“Triple Star” Discovery Shakes Up Stellar Evolution Theory

Researchers have made an exciting discovery that massive Be stars, known for their characteristic gas disks, may be part of triple star systems rather than binary systems as previously thought. This revelation, based on data from the Gaia satellite, challenges existing theories of star formation and has significant implications for understanding broader astronomical phenomena such as black holes, neutron stars and gravitational waves.

A groundbreaking study by scientists at the University of Leeds proposes that Be stars are part of triple star systems, not binary systems as previously thought. The discovery, derived from Gaia satellite data, challenges conventional theories of star formation and could affect our knowledge of black holes, neutron stars, and more. Gravitational waves.

A new discovery by scientists at the University of Leeds could change the way astronomers understand some of the largest and most common stars in the universe.

Research by PhD student Jonathan Dodd and Professor René Oudmaijer from the university’s School of Physics and Astronomy points to intriguing new evidence that massive Be stars – until now thought to be mainly binary stars – may actually be “triplets”.

The remarkable discovery will revolutionize our understanding of objects considered an important “test bed” for developing theories of how stars form in general – a subset of B stars.

HR 6819 chart

Artist’s impression of a star with a disk around it (a Be “vampire” star; foreground) and its companion star with its outer parts removed (background). Credit: ESO/L. Pants

Nature of stars

Be stars are surrounded by a characteristic disk of gas – like rings Sat In our own solar system. Although Be stars have been known for about 150 years — first identified by the famous Italian astronomer Angelo Cecchi in 1866 — until now, no one knew how they formed.

So far, the consensus among astronomers is that the disks are formed by the rapid rotation of Be stars, and that they can be caused by stars interacting with another star in a binary system.

Star vampire

Artist’s impression of a vampire star (left) stealing material from a victim. Credit: ESO/M. Kornmesser/SE de Mink

Manifesting triple systems

Corresponding author of the research Mr. Todd said: “The best reference for that is if you’ve seen Star Wars, they have planets with two suns.”

But now, by analyzing data from the European Space Agency’s Gaia satellite, scientists have found evidence that these stars are actually in three systems — three bodies interacting instead of two.

Mr. Todd added: “We’ve seen stars move across the night sky over periods as long as 10 years and as little as six months. If a star moves in a straight line, we know there is only one star, but if there is more than one, we see a slight wobble, or at best, a vortex.

“We applied this to two groups of stars that we see – B stars and B stars – and confusingly, B stars seem at first to have fewer companions than B stars. This is interesting because we would expect them to have a higher ratio.

However, principal investigator Professor Otmeijer said: “The reason we haven’t seen them is probably because they are too faint to detect now.”

Mass transfer

The researchers then looked at a different data set, looking for more distant companion stars, and found that at these large separations, the proportion of companion stars was very similar between B and Be stars.

From this, they were able to infer that in many cases a third star is acting, forcing the companion closer to the Be star – close enough to transfer mass from one to the other and form the characteristic Be star disc. This may also explain why we don’t see these guys anymore; After the “vampire” Be star absorbed their mass they became much smaller and fainter.

Broad astronomical impact

The discovery could have major implications for other areas of astronomy – including our understanding of black holes, neutron stars and gravitational wave sources.

Professor Oudmaijer said: “There is currently a revolution in physics around gravitational waves. We have only been observing these gravitational waves for a few years and they have been discovered to be caused by merging black holes.

“We know these enigmatic objects — black holes and neutron stars — exist, but we know little about the stars that become them. Our findings provide clues to understanding these gravitational wave sources.”

He added: “Over the last decade or so, astronomers have discovered that binarity is an incredibly important element in stellar evolution. We are now moving further towards the idea of ​​being more complex and considering three stars.

“In fact,” Oudmaijer said, “triplets have become the new binaries.”

Note: “hand Distinctions between B and Be star binaries at smaller magnitudes reveal: Jonathan M Todd, René D Oudmaijer, Isaac C Radley, Miguel Vioque and Abigail J Frost, 12 Oct 2023, “Evidence for mass transfer causing the Be event”. Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stad3105

PhD student Isaac Radley of the University of Leeds and two former Leeds academics, Drs. Miguel Vioque and Dr. in European countries. Along with Abigail Frost, PhD student from Leeds Mr. Todd and Prof. Oudmaijer is behind the discovery. Southern Observatory in Chile. The team received funding from the Science and Technology Facilities Council (STFC).

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