Question

The accompanying diagram shows two of Uranus' moons, Ophelia and Cordelia, which act as shepherd moons for the Epsilon ring. Explain what would happen to the Epsilon ring if a large asteroid struck Ophelia, knocking it out of the Uranian system.

Short answer

Without Ophelia, the Epsilon ring would likely spread out and thin over time.

Step-by-step solution

Understanding the Role of Shepherd Moons

Shepherd moons like Ophelia and Cordelia orbit near Uranian rings, exerting gravitational forces that maintain the ring's structure and stability. These moons confine the ring material by pulling particles back into the ring and keeping them from spreading out.

Analyzing the Effect of Ophelia's Absence

If Ophelia, one of the shepherd moons, is removed from its orbit (e.g., by an asteroid impact), the gravitational balance that helps maintain the Epsilon ring is disrupted. Without Ophelia's gravitational pull, the particles in the Epsilon ring would start to spread out and potentially thin out over time.

Predicting the Outcome for the Epsilon Ring

With Ophelia gone, the remaining gravitational forces might be insufficient to keep the Epsilon ring confined. Cordelia alone may not be able to prevent the dispersion of ring materials, which could lead to the Epsilon ring becoming more diffuse or even dissipating entirely over a long period.

Key concepts

Uranus and its Moons

Uranus, the seventh planet from the Sun, is encircled by a stunning ensemble of moons and rings. Among its 27 known moons, Ophelia and Cordelia play a special role as shepherd moons, particularly concerning the Epsilon ring.
The shepherd moons orbit close to this ring and, through their gravitational interaction, help maintain its structure. This dynamic partnership assists in keeping the ring stable, preventing the particles from drifting away into space.
These moons work like cosmic caretakers, using their gravitational might to ensure the ring's particles stay in line, similar to how a shepherd's dog keeps sheep from wandering off. The fascinating aspect of Uranus's moons goes beyond their beautiful names; these celestial objects are crucial to the appearance and persistence of the planet's ring system.

Epsilon Ring Dynamics

The Epsilon ring, one of the bright and prominent rings of Uranus, is a narrow band composed of tiny particles. The dynamics of this ring involve complex gravitational interplays between its particles and the nearby moons, especially Ophelia and Cordelia.
Shepherd moons induce a gravitational force that keeps the ring’s particles from scattering into space. The gravitational tug-o-war ensures that the particles oscillate within a narrow region, maintaining the ring's clearly-defined shape.

• Ophelia and Cordelia's gravitational forces confine the particles.
• Gravitational forces prevent the dispersion of ring material.

Without the correct balance of these forces, the ring's density and structure could not be maintained. If one of the shepherd moons were removed from this delicate system, as in the scenario where Ophelia is knocked out of orbit, the Epsilon ring's future would come into question.

Gravitational Forces and Ring Stability

Gravitational forces play an essential role in the stability of planetary rings, such as Uranus's Epsilon ring.
These forces are exerted primarily by nearby moons, like Ophelia and Cordelia, effectively keeping the ring particles in place and preventing them from spreading out.
When a shepherd moon like Ophelia is lost, the gravitational balance around the Epsilon ring is disturbed.
The absence of Ophelia would mean that Cordelia's influence alone might not suffice to maintain the ring's necessary gravitational bounds. This would likely lead to:

• Particles beginning to drift away.
• A potential thinning of the ring over time.
• Eventual dispersion or dissipation of the ring.

Understanding the delicate interplay of gravitational forces in ring stability highlights the intricate mechanics at work within our solar system, demonstrating just how even small objects can have substantial cosmic impacts.