‘Pinwheel’ system may upend star death theory

(Credit: Getty Images)

Scientists have discovered a new, massive star system—one that challenges existing theories of how large stars eventually die.

“This system is likely the first of its kind ever discovered in our own galaxy,” says Benjamin Pope, a NASA Sagan fellow at the Center for Cosmology and Particle Physics at New York University.

Specifically, the scientists detected a gamma-ray burst progenitor system—a type of supernova that blasts out an extremely powerful and narrow jet of plasma and which is thought to occur only in distant galaxies.

Apep structure animated gif
This animated gif illustrate the geometry of the structure that scientists witnessed in the Apep system. (Credit: U. Sydney)

“It was not expected such a system would be found in our galaxy—only in younger galaxies much further away,” Pope says. “Given its brightness, it is surprising it was not discovered a lot sooner.”

As reported in Nature Astronomy, the system, which astronomers have dubbed “Apep,” is an estimated 8,000 light years away from Earth and adorned with a dust “pinwheel”—whose strangely slow motion suggests current theories on star deaths may be incomplete.

Near and Mid Infrared composite image of the star system
This image is a composite of data astronomers collected from the near-infrared camera (NACO) together with longer wavelength data in the thermal infrared (from the VISIR instrument). Both instruments are on the European Southern Observatory’s VLT telescopes, Mt Paranal, Chile. The multi-color collage renders the central stars of the system in blue-white at the core, with the fainter companion to the North and a bit West of the heart of the system (actually, another binary so close that it can’t be resolved here). (Credit: Credit: U. Sydney/European Southern Observatory)

When the most massive stars in our universe near the end of their lives, they produce fast winds—typically moving at more than 1,000 kilometers per second—that carry away large amounts of a star’s mass. These fast winds should carry away the star’s rotational energy and slow it down long before it dies.

“These massive stars are often found with a partner, in which the fast winds from the dying star can collide with its companion to produce a shock that emits at X-ray and radio frequencies and produces exotic dust patterns,” says lead author Joseph Callingham, a postdoctoral fellow at the Netherlands Institute for Radio Astronomy.

“Apep’s dust pinwheel moves much slower than the wind in the system,” he says. “One way this can occur is if one of the massive stars is rotating so quickly that it is nearly tearing itself apart. Such a rotation means that when it runs out of fuel and begins to explode as a supernova, it will collapse at the poles before the equator, producing a gamma-ray burst.”

Additional coauthors are from the Netherlands Institute for Radio Astronomy, the University of Sydney, the University of Edinburgh, the University of Sheffield, and the University of New South Wales.

Researchers performed the work, in part, under contract with the Jet Propulsion Laboratory, which NASA funds through the Sagan Fellowship Program, which the the NASA Exoplanet Science Institute executes.

Source: New York University