“We were amazed at how well the size of the observed ring matched the predictions of Einstein’s general theory of relativity”, says EHT project scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics at Academia Sinica in Taipei. Their light is bent by the immense gravity of the black hole. But the glowing gas around it shows a tell-tale signature – a dark central region (shadow) surrounded by a bright ring-like structure. The black hole itself is not visible in the image because it does not emit any radiation. The image is the first direct visual proof of this. “Our discovery shows that the object at the galactic centre is indeed a black hole”, says Anton Zensus, Director at the Max Planck Institute for Radio Astronomy and founding chair of the Supervisory Board of the EHT. For this work, Andrea Ghez from the University of California and Reinhard Genzel from the Max Planck Institute for Extraterrestrial Physics in Garching were awarded the Nobel Prize in 2020. For many years, researchers have been examining this area of the Milky Way and observing stars that orbit an invisible, compact, and massive object. The recently published image is the long-awaited direct view of the object at the centre of our galaxy known as Sagittarius A*. The heights of the bars indicate the relative contributions of each cluster to the averaged image at top. Thousands of images fell into each of the first three clusters, while the fourth and smallest cluster contains only hundreds of images. The bar graphs show the relative number of images belonging to each cluster. The fourth cluster contains images that also fit the data but do not appear ring-like. Three of the clusters show a ring structure but, with differently distributed brightness around the ring. An averaged, representative image for each of the four clusters is shown in the bottom row. The images can also be clustered into four groups based on similar features. The image is an average of the various images extracted by the EHT collaboration from their observations in April 2017.
The image captures light bent by the strong gravity of the black hole and is four million times more massive than the sun. Although the event horizon itself is not visible because it does not emit light, glowing gas swirling around the black hole shows a tell-tale signature: a dark central region (shadow) surrounded by a bright ring-shaped structure. The EHT is named after the “event horizon”, the boundary of the black hole beyond which no light can escape. It was taken by the Event Horizon Telescope (EHT), a network that combines radio observatories around the world into a single virtual telescope the size of the Earth. Competitors estimate that there are 5,153 light-years from Earth to the object.Cosmic ring of fire: This is the first image of Sagittarius A*, the supermassive black hole at the centre of the Milky Way. The University of California claims that it is between 22 light years. The distance to the object is also different. In this case, the find is almost certainly a black hole. Scientists from the Space Telescope Science Institute in Baltimore have estimated that the weight of the “ghost” is closer to 7.1 than the mass of the Sun. Interestingly, the other team also studied found object, their numbers differ.
According to preliminary estimates, there are about 200 million “ghosts” in the galaxy. It is believed that such holes formed in large numbers after the Big Bang. This will help them study the evolution of stars and galaxies, and perhaps find out if there are any primary black holes in these objects.
Astronomers are going to determine how many such objects are in the Milky Way.
The detected object is the first dark stellar remnant – a stellar “ghost” – found roaming through a galaxy without a pair with another star.
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