James Webb Space Telescope Finds Unexpected Ultraviolet Radiation Around Young Protostars

Astronomers using NASA's James Webb Space Telescope have spotted puzzling high-energy ultraviolet radiation around five forming stars in a nearby stellar nursery. These young objects, called protostars, are still gathering mass from clouds of gas and dust. The unexpected UV light challenges existing star-formation models. A team led by Iason Skretas (Max Planck Institute for Radio Astronomy) and Agata Karska (Nicolaus Copernicus University, Poland) reported the discovery.

Unexpected ultraviolet in a star nursery

According to the study, astronomers turned the James Webb Telescope toward the Ophiuchus molecular cloud, a stellar nursery about 450 light-years away. They detected strong ultraviolet (UV) radiation around five young protostars there. This was surprising because infant stars normally cannot emit UV. “Young stars are not capable of being a source of radiation; they cannot 'produce' radiation.

So we should not expect it. And yet we have shown that UV occurs near protostars,” research team member Agata Karska said in a statement. The team, including researchers at the Max Planck Institute for Radio Astronomy, said this unexpected UV could force revisions to star-formation models.

Probing the source of the UV radiation

Scientists considered whether nearby massive stars could be bathing the protostars in UV light. They estimated external UV from surrounding stars and dust to predict how molecular hydrogen emission would vary. No such variation was seen, allowing the team to rule out external illumination.

“We can say with certainty that UV radiation is present in the vicinity of the protostar,” said Karska, “Therefore, its origin has to be internal”. Future JWST studies of gas, dust and ice may help reveal how these infant stars generate the unexpected UV.