The essence of the North Star

The North is the brightest star in the Big Dipper. With the Northern Hemisphere observer, it occupies a special place.Only a half degree difference from the Earth axis, so when the Earth turns around day and night, the North is almost stationary right on the North Pole.

In modern astronomy, this star is a seven-star array, the seven brightest in the boundary of the Big Dipper constellation in the northern hemisphere. The Big Hero is outside the 7 stars and many other stars.

Westerners also name these stars separately. After being systematized on astronomical maps, stars have astronomical names in the constellation Ursa Major .

"Big Dipper" is a folk call to talk about a star group consisting of many stars.

Location 7 The North Star star group is bright in the sky.

Because the Earth is spherical, the position of the North Pole for the horizon depends on the position of the observer. Specifically, the angle between the horizon north and north is equal to the latitude of the observer. For example, looking from the equator (latitude 0), the North is located at the northern horizon. When traveling to Houston, Texas (latitude 30), North Mountain is 30 degrees above the horizon. When moving to the right North, the North Pole is 90 degrees above the horizon, which is right above the observer's head.

In the past, northern sailors measured the angle between the horizon and the North Pole to determine their latitude. However, latitude alone is not enough to determine a position on the Earth's surface. So although many cultures successfully implement expeditions on the sea just by observing stars, weather and ocean currents, 'longitude problems' were the horrors of sailors for many years. century.

Currently the Southern Hemisphere has no stars corresponding to the North Pole. Moreover, the North Pole is not an accurate indication of the North Pole, because in addition to the 24-hour rotation, the Earth axis also moves in a cone. Therefore, the earth projection in the sky will be a circle of 26,000 years. So the North Pole also changes over time. 5,000 years ago, the Earth's axis was directed at the Draco and North Pole constellation, which was Thuban. Similarly, 12,000 years later, Vega in Lyra constellation will be the North Star.

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