Strange cosmic objects identified by NASA’s James Webb Space Telescope (JWST) are challenging existing astronomical classifications. Researchers have observed features that combine characteristics of both stars and galaxies, leading scientists to label them as “platypus” galaxies. This intriguing nomenclature reflects their eclectic nature and suggests that they may offer insights into the formation of galaxies during the universe’s early years.
The peculiar objects first appeared in JWST data shortly after the telescope began its operations in 2021. These objects initially resembled stars — small points of light — but subsequent analysis unveiled more complex, galaxy-like features. “If you look at any of the features separately, just putting them together makes a platypus look so odd,” stated Haojing Yan, an astronomer at the University of Missouri. He made these remarks during a news conference held on January 6, 2023, at the annual meeting of the American Astronomical Society in Phoenix.
In their quest for understanding, Yan and his team investigated approximately 2,000 compact sources, meticulously examining each one for unusual characteristics. Ultimately, they identified nine distinctive objects that were larger and more diffuse than typical point sources, leading to their classification as “point-like.” Yan noted, “It’s very close to a point source, but not exactly.”
Upon further investigation, the researchers discovered that, unlike stars, which emit broad lines of light, these objects exhibited narrow lines indicative of active star formation — a hallmark of galaxies. This finding led Yan’s team to consider the possibility that they might be a new class of Active Galactic Nuclei (AGN), a category that includes quasars. While the newfound objects share similarities with known quasars, they diverge in significant ways.
For instance, these objects are dimmer than expected and their spectral signatures are narrower than those of typical narrow-line quasars. “Our objects are not quasars,” Yan clarified.
Graphical representations illustrate how these spectra differ from those of known quasars, emphasizing the pronounced narrow peaks that caught the researchers’ attention. The graphic presented during the conference showcased the spectrum of galaxy CEERS 4233-42232, highlighting the differences in light emissions typical of distant point-like sources.
One potential classification for these mysterious objects is as narrow-line AGNs. However, existing narrow-line AGNs generally appear as point sources, complicating the categorization of these new discoveries. Yan suggested, “If our objects end up within the narrow-line AGN classification, they must be of a new kind.”
Another intriguing possibility is that these objects represent young star-forming galaxies. All galaxies undergo star formation, but star-forming galaxies do so at an accelerated pace, producing narrow emission lines. Bangzheng Sun, also from the University of Missouri, commented during the conference, “If the objects are star-forming galaxies, they must be young — no more than 200 million years old. They are still in their infancy.”
The researchers noted that if these objects are indeed galaxies, their slightly expanded size raises questions about their formation. Sun explained, “These galaxies must be sitting there, forming stars from the inside out. This is a process we have not seen before.”
Yan added that this inside-out process may occur in multiple galaxies. He remarked that while most stellar production induces chaotic motion, “our objects would imply that such processes in them could be happening in a very peaceful way, so that their point-like appearance remains intact.”
The team believes they have identified a new population of these objects, yet whether they represent a novel form of AGN or unusual young galaxies remains uncertain. Yan expressed optimism about future discoveries, stating, “These nine objects are special. They are our platypuses.”
As observations continue with the James Webb Space Telescope, astronomers hope to uncover more examples of these enigmatic objects, further illuminating the mysteries of the universe’s early formation.
