Porphyrion (radio galaxy)
Largest known radio galaxy at time of discovery.
Porphyrion is a Fanaroff–Riley class II radio galaxy whose host galaxy is J152932.16+601534.4, lying 7.5 billion light-years away in the constellation Draco. It was discovered in data from the Low-Frequency Array (LOFAR) by an international team led by Martijn Oei. At the time of its discovery, Porphyrion possessed the longest jets ever found in a radio galaxy, with its lobed structures stretching 7 megaparsecs (23 million light-years) across—the largest known structure of galactic origin at that point. In 2024, however, another radio galaxy, TXS 0033+252, surpassed it in size, with an estimated span of 8 megaparsecs (26 million light-years).
The discovery was first reported in a Nature paper by Martijn Oei (Leiden University/Caltech) and colleagues, which appeared on the cover of the 19 September 2024 issue. The findings came from the Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS), an interferometric radio survey of the Northern Sky. Porphyrion was one of many new giant radio galaxies uncovered by the team. Co-discoverer Aivin Gast of the University of Oxford named the system after Porphyrion, a Giant from Greek mythology.
To identify the host galaxy, the team used the Giant Metrewave Radio Telescope in India and ancillary data from the Dark Energy Spectroscopic Instrument in Arizona. These observations pinpointed J152932.16+601534.4, a galaxy roughly ten times more massive than the Milky Way.
The team described Porphyrion as a "black hole jets system" rather than a giant radio galaxy, arguing that the term "radio galaxy" is confusing because the jet structure is not formally part of the galaxy itself. Radio galaxies are defined by radio lobes generated by relativistic jets powered by a central supermassive black hole. Giant radio galaxies differ from ordinary ones in that they extend to much larger scales—several megaparsecs across—far exceeding the diameters of their host galaxies.
Observations from the W. M. Keck Observatory in Hawaii showed that Porphyrion is 7.5 billion light-years away, dating to a time when the universe was 6.3 billion years old. The data also revealed that its jets emerged from a radiative-mode active black hole, not a jet-mode one. The combined power of its two jets is 10³⁹ watts, equivalent to the energy output of trillions of suns.
Oei and his colleagues suggest that "every place in the universe may have been affec
- type
- Fanaroff–Riley class II radio galaxy
- distance_from_earth
- 7.5 billion light-years
- host_galaxy
- J152932.16+601534.4
- constellation
- Draco
- jet_span
- 7 megaparsecs (23 million light-years)
- jet_power
- 10^39 watts
- discovery_year
- 2024
Lore & Background
Porphyrion was discovered by an international team led by Martijn Oei (Leiden University/Caltech) using data from the Low-Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS). The giant black hole jet system was named after Porphyrion, a Giant from Greek mythology, by co-discoverer Aivin Gast from the University of Oxford. To locate the host galaxy, the Giant Metrewave Radio Telescope in India and ancillary data from the Dark Energy Spectroscopic Instrument in Arizona were used, pinpointing galaxy J152932.16+601534.4, which is about 10 times more massive than the Milky Way.
Reader's Guide
Porphyrion is significant as the largest known structure of galactic origin at the time of its discovery, with jets spanning 7 megaparsecs. The team described it as a 'black hole jets system' rather than a giant radio galaxy, noting that the jet structure is not formally part of the galaxy proper. Observations using the W. M. Keck Observatory showed Porphyrion dates to a time when the universe was 6.3 billion years old and emerged from a radiative-mode active black hole. Its combined jet power is 10^39 watts, equivalent to trillions of suns. The discovery suggests that giant jet systems like Porphyrion may have had a larger influence on galaxy formation in the young universe than previously believed and could have spread magnetism through the cosmos. In 2024, another radio galaxy, TXS 0033+252, exceeded Porphyrion in size with an estimated extent of 8 megaparsecs.
Did You Know?
- Porphyrion was named after a Giant from Greek mythology by co-discoverer Aivin Gast.
- Its host galaxy, J152932.16+601534.4, is about 10 times more massive than the Milky Way.
- The jets of Porphyrion span 7 megaparsecs, equivalent to 23 million light-years.
- In 2024, TXS 0033+252 exceeded Porphyrion in size with an extent of 8 megaparsecs.
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