NORTH STAR

1. Context

2. North Star

• Polaris, known as the North Star or Pole Star, is a very bright star around 2,500 times more luminous than the Sun. It is a part of the constellation Ursa Minor and is around 323 light years away from the earth.
• Since Polaris is less than 1 degree away from the north celestial pole, almost in direct line with the Earth's rotational axis, it appears to sit motionless in the northern sky, with all the other stars appearing to rotate around it.
• Its position and brightness have allowed humans to use it for navigation since late antiquity. Simply the elevation of the star above the horizon gives the approximate latitude of the observer.
• In the northern hemisphere, if you can spot Polaris, you can tell the north and by extension, the other three directions as well.
• However, upon crossing the equator to the south, the North star is lost over the horizon and hence stops being a useful navigational aid.

Image source: The Indian Express

3. Where is North star Located?

• When the earth rotates about its axis, the pole star 'appears' to remain stationary because the position of the earth remains unchanged with respect to the pole star. Pole stars are also known as Polaris or North Star.
• So no matter wherever we are residing on the earth and the time, the position of the pole star remains on this axis.
• However, this is not the case with the other stars in the galaxy. Only, the pole star is visible from the northern hemisphere.
• The pole star will not last forever. The earth's axis has been rotating slightly for the last thousand years. This is called 'Precession', resulting in the pole star shifting from the axis.
• A time will come, the present pole star will vanish and some other star, which is lying on the axis of the earth at that time will become our new pole star.

4. Ptolemy and Columbus

• Polaris seems to have been first charted by the Roman mathematician and astronomer Ptolemy, who lived from about 85 to 165 BC.
• While there is some evidence that the star was used for navigation in late antiquity, it became a central part of human history during the ‘Age of Exploration’.
• Christopher Columbus, on his first trans-Atlantic voyage of 1492, “had to correct (his ship’s bearings) for the circle described by the pole star about the pole”, and the star became an invaluable aid to the European colonists seeking out far-off lands across the seas.

5. Literary Metaphor

• The first well-known instance of the North star appearing in literature outside of a technical treatise on astronomy or a biography of an explorer is in Shakespeare's Julius Caesar, where the eponymous emperor describes himself as being "as constant as the Northern Star".
• However, the "constant" North star was probably not known to the real Caesar (reign 49-44 BC). Also, as the NASA page on Polaris points out, "North Star" is " a title that passes to different stars over time".
• As the Earth's axis of rotation wobbles in the same way as a spinning top, the celestial pole " wanders in a slow circle over the eons, sweeping past different stars.
• About 14,000 years ago, the celestial pole pointed toward the bright star Vega, and it will again point to Vega in about 12,000 years.

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