Free Astronomy Magazine May-June 2022

MAY-JUNE 2022 A s stars grow up, they often interact with their sibling stars—stars growing up near to them in space— but have rarely been ob- served interacting with outside, or intruder, objects. Scientists have now made observations of an intruder object disturbing the proto- planetary disk around Z Canis Majoris, a star in the Canis Major constellation, which could have major implica- tions for the development of baby planets. Perturbations, including long streams of gas, were observed in detail by the Subaru Telescope in the H-band, the Karl G. Jan- sky Very Large Array in the Ka-band, and using the Ata- cama Large Millimeter/sub- millimeter Array’s Band 6 receiver. [ALMA (ESO/NAOJ/NRAO), S. Dag- nello (NRAO/AUI/NSF), NAOJ] ! author on the paper added that in the case of Z CMa, it was the morphology, or structure, of these streams that helped scientists to identify and pinpoint the intruder. “When a stellar encounter occurs, it causes changes in disk morphology − spirals, warps, shadows, etc. − that could be considered as flyby finger- prints. In this case, by looking very carefully at Z CMa’s disk, we re- vealed the presence of several flyby fingerprints.” These fingerprints not only helped scientists to identify the intruder, but also led them to consider what these interactions might mean for the future of Z CMa and the baby planets being born in the system, a process that so far has remained a mystery to scientists. “What we now know with this new research is that flyby events do occur in nature and that they have major impacts on the gaseous circumstellar disks, which are the birth cradles of planets, sur- rounding baby stars,” said Cuello. “Flyby events can dramatically per- turb the circumstellar disks around participant stars, as we’ve seen with the production of long streamers around Z CMa.” Liu added, “These perturbers not only cause gaseous streams but may also impact the thermal history of the involved host stars, like Z CMa. This can lead to such violent events as accretion outbursts, and also im- pact the development of the overall star system in ways that we haven’t yet observed or defined.” Dong said that studying the evolu- tion and growth of young star sys- tems throughout the galaxy helps scientists to better understand our own Solar System’s origin. “Studying these types of events gives a win- dow into the past, including what might have happened in the early development of our own Solar Sys- tem, critical evidence of which is long since gone. Watching these events take place in a newly forming star system provides us with the in- formation needed to say, ‘Ah ha! This is what may have happened to our own Solar System long ago.’ Right now, VLA and ALMA have given us the first evidence to solve this mystery, and the next genera- tions of these technologies will open windows on the Universe that we have yet only dreamed of.”