A white hole is, in basic terms, the reverse of a black hole. If the latter absorbs all matter, including light, a white hole expels it. The brightness of an object detected by NASA is of such magnitude that, according to experts, it should not exist.
12 million light years from Earth is M82 X-2, an x-ray pulsar (a class of astronomical object that is a source of X-rays) that emits radiation 10 million times greater than that of the Sun… in short: it would be 10 million times brighter than our star. These types of objects, due to their luminosity, have long puzzled astronomers because they seem to exceed what is known as the Eddington limit, which restricts the brightness of an object based on its mass, by up to 500 times.
However, the case of M82 X-2 is so extreme that many scientists simply attributed its qualities to an optical illusion. But now a study published in The Astrophysical Journalanalyzed this pulsar for 7 years with NASA’s Nuclear Spectroscopic Devices (NuSTAR) and confirmed that it does indeed exceed the Eddington limit “by more than 150 times the mass transfer limit set by the Eddington luminosity”says the study.
Eddington’s limit it describes a delicate balance between the outward push of radiation produced by an object’s light and the pull generated by its gravity. If they are bright enough, the outgoing photons of light can overcome the object’s gravity, preventing stray matter from being drawn into its orbit and suspending it in equilibrium. The Eddington limit would determine the equilibrium between both actions.
The study authors, led by Matteo Bachetti, an astrophysicist at the Cagliari Astronomical Observatory, believe they have discovered the mechanism that enables this glow: magnetic fields so ridiculously strong that they are impossible to simulate in a laboratory.
“These observations allow us to see the effects of these incredibly strong magnetic fields that we could never reproduce on earth with current technology”, explains Bachetti in a statement from NASA.
Until recently, astronomers used to think of X-ray pulsars as black holes that surrounded themselves with enough gas and dust to gradually heat up over time and eventually radiate light. This explanation allowed the Eddington limit to be challenged.
But in 2014, it was discovered that M82 X-2 was actually a neutron star, the incredibly dense core of a once-massive star that collapsed in on itself without forming a black hole. Like some of the densest objects in the universe, neutron stars exert a gravitational pull about 100 trillion times stronger than Earth’s.
Thanks to this, the light from these objects can be produced by gases and dust crashing into the surface of the neutron star at millions of kilometers per hour. To give us an idea of the speed and what generates the collision of the dust, according to NASAan object the size of a jelly bean that crashes against these types of objects it would release the energy of a thousand hydrogen bombs.
In the study, Bachetti’s team determined that the M82 X-2 was extracting about 1.5 Earth masses of matter per year from a neighboring star: a huge amount. And all that mass, when colliding with the star, is what would generate its luminosity, one that exceeds the Eddington limit.
Thanks to the conclusions of this study, astronomers have more confidence in a recent hypothesis that suggests that, at least in this type of pulsars, its magnetic field could be distorting the shape of atoms nearby, allowing them to escape the overwhelming push of the star by radiating photons and crashing into its surface.
“It is the beauty of astronomy – concludes Bachetti -. We can’t really set up experiments to get quick answers: we have to wait for the universe to show us its secrets«.