Successful for the first time

Mega bubbles filmed on the surface of a star

(Bild: ALMA (ESO/NAOJ/NRAO)/W. Vlemmings et al.)

For the first time, astronomers have captured images of a star that is not the sun at such a high resolution that the movement of bubbling gas (see video above), which is produced during nuclear fusion, can be seen on its surface.

The images of the star called R Doradus were taken in July and August 2023 with the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope owned by the European Southern Observatory (ESO for short).

They show huge, hot gas bubbles that are 75 times the size of our sun. They emerge on the surface and sink back into the interior of the star faster than astronomers expected.

The gas bubbles on R Doradus are 75 times the size of our central star.(Bild: ALMA (ESO/NAOJ/NRAO)/W. Vlemmings et al.)

"This is the first time that the bubbling surface of a real star can be visualized in this way," Wouter Vlemmings from Chalmers University of Technology in Sweden is quoted as saying in the journal "Nature". "We never expected the data to be of such high quality that we could see so many details of the convection on the star's surface," says the scientist.

Energy rises to the surface in gas bubbles
Stars generate energy in their centers through nuclear fusion. This energy can be transported to the surface of the star in huge, hot gas bubbles, which then cool down and sink - like a lava lamp. This mixing, known as convection, distributes the heavy elements formed in the core, such as carbon and nitrogen, throughout the star.

Convection is also thought to be responsible for the stellar winds that carry these elements into the cosmos to form new stars and planets. Until now, convection motions have never been observed in detail in stars other than the sun.

180 light years from our Earth
R Doradus is a so-called red giant with a diameter about 350 times that of our Sun and is located about 180 light years from Earth in the constellation of Swordfish (Dorado).

Its size and proximity to Earth make R Doradus an ideal target for detailed observations. Furthermore, the star has a similar mass to the Sun, which means that it will probably look something like our Sun in five billion years when it blows up into a red giant.