Since the beginning of navigation, the system of stars called Polaris has been vital for sailors. Without land to reference, civilizations sailed vast oceans, relying on the star to guide their course. Polaris, also known as the North Star, is still used by sailors today. Learn more about this mysterious star. If you have never seen it in the night sky, you should. The constellation is represented on the flags of Alaska and Nunavut.
The position of Polaris as seen from different locations varies, depending on the latitude of the observer. In the equator, the North Star would be directly overhead, while in Houston, Texas, the Sun would be 30 degrees south of the North Pole. The pattern continues until the observer reaches the geographic North Pole, where the star appears overhead, a distance of 90 degrees. In general, the constellation has two purposes: to guide navigation and astrometry.
The brightness of Polaris has changed over the past 5,000 years. In the year 1,000 AD, Polaris was brighter than it is today. It was at magnitude 2.4 before Ptolemy noticed it. After the asteroid hit the Earth, it gradually decreased, until it dipped to 0.05 magnitude by the year 1966. Since then, Polaris has varied in brightness, but has remained close to its magnitude from 1966. The latest research shows that it is brightening again after a minor dip in brightness.
The star system of Polaris includes three members – Polaris Aa and Polaris B – both of which are gravitationally bound. The star Aa has 5.4 solar masses, making it a yellow supergiant. Polaris B is a main sequence star with a diameter of about two and a half million kilometers. The star Polaris system also has a Delta Cepheid variable, whose brightness changes by about 10ths of a magnitude every few days.
Although Polaris appears to be stationary in the sky, other stars appear to circle it. These motions are due to Earth’s rotation. The ancient navigators called Polaris the “star to steer by.” The early sailors relied on celestial objects for navigation, and this star provided the perfect reference. The star’s constant position has made it an integral part of navigation techniques for generations. It is just 0.7 degrees away from the North Celestial Pole, the pivot point of the Earth. The distance between Polaris and the North Celestial Pole is only 1.5 full moons across.
Observed by the naked eye, Polaris is an excellent way to find the North Star. Located five times between the Pointer Stars, Polaris is the first bright star in the direction. The Big Dipper makes a complete circle around Polaris every 23 hours and 56 minutes. You can even calculate the true azimuth of Polaris for different latitudes by calculating the distance between these stars. If you follow the star’s path, you will always find it.
The North Star, known as Polaris, lies one half degree from the North Celestial Pole and can be seen from almost anywhere in the northern sky. While it isn’t the brightest star in the sky, it can be easily spotted even in large cities. The North Star is also in the direction of true north, which is different from magnetic north. It sits more or less directly above the North Pole, and is thus often referred to as the North Star.
The North Star will continue to serve as the North Star for centuries to come. On March 24, 2100, Polaris will align with the North Celestial Pole, the point in the sky above the north rotational axis of Earth. At this time, the star will be 27’09” from the North Pole, or 0.4525 degrees from it. In contrast, the Southern Hemisphere will not see its celestial pole star for at least another 2,000 years.
Scientists have known about a third star orbiting Polaris for 50 years, but until recently, they couldn’t find it. Hubble Space Telescope was able to locate the star with all of its focus. The star is a dim white dwarf. The light from this star is lost in the emitted light from Polaris A. Therefore, it has been designated Polaris Ab. This discovery is important for scientists in determining the mass of this star.
The star is located almost directly above the Earth’s rotational axis, making it visible to observers in northern latitudes. It looks like a bear stalking its prey, and in ancient times, people in those places called it Cynosura. The star was also called al-kutb al-shamaliyy in medieval Islamic times. Despite being one of the faintest stars in the sky, its significance has soared in recent centuries.