CAPE CANAVERAL, Fla. — Astronomers have found what appear to be massive galaxies that are only 600 million years old, indicating that the early universe may have had a stellar fast-track that created these "monsters."

While the James Webb Space Telescope has discovered even older galaxies that are only 300 million years old, it is the size and maturity of these six apparent mega-galaxies that have astounded scientists. On Wednesday, they released their findings.

This close to the universe's creation, Swinburne University of Technology's Ivo Labbe and his team expected to find tiny baby galaxies rather than these giants.

He explained in an email that while the majority of galaxies in this era are still small and only gradually growing bigger over time, "there are a few monsters that fast-track to maturity." It is unclear why or how this would function.

The six objects appear to each be billions of times heavier than the sun. According to the researchers, who reported their findings in the journal Nature, one of them may have stars that are up to 100 billion times heavier than our sun in terms of their combined mass.

However, according to Labbe, these galaxies are thought to be incredibly compact, fitting as many stars in a relatively small area of space as our own Milky Way.

The findings still need to be confirmed, according to Labbe, who added that initially he and his team didn't believe the findings were accurate because galaxies, as developed as the Milky Way, couldn't exist so early in time. Some team members believed they had made a mistake because of how large and bright the objects appeared to be.

"We were stunned," Labbe said, to put it mildly.

They are referred to as "universe breakers" by Joel Leja from Pennsylvania State University, who participated in the study.

Leja said in a statement that the discovery that massive galaxy formation started very early in the history of the universe "upends what many of us had thought was settled science." It seems that we discovered something so unexpected that it actually poses difficulties for science. It casts doubt on the theory of early galaxy formation as a whole.

The $10 billion Webb telescope was launched just over a year ago, and among the first data set it produced were these galaxy observations. With the Hubble Space Telescope's 33rd anniversary approaching, NASA and the European Space Agency's Webb is widely regarded as its replacement.

Contrary to Hubble, the larger and more powerful Webb can use its infrared vision to see through dust clouds and find previously undiscovered galaxies. The first stars and galaxies that formed after the universe was created 13.8 billion years ago are something that scientists hope to observe in the future.

The scientists are being cautious in calling these candidate massive galaxies for the time being while they wait for official confirmation through sensitive spectroscopy. Some of the objects may not be galaxies, but rather hidden supermassive black holes, according to Leja.

The odds are good that at least some of them will turn out to be galactic giants, Labbe said, even though some may end up being smaller. "The following year will reveal,"

To "let go of your expectations and be ready to be surprised," Webb advised, is one of his early lessons.