(87) Sylvia
Asteroid (87) Sylvia |
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Asteroid Sylvia with two moons (ESO / VLT) | |
Properties of the orbit ( animation ) | |
Orbit type | Outer main belt of the Cybele group |
Asteroid family | Sylvia family |
Major semi-axis | 3.4812 AU |
eccentricity | 0.0926 |
Perihelion - aphelion | 3.1590 AU - 3.8035 AU |
Inclination of the orbit plane | 10.877 ° |
Length of the ascending node | 73.051 ° |
Argument of the periapsis | 263.529 ° |
Time of passage of the perihelion | 23rd August 2017 |
Sidereal period | 6 a 182.5 d |
Mean orbital velocity | 15.94 km / s |
Physical Properties | |
Medium diameter | 253.0 ± 3.0 km |
Dimensions | 385 × 265 × 230 km |
Dimensions | 1.48 x 10 19 | kg
Albedo | 0.046 ± 0.004 |
Medium density | 1.2 g / cm³ |
Rotation period | 5 h 11 min |
Absolute brightness | 6.94 mag |
Spectral class | P |
history | |
Explorer | Norman R. Pogson |
Date of discovery | May 16, 1866 |
Another name | A909 GA |
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. |
(87) Sylvia is an asteroid that moves in the outer reaches of the main asteroid belt . With a mean diameter of 253 km, Sylvia is the eighth largest asteroid in the main belt.
Discovery and naming
Sylvia was born on 16 May 1866 by the British astronomer Norman Pogson Robert at the Observatory of Chennai (Madras) in India discovered. The discovery was announced in June 1866.
The asteroid was named after Rhea Silvia , the mother of Romulus and Remus in Roman mythology .
A. Paluzie-Borrell incorrectly wrote in Paul Ergets The Names of the Minor Planets (1955) that the name was chosen in honor of Sylvie Petiaux-Hugo Flammarion, the first wife of the French astronomer Camille Flammarion . But discoverer Norman Pogson wrote in his discovery announcement that the name actually refers to the mythological figure Rhea Silvia.
In total, the asteroid has been observed by several earth-based telescopes, a total of 2862 times within 122 years. (As of Sept. 2017)
Track properties
Orbit
Sylvia orbits the sun in a prograde , elliptical orbit between 472,500,000 km (3.20 AU ) and 569,000,000 km (3.80 AU) from its center. The orbital eccentricity is 0.093, the web is at 11 ° to the ecliptic inclined . Its orbit is therefore in the outer asteroid belt .
The orbital period of Sylvia is 6.50 years.
rotation
Sylvia rotates around its axis once every 5 hours and 11 minutes. From this it follows that the asteroid performs 10,983.6 self- rotations ("days") in a Sylvia year . The orbital speed at the equator is 230 km / h.
Observations of the light curve show an alignment of Sylvias Pol in the direction of the ecliptic coordinates with only 0.5 ° uncertainty; this results in an axis inclination of 29.1 °; Sylvia's rotation is therefore as their orbit prograde .
Sylvia family
(87) Sylvia is the namesake of an asteroid family within the Cybele group with similar orbital elements and a predominantly similar mineralogical composition.
Asteroids of the Cybele group move beyond the Hecuba gap with orbital semi-axes between 3.27 and 3.7 AU. The objects have eccentricities of less than 0.3 and orbit inclinations of less than 25 °. The members of this group are in 7: 4 resonance with Jupiter, which stabilizes their orbit. They are likely fragments of a previous collision.
Physical Properties
size
The observations made so far indicate an elongated, irregularly shaped body; the most precise determination of the diameter ( geometric mean ) is 253.051 km. With regard to the exact dimensions, the most precise value is 385 × 262 × 232 km.
Assuming an average diameter of 253 km, this results in a surface area of around 201,000 km 2 , which is just about the size of Belarus .
