(21) Lutetia
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Asteroid (21) Lutetia |
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| Image taken by the Rosetta spacecraft | |
| Properties of the orbit ( animation ) | |
| Orbit type | Main belt asteroid |
| Major semi-axis | 2,434 AU |
| eccentricity | 0.165 |
| Perihelion - aphelion | 2.034 AU - 2.835 AU |
| Inclination of the orbit plane | 3.1 ° |
| Length of the ascending node | 80.9 ° |
| Argument of the periapsis | 250.1 ° |
| Time of passage of the perihelion | September 8, 2015 |
| Sidereal period of rotation | 3 a 291 d |
| Mean orbital velocity | 18.95 km / s |
| Physical Properties | |
| Medium diameter | 121 ± 1 × 101 ± 1 × 75 ± 13 km |
| Dimensions | (1.7 ± 0.1) 10 18 kg |
| Albedo | 0.19 ± 0.02 |
| Medium density | (3.4 ± 0.3) g / cm³ |
| Rotation period | 8 h 10 min 5.77 s |
| Absolute brightness | 7.35 likes |
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Spectral class (according to Tholen) |
M. |
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Spectral class (according to SMASSII) |
Xk |
| history | |
| Explorer | HMS Goldschmidt |
| Date of discovery | November 15, 1852 |
| 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. | |
(21) Lutetia is an asteroid of the main asteroid belt , which was discovered on November 15, 1852 by Hermann Mayer Salomon Goldschmidt from the windows of his mansard apartment and later named with the Celtic name of the city of Paris .
Lutetia was one of the first asteroids to be classified as an M-type asteroid . However, Lutetia has an unusually low radar albedo for an M-type asteroid.
Rosetta spacecraft
On July 10, 2010, 17:45 CEST, the Rosetta space probe passed Lutetia in a second orbit of the asteroid belt (21) at a distance of 3,162 km with a relative speed of 15 km / s, so that the majority of the camera panning only took half an hour . But two hours earlier, images with a resolution of not much more than one kilometer were obtained with the Osiris telecamera from a distance of 100,000 km. (21) Lutetia was 455 million km from Earth and 407 million km from the Sun. At a distance of 20,000 km, OSIRIS resolved the images at a phase angle of 156.8 ° with 0.375 km / pixel and showed the almost fully illuminated pane. The greatest resolution was 59 m / pixel with a phase angle of almost 90 °; after the flyby the phase angle reached a minimum of 0.15 ° in the backlight. Just over 50% of the surface could still be observed in the light.
The instruments used covered the light spectrum from UV (70 nm, ALICE spectrometer) through the visible range (21 more or less limiting color filters of the OSIRIS camera) and the IR (VIRTIS imaging spectrometer) up to millimeter waves (0.5 to 1 , 3 mm, MIRO microwave spectrometer). In addition, the evaluation of the Doppler effect in the radio signal made it possible to measure the deflection of the probe and thus to determine the mass of the asteroid. At the time, Lutetia's axis of rotation formed an acute angle with the direction of illumination, but the variation in the position of the sun was sufficient to determine the thermal properties of the surface.
Results so far
The first evaluations of the images on the night of July 10th to 11th, 2010 showed that (21) Lutetia is characterized by huge craters, ridges and landslides as well as rocks several hundred meters in size, which indicates a rather eventful history. Later evaluations suggest that the minor planet is covered by a layer of dust-like regolith up to 600 m thick . At least 240 rocks with a diameter of more than 100 m were found; many craters seem to be partially or completely covered by the material thrown up during impacts, because due to the escape speed of 60 m / s an estimated 90% of the material thrown up fell back onto the asteroid. The density calculated on the basis of the orbital and gravity field measurements is very similar to that of the earth.
See also
Web links
- Lutetia closest approach images ( Memento from July 13, 2010 in the Internet Archive ). (Engl.) - Images from Rosetta's closest approach. On: ESA rosetta blog ( Memento from September 6, 2008 in the Internet Archive ). (Retrieved July 11, 2010, 1:29 am.)
- ESO: Asteroid Lutetia: A Rare Witness to Earth's Birth + Photo & Animation - November 11, 2011
- Annotated map of asteroid (21) Lutetia sci.esa.int, (accessed January 12, 2012)
Individual evidence
- ↑ a b H. Sierks et al .: Images of Asteroid 21 Lutetia: A remnant planetesimal from the early Solar System . Science 334, 2011, doi: 10.1126 / science.1207325 ( online ( memento from November 1, 2016 in the Internet Archive ) by umd.edu).
- ↑ a b M. Pätzold et al .: Asteroid 21 Lutetia: Low mass, high density . Science 334, 2011, doi: 10.1126 / science.1209389 ( online ( memento from March 6, 2016 in the Internet Archive ) from mit.edu).
- ↑ B. Carry et al .: Physical properties of the ESA Rosetta target Asteroid (21) Lutetia. II. Shape and flyby geometry . Astron. Astrophys. 523, 2010, doi: 10.1051 / 0004-6361 / 201015074 (free full text).
- ↑ a b Comet probe Rosetta sends unique images of the asteroid Lutetia . In: www.dlr.de . (Accessed: July 11, 2010, 01:00 h.)
- ^ PH Hasselmann et al .: Asteroid (21) Lutetia: Disk-resolved photometric analysis of Baetica region . Icarus 267, 2016, 135–153, doi: 10.1016 / j.icarus.2015.11.023 ( online at researchgate.net).