In the far reaches of the Milky Way, about 22,000 light-years from Earth, a star unlike any other has a magnetic force greater than anything physicists have ever seen.
With a magnetic flux density of 1.6 billion tesla, a pulsar named “Swift J0243.6+6124” broke the previous record of 1 billion tesla. This star was discovered around the two pulsars named “GRO J1008-57” and “1A 0535 + 262”.
The physics that enabled access to this enormous power
To be clear, the average strength of a modern refrigerator magnet is about 0.001 Tesla. More powerful MRI machines were able to reach about 3 Tesla.
A few years ago, engineers managed to reach a magnetic force of 1,200 tesla, which they kept for a very short while, at just 100 microseconds.
So it stands to reason that reaching 1.6 billion Tesla would require an astonishing kind of physics, one that can only be achieved by massive objects crammed into very gigantic sizes and spinning at incredible speeds, enough to drive electrons to incredible speeds.
Chinese X-ray Observatory
“Swift J0243.6+6124” was considered a star worthy of attention. This star is a type of pulsar, which is known to be a very heavy and very small star, and is the only X-ray source in our galaxy that falls into the ultra-luminous category.
Also, this star is the only example in the Milky Way of a pulsar that emits X-rays with a companion star feeding it fast enough to generate radiation explosions of matter from its poles.
These features alone are a unique opportunity that makes astronomers rush to study them in detail. But measuring the magnetic field of a distant object is easy to say and hard to do. Despite their strength, these fields rapidly weaken until they become undetectable at distances of thousands of light years.
Fortunately, clues can be found in the way the very bright glow of X-rays is scattered across the ejected electrons, a property known as cyclotron resonance scattering.
China’s creation of the Insight-HXMT X-ray observatory in 2017 gives astrophysicists a way to capture such signals in distant emissions, allowing electron energies to be measured in the field of the star GRO J1008-57 in 2020.
Fortunately, too, Swift J0243.6+6124’s significant activity after the launch of the Insight-HXMT provided a glimpse into its high-strength magnetic field, with a cyclotron resonance scattering feature buried in its X-ray spectrum.
Researchers from the Chinese Academy of Sciences, Sun Yat-Sen University in China, and the University of Tübingen in Germany later analyzed this feature to calculate the energy of its electrons peaking at 146 keV.
Great victory for scientists
And since this star is the only ultra-luminous X-ray pulsar in our galaxy, having a precise measurement of its magnetic field gives astronomers a better idea of what might happen near its surface.
Pulsars are neutron stars made of atoms tightly compressed into configurations farther than anything we can create on Earth. Its magnetic properties help to rule out or support different models that explain the way its ultra-tiny shell behaves.
The magnetic nature of the neutron star confirms the possibility that its field is complex, consisting of multiple poles.
This is a huge victory for astrophysicists keen to understand the mysteries of some of the most exotic objects in space, and for the rest of us, it’s enough just to try to imagine a 1.6 billion Tesla magnet stuck on our refrigerator door.
sciencealert