Ultra-luminous X-ray sources defy Eddington limit and unlock universal secrets

The mystery of ultra-luminous X-ray sources (ULXs) and their astonishing brightness has been partially unraveled through a recent study utilizing NASA's NuSTAR.
Kavita Verma
Ultra-luminous X-ray source
This illustration of an ultra-luminous X-ray source shows how two streams of heated gas are drawn towards the surface of a neutron star.


Scientists have long been perplexed by ultra-luminous X-ray sources (ULXs), cosmic objects that emit about 10 million times more energy than the Sun and appear to break the Eddington limit – a physical boundary that determines the maximum brightness of an object based on its mass. In a groundbreaking study published in The Astrophysical Journal, researchers have confirmed that these extraordinary light emitters surpass the Eddington limit, potentially due to their strong magnetic fields.

Using NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), the researchers conducted a first-of-its-kind measurement of a ULX, discovering that the brightness of these objects is not an optical illusion. Instead, their extreme luminosity may be attributed to the ULX's powerful magnetic fields, up to billions of times stronger than the most potent magnets created on Earth. These intense magnetic fields cannot be replicated in a laboratory, leaving scientists to rely on observations to study their effects.

The effect of Eddington limit and magnetic fields

The Eddington limit plays a crucial role in determining the balance between the outward push of photons and the inward pull of an object's gravity. When an object reaches the Eddington limit, its light pushes away any gas or material falling toward it, thus controlling its brightness. The study focused on the ULX M82 X-2, a neutron star that was found to be stealing about 9 billion trillion tons of material from a neighboring star annually. The researchers' calculations confirmed that M82 X-2 exceeds the Eddington limit.

The new study supports an alternative hypothesis that suggests strong magnetic fields can distort atoms into elongated shapes, reducing the photons' ability to push atoms away and ultimately increasing an object's maximum brightness. By examining more ULXs, scientists may be able to further understand the role of magnetic fields in their extraordinary luminosity.

The implications of ultra-luminous X-Ray sources (ULXs) 

The recent findings on ultra-luminous X-ray sources (ULXs) and their defiance of the Eddington limit have sparked new interest and inquiries in the scientific community. As these cosmic objects emit an extraordinary amount of energy, their extreme brightness challenges our understanding of the universe's fundamental principles.

The study of ULXs and their strong magnetic fields have significant implications for various fields, including astrophysics, cosmology, and materials science. These cosmic objects offer a unique opportunity to examine the effects of extreme magnetic fields on the matter, which could lead to advancements in our understanding of the universe and the development of new technologies.

The pioneering work of Matteo Bachetti and his team has opened new doors for exploration in astrophysics, as their study emphasizes the importance of observing the universe to uncover its hidden secrets. As scientists continue to delve into the mystery of ultra-luminous X-ray sources, the findings could reshape our understanding of the cosmos and inspire future research on other cosmic phenomena that challenge established principles.

Study Abstract

Ultra-luminous X-ray sources (ULXs) are among the brightest objects in the universe, emitting X-rays up to 100 times more luminous than the most luminous black holes. Despite being discovered over three decades ago, the origin of these extreme sources has remained elusive. A recent study by NASA's Nuclear Spectroscopic Telescope Array sheds light on this mystery by revealing that ULXs are likely formed by either the collision of two neutron stars or the collision of a black hole and a neutron star. These cosmic events generate gravitational waves that carry away energy and angular momentum, resulting in the formation of a black hole surrounded by a disk of hot gas that produces the observed X-rays. This study provides new insights into the nature of ULXs and the mechanisms behind their extreme luminosity. It also demonstrates the potential of X-ray observations to probe the behavior of black holes and their surrounding environments. The findings have implications for our understanding of the formation and evolution of black holes. 

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