What direction does the North Star show and how to find it in the starry sky?

The polar star is perhaps one of the most frequently mentioned luminaries. About it it is said on the pages of fiction, in notes of seafarers, scientific research. His fame, even popularity, the luminary is due primarily to the direction the North Star shows. Its unique position for several hundred years helps to navigate travelers both by sea and by land. In addition, it plays a role in determining the distances on the cosmic expanses, and therefore is the object of many scientific studies. But first things first.

Dancing stars

The answer to the question as to which direction the Polar Star shows is inextricably linked to the place of the luminary on the imaginary celestial sphere. If you observe the stars from the Earth, it seems as if they are moving around the planet, then sinking to the horizon, then emerging again. On the images taken by the camera with a long exposure, it is clear that the luminaries travel along circular trajectories of different diameters. The smaller they are, the closer the star to the pole of the celestial sphere. In the center of the circle of stars formed by the motion, there is a fixed point in the Northern Hemisphere . This is the North Star, or, as it was called by some peoples, the North Nail, Star Prick, Iron or Celestial Kol, Golden Pile.

Features of the situation

Metaphor "nail" is very fortunate: if you continue an imaginary metal rod from the "cap", it is easy to understand what direction the North Star shows. This "nail" pierces the globe exactly at the North Pole, passes through all the inner layers of the planet and again appears at the point of the South Pole. Thus, the North Star in the sky is located on the continuation of the earth's axis. From the North Pole it is less than 1 °.

It should be noted that the Polaris moves in the same way as the rest of the stars. Its apparent fixed place for us is connected with the location on the extension of the axis. Indeed, in fact, rather rapid movement of stars is associated not only with their own movement, but also with the rotation of the planet. Turning around the axis, the Earth turns to the stars then one, then another side. And only the luminaries located above the poles always see the same part of the surface. By the way, at the South Pole also has its own polar star - Sigma Octanta, however it is very dull compared to others. However, after a while everything can change.

Post passed - the post accepted

The North Star shows the direction to the north from around 1100 AD. As close as possible, it will be to the world's pole only in 2100, and then it will begin to disappear. So, from the beginning of time the post of the main index is passed from one luminary to another. This is due to the proper motion of the stars, as well as to the phenomenon of precession of the earth's axis. An imaginary rod piercing the planet also moves: it slowly describes the circles. The reason lies in the peculiarities of the shape of the globe and the action of the force of attraction. The axis passes one circle in almost 26 thousand years.

Approximately 15 thousand years ago in the role of the North Nail acted Vega, the brightest point of the constellation of Lyra. And in a little less than 11 thousand years, she will again take this position. To replace the Polar star in the near future will come Alray (Gamma Cepheus), it will be in 3200. And in 5000, Alray will be replaced by Beta of the same constellation, Alfirk, and then, in 6500, - Alderamin (Alfa Cepheus). In the interval between 8500 and 13 000 years, the position of the Polar Star will be occupied by Deneb and Sadr from the constellation Cygnus.

How to find the North Star?

With the North Nail is associated one very persistent myth, born of his fame and popularity. It seems that the star, which everyone on their lips, should be if not the brightest in the sky, then at least overshadowing many others. However, it is not. The polar star is in the constellation of the Little Ursa and among other luminaries in its composition really stands out. At the same time, in the list of the brightest points of the entire night sky, it occupies only 46th place. Therefore it is important to know how to find the Polar Star.

The main landmark is the Big Dipper. The constellation is familiar to almost everyone since childhood. To discover the North Nail, you need to mentally connect one straight line to the two extreme stars of the Big Bucket - Dubge and Merak. If we continue the line by a distance approximately equal to five segments between Dubga and Merak, then the Polaris will be found at its end. It crowns the tail of the Little Ursa.

How to navigate the terrain along the North Star?

Since the moment the North Nail was in close proximity to the world's pole, it was used as a convenient reference point. The polar star indicates the direction to the north, and even more accurately than a different compass. In this case it is quite easy to determine the sides of the light. It is necessary to drop the perpendicular to the surface from the North Star. If you face him, then the south will be exactly behind, the east on the right, the west on the left.

Not only does the North Star show the direction to the north, it also serves as an indication of the geographical breadth of the terrain. To determine it, you need to measure the height of the light above the horizon. The smaller the value, the closer to the equator. At the North Pole the North Star is located at the zenith. At the equator, it almost merges with the horizon line. It was by determining the angle between the North Star and the horizon in the direction of the north that the sailors of the past centuries guided the terrain, plotted and corrected their route.

