A giant cosmic ‘fart’ is making a wobbling zombie star repeatedly flash us, ‘groundbreaking’ observations reveal

An enormous, ongoing cosmic “fart” is causing a mysterious zombie star to flare up repeatedly, shining bright pulses of X-rays toward Earth, a new study reveals. The unprecedented observations shed light on how some of the universe’s most extreme objects interact with one another.

Around 13,000 light-years from Earth lies an unusual binary star system, known as BP Crucis. It contains a blue hypergiant star roughly 60 times larger than the sun, dubbed Wray 977, alongside a neutron star — the undead and ultradense remains of a star that exploded via a supernova — that astronomers have labeled GX 301-2.

This stellar “zombie,” which contains the same mass as our home star packed into an object roughly 12 miles (20 kilometers) across, is a type of neutron star called a pulsar, which has an extremely powerful magnetic field and spins rapidly. This means it constantly shoots out a wobbling beam of powerful electromagnetic radiation, including X-rays, into the cosmos at regular intervals. When this beam aligns with Earth — approximately every 11 minutes, in the case of GX 301-2 — our planet’s telescopes detect a flash.

However, unlike most other known pulsars, GX 301-2 also emits frequent X-ray flares (separate from the regular beams), which cause it to shine much brighter at repeated intervals. And, until now, researchers were unsure why.

In the new study, published Sept. 18 in the journal Science Advances, researchers used the X-ray Imaging and Spectroscopy Mission (XRISM) — a space telescope jointly operated by NASA and the Japan Aerospace Exploration Agency — to take a closer look at BP Crucis. In doing so, they discovered that the neutron star flared up every time it passed through a giant plume of “stellar wind plasma” shooting out of its hypergiant partner.

This is the first time that researchers have ever detected this type of stellar material interacting with a neutron star, or with any other similar stellar remnant, opening the door to studying similar systems in the future.

“We’ve never before seen clear indications of wind plasma falling onto a compact object,” study first author Roi Rahin, a researcher at the University of Maryland, Baltimore County (UMBC) and NASA’s Goddard Space Flight Center, said in a statement. “We can now test our understanding of these processes in much greater detail.”

Whoever smelt it … explodes?

All stars that actively burn via nuclear fusion release streams of radiation and charged particles known as stellar wind. The sun emits such a stream, known as the solar wind, which can trigger vibrant aurora displays near Earth’s poles.

However, massive stars like Wray 977 blow stellar winds that are much more extreme. The blue hypergiant emits a single giant plume of concentrated ionized gas, or plasma, that spills out at around 335,000 mph (540,000 km/h). (Scientists think the stellar wind is likely sculpted into a single, concentrated plume due to the gravitational effects of the star’s ultradense neighbor.)

GX 301-2 circles Wray 977 every 41.5 days and experiences its X-ray flares when it reaches its closest and farthest points from its partner, with the strongest flares occurring at its closest point. As a result, researchers had long suspected that the flares occurred when the neutron star passed through the stellar wind plume. However, they had no way of proving this without more evidence.

During a 16-hour observation period coinciding with one of the neutron star’s flares, researchers used XRISM to capture highly detailed X-ray spectra, revealing “rapidly changing emission and absorption lines” that showed how the plume ebbed and flowed around GX 301-2, NASA representatives wrote.

“We could see how the dense stream of plasma acts very close to the neutron star,” study co-author Nazma Islam, an astronomer at the Manipal Centre for Natural Sciences in India and formerly a researcher at UMBC and NASA Goddard, said in the statement. “It was clear that these observations were groundbreaking, but at the same time this meant the analysis had to be especially detailed.”

Using this data, the researchers could simulate exactly how the plasma fell onto and swirled around the passing neutron star. When enough stellar material has accumulated on its surface, the stellar zombie explodes, unleashing the bright flashes we can detect on Earth.

The team now hopes to use XRISM to study future flaring events to better understand the relationship between GX 301-2 and Wray 977’s windy plume.

“The BP Crucis system is an ideal laboratory for studying wind-fed pulsar accretion,” Brian Williams, XRISM project scientist at NASA Goddard, said in the statement, and XRISM is “an ideal instrument for advancing our understanding of the processes involved.”