The beautiful Pinwheel Nebula is a cosmic cataclysm in the making

This image of a dusty, gas-rich nebula is pretty, but appearances can be misleading. Known as the Wolf-Rayet star system, he is about to unleash a catastrophic burst of gamma rays when he finally goes supernova. What is remarkable about this Wolf-Rayet system is that it is the first to be discovered in our own galaxy. Cue the sinister music …

This Wolf-Rayet stellar system is officially known as 2XMM J160050.7-514245, but for researchers who have recently explored this enigmatic object, it is simply "Apep", an exotic object named for the former Egyptian god of serpentine chaos. In a press release, Joseph Callingham, senior author of the new study and astronomer at the Netherlands Radio Astronomy Institute (ASTRON), said: "This is the first system of this type to be discovered in our own galaxy "- a system he did not expect to find" in our own backyard ". The details of this research were published today in Nature Astronomy.

Indeed, astronomers have already observed Wolf-Rayet stars, but only in other galaxies. These huge stellar systems are about to enter their agony, and at that moment, they will generate a type of supernova that emits an extremely powerful and narrow plasma jet, the frightful burst of gamma rays.

Apep is a gamma precursor system of this type, with a massive triple star system – a binary pair and an isolated star – and large spiral arms composed of gas and dust. The system is located about 8000 light-years from Earth, which is uncomfortably close given its explosive potential.

"It was a very fun project to do in some ways, in the sense that Joe had found this object and showed it to me for the first time in 2012 while we were undergraduate in Sydney. It took us six years to gather all the necessary data. reveals this amazing story, "Gizmodo Benjamin Pagan, NASA Sagan member at the Center for Cosmology and Particle Physics at the University of New York and co-author of the new study, told Gizmodo. "Sometimes science is slow! But I remember that last year, the day before my thesis defense at Oxford, he was visiting me and showed me the picture of the spiral of Apep – I & # 39; I literally gasped, it was so shocking. There is really nothing like it. "

Pope, Callingham and colleagues measured the velocity of dust inside the spiral arms using the VISIR camera in the very large telescope of the very large telescope of the European Southern Observatory. At this final stage of their short life cycle (these systems only last a few hundred thousand years – a wink in cosmological terms), the stars of the Wolf-Rayet systems rotate rapidly, producing stellar winds that move at appalling speeds. These winds carry significant amounts of stellar material into space and are responsible for the formation of majestic plumes of dust particles. In the case of Apep, his spiral arms measure several light-years.

By measuring rotational speeds in this nebula, the researchers concluded that at least one of the three stars in the system was spinning fast enough to trigger a long-lasting gamma-ray burst when it finally explodes as a supernova (the value exact). the timing is still impossible to predict). The speed of gasoline in the nebula was 12 million kilometers per hour, but the dust only moves at 570 million kilometers per hour. Researchers say this discrepancy is indicative of a star approaching almost critical rotation.

"The Apep dust wind wheel is moving much slower than the wind in the system," Callingham said. "This can happen if one of the massive stars rotates so fast that it almost tears. Such a rotation means that when it runs out of fuel and starts to explode as a supernova, it will collapse to the poles before the equator, producing a burst of gamma rays. "

The discovery of this system, said the Pope, is that no one had yet observed rapidly rotating Wolf-Rayet systems in our galaxy. In addition, many astronomers have assumed that these objects could not even exist in a galaxy like ours; The Milky Way is ancient and rich in metals, containing an abundance of heavy stars that should collapse rapidly. The new result suggests that our understanding of how massive stars die is still incomplete.

"Wolf-Rayet star systems are thought to be the spawners of long gamma-ray bursts, so if there is one in our galaxy, that's an interesting discovery," Pope told Gizmodo. "Even if it is not the case, something profoundly strange is happening in this star system and it's the best explanation we have."

As noted earlier, gamma ray bursts are among the most powerful explosions known to astronomers. With a duration ranging from two seconds to a few hours, long-lived gamma-ray bursts release as much energy as the Sun throughout its life. Disturbingly, some scientists have hypothesized that the Ordovician-Silurian extinction – a mass extinction event that occurred 440 million years ago on Earth – had been caused by an explosion of gamma rays in our own galaxy. Physicist Adrian Melott of the University of Kansas has hypothesized that a "dangerously close to GRB is expected to occur on average two or more times per billion years".

Pope said it would be "very bad" if one went nearby, but he is not particularly worried.

"As for why we have no worries, the best I can offer you is that it's very uncertain that Apep is gamma-raying. If this is the case, it is unlikely to be in the very near future. future."

Another point of encouragement: the gamma ray beams are highly directional and project their concentrated and high energy rays in a specific direction. So, for Apep to represent a threat, it would not only be necessary that it become a supernova, but also that it be directed in our general direction.

Anyway, we can not do anything about it except to learn more about Wolf-Rayet systems. It might also be useful to talk about the ancient Egyptian incantation to rid the world of the damaging powers of Apep:

Spitting on Apep, staining Apep of the left foot, taking a spear to hit Apep, Fconvert Apep, take a knife to hit Apep, fire Apep …

[Nature Astronomy]