NASA learns how a dead star launched a particle storm that lit up the universe

A NASA satellite has helped scientists trace the main power source of a weird, switching pulsar named J1023 to a fast, particle packed wind smashing into nearby gas.

The crucial clue is that X-ray light and optical light line up in the same polarization angle, pointing to a single engine behind both.

The full name of this object is PSR J1023+0038, a so-called transitional millisecond pulsar that flips between radio quiet and radio loud behavior.

The most important number from the new observations is a 12 percent X-ray polarization, high enough to demand an ordered process rather than random hot gas.

Why J1023 matters

Astronomers call J1023 a transitional millisecond pulsar because it cleanly shifts between feeding from a companion star and emitting radio pulses. This makes it a rare system where different energy sources can be separated.

“Transitional millisecond pulsars are cosmic laboratories, helping us understand how neutron stars evolve in binary systems,” said lead researcher Maria Cristina Baglio, from the Italian National Institute of Astrophysics Brera Observatory (INAF) in Merate, Italy.

Baglio coordinated an international effort that combined space and ground telescopes. The team tracked the system across X-ray, optical, and radio bands in a tightly timed campaign.

Finding the X-ray source

In a new study, the researchers measured the angle and strength of polarization, the way light waves prefer one orientation over others. Matching angles in different bands can reveal where the radiation comes from.

They used NASA’s Imaging X-ray Polarimetry Explorer (IXPE) is the only observatory in orbit dedicated to measuring X-ray polarization. They compared those results with optical polarimetry from the Very Large Telescope in Chile.

“That finding is compelling evidence that a single, coherent physical mechanism underpins the light we observe,” said Francesco Coti Zelati, Institute of Space Sciences in Barcelona, co-lead author of the findings. The optical and X-ray angles agreed within their uncertainties, a tough test to pass.

A wind with a signature

The measurements show the X-rays arise in the pulsar wind, a flow of magnetized particles moving near light speed, when it slams into material near the star. In X-rays, the polarization degree is about 12 percent, with the angle aligned to the optical band.

At optical wavelengths, the team measured a polarization of about 1.41 percent, small but steady. That is exactly what you would expect if the X-rays and optical light are produced by the same ordered process rather than by unrelated regions.

Earlier work on J1023 detected fast optical pulses and matching X-ray pulses, strengthening the case for a compact emission zone.

Those pulsations tie the light directly to the star’s rotation and show that the source changes on millisecond timescales.

The favored location is close to the light cylinder, the distance where co-rotation with the star becomes impossible, only about 50 miles from the neutron star for J1023.

That is exactly where a strong shock would form as the wind hits the inner edge of the accretion flow.

J1023 challenges old models

Standard accretion scenarios predict low X-ray polarization and spectral features that do not show up in these data.

The team instead sees a clean, power law like signal, consistent with synchrotron radiation, light from electrons spiraling in magnetic fields, which naturally produces moderate polarization and broad spectra.

A compact jet can also emit polarized synchrotron light, but its geometry would cap the polarization at lower values than seen in X-rays here. The matching optical and X-ray angles argue against a jet dominating the high energy output.

“IXPE has observed many isolated pulsars and found that the pulsar wind powers the X-rays. These new observations show that the pulsar wind powers most of the energy output of the system,” said Philip Kaaret from NASA Marshall Space Flight Center, the principal investigator for IXPE. 

What the alignment tells us

The steady angle through the pulse cycle points to a mostly ordered magnetic field in the emitting region. That stability is hard to produce if the light is bouncing around a turbulent accretion structure.

It also links J1023 to other binaries where a pulsar wind collides with nearby matter.

In the system PSR B1259 63, IXPE detected an X-ray polarization of about 8 percent, a level that matches the shock picture in a very different environment. That binary shows that wind shock emission can dominate across multiple systems.

Small differences across sources can be explained by viewing geometry and how tangled the local field becomes.

J1023 appears to have enough order to keep the angle steady, yet enough turbulence to limit the polarization to around a tenth of the maximum possible value for synchrotron light.

Lessons from pulsar J1023

The alignment across bands suggests one engine at work, not a patchwork of unrelated parts. That engine is the shock at the boundary where wind meets disk, accelerated by the star’s spin and guided by its magnetic field.

Timing results add context. Studies that compared the precise arrival times of optical and X-ray pulses in J1023 found a small lag that fits cooling and transport in a compact shock zone. Those results are consistent with the new polarization picture.

The approach also scales. Coordinated polarimetry and timing can sort power sources in other transitional millisecond pulsars, where accretion and rotation compete. It can even test how shocks behave under low accretion rates that are hard to probe elsewhere.

IXPE continues to survey pulsars, pulsar wind nebulae, and binaries where winds collide. Fresh targets will test whether J1023 is unique or the prototype of a larger class.

As instruments improve, phase-resolved polarization will reveal how the magnetosphere, the region dominated by the star’s magnetic field, threads the shock and sets the angle. That level of detail will tell us how the wind turns rotational energy into radiation we can measure on Earth.

The study is published in The Astrophysical Journal Letters.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–