Gorgoneion (moon)

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(93) Minerva II (Gorgoneion)
Provisional or systematic name S / 2009 (93) 2
Central body (93) Minerva
Properties of the orbit
Major semi-axis 375 ± 16 km
Periapsis 356 km
Apoapsis 394 km
eccentricity 0.05 ± 0.04
Orbit inclination 91.4 ± 24.1 °
Orbital time 1.1147 ± 0.0006 d
Physical Properties
Medium diameter 3.2 ± 0.9 km
discovery
Explorer
  • Franck Marchis
  • Brent Macomber
  • Jérôme Berthier
  • Frédéric Vachier
  • Joshua P. Emery
Date of discovery August 16, 2009
Remarks Smaller moon of the Minerva system

Gorgoneion is the inner and smaller of the two moons of the main belt asteroid (93) Minerva . Its mean diameter is 3.2 kilometers, which is about 1/48 of the Minerva diameter.

Discovery and naming

Gorgoneion was discovered on August 16, 2009 at 1:44 pm local time by Franck Marchis, Brent Macomber, Jérôme Berthier, Frédéric Vachier and Joshua P. Emery at the Keck Observatory II on Mauna Kea , Hawaii . Gorgoneion was found at 0.25 arc seconds from Minerva "at 5 o'clock" (209 °), with an apparent magnitude difference of 8. The discovery was announced on August 31, 2009; the moon was given the provisional designation S / 2009 (93) 2 .

On the same day, just 8 minutes before, the team discovered Aegis, another companion of Minerva, making the system the fifth known asteroid multiple system in the main belt and the eighth overall.

On December 17, 2013, both moons were officially named. They were named not after people but after magical insignia of the goddess Minerva . In Greek mythology , Athena , who corresponded to Minerva in Roman mythology , was Zeus' favorite daughter. For this reason Zeus let her use his artifacts: Aigis , his terrible mirror shield, and his devastating weapon, his beam. Hephaestus originally made the shield from goat skin. It was so strong that not even Zeus could have destroyed it with his lightning bolts. In the middle of the shield was the head of the Gorgoness Medusa , which was severed by Perseus , whom Athena lent the shield, and which, as a protective amulet, could freeze others to stone. As part of the shield, the head of Medusa became known as the Gorgoneion .

Track properties

Gorgoneion orbits Minerva on a slightly retrograde , almost perfect circular path at an average distance of 375 kilometers from its center (about 4.9 Minerva radii). The orbit eccentricity is 0.05, the orbit is inclined 91.4 ° with respect to the equator of Minerva . The orbit of the outer moon Aegis is on average about 150 miles from Gorgoneion's orbit.

The orbits of both moons are remarkably circular, although the inner Gorgoneion has a slightly more elliptical orbit. Overall, the orbits could be a result of the shape of the mother body Minerva, which is also remarkably round for an asteroid .

Gorgoneion orbits Minerva in 1 day, 2 hours and 45.2 minutes, which corresponds to about 1,498.7 orbits in a Minerva year (around 4.57 earth years). Conversely, it can be said that one orbit of Gorgoneion takes 4.47 Minerva days. It takes a little less than half as long as the outer moon Aegis to make one orbit.

Physical Properties

The diameter of Gorgoneion is about 3.2 kilometers.

Assuming a mean diameter of 3.2 km, the surface area is around 32 km 2 , which is slightly less than the area of ​​the Swiss canton of Basel-Stadt .

exploration

The Minerva observations in 2009 that led to the discovery of Aegis and Gorgoneion continued through 2011. Based on the assumption that the two moons orbit close to the equator of the mother body, it was found that in September 2009 the pole of Minerva was facing the earth, while in March 2011 an edge position of the system was observed. On March 9, 2011, the shadow of Gorgoneion on Minerva could also be observed.

See also

Web links

Individual evidence

  1. Franck Marchis: The discovery of a new triple asteroid - (93) Minerva moon discovery ( English )
  2. Franck Marchis: Asteroid Minerva finds its magical weapons in the sky Moon naming ( English )