The discovery of “triple stars” could revolutionize the understanding of stellar evolution

A groundbreaking new discovery by University of Leeds scientists could change the way astronomers understand some of the largest and most common stars in the universe. The paper, entitled “Gaia reveals small-scale binary divergence of B and Be stars: evidence for mass transfer causing the Be phenomenon,” was published in the journal. Monthly Notices of the Royal Astronomical Society.

PhD research. student Jonathan Dodd and Professor Rene Odemeyer, from the university’s School of Physics and Astronomy, have presented exciting new evidence that the massive Be star – until now thought to be contained in a double star – could actually be a “triple”.

This extraordinary discovery could revolutionize our understanding of the object – part of star B – which is an important “test case” for developing theories about how stars evolve in general.

These Be stars are surrounded by a distinctive disk made of gas, similar to the rings of Saturn in our solar system. Although the star Be has been known for about 150 years, first identified by the famous Italian astronomer Angelo Cecchi in 1866, until now no one knew how the star formed.

The consensus among astronomers so far is that the disk formed due to the rapid rotation of the Be star, and that this may be caused by the star’s interaction with another star in a binary system.

Triple system

“The best reference for this is if you’ve ever watched Star Wars, there’s a planet that has two suns,” said Mr. Dodd, the paper’s author.

But now, by analyzing data from… The European Space Agency’s Gaia satelliteScientists say they have found evidence that these stars actually exist in triple systems, where three objects interact, rather than just two.

Mr Dodd added: “We have observed the way stars move across the night sky, over longer periods such as 10 years, and shorter periods of around six months. If a star is moving in a straight line, we know there is only one star, but if there is more than one, and we will see a slight wobble, or at best, a vortex.

“We applied this to the two groups of stars we looked at – the B stars and the Be stars – and what we found, confusingly, was that initially the Be stars seemed to have a lower degree of companionship than the B stars. This is interesting because we expected them to get to a higher level.”

However, lead researcher Professor Odemeyer said: “The fact that we don’t see them is probably because they are now too faint to detect.”

Mass migration

The researchers then looked at a different data set, looking for a distant companion star, and found that at larger separation distances, the speed of the companion star was very similar between the B and Be stars.

From this, they were able to conclude that in many cases, a third star would come along, forcing its companion closer to the Be star, close enough so that mass could transfer from one star to the other and form the typical Be star disk. This could also explain why we don’t see these friends anymore; It became too small and faint to detect after the “vampire” star Be absorbed most of its mass.

This discovery could have a major impact on other areas of astronomy, including our understanding of black holes, neutron stars and the sources of gravitational waves.

Professor Odemeijer said: “There is currently a revolution in physics around gravitational waves. We have only been observing these gravitational waves for a few years, and it is known that they are caused by merging black holes.

“We knew that these mysterious objects – black holes and neutron stars – existed, but we didn’t know much about what stars they would become. Our findings provide clues to understanding the source of these gravitational waves.”

He added: “Over the last decade or so, astronomers have discovered that binaries are a very important element in stellar evolution. We are now moving more towards the idea that binaries are more complex than that, and that triple stars need to be considered. ”

“In fact, threes have become the new twos,” Odemeijer said.