There are 4 million radio sources, and astronomers can’t handle it all. They ask your computer for help in finding black holes!

Scientists are seeking the public's help in finding the origins of hundreds of thousands of galaxies discovered by LOFAR, one of the largest radio telescope arrays ever built. Where do these mysterious objects, stretching thousands of light-years across, come from? A new citizen science project, the LOFAR Radio Galaxy Zoo, gives anyone with a computer the exciting possibility to join in the search for the location of the black holes at the centers of these galaxies.

Astronomers use radio telescopes to take images of the radio sky, just as optical telescopes, such as the Hubble Space Telescope, take maps of stars and galaxies. The difference is that the images taken with radio telescopes are very different from those seen with optical telescopes. In the radio sky, stars and galaxies cannot be seen directly, but a large number of complex structures can be detected, which are related to the massive black holes at the centers of galaxies. Most of the dust and gas around supermassive black holes are consumed by the black hole, but some of the matter escapes and is ejected into deep space.

This material forms huge plumes of extremely hot gas, and it is this gas that forms the large structures observed by radio telescopes. The Low Frequency Array (LOFAR) telescope, operated by the Netherlands Institute for Radio Astronomy (ASTRON), is continuing its survey of the radio sky and has discovered 4 million radio sources. Hundreds of thousands of these have very complex structures. So complex that it is difficult to determine which galaxies belong to which radio source, or in other words, which black hole belongs to which galaxy?

(Shown in the picture above) Taking the famous radio signal source 3C236 as an example, the left side is the radio source, the middle shows the optical image of many stars and galaxies, and the image on the right is the superposition of the radio image and the optical image. In this case, the source of the radio emission is clear to the human eye, the bright spot-like radio source in the center of the radio image. This is where the massive black hole that drives all the radio activity is located. From where the optical image is overlaid, the galaxy where the black hole is located can be identified. Image: Aleksandar Shulevski, Erik Osinga & The LOFAR surveys team

Although the international LOFAR team consists of more than 200 astronomers from 18 countries, it is simply too small to undertake the difficult task of identifying which radio structures belong to which host galaxy. LOFAR astronomers are therefore seeking help from the public. In the context of the citizen science project "LOFAR Radio Galaxy Zoo", the public views LOFAR images together with galaxy images and then associates radio sources with galaxies. New research by LOFAR has revealed millions of previously undetected radio sources.

Huub Röttgering from Leiden University in the Netherlands says: "With the help of the public we can study the properties of these sources: Where are their black holes? In what kind of galaxies are the black holes located?" Tim Shimwell from ASTRON and Leiden University explains why this is important: "The public participant mission is to match radio sources with suitable galaxies. This will help researchers understand how radio sources are formed, how black holes evolve and how huge amounts of matter are ejected into deep space with such unprecedented energies."

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Bo Ke Yuan | Research/From: Netherlands Institute for Radio Astronomy

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