Pole star

A pole star is a visible star, preferably a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent position is close to one of the celestial poles, and which lies approximately directly overhead when viewed from the Earth's North Pole or South Pole. A similar concept also applies to planets other than the Earth. In practice, the term pole star usually refers to Polaris, which is the current northern pole star, also known as the North Star.

The south celestial pole lacks a bright star like Polaris to mark its position. At present, the naked-eye star nearest to this imaginary point is the faint Sigma Octantis, which is sometimes known as the South Star.

While other stars' apparent positions in the sky change throughout the night, as they appear to rotate around the celestial poles, pole stars' apparent positions remain virtually fixed. This makes them especially useful in celestial navigation: they are a dependable indicator of the direction toward the respective geographic pole although not exact; they are virtually fixed, and their angle of elevation can also be used to determine latitude.

Polestar (disambiguation)

A pole star is a visible star that is approximately aligned with the Earth's axis of rotation.

Pole star, polestar or polar star may also refer to:

USCGC Polar Star (WAGB-10)

USCGC Polar Star (WAGB-10) is a United States Coast Guard Heavy Icebreaker. Commissioned in 1976, the ship was built by Lockheed Shipbuilding and Construction Company of Seattle, Washington along with her sister ship, USCGC Polar Sea (WAGB-11).

Homeported in Seattle, Polar Star operates under the control of Pacific Area and coordinates its operations through the Ice Operations Section of the United States Coast Guard.

Design

Polar Star uses four different methods of electronic navigation to overcome the difficulties of high-latitude operations, and a computerized propulsion control system to effectively manage six diesel-powered propulsion generators, three diesel-powered ship's service generators, three propulsion gas turbines, and other equipment vital to the smooth operation of the ship. The extensive use of automation and low maintenance materials have greatly reduced staffing requirements.

Polar Star's three shafts are turned by either a diesel-electric or gas turbine prime mover. Each shaft is connected to a 16-foot (4.9 m) diameter, four-bladed, controllable-pitch propeller. The diesel-electric plant can produce 18,000 shaft horsepower (13 MW), and the gas turbine plant a total of 75,000 shaft horsepower (56 MW).