Research Highlights
Here we show recent research results from the Radio Astronomy/Very-Long-Baseline Interferometry department.
Fringes at 3.5 mm Wavelength Between APEX and Effelsberg!
23 May 2025
A symbolic moment in millimetre-wave VLBI at the Max-Planck-Institute für Radioastronomie (MPIfR): For the first time, the 12-meter APEX telescope in Chile and the 100-meter Effelsberg radio telescope in Germany have successfully detected VLBI fringes between them.
Both telescopes are operated by the MPIfR). APEX, located at 5100 m altitude on the Chajnantor Plateau in the Chilean Andes, and Effelsberg, nestled in the Eifel mountains, have vastly different designs and operating environments. Effelsberg has been a VLBI station since the mid-1970s; APEX since 2015. Thanks to the completion of N3AR at APEX, both now support a common frequency band.
In April 2026, as part of the Global mm-VLBI Array at 3.5-mm wave, the two telescopes observed the bright quasar 3C273, among other sources. This observation marks a symbolic handshake between both MPIfR telescopes—separated by 9637 km—as they detected the same wave from a distant quasar.
The figure shows the fringe plot confirming this detection. Adding APEX to the GMVA greatly improves the array's north-south resolution, resulting in much more enhanced images of quasars and black hole environments.
This milestone highlights the expansion of mm-wave VLBI capabilities and paves the way for even higher-resolution astronomy in the future.
Exploring the Magnetic Secrets of Blazar Jets
07 May 2025
How are the magnetic fields inside distant, powerful jets of plasma—launched from active galactic nuclei—shaped and structured? In a study led by Joana A. Kramer as part of her PhD work in our scientific department, researchers investigate this question using high-resolution observations of circular polarization in blazar jets. This study is published at the present issue of the journal Astronomy & Astrophysics, see here. By combining deep radio observations with cutting-edge simulations, the team examined the magnetic field signatures in a carefully selected group of nine blazars. The study focuses on how the sign and structure of circular polarization, along with the orientation of the electric vector position angle (EVPA), relate to theoretical predictions of jet magnetism. Their findings reveal compelling patterns: magnetic fields that appear toroidal, helical, or poloidal in nature, depending on frequency and source. This research brings us one step closer to understanding the complex and dynamic physics driving some of the universe’s most energetic phenomena.
Unravelling the Vortex Dynamics in a Cosmic Jet
08 April 2024
What creates the swirling, thread-like structures seen in powerful extragalactic jets? In a new study led by Georgios F. Paraschos from the MPIfR, researchers delve into the heart of the radio galaxy 3C 84 to uncover the physical processes shaping its jet. Using ultra-high-resolution observations from a global very-long-baseline-interferometry (VLBI) campaign, the team identified a striking pattern in the jet’s structure—consistent with a Kelvin-Helmholtz instability, a type of plasma turbulence that occurs when layers of fast-moving material interact. The analysis reveals a jet characterized by multiple instability modes, pointing to a Mach number of about 5 and a relatively low internal sound speed. This work provides compelling evidence that the inner dynamics of the jet may be directly influenced by activity in the galaxy’s accretion disc, offering a clearer picture of how such extreme cosmic outflows evolve. This work is published at the present issue of Astronomy & Astrophysics, see here.
Twisting Magnetic Fields: A Helical Structure Revealed in Quasar NRAO 150
25 March 2025
Quasars are among the most powerful objects in the universe, powered by supermassive black holes and their swirling jets. But what role do magnetic fields play in shaping these jets? In the latest issue of Astronomy & Astrophysics (see here) Jack Livingston and a team from the M2FINDERS project at the Max Planck Institute for Radio Astronomy (MPIfR) unveil a striking new discovery: a helical magnetic field twisting around the jet of quasar NRAO 150. Using high-resolution polarimetric very-long-baseline interferometry (VLBI), the researchers detected clear gradients in Faraday rotation, revealing the signature of a helical+toroidal magnetic field structure. This field appears to be concentrated within the innermost jet, influencing its flow and polarization properties. Such findings provide crucial evidence that magnetic fields play a key role in jet formation and stability, offering new insights into how quasars channel energy across vast cosmic distances.
Hunting for New Jet Launch Sites in Active Galaxies
12 March 2025
How do supermassive black holes launch their powerful, relativistic jets? Until now, detailed imaging of jet formation has been limited to just a few exceptional sources like M87. In the latest issue of Astronomy & Astrophysics (see here) Bia Boccardi, Otto Hahn Group leader at the Max Planck Institute for Radio Astronomy (MPIfR), presents a search for new prime targets to study jet formation up close. Using high-resolution very-long-baseline interferometry (VLBI) at centimeter and millimeter wavelengths, the team examined 16 previously underexplored radio galaxies, spanning a wide range of jet powers and accretion modes. Their results more than doubled the number of sources imaged on the smallest scales, revealing intriguing jet structures—some with limb brightening, others with two-sided symmetry. Among the most promising candidates for future ultra-high-resolution studies are 3C 31, 3C 66B, 3C 465, and 3C 452. These sources are now poised to become key targets for the next generation of telescopes, including the ngEHT and ngVLA, bringing us closer to unraveling the mechanisms behind jet launching in active galaxies.
