These objects show point like features that would normally place them in one of two categories, either stars within the Milky Way or quasars, the bright cores of distant galaxies powered by supermassive black holes. When the team examined their light with spectroscopy, they saw only narrow emission lines instead of the broad lines that mark quasars, a pattern that indicates active star formation typically observed in galaxies.
Because the objects combine characteristics that astronomers do not usually see together, the researchers nicknamed them platypus galaxies, referring to the animal that blends traits from different groups. Each property by itself is familiar, but their combination suggests a type of system that has not been recognized before. Each property on its own is familiar to us, Haojing Yan, a Mizzou astronomy professor and co author of the study, said. But when added together, they create something weve never seen before.
The discovery comes as scientists continue to analyze JWST deep space images, which show the universe as it appeared billions of years ago and give new insight into how galaxies formed. These platypus galaxies raise questions about standard models that describe galaxies assembling mostly through mergers and often through violent collisions.
Our ongoing theory states that galaxies were formed by merging with other galaxies, often through violent collisions, Yan said. But these platypus galaxies may have formed quietly, without such dramatic events. This suggests the early universe may have been more flexible and creative than we thought.
Researchers say the current data are not yet strong enough to replace existing theories, but the observations point to additional ways that galaxies may have taken shape in the early cosmos. The team now plans to obtain more information on hundreds of other cosmic objects to test whether they also show the same combination of point like appearance and narrow line spectra.
This effort will involve collecting spectroscopy for each candidate, breaking their light into a rainbow and reading it like a barcode to determine properties such as age, chemical composition, and patterns of star formation. The results should clarify how these systems compare with other galaxies at similar distances and whether they represent a distinct population.
If these objects are really a new type of galaxy, it tells us weve been missing part of the story, said Bangzheng Tom Sun, a graduate student in Yans lab and co author of the study. And were just beginning to uncover it.
The study A new population of point-like, narrow-line objects revealed by the James Webb Space Telescope was presented at the 247th meeting of the American Astronomical Society and lists Mizzou undergraduate student Riley Shive as a co author. The work underscores how JWST data are enabling students and researchers to probe structures in the early universe that blur traditional categories of stars, quasars, and galaxies.
Related Links
College of Arts and Science at University of Missouri-Columbia
Understanding Time and Space
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