The Event Horizon Telescope (EHT) is a vast telescope array consisting of a global network of radio telescopes. The EHT observes objects the size of a supermassive black hole’s event horizon. The project’s observational targets include the two supermassive black holes: the black hole at the center of the supergiant elliptical galaxy Messier 87 (M87), and Sagittarius A* (Sgr A*) at the center of the Milky Way.
EHT Produces the First Image of a Supermassive Black Hole About a Year Ago
A supermassive black hole is the largest type of black hole. It contains a mass of the order of hundreds of thousands to billions of times the mass of the Sun. They are astronomical objects that gravitationally collapsed, leaving behind spheroidal regions of space from which nothing can escape, not even light. Nearly all massive galaxies contain a supermassive black hole located at the galaxy’s center.
The first image of a black hole, at the center of galaxy Messier 87, was published by the EHT Collaboration on April 10, 2019. Located at the galactic core of Messier 87, it shows a heated accretion ring orbiting the object at a mean separation ten times larger than the orbit of Neptune around the Sun. The dark center is the event horizon and its shadow.
The image provided a test for Albert Einstein’s general theory of relativity under extreme conditions. Many of the features of the observed image match our theoretical understanding surprisingly well.
Messier 87 is a supergiant elliptical galaxy in the constellation Virgo. One of the most massive galaxies in the local universe. Its diameter is estimated at 240,000 light-years, which is slightly larger than that of the Milky Way.
A New Study Based on Image of the M87’s Supermassive Black Hole
A research today, predicts a substructure within supermassive black hole images from extreme gravitational light bending. The observational astronomers, theoretical physicists, and astrophysicists involved in the study say that the black hole’s substructure contains a series of photon rings that become sharper and sharper. The number of rings corresponds to the number of orbits that photons took around the black hole before reaching the observer. The image shows a bright ring of emission surrounding a “shadow” cast by the black hole.
With the help of EHT images, researchers have a new tool to study photon spheres. Also known as photon circle, a photon sphere is an area or region of space where gravity is so strong that photons are forced to travel in orbits. They can only exist in the space surrounding an extremely compact object, such as a black hole.
The photon sphere is located farther from the center of a black hole than the event horizon. Within a photon sphere, it is possible to imagine a photon that’s emitted from the back of one’s head, orbiting the black hole, only then to be intercepted by the person’s eyes, allowing them to see the back of their head. “This is an extremely exciting time to be thinking about the physics of black holes,” says Daniel Kapec from the Institute for Advanced Study.