Astronomers have discovered something unexpected in the birthplaces of young stars: ultraviolet (UV) radiation where it should not exist.
Using the powerful James Webb Space Telescope (JWST), researchers have found clear signs of UV light around five newly forming stars in the Ophiuchus region, a star-forming cloud about 450 light-years from Earth.
This finding challenges current ideas about how stars are born.
The study, published in Astronomy & Astrophysics, was led by researchers from the Max Planck Institute for Radio Astronomy and Nicolaus Copernicus University.
Their focus was on protostars — very young stars that are still gathering material from the clouds around them.
As these protostars grow, some of that material is also blasted out into space in fast-moving streams known as outflows or jets. These outflows are an important and visible sign that a star is forming.
What puzzled the scientists was the strong evidence of ultraviolet radiation in these regions. Normally, protostars are not hot enough to produce UV light. That made researchers ask a big question: if the young stars themselves cannot create ultraviolet radiation, where is it coming from?
To investigate, the team used JWST’s Mid-Infrared Instrument (MIRI), which can detect light that cannot be seen from Earth because our atmosphere blocks it. MIRI is especially good at detecting molecular hydrogen, or H₂, the most common molecule in the universe.
Molecular hydrogen is usually hard to observe in cold space, but when material is heated by shock waves from a star’s outflow, it starts to glow. That glow can reveal a lot about the environment around the star.
The telescope focused on five protostars located at different distances from larger, nearby stars in the same cloud. These larger stars, known as B-type stars, are hot enough to give off ultraviolet radiation. One possibility was that their light was reaching the protostars and affecting their surroundings.
However, when the team analyzed the data, something did not add up. Although the protostars were exposed to very different levels of external UV light, their molecular signals looked surprisingly similar. That suggested that the ultraviolet radiation affecting them was probably not coming from outside sources.
This led scientists to an even more surprising conclusion: the UV radiation must be coming from processes happening close to the protostar itself. One possibility is that it is produced by powerful shocks created as material crashes onto the surface of the forming star or as it is expelled through high-speed jets. These violent processes could generate enough energy to produce ultraviolet light, even though the protostar itself is still relatively cool.
This discovery changes how scientists think about early star formation. Ultraviolet radiation can influence the chemistry and structure of the material surrounding a young star, including the gas and dust that may one day become planets. If UV light is present at this early stage, it could affect how planetary systems form and evolve.
The researchers say that future studies will look more closely at both the gas and the icy dust particles in these stellar nurseries to better understand the source of the UV radiation. They also plan to examine more protostars and larger areas of space to see how common this phenomenon really is.
Thanks to the extraordinary power of the James Webb Space Telescope, astronomers are now uncovering hidden forces at work in the darkest corners of space — and rewriting what we know about how stars, and possibly even planets, are born.
Source: Max Planck Society.
