Quirks & Quarks

What are the major visible changes in the night sky in the last 3,000 years?

In the past 3,000 years, the rotational axis of the Earth has shifted, and that has changed the position of the pole star and the constellations.
The position of the pole star (North Star) changes as the Earth's axis shifts toward North America (green arrow) over time. Today it is Polaris, 3,000 years ago it was Thuban, in 12,000 years it will be Vega. (NASA/JPL-Caltech)
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This week's question comes to us from John Lawrence in Dunrobin, Ontario.  He asks:

What are the major visible changes in the night sky in the last 3,000 years, as seen by the naked eye?

Dr.John Moores, an associate professor in the Department of Space Science Engineering at York University in Toronto has the answer.

There are two major changes that have taken place in that period. The first is related to changes in the rotational axis of the Earth. Imagine the changes to the rotation of a spinning top. These changes also occur in the Earth's rotation over time as well.

This means that the North Star - or pole star - would have been in a different position from today. In fact, the position held by the North Star - or Polaris - as we know it, was actually occupied by a different star altogether. The North Star then was Thuban, in the constellation Draco. 

Also, the constellations would have looked the same as we know them today, but they would have been in a different region of the night sky. A final difference is that the night sky 3,000 years ago would not have included the many satellites we can see in a dark, clear sky today.       

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