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On a vu que si une grosse étoile meurt, elle pourra donner naissance à un trou noir.

Un trou noir est un endroit dans l’espace où la gravité est tellement forte, que même la lumière ne peut pas en sortir. La gravité est si forte parce que la matière a été compressée dans un espace minuscule. Cela peut arriver lorsqu’une étoile meurt.
Parce qu’aucune lumière ne peut sortir, on ne peut pas voir les trous noirs. Ils sont invisibles. Les télescopes spatiaux dotés d’outils spéciaux peuvent aider à trouver des trous noirs. Ainsi on peut voir comment les étoiles qui sont très proches des trous noirs agissent différemment des autres étoiles.

Un soir, repérez vous dans le ciel et rechercher la constellation du sagittaire, au bout de la voie lactée. Regardez bien, c’est là que se trouve le trou noir de notre galaxie, regardez bien, on ne peut pas le voir…

Sur le site de l’Eso.org vous pourrez découvrir de superbes images prises par les télescopes et offertes au public ; c’est une invitation au rêve.

Un trou noir…

On en entend parler, on en a détecté… mais qu’est-ce que c’est ?

Encore une fois, Henry va nous l’expliquer

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Captured with the MUSE instrument on ESO’s Very Large Telescope (VLT), this image of the distant spiral galaxy NGC 1097 shows a textbook example of a star-bursting nuclear ring. Located 45 million light-years away from Earth, in the constellation of Fornax, this ring lies at the very centre of its galaxy. It spans only 5,000 light years across, being dwarfed by the full size of its host galaxy, which extends some tens of thousands of light-years beyond its centre. The darker lanes seen in this MUSE image show dust, gas and debris from the galaxy (or possibly from a satellite galaxy), which are being funnelled into the supermassive black hole at its centre. This process heats up the surrounding matter forming an accretion disc around the black hole and launching huge amounts of energy into the surrounding area. Nearby dust is heated up and star formation accelerates in the area around the supermassive black hole, forming the star-bursting nuclear ring shown in pink and purple tones in the image. MUSE, which stands for Multi Unit Spectroscopic Explorer, is attached to Yepun, one of the four, 8.2-metre telescopes that make up the VLT at ESO’s Paranal Observatory. Its unique design has allowed researchers to map complex mechanisms within many galaxies and analyse the formation of stars and star clusters.
This is the first image of Sgr A*, the supermassive black hole at the centre of our galaxy. It’s the first direct visual evidence of the presence of this black hole. It was captured by the Event Horizon Telescope (EHT), an array which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope. The telescope is named after the event horizon, the boundary of the black hole beyond which no light can escape.   Although we cannot see the event horizon itself, because it cannot emit light, glowing gas orbiting around the black hole reveals a telltale signature: a dark central region (called a shadow) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun. The image of the Sgr A* black hole is an average of the different images the EHT Collaboration has extracted from its 2017 observations.  In addition to other facilities, the EHT network of radio observatories that made this image possible includes the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX) in the Atacama Desert in Chile, co-owned and co-operated by ESO is a partner on behalf of its member states in Europe.