(...) L’opération s’est toutefois soldée par un échec dans le cas de SgrA*, certes moins massif mais pourtant beaucoup plus proche. En effet, explique Frédéric Gueth : « Aux problèmes de calibration, s’est ajouté le constat que cette source est fluctuante et peut-être mal orientée par rapport à la Terre. » Que ce soit à cause des mouvements de matière dans le disque du trou noir ou d’un autre phénomène, les variations horaires de luminosité de l’ombre, brouillent les signaux.
 
Un souci que les équipes espèrent résoudre en augmentant, lors des prochaines campagnes, la sensibilité du réseau EHT par l’ajout de nouvelles stations d’observation. L’une d’entre elles sera située en France. Il s’agit de l’interféromètre Noema de l’Iram dont les dix (et bientôt douze) antennes de 15 mètres installées à 2500 mètres d’altitude, sur le Plateau de Bure, dans les Hautes-Alpes, vont rentrer dans la danse. Avec un objectif : arracher aux trous noirs leurs ultimes secrets.
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A gauche : Observation du trou noir supermassif par la collaboration EHT Au centre : Simulation de ce trou noir. A droite : Après "floutage" des simulations pour reproduire les limitations de l'EHT en terme de résolution, le modèle colle aux observations.

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

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

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

The huge halo around giant elliptical galaxy Messier 87 appears on this very deep image. An excess of light in the top-right part of this halo, and the motion of planetary nebulae in the galaxy, are the last remaining signs of a medium-sized galaxy that recently collided with Messier 87.
 
The image also reveals many other galaxies forming the Virgo Cluster, of which Messier 87 is the largest member. In particular, the two galaxies at the top right of the frame are nicknamed "the Eyes".
 
Credit:
Chris Mihos (Case Western Reserve University)/ESO

This diagram shows the location of the telescopes used in the 2017 EHT observations of M87.
 
Credit:
NRAO