Harvard Smithsonian Center for Astrophysics | 2020 Sep 17
Following extensive observations of stellar winds around cool evolved stars scientists have figured out how planetary nebulae get their mesmerizing shapes. The findings ... contradict common consensus, and show that not only are stellar winds aspherical, but they also share similarities with planetary nebulae.
- Gallery of stellar winds around cool aging stars, showing a variety of morphologies, including disks, cones, and spirals. The blue color represents material that is coming towards you, red is material that is moving away from you. Image 8, in particular, shows the stellar wind of R Aquilae, which resembles the structure of rose petals. Credit: L. Decin, ESO/ALMA
An international team of astronomers focused their observations on stellar winds—particle flows—around cool red giant stars, also known as asymptotic giant branch (AGB) stars. "AGB stars are cool luminous evolved stars that are in the last stages of evolution just before turning into a planetary nebula," said Carl Gottlieb ... “Through their winds, AGB stars contribute about 85% of the gas and 35% of the dust from stellar sources to the Galactic Interstellar Medium and are the dominant suppliers of pristine building blocks of interstellar material from which planets are ultimately formed."
Despite being of major interest to astronomers, a large, detailed collection of observational data for the stellar winds surrounding AGB stars—each made using the exact same method—was lacking prior to the study, which resulted in a long-standing scientific misconception: that stellar winds have an overall spherical symmetry. ...
Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile revealed something strange: the shape of the stellar winds didn't conform with scientific consensus. ...
Astronomers Capture Stellar Winds in Unprecedented Detail
Atacama Large Millimeter/submillimeter Array | 2020 Sep 18
(Sub)Stellar Companions Shape the Winds of Evolved Stars ~ L. Decin et al
- Science 369(6510):1497 (18 Sep 2020) DOI: 10.1126/science.abb1229