Exotic cosmic object caught stealing material from neighbouring star

NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) caught one of the ultra-luminous X-ray sources (ULXs) - astronomical objects that emit X-rays at extremely high luminosities - stealing tons of material from a neighbouring star.

ULXs are so brighter that they even exceed a physical boundary called the Eddington limit by 100 to 500 times. Their limit-breaking brightness has puzzled scientists for many years.

One hypothesis for this extreme brightness is that it is due to the ULX's strong magnetic fields. However, scientists cannot test this hypothesis in a lab as the magnetic fields of ULXs are billions of times stronger than the strongest magnets ever created on Earth. Therefore, the only way to test this hypothesis is through observations.

ULXs were thought to be black holes surrounded by bright coffers of gas. However, in 2014, NuSTAR data revealed that a particular ULX, named M82 X-2, was actually a neutron star - extremely dense objects that are the collapsed remnants of massive stars.

A new study has confirmed that these light emitters are indeed as bright as they seem and that they break the Eddington limit.

The study targeted M82 X-2 and found that, like a cosmic parasite, this ULX is stealing about 9 billion trillion tons of material per year from a neighbouring star - about 1.5 times the mass of Earth. By determining the amount of material that is being accreted onto the surface of the neutron star, scientists can measure the expected brightness of the ULX. The findings confirmed that M82 X-2 exceeds the Eddington limit.

If scientists can confirm the brightness of more ULXs, it may help to confirm or rule out a lingering hypothesis that could explain the brightness of these objects without exceeding the Eddington limit. This hypothesis suggests that strong winds form a cone around the light source, directing most of the emission in one direction. If pointed directly at Earth, this cone could create an optical illusion, making it appear as though the ULX was exceeding the brightness limit.

However, even if this hypothesis applies to some ULXs, the new study proposes an alternative hypothesis, which suggests that strong magnetic fields can distort atoms into elongated, stringy shapes, reducing the photons' ability to push atoms away and ultimately increasing an object's maximum possible brightness.

A class of objects called ultraluminous X-ray sources appear to be breaking the rules! Our NuSTAR telescope caught one of these sources stealing material from a neighboring star, helping us understand why it’s brighter than it should be for its mass: https://t.co/d3DYIT7eK4 pic.twitter.com/Umetf7no1A

— NASA Universe (@NASAUniverse) April 7, 2023