When you peer at the night sky with your telescope, what you see is only a small fraction of the information that the galaxies are sending out there. Regular telescopes only capture information in the visible light spectrum but celestial bodies are constantly emitting gamma waves, X-rays, long-wavelength microwaves, and even FM radiofrequency waves (88 - 108MegaHertz). Scientists in Europe have been concentrating on the information sent out in radio frequency waves and have been able to stitch together the most detailed images of galaxies so far.
To capture this FM radio frequency data, a European collaboration of scientists has laid out over 70,000 radio antennas across Europe. This Low-Frequency Array (LOFAR) of antennas are connected to each other with fiber-optic cable and backed by supercomputers who do all the data crunching and in principle make up a giant radio telescope that spans across Europe. With the center located at Exloo in The Netherlands, the entire operation was designed, built, and is currently operated by the Netherlands Institute of Radio Astronomy, ASTRON. When conceptualized, the project was limited to the Netherlands, and the LOFAR antennas were installed within the country making the diameter of the receiving 'lens' of the telescope about 75 miles (120km) wide.
During its ten years of operation, LOFAR has signed up partners such as France, Germany, Ireland, Italy, Latvia, the Netherlands, Poland, Sweden, and the UK. These countries have installed at least one LOFAR antenna station in their geographies extending the receiving 'lens' diameter to about 1200 miles (2000 km). Not just that, the collaboration also increased the resolution of the images by 20 times, said a press release from ASTRON.
Arrayed image processing is not a novel concept and signals from multiple antennas are processing simultaneously to produce an image. The team at LOFAR, however, used a different strategy. They first digitized the signals received at each antenna and then sent the image to a central processor to stitch together the final images, at very resolutions. The researchers have also published the data-processing pipeline to enable other researchers to replicate their strategy and use LOFAR for their own applications.
The researchers used the LOFAR to look at different galaxies. The Hubble Space Telescope (HST) does not have a radio wave sensor, so the team was able to look at galaxies that HST has captured and provide additional information using radio waves. Of special interest to the team were super-massive black holes that leave out jets of radiation outside the visible spectrum but visible in radio waves. Thanks to the higher resolution of the LOFAR, the scientists were able to capture detailed images of these jets too.
Processing these images wasn't easy. The massive array of 70,000 antennas generated huge amounts of data. To produce a single image, supercomputers processed 13 terabits (1.6 Gigabytes) of data per second, the equivalent of 300 DVDs into data that the scientists could use in only a couple of days, said Frits Sweijen of Leiden University, a partner in the LOFAR project.
The decade-long work has culminated into 11 research papers published in a special issue of Astronomy and Astrophysics.