For the first time, astronomers have observed, in the same image, the shadow of the black hole at the centre of the galaxy Messier 87 (M87) and the powerful jet expelled from it. 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). Thanks to this new image, astronomers can better understand how black holes can launch such energetic jets.
Most galaxies harbour a supermassive black hole at their centre. 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 new image published today 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 neighbourhood, 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. “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.
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 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.
The size of the ring observed by the GMVA network is roughly 50% larger in comparison to the Event Horizon Telescope image. "To understand the physical origin of the bigger and thicker ring, we had to use computer simulations to test different scenarios,” explains Keiichi Asada from the Academia Sinica in Taiwan. The results suggest the new image reveals more of the material that is falling towards the black hole than what could be observed with the EHT.
These new observations of M87’s black hole were conducted in 2018 with the GMVA, which consists of 14 radio-telescopes in Europe and North America [1]. In addition, two other facilities were linked to the GMVA: the Greenland Telescope and ALMA, of which ESO is a partner. ALMA consists of 66 antennas in the Chilean Atacama desert, and it played a key role in these observations. The data collected by all these telescopes worldwide are combined using a technique called interferometry, which synchronises the signals taken by each individual facility. But to properly capture the actual shape of an astronomical object it’s important that the telescopes are spread all over the Earth. The GMVA telescopes are mostly aligned East-to-West, so the addition of ALMA in the Southern hemisphere proved essential to capture this image of the jet and shadow of M87’s black hole. “Thanks to ALMA’s location and sensitivity, we could reveal the black hole shadow and see deeper into the emission of the jet at the same time,” explains Lu.
Future observations with this network of telescopes will continue to unravel how supermassive black holes can launch powerful jets. “We plan to observe the region around the black hole at the centre of M87 at different radio wavelengths to further study the emission of the jet,” says Eduardo Ros from the Max Planck Institute for Radio Astronomy. Such simultaneous observations would allow the team to disentangle the complicated processes that happen near the supermassive black hole. “The coming years will be exciting, as we will be able to learn more about what happens near one of the most mysterious regions in the Universe,” concludes Ros.
Notes
[1] The Korean VLBI Network is now also part of the GMVA, but did not participate in the observations reported here.
A view of the jet and shadow of M87’s black hole
This image shows the jet and shadow of the black hole at the centre of the M87 galaxy together for the first time. The observations were obtained 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. This image gives scientists the context needed to understand how the powerful jet is formed. The new observations also revealed that the black hole’s ring, shown here in the inset, is 50% larger than the ring observed at shorter radio wavelengths by the Event Horizon Telescope (EHT). This suggests that in the new image we see more of the material that is falling towards the black hole than what we could see with the EHT.
Credit:
R.-S. Lu (SHAO), E. Ros (MPIfR), S. Dagnello (NRAO/AUI/NSF)
Artist’s impression of the black hole in the M87 galaxy and its powerful jet
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 centre 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)
Messier 87 Captured by ESO’s Very Large Telescope
Messier 87 (M87) is an enormous elliptical galaxy located about 55 million light years from Earth, visible in the constellation Virgo. It was discovered by Charles Messier in 1781, but not identified as a galaxy until 20th Century. At double the mass of our own galaxy, the Milky Way, and containing as many as ten times more stars, it is amongst the largest galaxies in the local universe. Besides its raw size, M87 has some very unique characteristics. For example, it contains an unusually high number of globular clusters: while our Milky Way contains under 200, M87 has about 12,000, which some scientists theorise it collected from its smaller neighbours.
Just as with all other large galaxies, M87 has a supermassive black hole at its centre. The mass of the black hole at the centre of a galaxy is related to the mass of the galaxy overall, so it shouldn’t be surprising that M87’s black hole is one of the most massive known. The black hole also may explain one of the galaxy’s most energetic features: a relativistic jet of matter being ejected at nearly the speed of light.
The black hole was the object of paradigm-shifting observations by the Event Horizon Telescope. The EHT chose the object as the target of its observations for two reasons. While the EHT’s resolution is incredible, even it has its limits. As more massive black holes are also larger in diameter, M87's central black hole presented an unusually large target—meaning that it could be imaged more easily than smaller black holes closer by. The other reason for choosing it, however, was decidedly more Earthly. M87 appears fairly close to the celestial equator when viewed from our planet, making it visible in most of the Northern and Southern Hemispheres. This maximised the number of telescopes in the EHT that could observe it, increasing the resolution of the final image.
This image was captured by FORS2 on ESO’s Very Large Telescope as part of the Cosmic Gems programme, an outreach initiative that uses ESO telescopes to produce images of interesting, intriguing or visually attractive objects for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations, and produces breathtaking images of some of the most striking objects in the night sky. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through the ESO Science Archive.
Credit:
ESO
Anatomy of a Black Hole
This artist’s impression depicts a rapidly spinning supermassive black hole surrounded by an accretion disc. This thin disc of rotating material consists of the leftovers of a Sun-like star which was ripped apart by the tidal forces of the black hole. The black hole is labelled, showing the anatomy of this fascinating object.
Credit:
ESO
Messier 87 in the Constellation of Virgo
This chart shows the position of giant galaxy Messier 87 in the constellation of Virgo (The Virgin). The map shows most of the stars visible to the unaided eye under good conditions.
Credit:
ESO, IAU and Sky & Telescope
VIDEOS
First image of a black hole expelling a powerful jet (ESOcast 260 Light)
With the help of ALMA, astronomers have obtained a new image of the supermassive black hole at the centre of the M87 galaxy.
Credit:
ESO
Directed by: Angelos Tsaousis and Martin Wallner.
Editing: Angelos Tsaousis.
Web and technical support: Gurvan Bazin and Raquel Yumi Shida.
Written by: Jonas Enander.
Music: Stellardrone — Eternity.
Footage and photos: ESO/L. Calçada, M. Kornmesser, Digitized Sky Survey 2, ESA/Hubble, RadioAstron, De Gasperin et al., Kim et al., S. Dagnello (NRAO/AUI/NSF), R. S. Lu (SHAO), E. Ros and H. Rottmann/MPIfR, Nicolle R. Fuller/NSF, A. Duro.
Scientific consultants: Paola Amico and Mariya Lyubenova.
Zooming in on the black hole and jet of Messier 87
This zoom video starts with a view of ALMA and zooms in on the heart of the M87 galaxy, showing successively more detailed observations. The final image shows the shadow of the black hole and a powerful jet expelled from it, together for the first time in the same image. The observations were obtained with telescopes from the Global Millimetre VLBI Array (GMVA), ALMA, of which ESO is a partner, and the Greenland Telescope.
Credit:
ESO/L. Calçada, Digitized Sky Survey 2, ESA/Hubble, RadioAstron, De Gasperin et al., Kim et al., R.-S. Lu (SHAO), E. Ros (MPIfR), S. Dagnello (NRAO/AUI/NSF). Music: astral electronic.
Fuente: The ESO Department of Communication
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