by Wajiha Iftikhar, 2013-08-13

Alpha Ursae Minoris is a multiple star located in the constellation Ursa Minor. It is commonly known as Polaris, or the North star, and is the brightest star in its constellation. [1] Polaris is located in a close cluster of five stars: Polaris Aa, Polaris Ab, Polaris B, Polaris C, and Polaris D. [2]

Polaris is one of many cepheid variables, which are stars that have a close relationship between their period and luminosity. [3] These stars are often relied on by astronomers for measuring distance. Polaris is the closest of the cepheid variables, so it is studied the most.

With the amount of importance placed on Polaris, it is surprising to see that a controversy has arisen over its location. Toward the end of 2012, an international team of astronomers determined that Polaris may be 30% closer than previously thought. The researchers, led by David Turner, estimated that the distance to the star was actually 323 light years instead of 434. [4, 5] This estimate was challenged in 2013 by Floor van Leeuwen, a former member of the Hipparcos team that determined Polaris' distance previously. He stated that Turner's calculation model was not as accurate as the actual measurements and had more probability of being incorrect. [6, 7]

Polaris' pulsations last for four days and are steadily becoming longer. The variability of Polaris is unstable because it is nearing the end of its life. Polaris used to have greater variability a century ago, but began decreasing until it was almost steady. The variability revived again near the end of the 20th century and is constantly changing every day. [8]

The attached light curve of Polaris (created using the AAVSO Light Curve Generator) spans across 3 months, from early October 2012 to late December 2012. This short period displays small, frequent curves on the graph. [9]

Light curve for Polaris, created with AAVSO Light Curve Generator. [9]
October to December 2012 light curve for Polaris.