Astronomers stumble across nine galactic platypuses

Analysing more than 2,000 sources from several surveys conducted by the James Webb Space Telescope (JWST), a research team from the University of Missouri identified nine objects that defied standard classification. Lead author Haojing Yan likened them to platypuses because they possessed a combination of features that should not exist together.

These cosmic platypuses existed between 12 and 12.6 billion years ago. They appear as tiny, point-like dots even to JWST. This is a characteristic usually reserved for bright stars or active galaxies known as quasars. However, there is a showstopper for both options.

The nine sources are far too distant to be stars and the data collected by one of JWST’s spectrometers, an instrument that separates light into its constituent wavelengths, lacks the spectral hallmarks of quasars.

At the heart of every quasar, a supermassive black hole is surrounded by a swirling disc of fast-moving gas. This movement produces broad spectral lines in the data because of the Doppler effect. Yet, the platypuses betray much slower gas movement.

The mystery deepened when the team compared these nine objects to the ‘green pea’ galaxies discovered by citizen scientists in 2007. These were named because strong emission from oxygen atoms gives them a distinctly green hue in optical images.

While the spectra are similar, the newly found objects were much more compact and point-like.

The team estimates the platypuses to have ages between 110 and 170 million years and a radius ranging from 1600 light years to 3100 light years, leading the team to suggest the objects represent a missing link in galaxy evolution.

This discovery supports the ‘monolithic collapse’ idea, which states that galaxies start forming from an isolated, compact core.

“I think this new research is presenting us with the question, how does the process of galaxy formation first begin? Can such small, building-block galaxies be formed in a quiet way, before chaotic mergers begin, as their point-like appearance suggests?” asks Yan.

The team is currently preparing follow-up studies but for now, these nine platypus galaxies challenge our understanding of the early Universe and galaxy evolution.

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arxiv.org/pdf/2509.12177