They focus on a star until they see the bubbling gas on its surface

September 11 () –

For the first time, A team of astronomers has captured images of a star other than the Sun in enough detail to follow the motion of bubbling gas on its surface.

Images of the star, R Doradus, were obtained in July and August 2023 with the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope in which the European Southern Observatory (ESO) is a partner. They show giant bubbles of hot gas, 75 times the size of the Sun, that appear on the surface and sink back into the star’s interior faster than expected.

“This is the first time that the bubbling surface of a real star can be shown in this way,” he says. in a statement Wouter Vlemmings, professor at Chalmers University of Technology (Sweden) and lead author of the study published in Nature: “We never expected the data to be of such high quality that we could see so many details of the convection on the stellar surface.”

Stars produce energy in their cores through nuclear fusion. This energy can be transported to the surface of the star in the form of huge hot bubbles of gas that then cool and sink (like in a lava lamp). This mixing motion, known as convection, distributes heavy elements formed in the core, such as carbon and nitrogen, throughout the starIt is also believed to be responsible for the stellar winds that carry these elements into the cosmos to make new stars and planets.

Until now, convection motions had never been tracked in detail in stars other than the Sun. Using ALMA, the team was able to obtain high-resolution images of the surface of R Doradus over the course of a month. R Doradus is a red giant star, with a diameter approximately 350 times that of the Sun, located about 180 light years away from Earthin the constellation Dorado. Its large size and proximity to Earth make this star an ideal target for detailed observations. In addition, its mass is similar to that of the Sun, which means that R Doradus It is probably quite similar to what our Sun will look like in five billion years.once it becomes a red giant.

“Convection creates the beautiful granular structure seen on the surface of our Sun, but which is difficult to see on other stars,” adds Theo Khouri, a researcher at Chalmers and co-author of the study. “With ALMA, we have now not only been able to directly see convective granules (75 times the size of our Sun!) but we have also measured their speed of motion for the first time.”

The R Doradus granules appear to move on a monthly cycle, which is faster than scientists expected based on how convection works on the Sun. “We don’t yet know the reason for the difference. Convection appears to change as a star ages in ways we don’t yet understand.“,” Vlemmings said. Observations like the ones now being made of R Doradus are helping us understand how stars like the Sun behave, even when they grow as cool, large and bubbly as R Doradus is.

“It is spectacular that we can now directly image surface details of such distant stars and observe physics that was previously only observable on our Sun,” concludes Behzad Bojnodi Arbab, a PhD student at Chalmers who also participated in the study.