About 8,000 light-years distant from Earth is a star system that no astronomer has ever seen. And within that star system is a bomb: a large star that could one day produce one of the most powerful explosions in the universe, known as a gamma-ray burst.
Gamma ray bursts have been observed in other galaxies, it is true, but never in our galaxy. These powerful explosions can be found in two types: long-lasting and short-lived. They can emit more energy in a few seconds than our Sun will ever do in its lifetime. They are so powerful, it is believed that a gamma – ray burst could be behind an extinction event on Earth some 450 million years ago and b arrería the atmosphere if we give full.
The objects responsible for this poorly understood phenomenon are as interesting as gamma-ray bursts. Wolf-Rayet stars are massive, more than 20 times that of our Sun. These titans live for only a few million years – a blink of an eye considering that stars like our own Sun live for 10 billion years.
Now, an international team of researchers has revealed their findings on this new object, dubbed Apep in the journal Nature Astronomy.
Apep had been seen in X-ray and radio observations more than 20 years ago, but it had never been studied in depth.
In 2012, astronomer Joe Callingham came across the observations. He clearly noticed that something unusual was happening. Hoping for more data, he booked time at the Very Large Telescope at the European Southern Observatory in Chile. What he obtained also caught his attention: there, as clear as day, was an image that looked like nothing: a beautiful pinwheel.
The researchers suggest that at the heart of this cosmic pinwheel are two massive Wolf-Rayet stars (with a third much farther away) with winds colliding in the center and producing dust.
Researchers theorize that a star is spinning rapidly, producing fast winds at the poles, but not at the equator where the dust would be. But another possibility is that the system is further away than is believed. However, that would make it the brightest object in our galaxy.
“We say the best model is that it is a long gamma-ray burst parent, but it’s actually a really unique system that we don’t understand, and that’s our best model,” said Benjamin Pope, a co-author of the paper. “But we need more data. Whatever it is, it’s a highly unusual star system … and this is our best model for that.”
The two stars, known to astronomers as Wolf-Rayets, orbit each other every 100 years or so. Experts estimate that winds travel at nearly 12 million kilometers per hour, or 1% of the speed of light. One of the stars is at the end of its life and will undoubtedly die in a powerful explosion, which we know as a supernova.
“There is no question that it will explode. It will be a supernova, probably in 100,000 years,” Callingham said. “The question is, will it end in a gamma-ray burst? If it exploded today, yes, it would.” But whether or not these conditions will hold, astronomers can’t say for sure. The good news is that even if it does happen, it appears that Earth is not in the line of fire.
The research team hopes to make follow-up observations with other telescopes and believes this is just the beginning of the Apep story.
“I think this star is going to be written about for years,” Pope said. “This has puzzled every expert in the field. I think we are at the beginning of a really interesting story.”
Referencia: J. R. Callingham et al, Anisotropic winds in a Wolf–Rayet binary identify a potential gamma-ray burst progenitor, Nature Astronomy (2018). DOI: 10.1038/s41550-018-0617-7
Crédito imagen: Peter Tuthill/University of Sydney/ESO
