- NASA's IXPE measured magnetic fields of pulsar PSR J1101-6101 in the Lighthouse Nebula
- The pulsar spins 16 times per second and is a neutron star with a strong magnetic field
- IXPE observed the nebula for 18 days, studying two X-ray offshoots called filament and trail
For the first time, scientists have used NASA's IXPE (Imaging X-ray Polarimetry Explorer) to directly measure the magnetic fields of PSR J1101-6101, a pulsar located within what is often referred to as the Lighthouse Nebula. The results provide new insight into the structure of some of the most extreme objects in the cosmos as NASA continues to explore the secrets of how the universe works. A paper describing the results was published in the Astrophysical Journal, reported NASA.
A pulsar is a type of neutron star with a strong magnetic field that spins incredibly fast. The pulsar at the center of the Lighthouse Nebula is rotating 16 times per second.
Neutron stars are the leftover cores of massive stars formed at the end of their life cycles. They possess more mass than the Sun but are condensed down to the size of a city, making them natural laboratories for studying extreme physics.
Polarisation is a property of light that describes the direction of its electric field vibrations. The polarisation degree is a measurement of how aligned those vibrations are with each other.
In June 2025, IXPE spent nearly 18 days focused on the Lighthouse Nebula.
Astronomers studied two narrow X-ray offshoots extending from the pulsar to better understand how electrons moving at nearly the speed of light interact with this energetic system. The longer offshoot is known as the filament, while the shorter one is called the trail.
When high-energy particles from the pulsar collide with the gas of interstellar space, they form a bow shock, similar to the bow wave created at the front of a speeding boat. Most particles become trapped behind this bow shock, forming the turbulent trail behind the pulsar. Researchers have suspected since 2008 that the highest-energy particles escape through this bow shock into interstellar space, flowing along the galaxy's magnetic field lines to create the nebula's long, thin filament.
Jack Dinsmore, an undergraduate student at Stanford University who led the study, said they wanted to test that theory. He said the "smoking gun" would come from measuring the polarisation of the light, which indicates the magnetic field direction. He added that if the magnetic field points along the filament, it confirms that the filament's particles are flowing along the field.
One challenge with these measurements is that the Lighthouse Nebula is relatively faint. To address this, IXPE scientists developed advanced analysis methods that use every bit of data, avoiding simplifying steps that could limit information. With these new tools and the new observations of the Lighthouse, the science team successfully measured the filament's polarisation. These techniques also provided a polarisation measurement of the trail and the pulsar's emission signal.
Their analysis confirmed with more than 99% confidence that the magnetic field does indeed align with the particles' flow.
Roger Romani, a Stanford University professor and co-author of the paper, said many models for filaments assume strong magnetic turbulence. He said the high polarisation degree they measured indicates lower turbulence than such models require.
The IXPE observations also showed that the magnetic field responsible for X-ray emission had to be parallel to the trail. However, the authors collected radio frequency observations showing a magnetic field pointing almost exactly perpendicular.
