The North Star has changed its appearance: now it shines more
The North Star was considered the "perfect" star, but now the brightness exceeded by 2.5 times that perceived by the Romans
The North Star, which is the most constant reference point in the sky, is actually subject to anomalies. In the last fifty years it has become 10% brighter than in previous decades!
Going back through the centuries, today the Pole Star would be about two and a half times brighter than the one seen by Julius Caesar two thousand years ago.
It seems that the star is closer to Earth than previously thought: only 310 light years, instead of 430.
By scrutinizing with greater precision the northern celestial star to which navigators have clung over the centuries, astronomers have discovered anomalies and surprising changes.
In the 19th century its brightness was twenty percent lower than today and, going back in time, in the year 1500, according to the precious testimonies of the great Danish astronomer Tycho Brahe, it must have appeared even weaker.
Using the magnitude scale created by the Greek Hipparchus in 120 BC (he gave six values and 1 corresponded to the brightest star in the sky) Ptolemy, capable of perceiving even musical harmony in the stars, defined it as third magnitude.
Now, however, it is of second magnitude: the more the value decreases, the brighter the star is. In conclusion today the Pole Star would be two and a half times brighter than how Julius Caesar saw it two thousand years ago.
This means that the star is closer to the Earth than previously thought.
The Polar Star belongs to the Cepheid family, famous in the firmament for their regular life, transforming them into "reference candles", as astronomers have called them, precious for measuring cosmic distances. Their light shines with an exact rhythm, a pulsation with a maximum and a minimum which for Polaris is about four days. But here too an anomaly has emerged: this period is lengthening by about eight seconds per year. Therefore the theories that explain the behavior of the navigators' star must be revised while its reputation for unalterable constancy is undermined.
The position of the star remains unchanged. But it won't always be like this. Due to the movement of our Earth's axis which traces a circle in the sky, the reference star obviously changes. In approximately six thousand BC, Polaris was the star Iota of the constellation of the Dragon, in three thousand BC it was Thuban of the same constellation. At the time of Classical Greece Kochab of Ursa Minor (Little Dipper) appeared, while in two thousand years it will be the star Vega.