Is a Hidden Black Hole Warping the Jet of a High-Energy Neutrino Source?
11 March 2025
TXS 0506+056 is no ordinary blazar—it was the first active galactic nucleus linked to a high-energy neutrino, offering a rare glimpse into the cosmic engines that power these elusive particles. In a new study published in Astronomy & Astrophysics (see here) Silke Britzen and a team from the Max Planck Institute for Radio Astronomy (MPIfR) uncover an unexpected twist: the jet and core of TXS 0506+056 may be gravitationally lensed. Using long-term very-long-baseline interferometry (VLBI) data, the researchers found that the jet structure of TXS 0506+056 has undergone dramatic changes over time. Around 2016, coinciding with a major radio flare, the jet components began to arrange themselves in a ring-like structure—a pattern that defies typical blazar jet behavior. This unusual evolution could be explained by gravitational lensing, potentially caused by an unseen supermassive black hole acting as a cosmic magnifier. If confirmed, this discovery would reshape our understanding of both jet physics and the environments in which high-energy neutrinos are born.
X-ray Silence: Shedding Light on the Mysterious Energy Budget of a Hyperactive Fast Radio Burst
10 March 2025
Fast radio bursts (FRBs) are among the most enigmatic cosmic signals, and some—like FRB 20240114A—repeat at a staggering rate. But how much energy do they release beyond the radio spectrum? In the present issue of Astronomy & Astrophysics, Florian Eppel from the University of Würzburg and the Max Planck Institute for Radio Astronomy (MPIfR) presents a pioneering multiwavelength study of this hyperactive FRB, searching for an X-ray counterpart (see publication here). Using the Effelsberg 100-m radio telescope and XMM-Newton, the team observed 459 bursts in a single session. Yet, despite extensive X-ray coverage, no simultaneous high-energy flashes were detected. This non-detection allows for stringent constraints on the X-ray-to-radio fluence ratio, suggesting that FRB 20240114A emits far less X-ray energy than previously seen in magnetar-driven FRB-like bursts. Could this FRB still share a common origin with Galactic magnetars, or does it hint at a different engine? Future multiwavelength campaigns will push these limits further, helping to unravel the power source behind these cosmic signals.
How Blazar OJ 248’s Jet Unleashed a Gamma-Ray Flare
25 February 2025
Blazars are some of the most extreme objects in the universe, capable of launching powerful jets at nearly the speed of light. But what triggers their sudden bursts of high-energy radiation? In the present issue of Astronomy & Astrophysics (see here), G.F. Paraschos from the Max Planck Institute for Radio Astronomy (MPIfR) explores the dramatic γ-ray flare of the blazar OJ 248—the only one ever recorded from this source. Using ultra-high-resolution radio imaging (VLBI), the study reveals that during the flare, the jet’s polarization properties changed in a striking way: the electric vector position angles (EVPAs) rotated, aligning perpendicularly to the jet flow. The most likely culprit? A shockwave crashing through an existing jet structure, triggering a cascade of interactions that up-scatter photons to γ-ray energies. This "shock-shock" scenario offers new insight into how flares are powered in blazars, shedding light on the hidden physics of these cosmic accelerators.
JWST Unveils a Black Hole Flare in Unprecedented Detail
20 January 2025
For the first time, astronomers have detected a flare from our galaxy’s central supermassive black hole, Sgr A*, in the elusive mid-infrared (MIR) range—thanks to NASA’s James Webb Space Telescope (JWST). In a new study published in Astrophysical Journal Letters (see link here), Sebastiano von Fellenberg and colleagues from the Max Planck Institute for Radio Astronomy (MPIfR) report this groundbreaking observation, offering fresh insights into the extreme physics at play near black holes. The flare, lasting about 40 minutes, followed a pattern seen in near-infrared (NIR) and X-ray bursts, with its spectral properties revealing that high-energy electrons cooled rapidly via synchrotron radiation. A follow-up detection at millimeter wavelengths, delayed by about 10 minutes, hints at a dynamic interplay between magnetic fields and particle acceleration. With field strengths of 40–70 G in the emission region, this study provides a crucial missing piece in our understanding of how black holes power their flickering emissions.
Magnetic properties of the jet base in the radio galaxy NGC 315
14 January 2025
This study, led by MPIfR astronomer L. Ricci within the Otto Hahn research group headed by B. Boccardi, investigates the spectral and magnetic properties of the relativistic jet in the nearby radio galaxy NGC 315. Observations reveal a toroidal-dominated magnetic field structure, which influences the jet collimation and acceleration on sub-parsec and parsec scales. A steep radio spectrum at the base of the jet suggests intense synchrotron cooling, transitioning to flatter spectral regions at larger scales. At the jet base, magnetic energy dominates, gradually transitioning to equipartition with particles as the jet expands outwards. A nearly linear increase in magnetic field strength with distance from the core supports theoretical models of jet formation. This research provides critical constraints on the magnetization and geometry of the magnetic fields in relativistic jets, advancing our understanding of jet dynamics in active galactic nuclei. For a detailed discussion, see the original paper here.
