In an international collaboration (named ATOMIUM), French astronomers from the Paris Observatory - PSL, the University of Bordeaux and the Observatoire de la Côte d’Azur, as well as from the Institute of Millimetric Radioastronomy, have found an explanation for the fascinating shapes of planetary nebulae.
Published in the journal Science and supported by the National Program of Stellar Physics of the CNRS, this study is based on the largest and most detailed set to date of stellar wind observations around evolved cold giant stars, thanks to the ALMA interferometer in Chile.
Stars like our Sun, at an advanced stage of evolution, inflate and cool down to eventually become red giants and then planetary nebulae.
They produce stellar winds, streams of particles that the star expels, causing a progressive decrease in their mass.
Until this new study, these winds were supposed to be spherical, like the stars they surround, while their descendants, the planetary nebulae, are characterized by an extraordinary variety of shapes and colors.
The scientific team thus discovered that these stellar winds, far from being spherical, were in fact similar in shape to those of planetary nebulae, indicating that the same process shapes both the winds of evolved cold giant stars and planetary nebulae.
The researchers were able to demonstrate that "companion" objects - either low-mass stars or massive planets in the vicinity of the dying star - were responsible for the different shapes observed.
This study helps us to imagine what the Sun will look like when it dies in seven billion years. Jupiter or Saturn - because of their large masses - will influence the shape of its planetary nebula : at the heart of a spiral, a butterfly or any other bewitching and ephemeral shape...
Reference
« (Sub-)stellar companions shape the winds of evolved stars » L. Decin et al., Science, 18 septembre 2020