“Triple Star” Discovery Could Revolutionise Understanding of Stellar Evolution

Although star formation may be seen as trivial for stars like our sun, some types are more elusive than others. Massive Be type stars are one such example often found in binary systems, where two stars obit each other. “The best point of reference for that is if you’ve watched Star Wars, there are planets where they have two Suns” explains Johnathan Dodd, PhD student and collaborator on the research. However, not much is known about their formation.

A recent discovery was made by Professor René Oudmaijer, PhD student Johnathan Dodd along with PhD student Isaac Radley from the University of Leeds’ School of Physics and Astronomy and two former Leeds academics Dr Miguel Vioque of the ALMA Observatory in Chile and Dr Abigail Frost at the European Southern Observatory in Chile. It suggests that these stars may also exist in triplet systems (where there are three stars orbiting each other), as well as double. This may help to reveal the long-awaited mystery of their formation since their identification via their emission lines in 1866 by Angelo Secchi.

The “triple star” discovery by Professor Oudmaijer and his team was made by using European Space Agency’s Gaia satellite and could cause ripples of excitement in the astrophysics community. It may also aid our understanding of neutron stars, gravitational waves, and black holes.

Principal Investigator Professor Oudmaijer said “there’s a revolution going on in physics at the moment around gravitational waves. We have only been observing these gravitational waves for a few years now, and these have been found to be due to merging black holes.”  

“We know that these enigmatic objects – black holes and neutron stars – exist, but we don’t know much about the stars that would become them. Our findings provide a clue to understanding these gravitational wave sources.” 

He added that “over the last decade or so, astronomers have found that binarity is an incredibly important element in stellar evolution. We are now moving more towards the idea it is even more complex than that and that triple stars need to be considered.” 

“Indeed,” Oudmaijer said, “triples have become the new binaries”.

Video Credit: ESO/L. Calçada eso.org/public/archives/videos/hd_and_apple/eso2204b.m4v (Artist’s animation of what the system could look like)
New research using data from ESO’s Very Large Telescope and Very Large Telescope Interferometer has revealed that HR 6819, previously believed to be a triple system with a black hole, is in fact a system of two stars with no black hole. The scientists, a KU Leuven-ESO team, believe they have observed this binary system in a brief moment after one of the stars sucked the atmosphere off its companion, a phenomenon often referred to as “stellar vampirism”. This animation shows what the system might look like; it’s composed of an oblate star with a disc around it (a Be “vampire” star; foreground) and B-type star that has been stripped of its atmosphere (background).

Their research involved looking for further away secondary stars within various data sets to build a picture that at larger separations the number of companions stars is comparable between Herbig Be and B type stars.

“We observed the way the stars move across the night sky, over longer periods like 10 years, and shorter periods of around six months. If a star moves in a straight line, we know there’s just one star, but if there is more than one, we will see a slight wobble or, in the best case, a spiral.” Mr Dodd explained.

The two types of stars they were most interested in are B and Be; the former displays hydrogen emission lines and the latter are main sequence non-supergiant stars that have Balmer series emission lines.

“We applied this across the two groups of stars that we are looking at – the B stars and the Be stars – and what we found, confusingly, is that at first it looks like the Be stars have a lower rate of companions than the B stars. This is interesting because we’d expect them to have a higher rate” Mr Dodd added.

In a large proportion of the sample analysed had the inference that a third body was influencing the system, resulting in the Be star having a reduced distance from its companion. This causes mass transfer from the two stars as the Be star ‘sucks’ matter from the other. It’s been dubbed a “vampire” Be star and this behaviour forms the characteristic disc around the Be star.

Image credit: ESO/M. Kornmesser/S.E. de Mink (Artist’s impression of a vampire star and its victim | ESO)
Artist’s impression of a vampire star (left) stealing material from its victim: New research using data from ESO’s Very Large Telescope has revealed that the hottest and brightest stars, which are known as O stars, are often found in close pairs. Many of such binaries will at some point transfer mass from one star to another, a kind of stellar vampirism depicted in this artist’s impression.

A reason as to why the companion is hard to spot could be due to them being obscured by the disc and reduced so much by the Be star making them very small and faint.

Professor Oudmaijer said “the fact that we do not see them might be because they are now too faint to be detected.”

This breakthrough has opened up another area of exciting research.

Their paper entitled “Gaia uncovers difference in B and Be star binarity at small scales: evidence for mass transfer causing the Be phenomenon” was published on the 21st November and can be found here.

Researchers Identify Largest Ever Solar Storm using Ancient 14,300-year-old Tree Rings

The climate crisis has caused the Earth to be ravaged in more storms and extreme weather events in recent years. We see large scale storms on other planets – Jupiter’s famous ‘Great Red Spot’ is actually an ongoing storm that was first seen in 1879 – and even on our sun. Solar storms can impact us on Earth due to how close we are to our host star. Although the sun hasn’t had a massive solar outburst within recorded human history, scientists know there have been some in the past. Known as Miyake Events, there have been a total of nine such solar storms, but none previously have been on the same scale as the one discovered on the 9th October this year in tree rings found in the Drouzet river, France.

Earlier last month a team of international scientists from institutions all over the world, including the University of Leeds, have announced that they have discovered evidence of the largest ever solar storm that is thought to have occurred over 14,300 years ago. They were able to do this by slicing apart the subfossil (remains of tree trunks that are not yet fully fossilised) into separate tree rings so they were ready for analysis. “We then carefully pieced together the separate trees to create a longer timeline using a method called dendrochronology [the study of annual tree growth]. This allowed us to discover invaluable information on past environmental changes and measure radiocarbon over an uncharted period of solar activity” explains Associate Professor Cécile Miramont, a member of the research team.

What they were looking for was a large spike in radiocarbon levels. “Radiocarbon is constantly being produced in the upper atmosphere through a chain of reactions initiated by cosmic rays” said Professor Edouard Bard, the lead author of the study. “Extreme solar events including solar flares and coronal mass ejections can also create short-term bursts of energetic particles which are preserved as huge spikes in radiocarbon production occurring over the course of just a single year” he adds. The scientists compared the tree ring samples to Greenland ice core beryllium measurements and determined that both were caused by this giant solar storm.

As fascinating as this is, there is a warning to heed here. It’s imperative that research like this is done so that preparation can be done in the event that a solar storm does occur. Because of the way our energy and telecommunication systems work, if a solar storm hit tomorrow, they would be almost completely destroyed and cost billions of pounds to repair. Professor Tim Heaton, lecturer and researcher at the University of Leeds, warns that it could “permanently damage the transformers in our electricity grids, resulting in huge and widespread blackouts lasting months” as well as damaging satellites that “we all rely on for navigation and telecommunication, leaving them unusable. They would also create severe radiation risks to astronauts”.

Very little is known about these solar storms, especially as they have never been observed with scientific instruments directly. “A precise understanding of our past is essential if we want to accurately predict our future and mitigate potential risks. We still have much to learn. Each new discovery not only helps answer existing key questions but can also generate new ones” states Professor Heaton.

The team have published a paper detailing their findings and can be found here.

The Sea Under The Surface

Research published in Science has confirmed the discovery of evidence that there could be oceans hundreds of kilometres beneath us.

The Forgotten Mercury 13

Zoe Parker discusses the Artemis space missions, as well as Mercury 13, and the role which women played in these ground breaking developments.

Celebrating Forgotten Scientists: John Edmonstone

Charles Darwin is known as one of the greatest scientists of his time for his theory of evolution. The practice of collecting evidence for his theory can be credited to a free man living in Edinburgh at the same time as a young Darwin, who taught him the skills necessary for taxidermy.