Polaris the north star – alpha ursae minoris constellation guide american college in paris

Most of the names used for alpha ursae minoris (alpha umi) reflect the star’s role as the pole star. The name polaris itself is an ellipsis for stella polaris, the latin for “pole star.” in latin, the star is also known as stella maris, or “the sea star.“ in medieval islamic astronomy, polaris was known as mismar, meaning “needle” or “nail,” al-kaukab al-shamaliyy or “the north star,” and al-kutb al-shamaliyy or “the northern axle (or spindle).”

Alpha ursae minoris is slightly off the pole, making a circle around it roughly 1.5 degrees across. As a result of the 26,000 year precession of the earth’s axis, the celestial pole is currently moving closer to polaris. Once it reaches the separation of 14 arc minutes around the year 2105, the pole will start to move away from the star again. Eventually, another star will take over as the navigational benchmark for true north.


Because the little dipper is not bright enough to be seen from areas where there is too much light pollution, the easiest way to locate the north star is by using the stars of the bigger and brighter big dipper in the nearby ursa major constellation.

Polaris, the north star, is found by imagining a line from merak (β) to dubhe (α) and then extending it for five times the distance after dubhe (α). Legend: α uma (dubhe), β uma (merak), γ uma (phecda), δ uma (megrez), ε uma (alioth), ζ uma (mizar), η uma (alkaid) and α ursae minoris (polaris), image: alex zelenko

The stars dubhe and merak in ursa major, also known as the pointers, are the easiest way to find polaris. These are the two bright stars that outline the outer part of the bowl of the big dipper. An imaginary line through these stars leads directly to the north star. Polaris is located at about five times the distance between the pointer stars. Top 50 universities in the world it is the first bright star in that direction.

Polaris marks the end of the handle of the little dipper, or the tip of the tail of the smaller bear. The stars of the little dipper are relatively faint and can only be seen without binoculars in good conditions, with clear skies, no light pollution, and little or no moonlight. Pole star

Polaris lies almost in a direct line with the earth’s rotation axis, which is to say almost exactly “above” the north pole. Washington university university college the star is almost motionless, with all the other stars in the northern sky seemingly rotating around it. The north star never rises or sets at night, but stays in almost the same position above the northern horizon throughout the year, while other stars appear to circle around it. For observers at the north pole, the star lies directly overhead. For observers in new york, it stands 41 degrees above the northern horizon, which corresponds to the latitude of the city. For observers at the equator, polaris sits right on the horizon. The star clmbs higher in the sky the farther north you go and drops below the horizon for observers in the southern hemisphere.

Polaris wasn’t always the north star. Around the year 2500 BC, the celestial pole was near thuban, located in the constellation draco. Around the year 400 BC, the pole was closer to kochab, beta ursae minoris, than it was to alpha umi. Around the year 14,000, the much brighter vega in lyra constellation will be the nearest star to the pole.

Polaris will make its closest approach to the pole on march 24, 2100, when it will come within only 27.15 arc minutes of it. After the 21st century, the celestial pole will move away from polaris and, by the 41st century, it will come near gamma cephei in cepheus constellation.

Unlike the north celestial pole, the pole in the southern hemisphere doesn’t have a bright star close enough to be called the pole star, nor will it have one for the next 2,000 years. The nearest star to the south pole is sigma octantis, located in octans constellation. University rankings times with a visual magnitude of 5.45, it can barely be seen without binoculars, which doesn’t make it very useful in navigation. STAR SYSTEM

Polaris is not a single star, but a multiple star system. The main component, alpha ursae minoris aa, is an evolved yellow supergiant star belonging to the spectral class F7. It is 2,500 times more luminous than the sun, 4.5 times more massive, and has a radius 46 times that of the sun. The star is classified as a cepheid variable, showing pulsations over a period of about four days.