1150