(25143) Itokawa

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Asteroid
(25143) Itokawa
Model by (25143) Itokawa derived from radar observations
Properties of the orbit ( animation )
Orbit type Apollo type
Major semi-axis 1.324  AU
eccentricity 0.280
Perihelion - aphelion 0.953 AU - 1.695 AU
Inclination of the orbit plane 1.622 °
Sidereal period 1 a 191 d
Mean orbital velocity 25.885 km / s
Physical Properties
Medium diameter 535 × 294 × 209 m
Dimensions approx. 3.58 ± 0.18 × 10 10Template: Infobox asteroid / maintenance / mass kg
Albedo 0.53
Medium density 1.95 ± 0.14 g / cm³
Rotation period 12 h 9 min
Absolute brightness 18.96 mag
Spectral class S type
history
Explorer LINEAR
Date of discovery September 26, 1998
Another name 1998 SF 36
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(25143) Itokawa (1998 SF 36 ) is discovered on 26 September 1998, the Earth's orbit intersecting near-Earth asteroid . The celestial body was named after Hideo Itokawa , a Japanese aerospace engineer .

Orbit

Itokawa moves between 0.953 AU ( perihelion ) and 1.695  AU ( aphelion ) in around 556 days on an eccentric orbit around the sun . During the perihelion, the asteroid moves within the Earth's orbit . The orbital eccentricity is 0.280, with the orbit inclined 1.6 ° to the ecliptic .

Earthbound observations

Scheme of the two parts of Itokawa

Radar observations from the Goldstone and Arecibo observatories have shown that Itokawa is an elongated structure with a size of only 594 × 320 × 288 meters. The surface apparently consists mainly of silicate-containing material, similar to the common chondrites . The asteroid rotates around its own axis in around 12 hours.

When measuring Itokawa's rotational speed to calculate the YORP effect , a discrepancy between the actual and the expected change in speed was noticed. Only when the calculation was based on the assumption that the asteroid consists of two parts with differing densities did the measurement results agree with the calculated change in the rotational speed. Itokawa must therefore consist of one part with a density of 2850 kilograms per cubic meter and a second with a density of 1750 kilograms per cubic meter. This observation is so far unique for asteroids. It is believed that Itokawa was formed when two asteroids collided.

Hayabusa Mission

Container with particles from Itokawa

Itokawa was selected as the target for the Japanese Hayabusa mission. The images of the probe, which Itokawa reached in September 2005, show the surface of the asteroid with a resolution of less than one meter. The almost complete absence of impact craters , which dominate the surfaces of other asteroids, such as (243) Ida or (433) Eros , which were explored by space probes , is striking . Some areas on Itokawa are covered by regolith and boulders of various sizes, while elsewhere bare rock is apparently exposed. The size of Itokawa could be determined by Hayabusa at 535 × 294 × 209 meters and the mean density at 1.95 ± 0.14 g / cm³. The density of the asteroid corresponds roughly to that of sand and is well below the value of ordinary chondrites (approx. 3.2 g / cm³). These observations suggest that it is at the asteroid one only by the gravitational force (held together "rubble pile" English rubble pile ) with a porosity is of about 40%. However, this 2006 hypothesis needs to be reconsidered in the light of the 2014 discovery that the asteroid is made up of two parts with significantly different densities.

Hayabusa took samples from two different points on the asteroid's surface in November 2005. After the first attempt failed on November 19th, the sampling mechanism worked properly on the second attempt on November 26th. Due to a loss of communication with the ground station, the take-off window for the return flight in December 2005 could not be used; Hayabusa then launched back to Earth in 2007 using the ion thrusters . The return capsule of the spacecraft entered the earth's atmosphere via Australia on June 13, 2010 and landed on schedule at Woomera in the WPA .

See also

literature

Web links

Commons : (25143) Itokawa  - album containing pictures, videos and audio files

Individual evidence

  1. ↑ SJ Ostro, LAM Benner, C. Magri, JD Giorgini, R. Rose, RF Jurgens, DK Yeomans, AA Hine, MC Nolan, DJ Scheeres, SB Broschart, M. Kaasalained, JL Margot: Radar Observations of Itokawa in 2004 and Improved Shape Estimation . 37th DPS Meeting. In: Bulletin of the American Astronomical Society , Vol. 37, # 3, aas.org: [15.19] Radar Observations of Itokawa in 2004 and Improved Shape Estimation , accessed June 19, 2010
  2. ↑ RP Binzel, AS Rivkin, SJ Bus, JM Sunshine, TH Burbine: MUSES-C target asteroid (25143) 1998 SF36: A reddened ordinary chondrite . In: Meteoritics & Planetary Science , Vol. 36, p. 1167
  3. ^ SJ Ostro, AL Benner, MC Nolan, JD Giorgini, RF Jurgens, R. Rose, DK Yeomans: Radar Observations of Asteroid 25143 (1998 SF36) , American Astronomical Society, 33rd DPS Meeting. In: Bulletin of the American Astronomical Society , Vol. 33, p. 1117, aas.org: [41.13] Radar Observations of Asteroid 25143 (1998 SF36) , accessed June 19, 2010
  4. ↑ Cosmic peanut with a split personality. In: Zeit Online . February 5, 2014, accessed February 6, 2014.
  5. ↑ Th. Müller: A minor planet under the microscope . In: Stars and Space , 12/2006, p. 26