The funny thing about discoveries is that they often produce new mysteries, too. This year was no exception, as many remarkable space science findings generated puzzling problems for astronomers to look into.

In some cases the puzzles are brand new. Other times a discovery merely confirms how little we knew. Either way, there's plenty for astronomers to do.

Here then are the Top 10 Space Mysteries that astronomers will be pondering in the New Year and beyond:

1. Dark Energy

Nobody knows what the heck it is, but it is officially repulsive. And man is it powerful! More powerful than gravity, even.

While gravity holds things together at the local level (and by local I mean within galaxies and even between them, forming galactic clusters) some unknown force is working behind the scenes and across the universe to pull everything apart. Scientists have only come to realize this dark force in recent years, by discovering that the universe is expanding at an ever-increasing pace.

Having no clue what it is, they've labeled it dark energy.

The past year was a good one for proving that dark energy is at work. Calculations have been refined: The repulsive force dominates the universe, comprising 65 percent of its makeup.

(Similarly unseen and exotic dark matter makes up 30 percent of the universe, leaving us with a universe that contains just 5 percent normal matter and energy.)

Two curious ideas related to the accelerating expansion, both of which emerged in 2002: All galaxies are destined to become frozen in time or, perhaps, time never ends.

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