In last week’s column, I wrote about the springtime constellation Corona Borealis, the northern crown, and encouraged you to go out to find it.

I hope you’ve done so, because sometime this spring or summer it will get a new star. Well, not really a “new” star, but certainly one that few alive today have ever seen.

The star is called T Corona Borealis — aka the “Blaze Star” — and it will change the appearance of this constellation for a few days.

Such a new star appearing out of nowhere is not common, of course, but it does happen occasionally.

Ancient sky watchers called such a phenomenon a “nova” — a word that comes from the Latin “novus,” meaning new.

As it turns out, however, a nova is anything but new.

Back when I was a kid first learning about all things celestial, astronomers defined a nova as a dying star.

It had nearly exhausted its nuclear fuel before blasting into space much of its atmosphere and settling back into a small, degenerate stellar corpse known as a white dwarf. (I know this because I just checked one of my favorite childhood books from 1958 — yes, I’ve kept them all!)

Today, however, we believe that a nova originates from two stars orbiting one another. One is a tiny and dying white dwarf star and the other a red giant star with a bloated atmosphere.

As hydrogen from the red giant is sucked in by the nearby white dwarf’s intense gravitational pull, it accumulates and heats up on the surface until it triggers a runaway thermonuclear explosion.

Such blasts can cause a star to become tens of thousands of times brighter for a short time, and if the star is near enough, it might just appear as a new star in our night sky.

Astronomers now know that some of these novae can explode more than once. T CrB (in astronomers’ shorthand) is just such a star and is classified as a “recurrent” nova.

Its eruptions have been documented as far back as October 1217 by the abbot of the Ursberg Abbey in what is now known as Germany. Its last appearance came in 1946.

Stars like T CrB are rare; in our Milky Way galaxy of hundreds of billions of stars, we know of only about 10.

So, if and when it erupts, just about every telescope on this planet and in space will be aimed in its direction.

That’s because such novae are thought to eject into space elements critical to the formation of life, such as carbon, nitrogen and oxygen, and watching the process unfold with modern instrumentation has astronomers giddy with excitement.

Those of us without powerful telescopes will not be left out of the excitement, however.

T CrB may become as bright as the constellation’s main star Alphecca and easily visible to the unaided eye for a few days, before fading back into the darkness from which it came, building up explosive hydrogen for its next eruption, possibly around the beginning of the 22nd century.

In the meantime, keep your eyes on Corona Borealis; I’d hate for you to miss this truly once-in-a-lifetime sight!