At a Glance
- The blazar PKS 1424+240 was a major puzzle because it emitted powerful neutrinos and gamma rays despite having a jet that appeared to move very slowly.
- By combining 15 years of VLBA radio observations, scientists created an unprecedentedly deep image, reminiscent of the famed “Eye of Sauron” from J.R.R. Tolkien’s literary works, that revealed the blazar’s jet is aimed almost perfectly at Earth.
- This direct alignment causes extreme relativistic beaming, an effect that amplifies the jet’s brightness by a factor of 30 and makes it look deceptively slow.
- The study unambiguously detected a toroidal magnetic field within the jet, which is crucial for accelerating particles, such as protons, that are the source of high-energy neutrinos.
- This discovery resolves the longstanding “Doppler factor crisis” and strengthens the link between blazar jets and multimessenger astronomy by confirming them as powerful cosmic accelerators.
Astronomers have solved a decade-long cosmic puzzle surrounding a peculiar object known as PKS 1424+240, a type of galaxy called a blazar that is powered by a supermassive black hole. For years, this blazar has baffled scientists, being one of the brightest sources of high-energy gamma rays and cosmic neutrinos in the sky, yet its jet of plasma appears to move surprisingly slowly. This contradiction challenged core theories about how such immense energy is produced. The new research, published in the journal Astronomy & Astrophysics, reveals that a rare cosmic alignment is responsible for the blazar’s unusual characteristics.
Using the National Science Foundation’s Very Long Baseline Array (VLBA), a network of radio telescopes spread across the globe that work together as a single, Earth-sized observatory, researchers compiled 15 years of data. By stacking 42 images, they created an ultra-deep view of the blazar’s jet, revealing its structure with unparalleled detail and unveiling an image that evokes the “Eye of Sauron” from J.R.R. Tolkien’s “The Lord of the Rings” literary series. This technique, known as Very Long Baseline Interferometry (VLBI), enabled the team to peer directly into the heart of the powerful jet, which was aimed almost perfectly at Earth, with a viewing angle of less than 0.6 degrees.
This near head-on alignment is the key to the mystery. According to Einstein’s theory of special relativity, when a source of light or particles moves toward an observer at nearly the speed of light, its emission becomes intensely focused and amplified, a phenomenon known as relativistic beaming, or Doppler boosting. For PKS 1424+240, this effect boosts its apparent brightness by a factor of 30 or more, making it appear exceptionally luminous in gamma rays and neutrinos. At the same time, this unique geometric angle creates an optical illusion that makes the jet’s side-to-side motion in the sky appear sluggish.
The discovery not only resolves the apparent contradiction of the blazar’s slow jet but also provides a direct look at its engine. The observations revealed a distinct toroidal, or doughnut-shaped, magnetic field structure within the current-carrying jet. This field is believed to be crucial for accelerating particles, such as electrons and protons, to extremely high energies. By confirming that blazar jets can accelerate protons to produce the observed neutrinos, this work marks a significant milestone for multimessenger astronomy. This field studies the universe by combining data from various cosmic signals, including light and particles.
References
- Junkes, N. & Max Planck Society. (2025, August 12). Astronomers spot the ‘Eye of Sauron’ in deep space. Phys.Org; Max Planck Society. https://phys.org/news/2025-08-astronomers-eye-sauron-deep-space.html
- Kovalev, Y. Y., Pushkarev, A. B., Gómez, J. L., Homan, D. C., Lister, M. L., Livingston, J. D., Pashchenko, I. N., Plavin, A. V., Savolainen, T., & Troitsky, S. V. (2025). Looking into the jet cone of the neutrino-associated very high-energy blazar PKS 1424+240. Astronomy & Astrophysics, 700, L12. https://doi.org/10.1051/0004-6361/202555400
