Physical characteristics 1620 Geographos

1 physical characteristics

1.1 spectral type
1.2 rotation period
1.3 spin axis
1.4 shape , structure
1.5 diameter , albedo

physical characteristics
spectral type

in tholen , smass classification, geographos s-type asteroid. means highly reflective , composed of nickel-iron mixed iron- , magnesium-silicates.

rotation period

since 1970s, several rotational lightcurve of geographos have been obtained photometric observations. lightcurve analysis gave rotation period (retrograde sense of rotation) between 5.222 , 5.224 hours high brightness variation between 1.02 , 2.03 magnitude (u=3/3/3/2/3/3/3).

the yarkovsky effect causing decrease in orbital semimajor axis of 7001274000000000000♠27.4±5.7 m yr, while yorp effect increasing asteroid s rotation @ rate of 6997150000000000000♠(1.5±0.2)×10 rad yr.

spin axis

several lightcurve modeled abundant photometric observations. in 1994 , 1995, polish astronomers obtained concurring period 5.223328 hours , found spin axis of (54.0°, −52.0°) in ecliptic coordinates (λ, β) (q=3/3). radiometric observations gave period of 5.223327 hours , pole of (55.0°, −46.0°). 2 other international studies obtained period of 5.223326 hours , pole @ (56.0°, −47.0°) , (55.0°, −45.0°), respectively (q=3/3).

shape , structure

the light curve shows high amplitude, indicative of elongated shape, measuring 5.0 × 2.0 × 2.1 kilometers, corresponds mean-diameter of 2.5 km.

the interior of asteroid has rubble-pile structure. asteroid s high thermal inertia indicates surface mix of fine grains , large rocks , boulders. during asteroid s close approach earth in 1994, radar study of conducted deep space network @ goldstone observatory, california. resultant images show geographos elongated object in solar system.

diameter , albedo

according observations goldstone observatory , space-based surveys carried out infrared astronomical satellite iras , neowise mission of wide-field infrared survey explorer, geographos measures between 1.77 , 2.56 kilometers in diameter , surface has albedo between 0.26 , 0.3258.

the collaborative asteroid lightcurve link adopts albedo of 0.26 , diameter of 2.5 kilometers based on absolute magnitude of 15.09.

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