Astronomers discover most distant source of radio emission known to date © ESO/M Kornmesser

Astronomers discover most distant source of radio emission known to date

The source, a quasar, is so far away that its light has taken 13 billion years to reach Earth.

Astronomers have discovered and analysed the most distant source of radio emission known to date. The source is what scientists call a radio-loud quasar – a bright object with powerful jets emitting at radio wavelengths.

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According to the study, which was published in The Astrophysical Journal, the newly discovered quasar, nicknamed P172+18, is so distant that light from it has travelled for about 13 billion years to reach Earth.

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The quasar is seen as it was when the Universe was a youthful 780 million years old, and researchers say the discovery could help them understand the early Universe.

Quasars are highly luminous objects at the centre of some galaxies, and are powered by supermassive black holes. As the black hole consumes its surrounding gas, energy is released, making them visible to astronomers even when they are extremely far away.

Artist’s impression of quasar P172+18, the most distant source of radio emission known to date © ESO/M Kornmesser
Artist’s impression of quasar P172+18, the most distant source of radio emission known to date © ESO/M Kornmesser

This is the first time researchers have been able to identify the telltale signatures of radio jets in a quasar this early on in the history of the Universe. Only about 10 per cent of quasars have jets that shine brightly at radio frequencies. P172+18 is powered by a black hole about 300 million times bigger than the Sun.

Chiara Mazzucchelli, a fellow at the European Southern Observatory in Chile, led the discovery together with Eduardo Bañados of the Max Planck Institute for Astronomy in Germany.

“The black hole is eating up matter very rapidly, growing in mass at one of the highest rates ever observed,” said Mazzucchelli.

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Astronomers think there is a link between the rapid growth of supermassive black holes and the powerful radio jets spotted in quasars such as P172+18. The jets are thought to be capable of disturbing the gas around the black hole, increasing the rate at which gas falls in. Studying radio-loud quasars can provide insights into how black holes in the early Universe grew to their supermassive sizes so quickly after the Big Bang.

“As soon as we got the data, we inspected it by eye, and we knew immediately that we had discovered the most distant radio-loud quasar known so far,” said Bañados.

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P172+18 was first recognised as a far-away quasar at the Magellan Telescope at Las Campanas Observatory in Chile, but researchers believe this radio-loud quasar could be the first of many to be found – perhaps at even larger cosmological distances.

Reader Q&A: How big could a black hole get?

Asked by: Vanessa Taylor, Nottingham

There is no theoretical upper limit to the mass of a black hole. However, astronomers have noted that the ultra-massive black holes (UMBHs) found in the cores of some galaxies never seem to exceed about 10 billion solar masses. This is exactly what we’d expect from the rate at which we know black holes grow, given the time that’s elapsed since the Big Bang.

Furthermore, recent studies suggest that UMBHs cannot physically grow much beyond this anyway, since they would then begin to disrupt the accretion discs that feed them, choking the source of new material.

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