Video: Bubbling surface of a distant star captured by telescope

In an unprecedented development, astronomers have managed to capture detailed images of a star outside of our solar system, including gas bubbling on its surface.

These images, revealing giant hot gas bubbles larger than our sun, have been retrieved from the star R Doradus.

Interestingly, the gas bubbles seem to disappear into the interior of the star at a quicker rate than anticipated.

Bubbling surface of R Doradus

“This is the first time the bubbling surface of a real star can be shown in such a way,” noted study lead author Wouter Vlemmings, a professor from Chalmers University of Technology, Sweden.

“We had never expected the data to be of such high quality that we could see so many details of the convection on the stellar surface.”

How stars generate energy is a fascinating process. At their cores, stars undergo nuclear fusion. This prodigious energy then ascends toward the surface in the form of large, hot gas bubbles — resembling movement within a lava lamp.

The bubbles eventually cool down and descend back into the core in a process known as convection.

The mixing motion of convection helps distribute heavy elements like carbon and nitrogen across the star.

It is also believed to generate stellar winds that propel these elements into the cosmos, contributing to the birth of new stars and planets.

Convection outside of our star system

In an exciting first, detailed tracking of convection movements has been achieved for stars other than our sun, using the Atacama Large Millimeter/submillimeter Array (ALMA), jointly owned by the European Southern Observatory (ESO).

The target, R Doradus, a red giant star with a diameter nearly 350 times that of our sun, is conveniently located about 180 light-years away in the constellation Dorado.

Given its massive size and relative proximity to Earth, R Doradus proved to be an ideal candidate for the detailed observations. Interestingly, the star has a mass that is similar to the sun.

The researchers noted that convection bubbles have been previously observed in detail on the surface of stars, including with the PIONIER instrument on ESO’s Very Large Telescope Interferometer.

However, the new ALMA observations track the motion of the bubbles in a way that was not possible before.

Close observations of granular structures

“Convection creates the beautiful granular structure seen on the surface of our sun, but it is hard to see on other stars,” explained study co-author Theo Khouri, a researcher at Chalmers.

“With ALMA, we have now been able to not only directly see convective granules – with a size 75 times the size of our sun! – but also measure how fast they move for the first time.”

The granules of R Doradus seem to operate on a monthly cycle. This is a speedier pace than expected based on the sun’s convection process.

“We don’t yet know what is the reason for the difference. It seems that convection changes as a star gets older in ways that we don’t yet understand,” explained Vlemmings.

Evolution of R Doradus and sun-like stars

The recent observations are crucial as they deepen our understanding of sun-like stars when they mature into red giants as cool, large, and effervescent as R Doradus.

“It is spectacular that we can now directly image the details on the surface of stars so far away, and observe physics that until now was mostly only observable in our sun,” said Behzad Bojnodi Arbab, a PhD student at Chalmers who also participated in the study.

Glimpse into the sun’s future

The red giant R Doradus offers a preview of what our sun may become in about five billion years. As stars like the sun age, they expand dramatically, becoming cooler and more luminous as red giants.

During this phase, convection becomes a dominant process on their surface, where hot gas rises and cools, creating enormous granules of bubbling plasma.

This phase plays a crucial role in the distribution of elements across the star and into space, enriching the interstellar medium.

Understanding how red giants like R Doradus evolve not only helps astronomers study distant stars but also sheds light on the eventual fate of our own solar system.

The study is published in the journal Nature.

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