Scientists observing the compact radio core of M87 have discovered new details about the galaxy’s supermassive black hole. In this artist’s conception, the black hole’s massive jet is seen rising up from the center of the black hole. The observations on which this illustration is based represent the first time that the jet and the black hole shadow have been imaged together, giving scientists new insights into how black holes can launch these powerful jets. Credit:
S. Dagnello (NRAO/AUI/NSF)
In an exciting scientific discovery, astronomers have for the first time observed, in the same image, the shadow of the black hole at the center of the galaxy Messier 87 (M87) and the powerful jet expelled from it.
So, what, big deal, some may ask? Well, it is a very big deal because with each such image we learn so much more about the very nature of the universe. And, thanks to this new image, astronomers can better understand how black holes can launch such energetic jets.
The observations were done in 2018 with telescopes from the Global Millimetre VLBI Array (GMVA), the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner, and the Greenland Telescope (GLT).
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The scientists explained that most galaxies harbor a supermassive black hole at their center. While black holes are known for engulfing matter in their immediate vicinity, they can also launch powerful jets of matter that extend beyond the galaxies that they live in. Understanding how black holes create such enormous jets has been a long standing problem in astronomy.
“We know that jets are ejected from the region surrounding black holes,” says Ru-Sen Lu from the Shanghai Astronomical Observatory in China, “but we still do not fully understand how this actually happens. To study this directly we need to observe the origin of the jet as close as possible to the black hole.”
The image was obtained with the GMVA, ALMA and the GLT, forming a network of radio-telescopes around the globe working together as a virtual Earth-sized telescope. Such a large network can discern very small details in the region around M87’s black hole.
The new image shows precisely this for the first time: how the base of a jet connects with the matter swirling around a supermassive black hole. The target is the galaxy M87, located 55 million light-years away in our cosmic neighborhood, and home to a black hole 6.5 billion times more massive than the Sun. Previous observations had managed to separately image the region close to the black hole and the jet, but this is the first time both features have been observed together.
The new image shows the jet emerging near the black hole, as well as what scientists call the shadow of the black hole. As matter orbits the black hole, it heats up and emits light. The black hole bends and captures some of this light, creating a ring-like structure around the black hole as seen from Earth. The darkness at the centre of the ring is the black hole shadow, which was first imaged by the Event Horizon Telescope (EHT) in 2017. Both this new image and the EHT one combine data taken with several radio-telescopes worldwide, but the image released today shows radio light emitted at a longer wavelength than the EHT one: 3.5 mm instead of 1.3 mm.
“At this wavelength, we can see how the jet emerges from the ring of emission around the central supermassive black hole,” says Thomas Krichbaum of the Max Planck Institute for Radio Astronomy.
“This new image completes the picture by showing the region around the black hole and the jet at the same time,” adds Jae-Young Kim from the Kyungpook National University in South Korea and the Max Planck Institute for Radio Astronomy in Germany.
