See the torn apart “planetary factory” around a distant star

Planetary environments can be much more complex and chaotic than previously expected. This is evidenced by the new image of the star RU Wolf – a star in the constellation Wolf, located in a young star-forming region. Its siral structures seem to be torn apart and scattered around the star. Fresh shot with Atacama Large Millimeter/Submillimeter Array (ALMA). The results of the study of the find are published by the Astrophysical Journal.

All planets, including those in our solar system, are born in disks of gas and dust around stars, the so-called protoplanetary disks. Thanks to ALMA, we have stunning high-resolution images of many of these “factories” of planets, showing dusty discs with many rings and gaps that hint at the presence of emerging planets. The most famous examples of this are stars like HL Tauri and TW Hydra.

But the discs are not necessarily as neatly arranged as initial observations of dust show. A new image of ALMA RU Wolf, a young variable star in the constellation Wolf, showed a giant set of spiral arms of gas extending far beyond its more famous disk of dust. This ruptured spiral structure, reminiscent of a “mini-galaxy”, extends nearly 1000 astronomical units (AU) from the star. This is much farther than a compact disk of dust, which typically extends up to about 60 AU.

Previous ALMA observations of RU Wolf have already revealed signs of ongoing planet formation, as hinted at by dusty gaps in its protoplanetary disk.

But we also noticed some faint carbon monoxide (CO) gas structures that extended beyond the disk. This is why we decided to observe the disk around the star again, this time focusing on gas rather than dust.

Jane Huang of the Smithsonian Center for Astrophysics and lead author of the article

Protoplanetary disks contain much more gas than dust. While dust is essential for the accumulation of planetary cores, gas creates their atmosphere.

In recent years, high-resolution observations of dusty structures have revolutionized our understanding of planetary formation. However, this new image of the gas indicates that the current view of planetary formation is still overly simplistic and that it may be much more chaotic than previously assumed from known images of neatly concentric annular discs.

The fact that we observed this spiral structure in gas after longer observation suggests that we probably did not see the full variety and complexity of the environments that form the planets. We may have missed most of the gas structures in the other disks.

Jane Huang of the Smithsonian Center for Astrophysics and lead author of the article

Huang and her team offer several scenarios that might explain why spiral arms appeared around RU Wolf. It is possible that the disc collapses under its own gravity. Or maybe RU Wolf interacts with another star. Another possibility is that the disk interacts with the environment, accreting interstellar material along the spiral arms.

But none of these scenarios fully explains what scientists have observed. During the formation of planets, unknown processes can occur that astronomers have not yet taken into account in their models. Researchers will only know what they are if they find other discs similar to the RU Wolf.