Indian Scientists Discover Rare Accretion Disk Around Neutron Star 24,000 Light-Years Away

Scientists at the Raman Research Institute (RRI) in Bengaluru have discovered evidence of an unusual accretion disk surrounding Centaurus X-3, one of the brightest X-ray pulsars known to astronomers. Located approximately 24,000 light-years from Earth, the neutron star appears to draw matter from its massive stellar companion through a rotating disk rather than relying exclusively on the direct capture of stellar winds.

The research, announced on October 21, 2026, was led by RRI scientist Kinjal Roy, along with researchers H. Manikantan and Biswajit Paul. The team analysed X-ray observations collected by the European Space Agency’s XMM-Newton space observatory. Their findings reveal previously unresolved details about how matter moves around the highly magnetised neutron star and provide new evidence for understanding the behaviour of high-mass X-ray binary systems.

The study, titled XMM-Newton View of Pulsating Iron Fluorescent Emission from Centaurus X-3, was published in The Astrophysical Journal in 2025. The Raman Research Institute highlighted its scientific significance in an announcement on October 21, 2026.

Centaurus X-3: An Extraordinary Stellar System

Centaurus X-3 is a high-mass X-ray binary system located in the constellation Centaurus. It consists of a neutron star orbiting a massive companion star whose mass exceeds ten times that of the Sun. The system has attracted considerable scientific attention because of its intense X-ray emissions and its importance in the early development of X-ray astronomy.

A neutron star forms when the core of a massive star collapses following a supernova explosion. The resulting object contains an enormous amount of matter compressed into a sphere typically only a few tens of kilometres across. Its exceptional density produces an extremely powerful gravitational field capable of pulling material from nearby celestial objects.

When a neutron star possesses a strong magnetic field and rotates rapidly, it can produce concentrated beams of electromagnetic radiation from regions near its magnetic poles. As the star rotates, these beams sweep across space and may appear to pulse when observed from Earth. Astronomers refer to such objects as pulsars.

Centaurus X-3 was among the first X-ray pulsars discovered and remains one of the most extensively studied examples of a neutron star interacting with a massive companion. Its exceptional brightness allows scientists to examine physical processes that would otherwise be difficult to investigate across such enormous distances.

Indian Researchers Identify an Unusual Method of Matter Accretion

The central discovery concerns how the neutron star obtains material from its companion. In many high-mass X-ray binary systems, the massive companion continuously releases particles through powerful stellar winds. The neutron star’s gravitational field captures some of this material, allowing it to fall towards the compact object.

Scientists have generally considered direct stellar-wind capture an important accretion mechanism in these systems. However, the Raman Research Institute team found evidence that Centaurus X-3 also receives matter through an accretion disk.

An accretion disk forms when material drawn towards a compact astronomical object retains sufficient angular momentum to circulate around it. The material develops a flattened, rotating structure and gradually moves inward while releasing energy.

Near a strongly magnetised neutron star, the magnetic field can redirect the incoming material along field lines towards regions near the magnetic poles. The resulting flow of matter produces intense X-ray radiation as material approaches and interacts with the neutron star.

The researchers identified evidence of this disk-fed arrangement in Centaurus X-3, demonstrating that its accretion environment is more complex than a model based solely on direct stellar-wind capture.

XMM-Newton Observatory Provides Crucial Scientific Evidence

The research team examined observations obtained from XMM-Newton, an X-ray space observatory operated by the European Space Agency. The satellite was launched in December 1999 and carries advanced instruments capable of detecting and analysing X-ray radiation from distant astronomical objects.

X-ray observations provide valuable information about neutron stars because the matter falling towards them becomes extremely energetic. This material produces high-energy radiation that reveals conditions in regions surrounding compact objects.

Although Centaurus X-3 is exceptionally luminous, its distance makes it impossible for conventional telescopes to resolve the individual structures immediately surrounding the neutron star. Astronomers therefore study changes in the radiation reaching their instruments to infer the physical properties of these otherwise invisible regions.

The RRI team concentrated on four secondary X-ray emission lines present in the observational data. These spectral features arise when material surrounding the neutron star absorbs energetic radiation and subsequently re-emits it.

By examining how the intensity of these lines changed during the pulsar’s rotation, the scientists were able to investigate the behaviour of matter in the immediate environment of Centaurus X-3.

Pulsating X-Ray Signals Reveal a Hidden Accretion Stream

One of the most important findings emerged from the relationship between the pulsar’s rotation and the intensity of secondary X-ray emissions. The researchers observed that four secondary emission lines exhibited variations connected to the neutron star’s rotational cycle.

The analysis indicated that the structure responsible for these variations must rotate along with the pulsar. After examining the possible sources of secondary radiation, the team identified an accretion stream as the explanation for the observed behaviour.

An accretion stream channels material from the surrounding accretion disk towards the neutron star. As the material approaches the compact object, its powerful magnetic field guides the flow towards regions near the magnetic poles.

The geometry of this stream affects how radiation travels from the pulsar to the observing satellite. When the rotating stream passes through the observer’s line of sight, it can partially obscure the primary X-ray emission. At the same time, radiation reprocessed by the stream becomes more prominent.

This relationship explains why the primary and secondary emissions change during the pulsar’s rotation. The researchers concluded that the observed variations provide evidence of a rotating accretion stream connected to a surrounding disk.

