This switch, when light overcomes gravity, is important, because the material falling on a ULX is the source of its brightness. This is something scientists frequently observe in black holes: when their strong gravity pulls in stray gas and dust, those materials can heat up and radiate light. Scientists used to think that ULXs must be black holes surrounded by glowing gas chests. But in 2014, NuSTAR data revealed that a ULX named M82 X-2 is actually a less massive object called neutron star. Like black holes, neutron stars form when a star dies and collapses, packing more than the mass of our Sun into an area not much larger than a medium-sized city.
This incredible density also creates a gravitational pull on the surface of the neutron star roughly 100 trillion times stronger than the gravitational pull on the surface of Earth. Gas and other materials dragged by this gravity are accelerated to millions of miles per hour, releasing tremendous energy when they hit the surface of the neutron star. (A marshmallow falling onto the surface of a neutron star it would hit it with the energy of a thousand hydrogen bombs.) This produces the high-energy X-ray light that NuSTAR detects.
The recent study pointed to the ULX itself at the heart of the 2014 discovery and found that, like a cosmic parasite, M82 X-2 is stealing about 9 billion trillion tons of material a year from a neighboring star , or about 1 1/2 times. the mass of the Earth. By knowing how much material hits the neutron star’s surface, scientists can estimate how bright the ULX should be, and their calculations match independent measurements of its brightness. The work confirmed that M82 X-2 exceeds the Eddington limit.
No illusions
If scientists can confirm the brightness of more ULXs, they could posit a persistent hypothesis that would explain the apparent brightness of these objects without ULXs having to exceed the Eddington limit. This hypothesis, based on observations of other cosmic objects, posits that strong winds form a hollow cone around the light source, concentrating most of the emission in one direction. If pointed directly at Earth, the cone could create a kind of optical illusion, making it falsely appear as if the ULX is exceeding the brightness limit.
Even if this is the case for some ULXs, an alternative hypothesis supported by the new study suggests that strong magnetic fields distort the roughly spherical atoms into elongated, spindly shapes. This would reduce the ability of photons to push atoms apart, ultimately increasing the maximum possible brightness of an object.
“These observations allow us to see the effects of these incredibly strong magnetic fields that we could never reproduce on Earth with current technology,” said Matteo Bachetti, an astrophysicist at the Cagliari Observatory of the National Institute of Astrophysics in Italy and lead author of the recent study. . “That’s the beauty of astronomy. By looking at the sky, we expand our ability to investigate how the universe works. On the other hand, we can’t really set up experiments to get quick answers; we have to wait for the universe to tell us show his secrets”.
More information about the mission
A Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory in Southern California for the agency’s Science Mission Directorate in Washington, NuSTAR was developed in collaboration with the Technical University of Denmark and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp. in Dulles, Virginia. NuSTAR’s mission operations center is at the University of California, Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center at Goddard NASA Space Flight Center. ASI provides the mission’s ground station and mirror data archive. Caltech manages JPL for NASA.
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