A star emitting X-rays located in the Messier 82 galaxy, approximately 12 million light-years away from Earth, shines with an intensity that defies the laws of physics.
Simulating an ultra-bright X-ray-emitting neutron star with an extremely strong magnetic field. Image: NASA/JPL-Caltech
Astronomers refer to such rule-defying objects as Ultra-Luminous X-ray sources (ULXs), which emit energy over 10 million times that of the Sun. This energy level exceeds the limit defined by Eddington’s law, where an object’s brightness is constrained by its size. If an object surpasses the Eddington limit, researchers predict it will explode into many pieces. However, ULXs often exceed this limit by 100 to 500 times, perplexing scientists, according to NASA.
A recent study published in the Astrophysical Journal by NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), which observes the universe with high-energy X-rays, confirmed the extraordinary brightness of a particular ULX known as M82 X-2. Earlier hypotheses suggested that such extreme brightness could be a form of optical illusion, but the research findings have debunked that theory, revealing that M82 X-2 indeed challenges the Eddington limit, as reported by Live Science on April 11.
Astronomers once believed ULXs might be black holes, but M82 X-2 is a neutron star. Neutron stars are the dense, leftover cores of stars similar to the Sun after they’ve died. They are incredibly dense, with gravitational forces on their surface more than 100 billion times stronger than on Earth, meaning that any matter falling onto the surface of the dead star has explosive effects. For instance, a marshmallow-sized object impacting the surface of a neutron star would create an explosion equivalent to 1,000 nuclear bombs.
The new study reveals that M82 X-2 consumes matter at a rate of about 1.5 Earths per year from a neighboring star. When this matter collides with the surface of the star, it generates the observed brightness, leading researchers to believe there is something causing M82 X-2 to exceed the Eddington limit. Their current hypothesis revolves around the powerful magnetic field of the neutron star altering the atomic structure, allowing the star to maintain its form even as it becomes increasingly luminous.
“Observations allow us to understand the impact of an extremely strong magnetic field, which we can never replicate on Earth with current technology,” shared the research team’s leader, Matteo Bachetti, an astrophysicist at the Cagliari Observatory in Italy.