Encke’s gap

astronomy

Also known as: Encke’s Division

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June 26, 2026

Quick Summary

Encke's Gap is a notable feature within Saturn's A ring, located at approximately 2.21 Saturn radii from the planet's center. This gap is a region where fewer particles are present, creating a visible division within the ring system.1

The existence of such gaps, including Encke's Gap, is theorized to be caused by the gravitational influence of small moons orbiting within or near the gap. These moons, sometimes referred to as "shepherd moons," can clear out particles through gravitational perturbations. In the case of Encke's Gap, the moon Pan has been discovered within it, supporting this theory.1

Johann Franz Encke, a German astronomer, is credited with discovering this gap, which now bears his name. His work in astronomy also included establishing the orbital period of Encke's Comet and deriving a value for the solar parallax.2

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Johann Franz Encke
…known for his discovery of Encke’s Division, in the outermost ring of Saturn. From observations of the transits of Venus recorded in 1761 and 1769, he derived a value for the solar parallax (in effect, for the Sun’s distance from the Earth) that, at 8″.57, is close to the presently…
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…known for his discovery of Encke’s Division, in the outermost ring of Saturn. From observations of the transits of Venus recorded in 1761 and 1769, he derived a value for the solar parallax (in effect, for the Sun’s distance from the Earth) that, at 8″.57, is close to the presently…
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Saturn
The ring system
…of the B ring; the Encke gap (2.21 Saturn radii), a gap in the outer part of the A ring; and the Keeler gap (2.26 Saturn radii), almost at the outer edge of the A ring. Of these gaps, only Encke was known prior to spacecraft exploration of Saturn.
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…of the B ring; the Encke gap (2.21 Saturn radii), a gap in the outer part of the A ring; and the Keeler gap (2.26 Saturn radii), almost at the outer edge of the A ring. Of these gaps, only Encke was known prior to spacecraft exploration of Saturn.
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