Astronomers from the George Washington University (GWU) in Washington, DC, and elsewhere have employed NASA’s Chandra X-ray spacecraft to observe a pulsar wind nebula inside a supernova remnant known as CTA 1. Results of the observational campaign, presented in a research paper published May 20 on the arXiv preprint server, shed more light on the morphology and properties of this nebula.
Pulsar wind nebulae (PWNe) are nebulae powered by the wind of a pulsar. Pulsar wind is composed of charged particles and when it collides with the pulsar’s surroundings, in particular with the slowly expanding supernova ejecta, it develops a PWN.
SNR-PWN-pulsar system
CTA 1 is a composite shell-type supernova remnant (SNR) at a distance of some 4,600 light years away from Earth. It contains a PWN powered by PSR J0007+7303—a radio-quiet pulsar with a spin period of 315.8 milliseconds, magnetic field strength at a level of 10 trillion Gauss, and characteristic age of 14,000 years.
A team of astronomers led by GWU’s Seth Gagnon decided to take a closer look at CTA 1’s PWN, hoping to get more insights into its nature. For this purpose, they performed deep Chandra observations of this nebula and analyzed archival data from this spacecraft. Their study was complemented by data from NASA’s Fermi Gamma-ray Observatory.
“We have presented a detailed analysis of new and archival Chandra observations of the PWN powered by PSR J0007+7303 in CTA 1, supplemented by Fermi-LAT data analysis and broadband SED [spectral energy distribution] modeling,” the researchers write.
Compact morphology and properties revealed
The study found that the PWN showcases a compact morphology, identifying a jet (about 20 arcseconds long) extending south of the pulsar and bending toward the southwest, a faint counter-jet to the north, and a compact torus oriented approximately perpendicular to the jet axis. The astronomers assume that bending of this jet is likely influenced by interaction with the ambient medium or the SNR reverse shock.
By analyzing the data, the astronomers found that the traverse velocity of PSR J0007+7303 is below 200 km/s, therefore significantly lower than previous estimates based on its displacement from the SNR center. This suggests that the system may be older or points to an asymmetric expansion of CTA 1.
Furthermore, the study revealed hard spectra in the compact PWN components and low X-ray radiative efficiency. The broadband SED indicates a low magnetic field (between 1.4 and 3.2 µG) and a high electron cutoff energy (at a level of 0.2–0.3 PeV).
“Overall, CTA 1 emerges as a low-magnetization, low efficiency PWN capable of accelerating particles to PeV energies, providing an important laboratory for studying particle acceleration and evolution in young pulsar wind nebulae,” the authors of the paper conclude.
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Publication details
Seth Gagnon et al, Chandra X-ray Observations of the Pulsar Wind Nebula within CTA 1, arXiv (2026). DOI: 10.48550/arxiv.2605.21278
Journal information:
arXiv
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Pulsar wind nebula inside supernova remnant explored with Chandra (2026, May 30)
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