How big is yonder star group?

Posted by Michael Bakich
on Monday, February 12, 2007

The sky contains approximately 41,253 square degrees of measurable "surface" area. Trust me, I'm going somewhere with this, and it's not to math class.

Since 1930, when astronomers formalized the number of constellations and their boundaries, 88 star patterns have filled this area. No gaps exist between constellations, and there are no overlaps or shared stars.

Because constellation boundaries follow lines of right ascension and declination, we can calculate the area each occupies. Here are the top 10 constellations by size. I've rounded the areas off to the nearest degree, and sky percentages to the nearest 0.01 percent.

Every time I scan this list, I find another surprise. You can see the three largest constellations at the same time in the Northern Hemisphere spring sky. Oh, and Orion, many observers' favorite constellation, doesn't appear in the top 10 — it ranks only 26th in size. What a letdown.

What surprises you about this list? E-mail me here.

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