1131 Porzia

1131 Porzia

Discovery[1]
Discovered by	K. Reinmuth
Discovery site	Heidelberg Obs.
Discovery date	10 September 1929
Designations
MPC designation	(1131) Porzia
Pronunciation	German: [ˈpɔʁtsi̯aː]
Named after	Porcia Catonis (in Shakespeare's play) Julius Caesar[2]
Alternative designations	1929 RO · 1939 TJ 1962 MB
Minor planet category	Mars-crosser[1][3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	87.55 yr (31,978 days)
Aphelion	2.8667 AU
Perihelion	1.5893 AU
Semi-major axis	2.2280 AU
Eccentricity	0.2867
Orbital period (sidereal)	3.33 yr (1,215 days)
Mean anomaly	165.22°
Mean motion	0° 17^m 47.04^s / day
Inclination	3.2292°
Longitude of ascending node	100.71°
Argument of perihelion	248.01°
Physical characteristics
Dimensions	6.53±0.65 km[5] 7.13 km (calculated)[4]
Synodic rotation period	4.0±0.2 h (dated)[6] 4.6584±0.0005 h[7] 4.6601±0.0006 h[8]
Geometric albedo	0.20 (assumed)[4] 0.287±0.057[5]
Spectral type	SMASS = S[1] · S[4][9]
Absolute magnitude (H)	11.94±0.70[10] · 12.00[9] · 12.90[5] · 13.0[1] · 13.10±0.14[4][6][11]

1131 Porzia, provisional designation 1929 RO, is a stony asteroid and sizable Mars-crosser from the innermost regions of the asteroid belt, approximately 7 kilometers in diameter. It was discovered on 10 September 1929, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany.^[3] The asteroid was named after Porcia wife of Brutus, who assassinated Julius Caesar.^[2]

Orbit and classification

Porzia is a Mars-crossing asteroid, a dynamically unstable group between the main belt and the near-Earth populations, crossing the orbit of Mars at 1.666 AU. It orbits the Sun at a distance of 1.6–2.9 AU once every 3 years and 4 months (1,215 days). Its orbit has an eccentricity of 0.29 and an inclination of 3° with respect to the ecliptic.^[1] The body's observation arc begins at Heidelberg, 19 days after its official discovery observation.^[3]

Physical characteristics

In the SMASS taxonomy, Porzia is a common stony S-type asteroid.^[1]

Lightcurves

Two rotational lightcurves of Porzia were obtained by Vladimir Benishek at Belgrade Observatory shortly before its opposition in November 2009, and by French amateur astronomer René Roy in December 2012. Lightcurve analysis gave a well defined rotation period of 4.6584 and 4.6601 hours with a brightness variation of 0.15 and 0.19 magnitude, respectively (U=3/3).^[7][8]

The results supersede photometric observations taken by Polish astronomer Wiesław Wiśniewski in January 1990, which rendered a lightcurve with a period 4.0±0.2 hours and an amplitude of 0.23 magnitude (U=2).^[6]

Diameter and albedo

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer and its subsequent NEOWISE mission, Porzia measures 6.53 kilometers in diameter and its surface has an albedo of 0.287,^[5] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 7.13 kilometers with an absolute magnitude of 13.10.^[4]

This makes Porzia one of the larger mid-sized Mars-crossing asteroids comparable with 1065 Amundsenia (9.75 km), 1139 Atami (9.35 km), 1474 Beira (8.73 km), 1011 Laodamia (7.5 km), 1727 Mette (est. 9 km), 1235 Schorria (est. 9 km), 985 Rosina (8.18 km), 1310 Villigera (15.24 km) and 1468 Zomba (7 km), but far smaller than the largest members of this dynamical group, namely, 132 Aethra, 323 Brucia, 1508 Kemi, 2204 Lyyli and 512 Taurinensis, which are all larger than 20 kilometers in diameter.

Naming

This minor planet was named after the wife of Brutus, Porcia Catonis, who kills herself at news of her husband's death in Shakespeare's play Julius Caesar.^[2] The official naming citation was also published by Paul Herget in The Names of the Minor Planets in 1955 (H 106).^[2]

References

1. "JPL Small-Body Database Browser: 1131 Porzia (1929 RO)" (2017-03-30 last obs.). Jet Propulsion Laboratory. Retrieved 26 July 2017.
2. Schmadel, Lutz D. (2007). "(1131) Porzia". Dictionary of Minor Planet Names – (1131) Porzia. Springer Berlin Heidelberg. p. 96. doi:10.1007/978-3-540-29925-7_1132. ISBN 978-3-540-00238-3.
3. "1131 Porzia (1929 RO)". Minor Planet Center. Retrieved 8 February 2017.
4. "LCDB Data for (1131) Porzia". Asteroid Lightcurve Database (LCDB). Retrieved 8 February 2017.
5. Alí-Lagoa, V.; Delbo', M. (July 2017). "Sizes and albedos of Mars-crossing asteroids from WISE/NEOWISE data" (PDF). Astronomy and Astrophysics. 603: 8. arXiv:1705.10263. Bibcode:2017A&A...603A..55A. doi:10.1051/0004-6361/201629917. Retrieved 20 October 2017.
6. Wisniewski, W. Z.; Michalowski, T. M.; Harris, A. W.; McMillan, R. S. (March 1995). "Photoelectric Observations of 125 Asteroids". Abstracts of the Lunar and Planetary Science Conference. 26: 1511. Bibcode:1995LPI....26.1511W. Retrieved 8 February 2017.
7. Benishek, Vladimir; Protitch-Benishek, Vojislava (April 2010). "Period Determination for 1131 Porzia and 1819 Laputa". The Minor Planet Bulletin. 37 (2): 64–65. Bibcode:2010MPBu...37...64B. ISSN 1052-8091. Retrieved 8 February 2017.
8. Behrend, Raoul. "Asteroids and comets rotation curves – (1131) Porzia". Geneva Observatory. Retrieved 8 February 2017.
9. Carry, B.; Solano, E.; Eggl, S.; DeMeo, F. E. (April 2016). "Spectral properties of near-Earth and Mars-crossing asteroids using Sloan photometry". Icarus. 268: 340–354. arXiv:1601.02087. Bibcode:2016Icar..268..340C. doi:10.1016/j.icarus.2015.12.047. Retrieved 8 February 2017.
10. Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 8 February 2017.
11. Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026. Retrieved 8 February 2017.

External links

• Photometry of Asteroids at The Belgrade Astronomical Observatory, Vladimir Benishek's Page
• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 1131 Porzia at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 1131 Porzia at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters