1036 Ganymed

1036 Ganymed, provisional designation Template:Mp, 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.<ref name="MPC-object" /><ref name="springer" /> With a diameter of approximately Template:Convert, 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.

Orbit and classification

Template:Stack 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 1,589 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.<ref name="jpldata" />

Close approaches

Earth approach

Ganymed has a minimum orbit intersection distance with Earth of Template:Convert, or 134 lunar distance.<ref name="jpldata" />

Mars approach

Due to the high eccentricity of its orbit, Ganymed is also a Mars-crosser, intersecting the orbit of the Red Planet. On Template:Start date and age, it will pass at a distance of Template:Convert from Mars.<ref name="jpl-close" />

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 astronomer Galileo Galilei.<ref name="springer" />

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,<ref name="Putilin" /> 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,<ref name="Fieber-Beyer-2007" /> indicating a surface rich in orthopyroxenes, and possibly metals (although if metals are present they are covered and not readily apparent in the spectra).<ref name="Fieber-Beyer-2007" />

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Ganymed measures between 31.66 and 37.67 kilometers in diameter and its surface has an albedo between 0.238 and 0.293.<ref name="SIMPS" /><ref name="AKARI" /><ref name="Mainzer-2011" /><ref name="Mainzer-2016" /><ref name="WISE" />

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.<ref name="lcdb" /> Carry published a diameter Template:Val kilometers in 2012.<ref name="Carry-2012" />

An occultation of a star by Ganymed was observed from California on 22 August 1985.<ref name="Ferret" /> Additional observations in 2011 gave an occultation cross-section with a semi-major and minor axis of 39.3 and 18.9 kilometers, respectively.<ref name="Ferret" />

Rotation and poles

A large number of rotational lightcurves of Ganymed have been obtained from photometric observations since 1985.<ref name="Harris-1985" /><ref name="Lupishko-1987b" /><ref name="Lupishko-1988b" /><ref name="Hahn-1989" /><ref name="Skiff-2012a" /><ref name="Velichko-2012" /><ref name="Velichko-2013" /><ref name="Warner-2015r" /><ref name="geneva-obs" /> Analysis of the best-rated lightcurves obtained by American photometrist Frederick Pilcher at his Organ Mesa Observatory Template:Obscode 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 (Template:Small).<ref name="lcdb" /><ref name="Pilcher-2012g" />

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.<ref name="Kaasalainen-2002a" /><ref name="Hanus-2015a" /><ref name="Viikinkoski-2017" />

In 1998, radar observations of Ganymed by the Arecibo radio telescope produced images of the asteroid, revealing a roughly spherical object.<ref name="Radar-Images">Template:Cite web</ref> 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.<ref name="Nakayama-2000" /> 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.<ref name="Nakayama-2000" />

Further reading

• Template:Cite journal

External links

• Radar Images of 1036 Ganymed, Arecibo Observatory project R1150
• Frederick Pilcher – lightcurves, Astronomical Society of Las Cruzes
• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Geneva Observatory, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• Template:NeoDys
• Template:ESA-SSA
• Template:JPL Small Body