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December 26, 2017

Until almost a century ago, the constellations were little more than stick figures. Various astronomers connected different dots to define their characters. And they used different borders to define each constellation’s chunk of celestial real estate.

Order was imposed upon the heavens in 1930. Belgian astronomer Eugene Delporte defined the borders of the 88 official constellations for the International Astronomical Union. Those borders have been maintained ever since.

The list of constellations includes Aries, the ram. It’s well up in the east as night falls right now, and stands due south a few hours later.

Despite its fame as a member of the zodiac, Aries includes only three bright stars. A fourth star is added to those to create a stick figure that looks like a lopsided boomerang.

But the formal constellation covers a much wider area — about one percent of the entire sky. It looks like a horizontal rectangle with chunks missing from the lower left and top right corners.

Its borders consist of 12 individual lines. When Delporte drew those borders, they followed strict lines of declination and right ascension — the equivalent of latitude and longitude on Earth’s surface.

Since then, thanks to a wobble in Earth’s axis, the borders have shifted position a bit. So some day, astronomers will have to redefine the borders — or watch as the stars of all the constellations shift across the borders of their neighbors.

More about Aries tomorrow.


Script by Damond Benningfield

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