North Star Dims for a Century...

...Suddenly Gets Brighter

After about one hundred years of growing increasingly dimmer, the North Star (Polaris), according to international astronomers, is now growing brighter. Why it’s happening is a mystery to astronomers.

According to the press release of the University of St. Andrews, “The Northern Star, whose vibrations were thought to be dying away, appears to have come to life again.” [St. Andrews: “The Pole star comes to life again”] Dr. Alan J. Penny (of the School of Physics and Astronomy, University of St. Andrews) will present the conclusions of a nearly continuous observation of Polaris over a 4.5-year period by the 350-member team. The presentation by Dr. Penny was conducted on Monday, July 21, 2008, at the Cool Stars 15 conference. The CS15 conference, the world's largest international astronomical conference, is being held from July 21 to 25, 2008, at the University of St. Andrews in Scotland.

The St. Andrews press released went on to say, “The astronomers were watching Polaris in the expectation that they would catch the star switching off its vibrations completely when they made the surprising observation of its revival.” The astronomers wanted to examine Polaris to learn more about magnitude variation in Cepheid variable stars—because Polaris is a type of Cepheid. That is, a Cepheid variable star is a type of star that gets brighter and fainter on a regular basis—however, astronomers are not sure just how Cepheids function, nor why.

Cepheids help to determine the size of the Universe because they are used as “standard candles” (or "cosmic yardsticks") to determine distances to various astronomical bodies. In the case of Polaris, it has a brightness cycle of four days (getting brighter and fainter in cycles of every four days).

Because of the dimming of Polaris, astronomers thought Polaris, like many older stars, was changing its physical structure. They were hoping to learn more about the aging of stars from observations with Polaris.

However, when these astronomers were measuring Polaris, they found quite a surprise. Dr. Penny explains how they found that Polaris was gaining in brightness, "It was only through an innovative use of two small relatively unknown telescopes in space and a telescope in Arizona that we were able to discover and follow this star's recovery."

[The Herald: “North Star glows more brightly after fading away”]