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Big and Little

May 5, 2013

Eighty-eight constellations cover the sky like the patches of a giant quilt. Some are huge, while others are tiny. The two most extreme constellations are a bit of a surprise, because the largest is a dud while the smallest is a spectacle.

The largest constellation is so obscure that you may never have seen it. Hydra, the water snake, serpentines across the sky just like its namesake. It stretches all the way from the constellation Cancer to the constellation Libra.

Despite its vast size, Hydra has no brilliant stars and only one moderately bright star, Alphard. It’s an orange giant that’s bright enough to see even from most suburbs. With a good star map, you can find Alphard high in the southwestern sky as night falls. There aren’t any other bright stars around it, which enhances the view.

On the other hand, the smallest constellation is brilliant. Crux, better known as the Southern Cross, is so well known that it even appears in songs — “Blue Wide Open” by Sieges Even and “Southern Cross” by Crosby, Stills, and Nash, among others.

The Southern Cross boasts four bright stars. There is a catch, though: as its name suggests, you need to live far to the south to see it. In fact, it’s best seen from the southern hemisphere, although it’s also visible from Hawaii and much of Mexico.

Hydra and Crux illustrate a paradox of constellations: bigger isn’t always better. Instead, small constellations like the Southern Cross can pack a big stellar punch.


Script by Ken Croswell, Copyright 2013

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