140 Siwa

Lightcurve-base 3D-model of 140 Siwa.

Discovery
Discovered by| J. Palisa
Discovery site| Austrian Naval Obs.
Discovery date| 13 October 1874
Designations

MPC designation

| (140) Siwa
Pronunciation| /ˈʃiːwə/
Named after| Živa

Alternative designations

| A874 TB; 1948 AL
Minor planet category| Main belt
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc| 139.10 yr (50805 d)
|{{{apsis}}}|helion}}| 3.3224 astronomical unit|AU (497.02 Gm)
|{{{apsis}}}|helion}}| 2.14323 AU (320.623 Gm)

Semi-major axis

| 2.73283 AU (408.826 Gm)
Eccentricity| 0.21575
Orbital period| 4.52 yr (1650.1 d)
Average Orbital speed| 17.80 km/s
Mean anomaly| 200.674°
Mean motion| 0° 13m 5.398s / day
Inclination| 3.1860°
Longitude of ascending node| 107.263°

|{{{apsis}}}|helion}}

| 196.711°
Physical characteristics
Dimensions| 109.79±3.0 km
Mass| 1.4×1018 kg
Rotation period| 34.445 h (1.4352 d)[1]
34.407 h[2]
Geometric albedo| 0.0676±0.004

Spectral type

| C-type asteroid[3]
Absolute magnitude (H)| 8.34

140 Siwa is a large and dark main-belt asteroid that was discovered by Austrian astronomer Johann Palisa on October 13, 1874. It was named after Živa (Šiwa), a Slavic goddess of fertility. This object is orbiting the Sun at a distance of 2.73 astronomical unit|AU with an eccentricity of 0.22 and an orbital period of 4.52 years. The orbital plane is inclined at an angle of 3.2°.

A 2004 study of the spectrum of 140 Siwa matched a typical C-type asteroid with typical carbonaceous chondrite makeup. There are no absorption features of mafic minerals found.[3] The classification was later revised to a P-type asteroid.[4]

Infrared measurement yields a diameter estimate of 110 km. Attempts to measure the rotation period of 140 Siwa have produced inconsistent results ranging from 14.7 to 32 hours. Photometric observations of this asteroid at the Organ Mesa Observatory in Las Cruces, New Mexico during 2010 gave an irregular light curve with a period of 34.407 ± 0.002 hours and a brightness variation of 0.05 ± 0.01 in magnitude.[2]

The Rosetta comet probe was to visit Siwa on its way to comet 46P/Wirtanen in July, 2008. However, the mission was rerouted to comet 67P/Churyumov-Gerasimenko and the flyby had to be abandoned.[5]

## References

1. ↑ 1.0 1.1 Yeomans, Donald K., "140 Siwa", JPL Small-Body Database Browser (NASA Jet Propulsion Laboratory), https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=140, retrieved 12 May 2016.
2. ↑ 2.0 2.1 Pilcher, Frederick (April 2011), "Rotation Period Determinations for 25 Phocaea, 140 Siwa, 149 Medusa 186 Celuta, 475 Ocllo, 574 Reginhild, and 603 Timandra", The Minor Planet Bulletin 38 (2): pp. 76–78, Bibcode: 2011MPBu...38...76P.
3. ↑ 3.0 3.1 Birlan, Mirel et al. (April 2004), "Near-IR spectroscopy of asteroids 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin and 5480 (1989YK8), potential targets for the Rosetta mission; remote observations campaign on IRTF", New Astronomy 9 (5): pp. 343–351, doi:10.1016/j.newast.2003.12.005, Bibcode: 2004NewA....9..343B, https://hal.archives-ouvertes.fr/hal-00000987.
4. ↑ Takir, Driss; Emery, Joshua P. (June 2012), "Outer Main Belt asteroids: Identification and distribution of four 3-μm spectral groups", Icarus 219 (2): pp. 641–654, doi:10.1016/j.icarus.2012.02.022, Bibcode: 2012Icar..219..641T.
5. ↑ Greyzeck, Ed (2013), "Rosetta", NSS Data Center (NASA), https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2004-006A, retrieved 2013-03-30.

## External links

* 140 Siwa at AstDyS-2, Asteroids—Dynamic Site
* Ephemeris * Observation prediction * Orbital info * Proper elements * Observational info
* 140 Siwa at the JPL Small-Body Database
* Close approach * Discovery * Ephemeris * Orbit diagram * Orbital elements * Physical parameters

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