87 Sylvia
87 Sylvia is one of the biggest main-belt asteroids. It is a member of the Cybele group. It is beyond the middle of the belt. Sylvia is famous for being the first asteroid known to have more than one moon.
.jpg) Image showing the positions of Remus and Romulus around 87 Sylvia on 9 different nights. The small image shows the potato form of 87 Sylvia. | |
| Discovery | |
|---|---|
| Discovered by | Norman Robert Pogson |
| Discovery date | May 16, 1866 |
| Designations | |
| A909 GA | |
| Main belt (Cybele) | |
| Orbital characteristics | |
| Epoch July 14, 2004 (JD 2453200.5) | |
| Aphelion | 563.679 Gm (3.768 AU) |
| Perihelion | 480.594 Gm (3.213 AU) |
| 522.137 Gm (3.490 AU) | |
| Eccentricity | 0.080 |
| 2381.697 d (6.52 a) | |
Average orbital speed | 15.94 km/s |
| 352.763° | |
| Inclination | 10.855° |
| 73.342° | |
| 266.195° | |
| Physical characteristics | |
| Dimensions | 385×265×230 ± 10 km[1][2] |
| Mass | 1.478±0.006×1019 kg[1] |
Mean density | 1.2 ± 0.1 g/cm³[1] |
| 0.027 m/s² | |
| 0.10 km/s | |
| 0.2160 d (5.183642 h)[3][4] | |
| Albedo | 0.0435[5] |
| Temperature | ~151 K max: 223 K (-52°C) |
Spectral type | X[6] |
| 6.94 | |
Discovery and naming change
Sylvia was found by N. R. Pogson on May 16, 1866 from Madras (Chennai), India.[7] In the article announcing the discovery of this asteroid (MNRAS, 1866), Pogson said he selected the name in reference to Rhea Silvia, mother of Romulus and Remus.
Physical characteristics change
Sylvia is very dark in color and probably has a primitive composition. The discovery of its moons made possible an accurate measurement of the asteroid's mass and density. Its density is very low (around 1.2 times the density of water), indicating that the asteroid has a lot of empty spaces; From 25% to as much as 60% of it may be empty space.[1] The mineralogy of X-type asteroids is not well known. Sylvia is a fairly fast rotator, turning about its axis every 5.18 hours (giving an equatorial rotation speed of about 230 km/h or 145 mph).
Moons change
Sylvia is orbited by two small moons. They have been named Romulus and Remus (the formal names are (87) Sylvia I Romulus and (87) Sylvia II Remus, respectively), after the children of the mythological Rhea Silvia.
It is thought likely that both Sylvia and its moons are rubble piles from a past asteroid collision[1] Other, smaller moons formed in a similar way may also be found.
References change
- ↑ 1.0 1.1 1.2 1.3 1.4 F. Marchis; et al. (2005). "Discovery of the triple asteroidal system 87 Sylvia". Nature. 436 (7052): 822–824. Bibcode:2005Natur.436..822M. doi:10.1038/nature04018. PMID 16094362. S2CID 4412813.
- ↑ Data sheet compiled by W. R. Johnston
- ↑ M. Kaasalainen; et al. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus. 159 (2): 369–395. doi:10.1006/icar.2002.6907. Archived from the original (PDF) on 2008-02-16. Retrieved 2007-12-23.
- ↑ PDS lightcurve data
- ↑ Supplemental IRAS Minor Planet Survey
- ↑ PDS spectral class data
- ↑ Pogson, N. R. (1866), Minor Planet (87) Sylvia, Monthly Notices of the Royal Astronomical Society, Vol. 26, p. 311 (June 1866)
Other websites change
- Pogson, N. R. (1866), Minor Planet (87) Sylvia, Monthly Notices of the Royal Astronomical Society, Vol. 26, p. 311 (June 1866)
- Data on (87) Sylvia from Johnston's archive (maintained by W. R. Johnston)
- Rubble-Pile Minor Planet Sylvia and Her Twins Archived 2008-07-24 at the Wayback Machine (ESO news release, August 2005) Includes images and artists impressions
- Adaptive Optics System Reveals New Asteroidal Satellite (SpaceDaily.com, March 2001) Includes a discovery image.
- Space.com: First asteroid trio discovered
- IAUC 7588, reporting discovery of S/2001 (87) 1
- IAUC 7590, confirming the discovery
- IAUC 8582, reporting discovery of S/2004 (87) 1 and naming Romulus and Remus
- An animation of (87) Sylvia and its moons (23 MB, DivX) Archived 2007-11-01 at the Wayback Machine
- Shape model derived from lightcurve (on page 19) Archived 2008-02-16 at the Wayback Machine