21 Lutetia
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| Discovery | |
|---|---|
| Discovered by: | Hermann M. S. Goldschmidt |
| Discovery date: | November 15, 1852 |
| Alternative names: | none |
| Minor planet category: | Main belt |
| Orbital characteristics | |
| Epoch January 30, 2005 (JD 2453400.5) | |
| Aphelion distance: | 423.955 Gm (2.834 AU) |
| Perihelion distance: | 304.600 Gm (2.036 AU) |
| Semi-major axis: | 364.277 Gm (2.435 AU) |
| Eccentricity: | 0.164 |
| Orbital period: | 1387.902 d (3.80 a) |
| Avg. orbital speed: | 18.96 km/s |
| Mean anomaly: | 75.393° |
| Inclination: | 3.064° |
| Longitude of ascending node: | 80.917° |
| Argument of perihelion: | 250.227° |
| Physical characteristics | |
| Dimensions: | 120×100×80 km [1][2][3] |
| Mass: | ~1.3×1018 |
| Mean density: | ~2.7 g/cm³ [4] |
| Equatorial surface gravity: | ~0.025 m/s² |
| Escape velocity: | ~0.05 km/s |
| Rotation period: | 0.3402 d (8.165 h) [5] |
| Albedo: | 0.208 [3] |
| Temperature: | ~172 K max: 266 K (-7 °C) |
| Spectral type: | M [5] |
| Absolute magnitude: | 7.29 [6] |
21 Lutetia (IPA: [luˈtʰiʃə]) is a large Main belt asteroid of the M spectral type, about 100 kilometers in diameter. It will be the subject of a flyby by the Rosetta space probe in 2010.
Contents |
[edit] Characteristics
The composition of Lutetia has puzzled astronomers for some time, and its investigation has picked up in recent years in anticipation of the upcoming Rosetta flyby. While classified as the M spectral type, it is one of the anomalous members which do not display much evidence of metal on their surface. In fact, there are various indications of a non-metallic surface: A flat low frequency spectrum similar to that of carbonaceous chondrites and C-type asteroids [7] and not at all like that of metallic meteorites, a low radar albedo whereas strongly metallic asteroids like e.g. 16 Psyche have a high one [6], evidence of hydrated materials on its surface [8], abundant silicates [9] and a thicker regolith than most asteroids [10].
Lightcurve analysis indicates that Lutetia's pole points towards either ecliptic coordinates (β, λ) = (3°, 40°) or (β, λ) = (3°, 220°) with a 10° uncertainty [2]. This gives an axial tilt of 85°, or 89°, respectively, meaning that Lutetia spins at an approximately right angle to the ecliptic like e.g. Uranus.
[edit] Exploration
Lutetia was discovered on November 15, 1852 by Hermann Mayer Salomon Goldschmidt from the balcony of his apartment in Paris. The name Lutetia derives from the Latin name for Paris.
On July 10, 2010, the European Rosetta comet probe will pass the asteroid with a minimum distance of 3000 km and a velocity of 15 kilometres per second on its way to 67P/Churyumov-Gerasimenko. In the run-up to this event the attention of astronomers has been drawn to Lutetia.
The flyby will be important for the understanding of the asteroids, since Lutetia will be the first M-type asteroid to be visited by a spacecraft.
There have been two reported stellar occultations by Lutetia: from Malta (1997) and Australia (2003), with only one chord each, roughly agreeing with IRAS measurements.
[edit] Aspects
| Stationary, retrograde |
Opposition | Distance to Earth (AU) |
Maximum brightness (mag) |
Stationary, prograde |
Conjunction to Sun |
|---|---|---|---|---|---|
| 28 December 2005 | 15 February 2006 | 1.84371 | 11.1 | 9 April 2006 | 3 July 2005 |
| 16 April 2007 | 30 May 2007 | 1.30257 | 9.9 | 17 July 2007 | 5 October 2006 |
| 12 October 2008 | 29 November 2008 | 1.42348 | 10.1 | 14 January 2009 | 1 March 2008 |
| 14 January 2010 | 4 March 2010 | 1.82843 | 11.1 | 27 April 2010 | 23 July 2009 |
| 23 May 2011 | 3 July 2011 | 1.13050 | 9.4 | 14 August 2011 | 25 October 2010 |
| 2 November 2012 | 22 December 2012 | 1.58913 | 10.5 | 7 February 2013 | 9 April 2012 |
| 1 February 2014 | 21 March 2014 | 1.76440 | 11.0 | 14 May 2014 | 10 August 2013 |
| 6 July 2015 | 13 August 2015 | 1.03631 | 9.3 | 22 September 2015 | 17 November 2014 |
| 21 November 2016 | 10 January 2017 | 1.71894 | 10.8 | 1 March 2017 | 12 May 2016 |
| 20 February 2018 | 9 April 2018 | 1.65344 | 10.8 | 2 June 2018 | 28 August 2017 |
| 16 August 2019 | 24 September 2019 | 1.07768 | 9.4 | 5 November 2019 | 15 December 2018 |
| 9 December 2020 | 28 January 2021 | 1.80461 | 11.0 | 20 March 2021 | 8 June 2020 |
[edit] External links
[edit] References
- ^ Supplemental IRAS Minor Planet Survey
- ^ a b J. Torppa et al. (2003). "Shapes and rotational properties of thirty asteroids from photometric data". Icarus 164: 346.
- ^ a b M. Mueller et al. (2006). "The size and albedo of Rosetta fly-by target 21 Lutetia from new IRTF measurements and thermal modeling". Astronomy & Astrophysics 447: 1153.
- ^ G. A. Krasinsky et al. (2002). "Hidden Mass in the Asteroid Belt". Icarus 158: 98.
- ^ a b PDS lightcurve data
- ^ a b C. Magri et al. (1999). "Mainbelt Asteroids: Results of Arecibo and Goldstone Radar Observations of 37 Objects during 1980-1995". Icarus 140: 379.
- ^ Birlan, M., et al. (2004). "Near-IR spectroscopy of asteroids 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin and 5480 (1989YK8) [sic], potential targets for the Rosetta mission; remote observations campaign on IRTF". New Astronomy 9: 343.
- ^ M. Lazzarin et al. (2004). "Visible spectral properties of asteroid 21 Lutetia, target of Rosetta Mission". Astronomy and Astrophysics 425: L25.
- ^ M. A. Feierberg et al. (1983). "Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids". Icarus 56: 393.
- ^ A. Dollfus & J. E. Geake (1975). "Polarimetric properties of the lunar surface and its interpretation. VII - Other solar system objects". Proceedings of the 6th Lunar Science Conference, Houston, Texas, March 17-21 3: 2749.
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Vulcanoids · Near-Earth asteroids · Main belt · Jupiter Trojans · Centaurs · Damocloids · Comets · Trans-Neptunians (Kuiper belt • Scattered disc • Oort cloud)
For other objects and regions, see Asteroid groups and families, Binary asteroids, Asteroid moons and the Solar System.
For a complete listing, see List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.
