Today in Nature, the origins of the powerful jet emanating from the supermassive black hole at the center of the M87 galaxy were unveiled, alongside the first-ever image of the jet and its source together. The observations also revealed that the black hole’s ring is considerably larger than previously thought. The Global mm-VLBI Array (GMVA) brought together radio telescopes from around the world, including the Atacama Large Millimeter/submillimeter Array (ALMA), Green Bank Observatory (GBO), National Science Foundation’s National Radio Astronomy Observatory (NRAO), Very Long Baseline Array (VLBA), and Green Bank Telescope (GBT).
The SMBH in M87 is the most renowned black hole in the cosmos, and was the first to have its image captured by the Event Horizon Telescope (EHT) and released to the public in 2019. The image of its dense, dark core surrounded by a blurry, glowing ring captured global attention.
According to Ru-Sen Lu, leader of a Max Planck Research Group at the Chinese Academy of Sciences and an astronomer at the Shanghai Astronomical Observatory, M87 has been under observation for decades, with the presence of the jet having been noted a century ago. However, it was difficult to interpret its significance without a proper contextual understanding. With the Global mm-VLBI Array (GMVA), which utilizes advanced instruments at the National Radio Astronomy Observatory (NRAO) and Green Bank Observatory (GBO), the team was able to observe M87 at a lower frequency, resulting in more detailed observations that revealed there was even more to see.
Eduardo Ros, Scientific Coordinator for Very Long Baseline Interferometry (VLBI) at the Max Planck Institute for Radio Astronomy, added that while the ring had been previously observed, the discovery of the jet puts the ring in perspective, revealing that it is actually larger than initially thought. To use a metaphor, he said that it was like observing a fire-breathing monster, where before, only the dragon and the fire were visible, but now the team could see the dragon actually breathing the fire.
The team’s use of multiple telescopes and instruments provided a more comprehensive understanding of the supermassive black hole’s structure and jet compared to previous observations made with the EHT alone. Each of the telescopes played a crucial role in revealing different aspects of M87’s black hole, with the VLBA providing a full view of both the jet and the black hole, ALMA resolving the bright radio core, and GBT enabling astronomers to observe both the large and small-scale parts of the ring in finer detail.
According to Toney Minter, GMVA coordinator for the GBT, changing the observing wavelengths from 1.3 millimeters to 3.5 millimeters allowed the team to see more of the accretion disk and jet simultaneously. This revealed that the ring surrounding the black hole is 50% larger than previously believed. Additionally, the observations confirmed that the jet originated from the magnetic fields surrounding the spinning core of the black hole and winds rising up from the black hole’s accretion disk.
Harshal Gupta, NSF Program Officer for the Green Bank Observatory, emphasized that the team’s findings demonstrate how complementary capabilities of different radio telescopes can be used to enhance our understanding of astronomical objects and phenomena. He also noted that the success of the GMVA in providing a big picture view of M87’s black hole and jet is a testament to the collaborative efforts of various radio telescopes supported by NSF.