Hellenica World

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15 Eunomia
Discovery A
Discoverer Annibale de Gasparis
Discovery date July 29, 1851
Alternate
designations
none B
Category Main belt, Eunomia family
Orbital elements C D
Epoch October 22, 2004 (JD 2453300.5)
Eccentricity (e) 0.186
Semi-major axis (a) 395.872 Gm (2.646 AU)
Perihelion (q) 322.290 Gm (2.154 AU)
Aphelion (Q) 469.453 Gm (3.138 AU)
Orbital period (P) 1572.323 d (4.30 a)
Mean orbital speed 18.15 km/s
Inclination (i) 11.732°
Longitude of the
ascending node (Ω))
293.399°
Argument of
perihelion (ω)
97.577°
Mean anomaly (M) 148.829°
Physical characteristics
Dimensions 255.3 km
Mass 8.4 1018 kg
Density 0.96 g/cm³ 1
Surface gravity 0.0343 m/s²
Escape velocity 0.0935 km/s
Rotation period 0.2535 d (6.083 h) 2
Spectral class S-type asteroid
Absolute magnitude 5.28
Albedo 0.209 3
Mean surface
temperature
~166 K

15 Eunomia (ew-noh'-mee-a) is the 12th largest Main belt asteroid. It is also the largest member of the Eunomia family of asteroids. Like other true members of the family, it is composed of silicates and nickel-iron. It is light in colour.

It was discovered by A. de Gasparis on July 29, 1851 and named after Eunomia, one of the Horae (Hours), a personification of order and law in Greek mythology.

Eunomia has rather variable lightcurve indicating an elongated object. This led to a suggestion that Eunomia may be a binary object. However, it was refuted later. [1]

Eunomia has been observed occulting stars three times.

Eunomia in fiction

One chapter of Arkady and Boris Strugatsky's novel Space Apprentice (1962) is staged on Eunomia. A scientific station on the asteroid is annihilating large fragments of the asteroid in its advanced experiments.











Appearance

Stationary, retrograde Opposition Minimum distance (AU) Maximum brightness (mag) Stationary, prograde Conjunction to Sun
4 March 2005 30 April 2005 2.14777 9.8 18 June 2005 10 December 2005
10 June 2006 30 July 2006 1.47916 8.3 17 September 2006 16 April 2007
23 November 2007 10 January 2008 1.47650 8.2 26 February 2008 2 September 2008
8 February 2009 8 April 2009 2.14940 9.8 26 May 2009 17 November 2009
7 May 2010 27 June 2010 1.75731 9.0 18 August 2010 22 February 2011
15 October 2011 28 November 2011 1.24553 8.0 3 January 2012 4 August 2012
16 January 2013 16 March 2013 2.04489 9.6 4 May 2013 26 October 2013
8 April 2014 31 May 2014 1.98596 9.5 21 July 2014 15 January 2015
14 August 2015 2 October 2015 1.21174 7.9 6 November 2015 27 June 2016
25 December 2016 19 February 2017 1.84200 9.2 9 April 2017 4 October 2017
12 March 2018 7 May 2018 2.12485 9.8 26 June 2018 18 December 2018
23 June 2019 12 August 2019 1.39369 8.2 28 September 2019 5 May 2020
1 December 2020 21 January 2021 1.56826 8.4 9 March 2021 11 September 2021


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