Astronomers at the University of Warwick uncovered a new phenomenon called the “rocking shadow” effect that explains how disks are oriented in forming planetary systems, and how they move around their host star. The effect also gives clues as to how they may have evolved over time. Dr. Rebecca Nealon presented the new work at the 2022 National Astronomy Meeting at the University of Warwick this week.
Stars are born when a large cloud of gas and dust collapses on its own. The rest of the material that doesn’t make it into the star travels around it, not unlike how the water spins around the creek before falling. This swirling mass of gas and dust is called the protoplanetary disk, and is where planets such as Earth are born.
Protoplanetary discs are often thought to be the shape of a dinner plate—thin, round, and flat. However, recent telescope images from the Atacama Large Millimeter/submillimeter Array (ALMA) show that this is not always the case. Some of the disks seen by ALMA have shadows on them, where the part of the disk closest to the star blocks some stellar light and casts a shadow on the outer part of the disk. From this shadow pattern, it can be inferred that the inner part of the disc is oriented completely differently to the outer part, which is called a ruptured disc.
In this research, the team used high-performance computers to run three-dimensional simulations of the broken disk. The team then produced a simulated observation, modeling what such a disk would look like if viewed through a telescope and how it would change over time.
As the inner disk progressed through the gravitational pull of the central star, its shadow moved onto the outer disk. But instead of the clockwise-hand-like shadow pattern swirling around the disc as expected, it shook back and forth with a see-saw-like motion. So although the disc inside kept turning in the same direction, its shadow looked like it was moving back and forth. The team suggests that this is caused by a geometric projection effect, which is likely to occur in all ruptured discs.
Our research is important because it bridges the gap between theory and observation. In light of new observations from telescopes like the JWST, our state-of-the-art numerical techniques mean we have a variety of tools to interpret these data and learn more about the birth of planets.
Rebecca says: “JWST promises us a look at embryonic planetary systems in unprecedented detail, and with our new model we will be able to find out much more about the birth of planets.”
Video: https://youtu.be/jGYLuEx-I78
Story Source:
material provided by Royal Astronomical Society, Note: Content can be edited for style and length.