Astronomy: Waves on giant star three times larger than our whole sun

Tides can also exist on the surface of stars, and now two US astronomers have discovered one where the waves are three times higher than our Sun and even break like those in our oceans. This is reported by the Harvard-Smithsonian Center for Astrophysics and explains that MACHO 80.7443.1718 is a so-called “heartbeat star”. The two stars of the double system regularly come into comparison, causing the brightness to change by up to 20 percent. They have now determined the background with simulations.

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Simulations explain differences in brightness

As the researchers explain, “heartbeat stars” regularly pulsate in brightness. As the binaries get closer in their orbits, their gravity causes them to deform, and as a result, less and less starlight reaches us. Normally, however, the brightness of such systems changes by about 0.1 percent and not by an immense 20 percent as with MACHO 80.7443.1718. To explain this, Morgan MacLeod and Abraham Loeb have now created models of the two stars and simulated how they behave.

It has been shown that when the two stars meet, “smooth and orderly” waves form on the larger of the two, which eventually roll over one another and even break. Also because the star is significantly larger than our sun and 35 times as massive, they are gigantic structures. According to the calculations, they will eventually pile up to a fifth of its radius, which is more than four million kilometers or three times the diameter of our sun. Overall, this happens around once a month and the two also associate measurement data with the statement.

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MacLeod and his colleague do not believe that the star they describe is unique. At present, almost 1000 “heartbeat stars” are known and 20 would show similar strong fluctuations in brightness as MACHO 80.7443.1718. This could be the first of a class of astronomical objects, so they want to keep looking. They could betray themselves not only through the differences in brightness, but also through a characteristic glow in the stellar atmosphere, which goes back to the breaking waves. They present their work in the scientific journal Nature Astronomy.

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