Strange cosmic objects spotted by NASA’s James Webb Space Telescope (JWST) are currently intriguing astronomers. The strange observations show features of both stars and galaxies, leading researchers to call them “platypuses,” named after the animal with a hodgepodge of parts. These features could provide clues about how galaxies formed billions of years ago, early in the life of the universe.
At first glance, the new objects look like stars, small points of light in the JWST data. Scientists found, however, that closer observations revealed more galaxy-like features. “If you look at each of these features separately, just putting them together makes a platypus look so strange,” said Haojing Yan, an astronomer at the University of Missouri. “Our objects are exactly like that.”
Close but not quite
Shortly after JWST came into existence in 2021, it began revealing a number of unusual objects of unknown origin. Inspired by these discoveries, Yan and two of his students began exploring other compact sources in an effort to determine whether any strange objects had escaped our attention.
The researchers looked at about 2,000 objects, visually examining each one for oddities. This left nine peculiar small objects slightly larger than a single point of light in the data. Usually these compact objects are classified as point sources and most are stars. But upon closer inspection, the researchers realized that the objects were larger and more diffuse than a point source, leading them to classify the objects as “point.”
“It’s very close to a point source, but not exactly,” Yan said.
However, instead of the broad emission lines linked to stars, the researchers found narrow lines indicating active star formation usually found in galaxies. They turned their gaze towards quasarsquasi-stellar objects propelled by the supermassive black holes in galactic centers. Quasars – a type of active galactic nuclei (AGN) – are classified based on the light they emit.
But even though the new objects closely resemble known classifications of quasars, they don’t quite match. For one thing, they’re darker than expected. Their spectral footprint is also narrower than that of quasars, even at narrow lines.
“Our objects are not quasars,” Yan said.
This does not, however, prevent them from being a different form of AGN. Yan said it could be a class of objects known as Narrow-line AGN. However, known narrow-line AGNs tend to appear as point sources rather than point sources.as.
“If our objects end up in the narrow AGN classification, they must be of a new type,” Yan said.
Another possibility is that the unusual objects form stars. galaxies. Although all galaxies form stars, galaxies that form stars do so at an accelerated rate. They also produce narrow emission lines, “like duckbills are normally seen in ducks,” Bangzheng Sun, also of the University of Missouri, said at the news conference.
If the objects are star-forming galaxies, Sun says, they must be young – no more than 200 million years old. “They’re still in their infancy,” he said.
Additionally, if the strange spots are galaxies, their slightly enlarged size is difficult to understand. “These galaxies must be there, forming stars from the inside out,” Sun said. “This is a process we’ve never seen before.”
The rollback process could occur in multiple galaxies, Yan told Space.com. But while most stellar production induces violent, chaotic motion, “our objects would imply that such processes could take place very peacefully (as opposed to the usual merger process) so that their point-like appearance remains intact,” Yan said by email.
Researchers believe they have identified a population of these new objects, but the question remains whether they are a new form of AGN or strange young galaxies. They hope to find more examples in future observations with JWST.
“These nine items are special,” Yan said. “These are our platypuses.”