Provisions of the diameter for Sylvia
year | Dimensions km | source |
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2001 | 260.9 | Tedesco ( IRAS ) u. a. |
2005 | 271 ± 13.3 | Marchis et al. a. |
2005 | 289 ± 11 | Marchis et al. a. |
2005 | 385 × 265 × 230 ± 10 | Marchis et al. a. |
2006 | 348 ± 1 × 217 ± 6 | Marchis et al. a. |
2006 | 282 | Marchis et al. a. |
2014 | 253.051 ± 2.953 | Masiero et al. a. |
2016 | 385 × 262 × 232 | Yu Jiang et al. a. |
The most precise determination is marked in bold .
internal structure
Sylvia belongs to the X – type asteroids (according to another classification: P) and therefore has a dark, carbon-rich surface with an albedo of 0.05. The surface color is therefore darker than coal. The unusually low mean density of 1.2 g / cm 3 indicates that the celestial body is porous and therefore a rubble pile , a loose collection of dust and rocks. It is believed that the voids may constitute 25% up to 60% of the body, depending on its exact composition; however, the mineralogy of X-type asteroids is not yet sufficiently known to determine this more precisely.
The mass of Sylvia could previously be calculated to be 1.48 ∙ 10 19 . The absolute brightness is given as 6.94 mag.
The mean surface temperature is around 151 K (−122 ° C) and can rise to a maximum of 223 K (−50 ° C) at noon.
The Sylvia triple system
On February 23, 2001, a first companion was discovered with Sylvia at the Keck Observatory with the help of adaptive optics . The moon, initially designated as S / 2001 (87) 1 , has a diameter of 10.8 km and orbits Sylvia at a distance of 1,354 km in 3.65 days.
Through further observations with the Very Large Telescope in 2004, another companion could be found, which was named S / 2004 (87) 1 . This orbits Sylvia within the orbit of the outer moon and is 10.6 km tall; it moves around the asteroid at a distance of 702 km in 33 hours.
Both objects orbit the asteroid at regular intervals on almost circular (eccentricities less than 0.01) and approximately equatorial (orbit inclination less than 2 °) orbits. As a fitting name for the two satellites in 2005 the names were Romulus and Remus by the International Astronomical Union defined (IAU).
Sylvia is the first asteroid to have two moons detected. Other asteroids with two moons are now known. It is now assumed that multiple systems are not uncommon in the solar system.
Components | Physical parameters | Path parameters | discovery | |||||
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Surname | Throughput diameter (km) |
Relative size % |
Mass (kg) |
Major semi-axis (km) |
Orbital time (d) |
eccentricity |
Inclination to Sylvia's equator |
Date of discovery Date of publication |
(87) Sylvia | 253.0 | 100.00 | 1.5 · 10 19 | - | - | - | - | May 16, 1866 June 1866 |
Remus (Sylvia II) |
10.6 | 3.7 | 7.3 · 10 14 | 701.64 | 1.373 | 0.093 | 2.0 | August 9, 2004 August 10, 2005 |
Romulus (Sylvia I) |
10.8 | 3.8 | 9.3 · 10 14 | 1351.35 | 3,654 | 0.007 | 1.7 | February 18, 2001 February 23, 2001 |
See also
Web links
- Wm. Robert Johnston: (87) Sylvia, Romulus and Remus (English)
- Asteroid (87) Sylvia Rotatable 3D model of Sylvia (English)
- Asteroids in a pack of three. On: Wissenschaft.de from August 11, 2005.
- The moonlets of asteroid 87 Sylvia (English)
- Letter to Nature - Discovery of the triple asteroidal system 87 Sylvia (English)
Individual evidence
- ^ Discovery Circumstances: Numbered Minor Planets. The international Astronomical Union - Minor Planet Center, accessed August 7, 2020 .
- ↑ (87) Sylvia in the Small-Body Database of the Jet Propulsion Laboratory (English).
- ↑ IRAS (2001): The Supplemental IRAS Minor Planet Survey. Retrieved September 13, 2017 .
- ↑ Franck Marchis et al. a .: Discovery and characterization of binary asteroids 22 Kalliope and 87 Sylvia . bibcode : 2001DPS .... 33.5202M .
- ↑ Franck Marchis et al. a .: Discovery of the triple asteroidal system 87 Sylvia . 2005, PMID 16094362 .
- ↑ Jim Baer: Recent Asteroid Mass Determinations (2010). (No longer available online.) Archived from the original on July 8, 2013 ; accessed on September 4, 2017 .
- ^ A b Franck Marchis et al .: Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey . 2006, PMC 2600456 (free full text).
- ↑ Joseph R. Masiero et al. a .: Main-belt Asteroids with WISE / NEOWISE: Near-infrared Albedos . 2014, bibcode : 2014ApJ ... 791..121M .
- ↑ Yu Jiang et al. a .: Dynamical Configurations of Celestial Systems Comprised of Multiple Irregular Bodies (2016). Retrieved September 4, 2017 .