The finding is especially important because the presence of such a stream indicates that matter is being channelled from an accretion disk rather than reaching the neutron star solely through direct capture of stellar winds.

Discovery Challenges Conventional Models of High-Mass X-Ray Binaries

High-mass X-ray binaries contain compact objects such as neutron stars or black holes interacting with massive stellar companions. These systems provide natural laboratories for studying gravity, magnetic fields, radiation and the behaviour of matter under extreme physical conditions.

In many such binaries, astronomers model accretion primarily through the direct capture of material released by the companion star. The presence of an accretion disk introduces additional physical processes that can influence the distribution and intensity of X-ray radiation.

The Raman Research Institute discovery indicates that scientific models of Centaurus X-3 must account for radiation generated or reprocessed by the disk and the associated accretion stream. Ignoring these structures could lead to an incomplete interpretation of the observed X-ray signals.

Kinjal Roy explained that accretion disks are not generally expected to dominate the accretion process in high-mass X-ray binaries. The evidence from Centaurus X-3 therefore requires researchers to reconsider how the system’s emission is represented in future theoretical calculations.

The study does not imply that accretion disks are absent from every other high-mass X-ray binary. Instead, it establishes evidence for a disk-fed mechanism in a system where direct stellar-wind accretion has traditionally been an important part of the physical interpretation.

Understanding Magnetic Fields and Extreme Matter Around Neutron Stars

The newly identified accretion structure also provides opportunities to investigate the interaction between magnetic fields and matter surrounding neutron stars. These objects possess magnetic fields vastly stronger than those encountered in ordinary stellar environments.

As material approaches the neutron star, the magnetic field influences its movement and determines where it can reach the stellar surface. The arrangement of the accretion stream can therefore reveal information about the geometry of the magnetic field and the distribution of matter close to the compact object.

Secondary X-ray emissions provide an indirect method of studying these regions. By analysing how surrounding material absorbs and re-emits radiation, scientists can investigate structures that cannot be observed directly.

Such observations may improve estimates of the orientation of the system and help researchers understand how radiation interacts with rapidly moving, highly energetic material.

The Centaurus X-3 findings demonstrate how detailed analysis of existing space-observatory data can reveal previously unrecognised physical processes within extensively studied astronomical systems.

Raman Research Institute Strengthens India’s Astrophysics Research

The discovery highlights the contribution of Indian scientists to international research on compact stars and high-energy astrophysics. The Raman Research Institute, an autonomous institution under the Department of Science and Technology, conducts research across astronomy, astrophysics, theoretical physics, quantum technologies and related scientific disciplines.

The institute has developed expertise in studying neutron stars, pulsars and other high-energy astronomical sources. Its scientists use observations from international space missions alongside theoretical analysis and computational modelling to investigate complex astrophysical phenomena.

The Centaurus X-3 study illustrates the value of international scientific infrastructure in supporting Indian research. Although the XMM-Newton observatory operates under the European Space Agency, its scientific observations provide researchers worldwide with opportunities to investigate distant astronomical objects.

By identifying a rotating accretion stream through the analysis of secondary X-ray emission, the RRI team has added new evidence to the scientific understanding of a well-known pulsar. The work also demonstrates India’s growing contribution to the interpretation of high-energy astronomical observations.

New Evidence Opens Opportunities for Future Pulsar Research

The discovery provides a foundation for more detailed investigations of accretion processes in Centaurus X-3 and other high-mass X-ray binary systems. Researchers can now incorporate the disk and associated accretion stream into models that describe how matter moves towards the neutron star and produces X-ray radiation.

Future observations and theoretical studies may help scientists determine how the accretion disk forms, how its structure changes over time and how the neutron star’s magnetic field influences the flow of matter.

The findings also demonstrate the importance of examining secondary radiation rather than concentrating exclusively on the primary X-ray signals emitted near a pulsar’s magnetic poles. Reprocessed radiation can reveal information about surrounding structures that remain hidden in direct observations.

With the discovery of an unusual accretion mechanism around Centaurus X-3, scientists at the Raman Research Institute have contributed to a more detailed understanding of one of astronomy’s best-known X-ray pulsars. Their work strengthens India’s participation in fundamental astrophysics research and advances the scientific investigation of some of the most extreme environments in the universe.

---

References

1. Raman Research Institute, October 21, 2026: Pulsing Signals Reveal Hidden Structure Around a Famous Neutron Star.
   https://www.rri.res.in/highlights/pulsing-signals-reveal-hidden-structure-around-famous-neutron-star
2. Roy, K., Manikantan, H. and Paul, B. (2025): XMM-Newton View of Pulsating Iron Fluorescent Emission from Centaurus X-3. The Astrophysical Journal, Volume 991, Issue 2, Article 162.
   https://doi.org/10.3847/1538-4357/adf8e6
3. Ministry of Science and Technology, Government of India, October 21, 2026: Pulsing Signals Reveal Hidden Structure Around a Famous Neutron Star. Press Information Bureau.
4. European Space Agency: XMM-Newton Mission – Scientific Objectives, Observatory Instruments and X-ray Astronomy Research.
   https://www.esa.int/Science_Exploration/Space_Science/XMM-Newton

---