LOFAR image is the sharpest yet at low radio frequencies

An international team led by Leiden University has used the Low Frequency Array (LOFAR) to make the sharpest and most sensitive radio image of the sky yet produced at low radio frequencies, according to a summary distributed by the Netherlands Research School for Astronomy and published by Phys.org on November 5, 2026. The image covers ELAIS-N1, a well-studied patch of the northern sky that holds many faint and distant galaxies.

The gain comes from resolution. The team reports that the new image is 20 times sharper than the previous most sensitive LOFAR image of this field. The researchers say it could pick out a coin from about 10 kilometers (6 miles) away, and that the full image holds 8 billion pixels. It rests on 200 hours of observation that produced 400 terabytes of data.

Processing that volume at this resolution was out of reach for years. The summary says improved calibration and data-reduction methods developed by the team and collaborators have cut the cost by more than a factor of 10 in the past few years. "The entire data set could be processed on Spider, the high-performance data-processing platform hosted at SURF in the Netherlands, in just a few months," said Jurjen de Jong, who led the work and is a postdoctoral researcher at Leiden Observatory and ASTRON.

Sharper resolution matters because, in low-resolution radio images, distant galaxies and the jets driven by black holes appear as featureless blobs. It is then hard to tell whether a blob is several galaxies or components, or whether its emission comes from a jet or from star formation across the galaxy. In the new data the team says components and emission sources can be separated more easily, and massive jets can be traced in detail. Active galactic nuclei, the luminous centers of galaxies powered by matter falling onto a supermassive black hole, are one of the two dominant populations in the image. LOFAR is especially suited to detecting the jetlike outflows they can drive because it is sensitive to extended, faint radio emission.

The other major population is small star-forming galaxies. Radio waves pass through the dust that hides star formation from optical and infrared telescopes, so the observations give an unobscured view of star formation in distant galaxies.

"With this sharp and sensitive view of our sky at low radio frequencies, we have a new window to study how these radio jets interact with their environment and how they evolve over cosmic time," said Reinout van Weeren, associate professor at Leiden Observatory and a co-author.

The data have been made publicly available. Much of their scientific value, the team says, will come from combining them with images of the same patch taken at optical, infrared and X-ray wavelengths. That combination would let astronomers derive properties such as the distance and mass of each radio source.

The scientists also say the work shows the potential of LOFAR2.0, the upgrade ASTRON is carrying out with its European partners, which would allow more sensitive and wider images at high resolution. De Jong says the image shows LOFAR2.0 will stay competitive during the era of the Square Kilometre Array, now under construction in South Africa and Australia.

The results have been accepted for publication in Astronomy & Astrophysics. The paper, by J. M. G. H. J. de Jong and colleagues, is available on the arXiv preprint server under DOI 10.48550/arxiv.2611.06152. The team says the distance and mass of the sources have yet to be derived from the multiwavelength data.