An international team of scientists examined images taken by the James Webb Space Telescope (JWST) and confirmed the conclusions drawn earlier from observations using the Hubble Telescope: protoplanetary disks can persist around stars for tens of millions of years.
The NGC 346 nebula in Hubble (left) and James Webb (right) images. Image source: nasa.gov
«James Webb helped image the nebula NGC 346 in the dwarf galaxy Small Magellanic Cloud, located near our Milky Way. This nebula, in which active star formation occurs, according to some criteria, repeats the conditions that existed in the early Universe – in particular, it lacks the heavy elements that are traditionally associated with the formation of planets. Spectral analysis showed that protoplanetary disks are still present around the stars in this region. This contradicts the theory that these disks should fly apart within a few million years.
Yellow circles indicate ten stars that became objects of study
«Hubble observations of NGC 346 since the mid-2000s have revealed many stars approximately 20–30 million years old that apparently still have planet-forming disks,” NASA notes. Without detailed evidence, such an assumption seemed controversial, but James Webb confirmed it: disks in neighboring galaxies have much more time to collect dust and gas from which the basis of a new planet is formed.
Scientists have proposed two explanations for this phenomenon. The first is that the stars in NGC 346 create “radiation pressure” that causes protoplanetary disks to take longer to disperse. The second explanation is that the large cloud of gas required to form a star like the Sun in an environment with fewer heavy elements naturally forms larger disks that take longer to disperse.