The brightness of Polaris has increased considerably over the last few centuries. In fact, this star is 2.5 times brighter than it was when Ptolemy observed it more than 2000 years ago. This change is remarkable, astronomer Edward Guinan says. The change is 100 times greater than what is predicted by current stellar evolution models. Whether or not this change is a result of human intervention remains to be seen. In any case, the change in brightness is very dramatic.
During the observation, scientists will look for any movement of its companion. Polaris lies just a few degrees off the North celestial pole, so it rotates very slowly. Stars farther from the pole move in much larger circles. Some of these stars travel enormous distances. The orbit of Polaris will give scientists a more accurate mass of the star. The researchers plan to observe the system for several years. The next step will be determining its motion.
The ancient Egyptians had a North Star during the Old Kingdom. They symbolically represented Polaris by an hippopotamus. The first person to chart Polaris was Claudius Ptolemy, who lived between 85 and 165 B.C.E. Ptolemy also discovered that Polaris is close to the celestial North Pole. This discovery made Polaris a helpful navigation aid. And since it had a directional quality, it was useful to sailors, and later on, mariners and merchants.
However, the position of Polaris varies according to where you are in the Northern Hemisphere. It is at its closest point to the northern horizon during classical antiquity, and it is at the same distance from Kochab (b UMi) during late antiquity. Thus, in 320 BC, Pytheas described it as “devoid of stars.” At that time, brighter stars were used for navigation. However, the position of the star Polaris changed and New York, whose latitude is 41 degrees N, did not receive the same alignment as the North Pole.
The North Star is located between 323 and 433 light-years away from Earth. It is called the North Star because it is closest to the northern celestial pole. The star is also a reference point for navigators, and is a benchmark for where to aim their navigational instruments. It is slightly off the pole, so it has a small circle surrounding it, which is about 1.5 degrees wide. This small circle represents the true north.
When observing the northern sky, you may be able to find Polaris during the daytime. If you go to a clear location, you can even use a telescope to observe it. During the day, Polaris does not move much. You can observe it at dawn or sunrise, but once the sun rises, it should still be in your field of view. If it’s not, Polaris has moved 30 arcminutes in the past three hours.
If you want to know where Polaris is in the night sky, first learn to find Ursa Major. This constellation is home to the famous Big Dipper, or “Little Dipper.” Using the Big and Little Dipper, you can find Polaris by following the stars in the Little Dipper. The stars in Ursa Major point toward Polaris, and the constellation makes a complete circle around it every 23 hours and 56 minutes.
As far as stellar evolution is concerned, the star Polaris is a binary star system. It consists of two stars, Polaris Aa and Polaris B. Polaris Aa is 5.4 solar masses and spectral type F7, while Polaris B is a main-sequence star with a mass of only 1.39 solar masses. Their orbital distance is approximately 2.400 AU, or around 240 billion miles/370 billion km.
Historically, the star’s brightness fluctuates by more than a quarter of a magnitude every four days. This fluctuation had been reducing steadily until 1965, when the star’s period abruptly increased to less than five seconds. In recent years, however, the variability has increased to 4%, a result of its orbit with Polaris Ab. The brighter Polaris is, the more likely we’re going to see it in our night sky.
The star Polaris is a multiple star system with a bright yellow supergiant at its core. It is also known as the North Star. It is a relatively large star that can be seen from Earth, despite its distance. Its main component, Alpha Ursae Minoris Aa, is the brightest star in the constellation. Its radius is 46 times greater than that of the Sun. In addition, it is a Cepheid variable, which fluctuates in brightness over a period of four days.