The Satellites of Jupiter

By Daniel Zimmermann

This e-book treats the rings of Jupiter and its moons: the inner moons, the Galilean moons, Themisto, the Himalia group, Carpo, the Ananke group, the Carpo group, and the Pasiphae group. Considerable space is alloted to the meaning of the names of the satellites.

• Language: English
• Publisher: Lulu.com
• Release date: Mar 3, 2019
• ISBN: 9780359478170

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The Satellites of Jupiter

The Satellites of Jupiter

By Daniel Zimmermann

The Three Rings of Jupiter

Names

The rings of Saturn, Uranus, and Neptune do not have descriptive names. The chief rings of Saturn bear the names of capital letters, such as the B Ring and C ring. Some of the rings of Uranus are simple numbers; others are Greek letters. The rings of Neptune have more imaginative names. They are named after people involved in the discovery of Neptune and its satellite Triton, such as Adams and Galle. However, these names do not tell us anything about the appearance of the rings.

In contrast, the names of Jupiter’s rings are descriptive. They are the Halo Ring, the Main Ring, and the Gossamer Ring.

The Halo Ring

A halo should not be too far away from a head, so the Halo Ring is the closest to the planet Jupiter. It has also been described as toroidal. A torus is donut-shaped, so the ring is not flat, but contains particles that lie above and below its equatorial plane. Wikipedia describes it as the vertically thickest Jovian ring.

According to Cornell University, the Halo Ring has a radial width of about 30,500 kilometers.. Its inner edge is about 92,000 km from the center of Jupiter, and its outer edge is 122,500 km from the center.

The Main Ring

The Main Ring is the brightest of the three. It is a slender ring. According to Cornell University, its approximate radial width is only 6,440 km. It begins more or less at the boundary of the Halo Ring and ends about 128,940 km from the center of Jupiter. It is also considerably flatter than the Halo Ring.

The orbit of the satellite Metis lies within the Main Ring, and the orbit of Adrastea lies close to its outer edge. These two moons are closer to Jupiter than any other moon that has thus far been discovered.

It is thought that the Main Ring acquires particles from Metis and Adrastea when meteor impacts cause materials to scatter.

The Gossamer Ring

The term gossamer refers to some wispy substance, such as cobwebs, gauze, or delicate fabrics. Hence the Gossamer Ring has a sort of airy, tenuous nature. This is because there are relatively few particles per unit area in the ring.

The Gossamer Ring actually consists of two rings: the Amalthea Gossamer Ring and the Thebe Gossamer Ring. According to Cornell University, the Amalthea Gossamer Ring is somewhat brighter than its companion. It begins near the outer edge of the Main Ring and extends outward to the orbit of the satellite Amalthea, which is about 181,000 km from the center of Jupiter. The Thebe Gossamer Ring is more tenuous. It also begins near the outer edge of the Main Ring and extends outward to the orbit of the satellite Thebe, which is about 220,000 km from the center of Jupiter. The particles of the Thebe Gossamer Ring lie above and below the particles of the Amalthea Gossamer Ring, so that the former completely envelops the latter, just as bread encloses meat in a hamburger.

Composition

The rings are composed of small particles that revolve around Jupiter as small satellites. In contrast to the ice particles in the principle rings of Saturn, it is thought that the particles in the rings of Jupiter are largely dust, often a few micrometers in diameter or less. Other particles are thought to be rocks up to a half kilometer in diameter. However, it has not been possible to measure any of these particles in the laboratory, of course.

In each of the rings, the particles are unevenly distributed. The uneven distribution is especially pronounced in and around the orbits of satellites, where gaps and denser ringlets are likely to occur.

Himalia Ring?

The New Horizons spacecraft may have found a fourth ring associated with the satellite Himalia, but the evidence is inconclusive.  There is speculation that another satellite crashed into Himalia causing particles to be scattered.

References

Cornell University: Jupiter Fact Sheet

http://www.news.cornell.edu/releases/sept98/jupiter.facts.html

Wikipedia: Rings of Jupiter

http://en.wikipedia.org/wiki/Rings_of_Jupiter

NASA: Himalia

http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Himalia

Windows to the Universe: The Rings of Jupiter

http://www.windows2universe.org/jupiter/rings.html

Nine Planets: Jupiter

http://nineplanets.org/jupiter.html

Metis, Adrastea, Amalthea, and Thebe

Four Jovian moons are very close to the mother planet. The closest is Metis, followed by Adrastea, Amalthea, and Thebe. They all have fairly circular orbits, and the planes of their orbits are close to the plane of the