SOUTH BEND — For nearly 2,000 years, it's been the one puzzle astronomers haven't been able to fully solve. But now, one Notre Dame professor thinks he may have discovered the origin of the star of Bethlehem.

Look at an artist's rendering of Jesus' birth and you can always find it.

Listen to songs like "We Three Kings" and it's clear.

The star of Bethlehem plays a pivotal role in the Christmas story.

Still, it's role in the Bible is fairly small. In fact, there's only one reference — in the Gospel of Matthew. "Where is he born the King of the Jews?" it reads. "For we have seen his star in the East, and have come to worship him."

But did that star really exist? If so, where was it? What was it? Why was it so bright?

They are questions Notre Dame Astrophysicist Dr. Grant Mathews began to ask about three years ago. And what he found took him by surprise.

"The standard viewpoint over the years is that it's a massing of planets, or what we call planetary conjunction, when planets move past each other," he said.

But here's the curious thing:

Mathews says this conjunction wasn't just a few planets.

"Basically every known planet at the time was amassed all at once," he said.

And it wasn't anything astronomers had recorded before.

"To have all of them line up like that at once was a very rare event," Mathews said.

On April 17, 6 B.C., Jupiter, Saturn, the sun, and the moon all aligned in the constellation Aries. Venus and Mars lined up in neighboring constellations.

Dr. Mathews says, for the so called "wise men" this would have had great significance.

"That would have signaled to the Magi that there was newborn leader with a special destiny — a very powerful leader that was going to appear in Jerusalem," he said.

But Mathews wasn't convinced the planets fully explained that bright light in the East referenced in the Gospel of Matthew. So he went "back in time" to see if something else might have been there too.

He found two likely candidates. The first, is a nova — a combination of two stars that shines thousands of times brighter than a normal star.

The second is a supernova — a single star 10-20 times the size of our sun that collapses in a massive nuclear explosion. Supernovas can create light up to 100 million times as bright as a normal star.

"It is as bright as this entire galaxy of stars," Mathews said, pointing to a picture from NASA's Hubble Telescope.

Using other Hubble images, pictures from the Chandra X-Ray Observer Satellite, and ancient Chinese astronomy charts, Mathews scanned the skies and was astonished.

"Sure enough, in the archives, there is a supernova in Aquilla — the constellation they saw. And it's about 2,000 years old," he said.

It's called Kestovan 75, and it appeared about the same time as the planetary alignment 4 to 6 B.C.

But is that close enough to Jesus' birth?

Some Biblical scholars say it's possible. Records of the birth aren't completely accurate. And for that matter, neither is the determined age of the star.

And that's not enough to prove the star's existence to everyone.

"It's a really neat coincidence, but I don't know if it adds any weight to the Christmas story," said one South Bend resident.

"It neither proves nor disproves, because a faith story needs no proof," said another.

Still, for some it's a reinforcing message of the reason for the season.

"I think that's pretty much a miracle," said a man from South Bend.

"I'll still believe what I've always believed," said a woman from Niles.

For Mathews, there may never be a certain answer. But he's convinced this may be the brightest light shined yet on a Christmas mystery now centuries in the making.

The ages of those potential stars can only be accurately placed within about 100 years. But Dr. Mathews hopes new technology will be able to narrow the mystery down even further.

He's working on a book about his research and hopes to have it published by next year.