Which of the following stars is considered a northern pole star?

The star considered the northern pole star is Polaris, also known as the North Star. However, among the options given, the correct answer is Deneb. Deneb is part of the constellation Cygnus and is located near the northern celestial pole, making it a significant reference point in the northern sky.

While Sirius, Vega, and Alpha Centauri are notable stars, they are not positioned at or near the celestial pole. Sirius, for example, is the brightest star in the night sky but is located far south relative to the celestial north pole. Vega, also well-known, is part of the Summer Triangle but does not have the polar significance that Deneb does. Similarly, Alpha Centauri, the closest star system to Earth, lies in a southern constellation and does not serve as a pole star.

Deneb's location and brightness make it crucial for navigation and observations in the northern hemisphere, particularly due to its role in the seasonal changes of the night sky. Hence, it is the star associated with the northern celestial pole among the given options.