On other planets

On the expanses of space there are many analogues of our Polar star. Rotation around the axis is an inalienable property of all planets, and therefore, if you observe the movement of stars from their surface, it is easy to find fixed points pointing to the South and North poles. For Mercury, for example, the polar star - Omicron Ophiuchus, her southern fellow - Alpha constellation Painter. There is the North Nail and the Moon is the Golden Fish Delta.

Significance for astronomy

The Polar Star, or the Alpha of the Ursa Minor, also has a whole set of features that make it unique. Among them - periodic pulsations, allowing to classify the luminary to the class of cepheids. They are characterized by a change in brightness, temperature and size. The period of pulsation of the Polar star is 3.97 days. At the same time, changes in brightness from the Earth are invisible.

Studies have shown that there is a connection between periods of pulsation and luminosity of cepheids. It turned out that the longer the period, the greater the luminosity. This ratio is used in astronomy to determine the distance to remote objects. And since the Polaris is the closest Cepheid to the solar system, its role in calculations can not be overestimated, especially given that with increasing distance to a periodic star, the accuracy of the data decreases.

Non-standard

This property of the Polar Star has attracted the attention of many researchers to it. In the process of studying it became known that the North Nail - cepheid is not easy. Its pulsations have a feature: they gradually fade out. At the end of the last century there was a suggestion that in the early 2000s a star could cease to be a cepheid, something that has never happened in scientific history. However, this did not happen: in 1993, changes in the amplitude of pulsations stopped. In addition, during this time the star became brighter by 15%.

Cosmic Infinity

Data on the luminosity and location of all nearest cepheids are used to determine the distance to distant objects. Applying this method, in the first quarter of the last century the famous Edwin Hubble determined the distance to the Andromeda nebula and proved the existence of other galaxies. Today, based on the methodology, the sizes of many star "commonwealths" are calculated. It also creates a modern understanding of the scale of the universe.

A small "but"

The catch is that for today among researchers there is no common opinion about the distance to the Polar Star itself. The adopted figure, 400 with a small light-year, was obtained by the satellite "Gipparcos" in 1990. However, at the beginning of this century this assessment underwent changes: first it was reduced to 330, then raised to 359 light years. Finally, in 2012, David Turner put forward a new assumption - 323 light years.

As already noted, the Polaris is the nearest cepheid to the solar system. With the reduction or increase in the distance to it, our understanding of cosmic scales also changes. Decreasing the value not only makes the stars and galaxies slightly closer, but also influences the estimation of the size of the universe. Clarifying the distance to the Polar Star will make its corrections in understanding the scales of the cosmos, will force to overestimate the magnitude of the mass of the dark matter, can lead to a revision of certain aspects of the theory of expansion of the universe.

Astronomical features

The direction that the polar star shows, on the whole, depends little on some of its cosmic characteristics. However, they, it can be said, compensate for the modesty of the brightness of the luminary so important for orientation on the terrain .

The polar star is brighter and larger than the Sun. It belongs to the class of supergiants, has a radius exceeding the solar one by 46 times. The luminosity of the North Nail is 2500 times greater than the similar parameter of our star.

But that's not all: Polar is not a single star. It comes in a system of three luminaries, differing in size and brightness. Polar A is the center of the system, the same supergiant, at an impressive distance from it is Polyarnaya V. This star is much smaller, its mass is only 1.39 solar (the mass of Polar A is 4.5 solar). Very close to the supergiant is his companion, Polar Ab (1.26 times the mass of the Sun). Because of the short distance separating the two luminaries, a "humble companion" could not be found for a long time. His image was obtained only with the help of the Hubble telescope.

It turns out, not only where the North Star shows, it makes it unique in the sky. Non-standard cepheid and triple system, it takes the minds of many astronomers. And it looks very symbolic. For a long time in history, the direction of the Polar Star (the path indicated by it) helped to navigate the night in the vastness of the ocean or in an unfamiliar terrain.

Today, when instead of natural signs more often different devices and gadgets are used, the Polar Star remains a reference point in outer space. And although the North Nail in its new quality does not indicate direction, but helps to determine the distance, its value and significance for man and science as a whole does not decrease. And so the researchers are working on a precise definition of how far the Polar Star is removed from the Sun, why its pulsation is dying, and do not disregard this small and even unattractive, in the eyes of a simple terrestrial observer, a star.