The Astronomia Tourbillon is a poetic visual rendering of the celestial world...
With every element in constant and visible motion, all under the control of the oscillator at the heart of the tourbillon, the very essence of the wonder with which we gaze upon the stars is applied to a timepiece.

Astronomia Tourbillon Timepiece by Jacob & Co.

The heart of the Astronomia is a four-armed carrier, which rotates once every twenty minutes. On one arm is the tourbillon, which in addition to rotating once around the dial every twenty minutes, also rotates around the axis of the arm carrying it once every five minutes, and around its own axis once every 60 seconds.
The tourbillon cage is constructed with a large, screw-poised balance beating at 18,000 vibrations per hour, with an overcoil balance spring featuring a mathematically correct Phillips terminal curve.
Opposite the balance is the dial showing the hours and minutes.
The openworked dial makes for a beautifully visually balanced counterpoint to the revolving tourbillon carriage, and its Roman numerals lend a touch of classicism and formal beauty to the overall design. The dial is mounted on a unique and specially designed differential system, which causes it to rotate as the central carrier turns –this ensures that the 12:00 marker is always uppermost and that the time can always be easily read.

Jacob & Co.’s Astronomia Tourbillon

Two celestial objects complete the composition: the Earth and the Moon.
The Moon being represented by a spherical, briolette-cut diamond which, in addition to rotating around the dial once every 20 minutes on the carrier, also rotates on its own axis once every sixty seconds, with each of its 56 facets constantly catching and refracting the light, produce a spectacular kinetic display of the diamond’s fire.
The Earth, which rotates once every sixty seconds on its own axis, is represented by a globe made of white gold, with the oceans represented by the deep blue, translucent grand feu (fired) enamel that requires the extremely demanding technique of applying and firing enamel on a spherical surface.
The orbiting display floats above a dial of deep blue aventurine –a precious stone that gives an incredible three-dimensional depth and the appearance of a midnight sky dusted with stars.

With all these elements turning and spinning, the display of the watch will never be the same each time you marvel at it on your wrist. The entire dazzling mechanical display takes place under a complex, highly domed sapphire crystal, almost hemispherical in shape, which emphasizes the universe-in-miniature flavour of the watch.

Source: Sparkle PR Solutions for Jacob & Co.