According to our current knowledge, planets should form in a disk that is orbiting around forming stars, creating complex and very interesting systems for the scientific community. One of these systems is HD169142, which has one of the most studied protoplanetary disks due to its particular inclination, facing us when we observe it from the earth observers. This disk has multiple grooves on its surface and a central cavity, suggesting that there are already formed planets orbiting in the disk. However, in the innermost regions, the disk displays strange concentrations of dust that are difficult to reproduce by considering planets alone.
As a matter of fact, many systems have more than one central star, such as binary systems, which have two. In such a case, the interaction with the protoplanetary disk will be very different, since the constant motion of the stars generates abrupt changes in the material -gas and dust-, drastically influencing their behavior. Precisely, the presence of another star could explain the distribution observed in the disk of HD169142.
To find the best combination of a pair of stars that could be responsible for the structures observed in this disk, an international group of scientists led by Pedro Poblete, PhD student in astrophysics at the Universität Jena, Germany, and member of the Nucleus Millennium of Planetary Formation (NPF), used computer simulations to reproduce the observations, concluding that there could be a binary system at the center, not yet observed, and, very surprisingly, perpendicular to the disk.
The research, published in the prestigious scientific journal Monthly Notices of the Royal Astronomical Society (MNRAS), also involved Jorge Cuadra, research associate of the NPF, Matias Montesinos, adjunct researcher, Sebastián Zúniga-Fernández, recently graduated with a PhD in Astrophysics from the University of Valparaíso, also a member of NPF, and Amelia Bayo, director of the center.
The model used by the scientists contemplates a disk composed of gaseous and solid material (dust), and also includes a binary perpendicular to the disk in the center as well as a planet, which may well explain the morphology observed in the outer regions of the disk.
“The presence of the companion star could be problematic, since a star shines much brighter than a planet, and it would be logical to think that if there was a secondary star, it would have already been detected. However, the binary we are considering has a primary star that is 50% more massive than the Sun and a companion with only one-tenth the mass of the primary. We have analyzed our results rigorously and the results, which have been confronted to observations with observations, suggest that such a scenario is feasible”, says Poblete.
The implications of this binary scenario are important. It is known from observations that it is not uncommon to find planetary systems in binary systems, however, it has not been observed how these planets form around a binary. “If our prediction is corroborated, the HD169142 system would attract even more interest from the scientific community, since we would be observing a planetary system in formation, with planets already formed, around a binary”, emphasizes Poblete.
“This work was very interesting, since we realized that the abstract study of Pedro’s master’s thesis could be applied to the observations of HD169142, which until now had not been considered a possible binary,” says Jorge Cuadra, who also works as an academic at the Universidad Adolfo Ibáñez.
The next step in this research is to detect the companion star, from observations. “Our model, although consistent and rigorous, is only a guide, a hypothesis for observers to confirm,” concludes Pedro Poblete.