Headline: Giant 'farting' star helps send X-rays to Earth
Caption:
BY MARK WORGAN
A giant ‘farting’ star is creating mysterious X-ray pulses that can be observed 13,000 light-years away on Earth.
Astronomers have directly observed the gas from a giant star being captured by a neighbouring neutron star, helping explain the powerful bursts of X-rays.
The observations were made using the Japan-led X-ray Imaging and Spectroscopy Mission (XRISM) and provide researchers with a detailed view of how material passes between some of the most extreme objects in the Universe.
The system, known as BP Crucis, lies in the southern constellation Crux and consists of a blue hypergiant called Wray 977 and a neutron star known as GX 301-2.
Wray 977 is about 40 times the mass and 60 times the size of the Sun. Its high temperature and luminosity cause ionised gas to stream continuously away from the star in what astronomers call a stellar wind.
Researchers have now detected evidence of some of that material falling towards its much smaller companion and providing the fuel for powerful X-ray flares.
“We’ve never before seen clear indications of wind plasma falling onto a compact object,” said Roi Rahin, a researcher at UMBC (University of Maryland, Baltimore County) and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We can now test our understanding of these processes in much greater detail.”
The findings have been published in the journal Science Advances. GX 301-2 is the dense remnant of a star which exploded as a supernova.
Despite being only about 12 miles (20km) across, it contains more mass than the Sun.
The neutron star rotates once every 11 minutes and produces a beam of X-rays which periodically sweeps towards Earth, meaning it is classified as a pulsar. It takes about 41.5 days to orbit Wray 977.
Strong X-ray flares lasting several days occur twice during each orbit, around the points at which the neutron star is closest to and furthest from its giant companion.
Astronomers believe the neutron star's gravitational influence creates a particularly dense stream of plasma flowing from Wray 977.
When the pulsar passes through this stream, it captures some of the material, producing the X-ray flares.
The strongest eruptions take place when the neutron star is closer to Wray 977, where the stream of material is denser.
Researchers used XRISM to observe BP Crucis on 1 February 2025, monitoring the system for about 16 hours towards the end of one of its stronger flares.
Scientists detected rapidly changing emission and absorption lines, which allowed them to study the behaviour of the gas around the neutron star.
In particular, absorption lines produced by highly ionised iron revealed information about the speed and direction of plasma relatively close to the pulsar.
The researchers say the observations provide an opportunity to test models of how stellar winds are captured by compact objects and how that process generates X-rays.
The work could also improve scientists' understanding of how massive stars and their remnants interact in binary systems.
Keywords: feature,video,photo,space,pulsar,star
PersonInImage: This artist’s concept of the BP Crucis system follows the pulsar on a passage through the dense stream of plasma flowing from its companion, a blue hypergiant 40 times the Sun’s mass. During each four-day passage, the pulsar’s X-ray brightness flares as it pulls in some of the gas.