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Astronomers discover furthest radio galaxy ever

After almost twenty years the record for the most distant radio galaxy has been broken. A team of astronomers led by Leiden PhD candidate Aayush Saxena has discovered a radio galaxy from the time when the universe was just one billion years old. The galaxy is at a distance of 12 billion light years from Earth.

Jetstreams in space

The team is made up of astronomers from the Netherlands, Brazil, the UK and Italy. Their research will be published shortly in the  Monthly Notices of the Royal Astronomical Society. Radio galaxies - colossal stellar galaxies with a super-heavy black hole at their centre - are rare. The black hole draws active gas and dust from the environment into itself. This characteristic causes high-energy jet streams to be launched, which eject charged particles into space at almost the speed of light. These jet streams can be seen clearly at radio wavelengths.

Red light

The astronomers used the Giant Meter-wave Radio Telescope in India to identify the radio galaxy. They then used the Gemini Telescope on Hawaiï and the Large Binocular Telescope in Arizona to determine the distance, by measuring the redshift of the galaxy.  The further away galaxies are, the faster they are moving away from us. The light from these galaxies is therefore more red. As the speed of travel becomes higher, the redshift becomes greater. 

The team measured a redshift of z = 5.72. This means that the light from the galaxy is 12 billion years old. What we are seeing is the galaxy as it appeared when the universe was just one billion years old.  

Primordial black holes

The discovery of these kinds of galaxies at extreme distances is important for our understanding of the formation and evolution of such galaxies. This discovery may also tell us more about the formation of primordial glack holes, that have driven and regulated the growth of stellar galaxies. Astronomers are amazed that such galaxies exist.  

Lead author Aayush Saxena (Leiden Observatory): ‘We are curious about how these very heavy, distant galaxies have built up their mass.' Co-author Huub Röttgering  (Leiden Observatory): ‘Bright radio galaxies conceal super-heavy black holes. It is amazing to come across such objects from so early in the history of the universe.' Röttgering is surprised that such heavy black holes could reach maturity in the relatively short period of a billion years. 

A radio galaxy with a redshift of  z=5.19 was the previous record-holder since its discovery in 1999. Researchers are currently constructing the next generation of radio telescopes. In combination with the world's largest optical and infrared telescopes, these will be able to discover radio galaxies with even bigger redshifts.   


Saxena, A.; Marinello, M.; Overzier, R.A.; Best, P.N.; Röttgering, H.J.A.; Duncan, K.J.; Prandoni, I.; Pentericci, L.; Magliochetti, M.; Paris, D.; Cusano, F.; Marchi, F.; Intema, H.T. and Miley, G.K., 2018. Discovery of a radio galaxy at z = 5.72


Source: astronomie.nl
Cover photo: the Giant Meter-wave radio telescope in India.

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