Astronomers uncover over 1,000 radio galaxies with ‘wings,’ expanding a rare cosmic class

Astronomers recently carried out a comprehensive search for strange “winged” radio galaxies using data from the LOFAR Two-meter Sky Survey Data Release 2 (LoTSS DR2) and discovered over 1,000 new systems. The paper outlining these results was submitted to the arXiv preprint server on April 24, 2026.

‘Winged’ enigmas

Radio galaxies are powered by accreting supermassive black holes that launch powerful jets of charged particles in opposite directions. These jets glow in radio waves and can stretch across millions of light-years. Some of these objects have irregular shapes, rather than just two lobes on either side of the core. One particularly interesting class among these is galaxies with distinctive X- or Z-shaped structures, created by an extra pair of fainter lobes called “wings.”

Depending on how the wings are ejected and arranged with the main pair of lobes, they look like an X or a Z shape, classifying them into X-shaped radio galaxies (XRGs) and Z-shaped radio galaxies (ZRGs). While the wings in XRGs appear to emerge from near the center of the galaxy, in ZRGs they branch off from the outer edges of the primary lobes.

The origin of this small and strange subset of radio galaxies is not completely understood. Leading theories include a change in the orientation of jets due to black hole mergers, the presence of an extra accreting black hole at the galaxy’s center, plasma flowing back from the peak regions of radio lobes toward the core, and interactions with surrounding gas under special conditions.

A radio scan

To better understand why and how these radio galaxies get wings, researchers need to find more of these sources and build a larger, more complete catalog. Therefore, a team of researchers led by Soumen Kumar Bera of Xiamen University, China, conducted a systematic hunt for these unusually-shaped radio galaxies using LoTSS DR2—a massive radio survey containing over 4.3 million radio sources.

The team applied a size filter to select sources larger than half of the typical minimum size of known winged sources. This narrowed the data down to 204,789 sources which they then visually examined to identify potential winged structures.

Their search identified 1,024 newly discovered winged radio galaxies, of which 621 were confirmed winged sources. Wings are not always clearly visible, as sometimes the wings may be too faint, only one pair of lobes may be brighter, or the galaxy may be tilted at an angle, blocking the view of one of the wings.

Out of 1,024 radio galaxies, 403 sources showed some evidence of wings but only on one side, are too small, or aren’t clearly visible enough to be confirmed. Of the confirmed ones, 382 are X-shaped and 239 are Z-shaped.

These objects, on average, are roughly 1.6 million light-years wide. They also found that a fraction of the population has a much larger size, falling into a special category of radio galaxies.

“A total of 102 sources have a linear size exceeding 0.7 Mpc (roughly 2.2 million light-years), making nearly 16% of the total population candidates for giant radio galaxies (GRGs),” researchers write in the paper.

This study has turned a once-rare subclass of radio galaxies into a significantly large population, laying the groundwork for follow-up studies on the origin of their shapes. This study presents the first part of a broader effort to search for more winged radio sources. Future studies will also present the optical and radio properties of these sources in greater detail.

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