Kaboom, indeed.

In a cascade of superlatives that belies the traditional cerebral reserve of their profession, astronomers reported Monday that they had seen the brightest and most powerful stellar explosion ever recorded.

The cataclysm — a monster more than a hundred times as energetic as the typical supernova in which the more massive stars end their lives — might be an example of a completely new type of explosion, astronomers said. Such a blast — proposed but never seen — would explain how the earliest and most massive stars in the universe ended their lives and strewed new elements across space to fertilize future stars and planets.

“It is quite possibly the most massive star that has ever been seen to explode,” said Nathan Smith of the University of California, Berkeley, who estimated the star as “freakishly massive,” about 150 times the mass of the Sun.

“We’re really excited about this,” Dr. Smith said. “If it really is what we think it is, it forces us to rethink how massive stars die.” He led a team of astronomers from the University of California, Berkeley, and the University of Texas, who have submitted a paper about the supernova to the Astrophysical Journal and discussed the results in a news conference from NASA headquarters today.