NASA scientist Rebekah Hounsell has called it "a once-in-a-lifetime event that will create a lot of new astronomers out there."

Once you see it, however, don't get too attached to it. The so-called recurring nova star, T. Coronae Borealis, which periodically mutates into an earth-size hydrogen bomb, will flame out in less than a week. But if you're around, you'll get another shot at seeing it at the beginning of the 22nd century.

Precisely when the nova, affectionately known as T CrB in the astronomical community, will be visible is unclear, astronomers say, and nailing the timing is a bit more complicated than predicting what time the sun will rise.

It could be sometime this month, maybe even this week, or maybe not until winter. But the evidence is unmistakable that it will appear soon.

When will the star explosion happen?

It already has, about 3,000 years ago, around the time of King David (he who felled Goliath in one of the great upsets in human history); Zoroaster; the Iron Age; and the golden age of the Villanovan people, who overran northern Italy.