Capturing a Cosmic Feeding Frenzy
Astronomers have leveraged the advanced capabilities of the XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft to capture detailed observations of a volatile cosmic interaction: a hypergiant star feeding a dense, compact stellar remnant known as a neutron star.
The Nature of Neutron Stars
Neutron stars represent the final, extreme stage of massive stellar evolution. These objects are incredibly dense, packing the equivalent of one to two solar masses into a sphere merely 12 miles (20 kilometers) in diameter. The density is so profound that a single teaspoon of neutron star material would weigh approximately 10 million tons—a mass comparable to 85,000 blue whales. Furthermore, many young neutron stars, identified as pulsars, rotate hundreds of times per second while emitting intense beams of radiation, similar to a cosmic lighthouse.
Analyzing the BP Crucis System
The research team focused their instruments on BP Crucis, a system situated 13,000 light-years from Earth. The system consists of a pulsar named GX 301-2 and its donor, a blue hypergiant star designated Wray 977. Wray 977, possessing 40 times the mass and 60 times the radius of our sun, is so energetic that it continuously sheds a powerful stream of ionized gas, or plasma.
GX 301-2 completes a rotation every 11 minutes and orbits its companion over a 42-day cycle. Scientists propose that the neutron star's immense gravity pulls this plasma into a dense stream, triggering intense X-ray flares, particularly when the pulsar is closest to the hypergiant.
Groundbreaking Data from XRISM
In February 2025, XRISM spent roughly 16 hours observing the system via its Resolve instrument, capturing the conclusion of a significant flaring event. The data revealed that the plasma stream moves at a staggering speed of 335,000 miles per hour (540,000 kilometers per hour), roughly 200 times the top speed of an F-16 fighter jet.
Nazma Islam, a researcher at the Manipal Center for Natural Sciences in India, remarked on the significance of the findings: «It was clear that these observations were groundbreaking, but at the same time this meant the analysis had to be especially detailed. We could see how the dense stream of plasma acts very close to the neutron star.»
Dynamics of the Plasma Flow
The researchers hypothesize that as the neutron star enters the stellar wind, it attracts plasma, forming a temporary, thick accretion disk around itself. Heat generated as this gas is consumed produces the observed X-rays. As the neutron star progresses deeper into the densest region of the plasma flow, the disk eventually fragments due to a lack of angular momentum.
Once the disk dissipates—or in some cases, briefly reverses its rotation—the plasma impacts the neutron star's surface directly, causing the most powerful X-ray flares. The entire transit through this dense stream lasts approximately four days.
Brian Williams, the mission's project scientist at NASA's Goddard Space Flight Center, noted the importance of the technology used: «The BP Crucis system is an ideal laboratory for studying wind-fed pulsar accretion, and XRISM's sensitive, high-resolution Resolve spectrometer is an ideal instrument for advancing our understanding of the processes involved.»
The findings regarding this cosmic interaction were recently published in the journal Science Advances.