A mysterious nebula in which almost everything is different from what was expected, turns out to have experienced something very “wonderful”.

Both the nebula itself and the two stars inside it fascinate astronomers. They are completely different than expected. But there's a good reason for that, new research reveals. It turns out that the mysterious nebula is the result of something “wonderful”: a massive collision between two stars.

The researchers write this in the journal Sciences. Their study concerns the HD 148937 system, which is located in the Norma (Finklehack) galaxy, about 3,800 light-years from Earth. The system consists of two massive stars, surrounded by a beautiful nebula: a cloud of gas and dust. “The presence of a nebula around two massive stars is rare,” says researcher Abigail Frost. “This gave us a feeling that something wonderful must be happening in this system. And when we looked at the data, that feeling became even stronger.”

Two crazy stars
Normally, pairs of stars look similar. But in HD 148937, to the astonishment of astronomers, things are very different. One star appears younger than the other by at least one and a half million years. This younger star – unlike the other star – is also magnetic. That's really weird, Frost says. “After a comprehensive analysis, we concluded that the more massive star appears much younger than its companion, which is illogical because they must have formed at the same time!”

Crazy fog
But it doesn't stop there. Because analysis of the nebula reveals that it is only 7,500 years old, and therefore it is hundreds of times younger than stars. It also appears to contain a lot of nitrogen, carbon and oxygen. Which is also surprising, because these elements are usually found deep within the star, rather than outside it.

Puzzles and solve them
Thus, this nebula is filled with mysteries. But researchers have now come up with a scenario that can solve all these mysteries in one fell swoop, says researcher Hughes Sanna. “We think this system originally consisted of at least three stars. Two of them must have gotten very close together at some point, while another star was very far away. The two inner stars then merged to form a magnetar. Some material was also shed , causing the haze. “The distant star migrated to a new orbit around the newly merging star, which is now a magnetar, creating the double star we now see at the center of the nebula.”

Very large telescope
The researchers arrived at this solution after examining the nebula with the help of the European Southern Observatory Very large telescope Checked again. “Finding an age difference between the stars indicates that this scenario is the most plausible,” explains researcher Laurent Mahé. “This can only be proven by new ESO data.”

Another astral mystery solved
Through their studies, scientists were not only able to solve the mystery surrounding this particular nebula. They also appear to have found an answer to a more general stellar mystery: how some massive stars obtain a magnetic field. We often see magnetic fields in light stars, such as our Sun. And don't actually expect heavy stars from them. Simply because they are unable to maintain a magnetic field the way low-mass stars do. However, massive magnetars have been discovered in the past. Astronomers already suspect that these massive stars got their magnetic field because they are the result of the merger of two stars, but there is no conclusive evidence for this. But HD 148937 seems to be offering us this evidence on a silver platter. And we're very lucky about that,” Frost says. “Magnetism in massive stars is not expected to persist for long relative to the lifetime of the star, so we appear to have observed this rare event soon after it occurred.”

Researchers are certainly not finished with the nebula and the stars within it. In the future, they hope to have this with the building under construction Very large telescope It can be studied in more detail. At this stage, it certainly cannot be ruled out that they will face other surprises.