There are many star pairs in the universe, and most often, both stars are very similar to each other, like twins. But in the binary system HD 148937, one star seemed to be much younger and unlike its pair, magnetic. The European Southern Observatory on Thursday announced that this system actually had three stars, until two clashed and merged. The violent merger created clouds of dust and gas surrounding the system and changed its fate forever. A study on the system 3,800 light-years away from our planet was published in the journal Science on Thursday. Its two stars are much more massive than the Sun and the clouds surrounding make for a beautiful and vibrant nebula. “When doing background reading, I was struck by how special this system seemed. A nebula surrounding two massive stars is a rarity, and it really made us feel like something cool had to have happened in this system. When looking at the data, the coolness only increased,” said Abigail Frost, lead author of the paper, in a press statement. The researchers analysed the system in detail and found that the most massive star appeared to be much younger than its pair. The age difference seemed to be at least 1.5 million years younger than the other. The nebula around the stars offered some clues — it is only about 7,500 years old, which is hundreds of times younger than both the stars. It also had large amounts of nitrogen, carbon and oxygen. That was also surprising since these are usually expected inside a star and not outside — this suggested that some violent event had brough them outside. The team then assembled nine years of data from multiple ESO experiments and analysed them. “We think this system had at least three stars originally; two of them had to be close together at one point in the orbit whilst another star was much more distant. The two inner stars merged in a violent manner, creating a magnetic star and throwing out some material, which created the nebula. The more distant star formed a new orbit with the newly merged, now-magnetic star, creating the binary we see today at the centre of the nebula,” explained Hugues Sana, a professor at KU Leuven in Belgium and the principal investigator of the observations, in a press statement.
