Aegaeon (moon)

Aegaeon
Aegaeon appears as a bright point inside the G-ring
Provisional or systematic name	S / 2008 S 1
Central body	Saturn
Properties of the orbit
Major semi-axis	167,500 km
Periapsis	167,477 km
Apoapsis	167,534 km
eccentricity	0.0002
Orbit inclination	0.001 °
Orbital time	0.80812 d
Mean orbital velocity	15.05 km / s
Physical Properties
Albedo	?
Apparent brightness	27.0 likes
Medium diameter	≈ 0.6 km
Dimensions	~ 1.0 · 10 11 kg
Medium density	0.5 g / cm 3
Acceleration of gravity on the surface	≈ 0 m / s 2
Escape speed	≈ 0 m / s
discovery
Explorer	Cassini Imaging Science Team
Date of discovery	August 15, 2008
Remarks	Smallest moon named so far

Aegaeon (also Saturn LIII ) is the ninth and one of the smallest inner of the 82 known moons of the planet Saturn . It is the only known moon from Saturn's G- ring .

Discovery and naming

Aegaeon was discovered on August 15, 2008 on two images taken by the Cassini spacecraft during a 600-day targeted observation of the G-ring by the Imaging Science Team of the Cassini mission. The G-ring (→ below ) was the only outer known Saturn ring, of which no moon feeding it was known. The discovery initially took place on these recordings from August 15, 2008, later the moon appeared on numerous recordings from June 15, 2007 to February 20, 2009.

The discovery was announced on March 3, 2009 by Carolyn C. Porco , director of the Imaging Science Team for the Cassini Mission; According to the system of the International Astronomical Union (IAU), the moon was initially given the provisional designation S / 2008 S 1 .

With Aegaeon the smallest and so far the last of 53 Saturn moons ( LIII ) was named at this time .

In May 2009 it was named after the Hekatoncheiren Briareos (also called Aigaion ) from Greek mythology , not to be confused with the sea god Aigaion , the son of Gaia and Pontos . In Homer , Aigaion appears as the father of Briareos, after Virgil and Ovis as Briareos (Aigaion) himself. The three Hekatoncheiren were 50-headed and 100-armed beings who made a decisive contribution to the victory of the Olympic gods over the Titans in the titan fight . They were once banished to the Erebos by their father Uranos , who hated them from the beginning , whereupon their mother Gaia incited the Titans to castrate their father with a flint sickle, which Kronos ( Roman equivalent of Saturnus ) was the only titan to do . Zeus and his siblings had fought against the titans for ten years and only managed to defeat the titans after the liberation of the Hekatoncheiren by Zeus, when they ( Briareos , Gyges and Kottos ) piled up 300 rocks above the titans. The vanquished were tied up and banished to the Tartaros , but the Hekatoncheirs were appointed to their guards. Briareos also received the hand of his daughter Kymopolea from Poseidon , who gave birth to the nymph Oiolyke .

Aigaion, mentioned by Homer as the father of Briareos, was so called by the gods, but people should call him Aigaion because he was superior to the father in strength. When Hera , Poseidon and Athena conspired against Zeus, Thetis called Briareus to Olympus. Briareos is said to have been so powerful that even the gods did not dare to face him.

At Kallimachus, however, Aigaion is a giant trapped under Mount Etna , thus one of Zeus's opponents in the giant battle .

The name comes from the sea god of the Aegean Sea , Aigaion , the mighty son of Thalassa .

Track properties

G-Ringbogen: Three recordings from a distance of 1.2 million km, recorded every 10 minutes (Cassini, October 27, 2008)

Orbit

Aegaeon orbits Saturn on a prograde , almost perfectly circular orbit at an average distance of 167,500 km (approx. 2,779 Saturn radii) from its center, i.e. about 107,230 km above its cloud ceiling. The orbital eccentricity is 0.0002, the web is 0.001 ° relative to the equator of Saturn inclined , that is almost exactly in the equatorial plane of the planet. Due to the low eccentricity, the orbit varies in distance to Saturn by only around 70 km.

The orbits of the next inner co - orbital moons Epimetheus and Janus are on average about 16,000 km from Aegaeon's orbit, the distance of the orbit of the next outer moon Mimas is on average about 17,900 km.

Aegaeon orbits Saturn in 19 hours, 23 minutes and 41.6 seconds. This lies between the orbital times of the Uranus moons Puck and Mab . Aegaeon needed 2 hours and about 43.3 minutes longer to complete one orbit than its inner neighbors Epimetheus and Janus.

Aegaeon is in a 7: 6 orbital resonance with its outer neighbor Mimas, which causes Aegaeon's major orbital half-axis to oscillate over an estimated period of 4 years of about four kilometers.

G-ring

G-ring interrupted by Saturn's shadow (Cassini, October 9, 2009)

The so-called G-ring , which runs along the orbit of Aegaeon around Saturn, has a width of about 9,000 km. Centered on Aegaeon is a slightly lighter 250 km wide ring arch compared to the entire ring, which is comparable to the ring arches in Neptune's Adam's ring and extends and distributes from Aegaeon about 1/6 of the total circumference of the G-ring. In contrast to the ubiquitous dust in the ring, the ring arch appears to consist of ice particles up to a few meters in size and is fed by the impacts of micrometeorites on Aegaeon, similar to that of Enceladus and the E-ring . Due to the deviations of the Aegaeon orbit due to the orbital resonance with Mimas and the interaction with Saturn's magnetosphere , dust is also distributed outwards, as the plasma of the magnetosphere rotates faster than the G-ring. As a result, the ring loses mass over the millennia and is refreshed by further impacts on Aegaeon.

rotation

Aegaeon's period of rotation is not known, but it can be assumed that Aegaeon rotates synchronously and its axis has an inclination of about 0 °.

Physical Properties

Aegaeon (Cassini, January 27, 2010)

size

Aegaeon is about 600 meters in diameter, assuming the same albedo as Pallene's . It is the second smallest known (and accepted) as well as the smallest named moon of a planet (with asteroids one knows smaller ones) in Saturn and in the solar system in general.

internal structure

At an estimated 0.50 g / cm³, the mean density of Aegaeon is far lower than that of Earth and even lower than the density of Saturn; it is so low that Aegaeon would swim on water. This indicates that the moon is predominantly composed of water ice . It can be assumed that it belongs to the so-called rubble piles , which have cavities inside due to the comparatively weak gravity.

exploration

Due to the low apparent brightness of 27.0 ^m next to Saturn, which is only a few arc seconds away and 100 billion times brighter, Aegaeon cannot be observed through earth-based telescopes. Since it was still unknown at the time of the flyby of the Voyager probes Voyager 1 and 2 , there are no data or images of Aegaeon from these probes.

Since its discovery in 2008, the Cassini Aegaeon spacecraft has photographed several times.

media

Commons : Aegaeon (moon)  - collection of images, videos and audio files

Web links

• IAUC 9023: S / 2008 S 1  (currently still requires registration) March 3, 2009 (discovery)
• Extract from IAUC 9023 March 3, 2009 (discovery)
• IAUC 9041: Satellite of Saturn  (access still requires registration at the moment) May 5, 2009 (designation)
• Saturnian Satellite Named Aegaeon May 5, 2009 (naming)

Individual evidence

1. ↑ Paul Rincon: Saturn overtakes Jupiter as planet with most moons. BBC , October 7, 2019, accessed March 20, 2020 . 

further inside	Saturn moons	further outside
Janus	Semi- major axis  (km) Aegaeon 167.500	Mimas