Most detailed-ever images of galaxies revealed

18 August 2021

After almost a decade of work, an international team of astronomers has published the most detailed images yet seen of galaxies beyond our own, revealing their inner workings in unprecedented detail.

The images were created from data collected by the Low Frequency Array (LOFAR), a network of more than 70,000 small antennae spread across nine European counties. The results come from years of work, including work from a team at the University of Hertfordshire, with the overall project led by Dr Leah Morabito at Durham University. The team was supported in the UK by the Science and Technology Facilities Council (STFC), and much of the data was processed on the LOFAR-UK computing cluster, managed by the University of Hertfordshire. STFC also funds the UK subscription to LOFAR including upgrade costs and operation of its LOFAR station in Hampshire.

Revealing a hidden universe of light in HD

The universe is awash with electromagnetic radiation, of which visible light comprises just the tiniest slice. From short-wavelength gamma rays and X-rays, to long-wavelength microwave and radio waves, each part of the light spectrum reveals something unique about the universe.

The LOFAR network captures images at FM radio frequencies that, unlike shorter wavelength sources like visible light, are not blocked by the clouds of dust and gas that can cover astronomical objects. Regions of space that seem dark to our eyes, actually burn brightly in radio waves – allowing astronomers to peer into star-forming regions or into the heart of galaxies themselves.

The new images, made possible because of the international nature of the collaboration, push the boundaries of what we know about galaxies and super-massive black holes. A special issue of the scientific journal Astronomy & Astrophysics is dedicated to research papers describing these images and the scientific results.

Better resolution by working together

The images reveal the inner workings of nearby and distant galaxies at a resolution 20 times sharper than typical LOFAR images. This was made possible by the unique way the team combined the signals of 70,000+ LOFAR antennae spread across Europe, with the majority located in the Netherlands. Unlike conventional array antennae that combine multiple signals in real time to produce images, LOFAR uses a new concept where the signals collected by each antenna are digitised, transported to central processor, and then combined to create an image.

Revealing jets and outflows from super-massive black holes

Super-massive black holes can be found lurking at the heart of many galaxies and many of these are ‘active’ black holes that devour in-falling matter and belch it back out into the cosmos as powerful jets and outflows of radiation. These jets are invisible to the naked eye, but they burn bright in radio waves and it is these that the new high-resolution images have focused upon.

A team led by Dr Jeremy Harwood at the University of Hertfordshire, who have been investigating the famous quasar 3C 273, said “We are now able to investigate the small-scale structure of radio jets at low frequencies, something that just wasn’t possible before the LOFAR international baselines became available. This is a significant step forward in understanding how these jets and the galaxies that host them evolve over cosmic time and how the Universe came to be the way we observe it today.”

A decade-long challenge

Even before LOFAR started operations in 2012, the European team of astronomers began working to address the colossal challenge of combining the signals from more than 70,000 antennae located as much as 2,000 km apart. The result, a publicly-available data-processing pipeline, will allow astronomers from around the world to use LOFAR to make high-resolution images with relative ease.

Dr Leah Morabito of Durham University, said: “Our aim is that this allows the scientific community to use the whole European network of LOFAR telescopes for their own science, without having to spend years to become an expert.”

Super images require supercomputers

The relative ease of the experience for the end user belies the complexity of the computational challenge that makes each image possible. To produce a single image, more than 13 terabits of raw data per second – the equivalent of more than a three hundred DVDs – must be digitised, transported to a central processor, and then combined.

Dr Jeremy Harwood of the University of Hertfordshire said “Processing such large volumes of data requires immense computing power. The LOFAR-UK computing cluster that is based and managed at the University of Hertfordshire has therefore proved vital in providing the infrastructure needed to produce the high-quality images that allow researchers to make these new and exciting discoveries”.

'The resolved jet of 3C 273 at 150 MHz' is now published in Astrophysics of Galaxies.


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