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Posted on 31 Oct. 2018
"It's amazing to see objects gravitate around a huge black hole at 30% of the speed of light," wondered Oliver Pfuhl, a scientist at the Max Planck Institute for Extraterrestrial Physics.
Astronomers have found something in orbit around the deepest possible orbit of the supermassive black hole in the center of the Milky Way. Their measurements suggest that this material – perhaps consisting of plasma drops – is not far from the deepest orbit allowed by the laws of physics, says Joshua Sokol in Quanta. If this is the case, he wrote, astronomers will be closer and closer to the mirrored space-time surrounding a black hole. And over time, additional observations will indicate whether these known laws of physics really describe what is happening at the brink of space-time disruption.
"They clearly saw something move," said Shep Doeleman, an astronomer at the Harvard – Smithsonian Astrophysical Center, who did not take part in what he calls the "extraordinary" steps of the day. team, which will be published tomorrow in Astronomy & Astrophysics. "What it is, is not exactly clear."
The extremely sensitive ESO GRAVITY instrument has added new evidence to the long-standing assumption that a supermassive black hole is hiding in the center of the Milky Way. New observations show that masses of gas were swirling at about 30% of the speed of light in a circular orbit just outside its event horizon – the first time that a material was observed in orbit near the point of no return, and the most detailed observations ever made. material in orbit near a black hole.
For astrophysicists, this glimpse of plasma is interesting in itself. "We have a totally new environment, which is totally unknown," said Nico Hamaus, cosmologist at the Ludwig Maximilian University in Munich, who also developed the theory of the first hot spots.
ESO's GRAVITY instrument on the Very Large Telescope Interferometer (VLT) has been used by scientists from a consortium of European institutions, including ESO, to observe bursts of infrared radiation from accretion around Sagittarius A *, the immense object located at the heart of the Milky Way. The light from the four telescopes of the very large Cerro Paranal telescope network in Chile can be combined to create, in reality, a single huge telescope.
The observed eruptions provide the long-awaited confirmation that the object at the center of our galaxy is, as has long been assumed, a supermassive black hole. The eruptions come from materials in orbit very close to the horizon of the events of the black hole. These are the most detailed observations ever made to date around a black hole.
While some objects in the accretion disk – the gas belt orbiting Sagittarius A * at relativistic speeds – can safely orbit the black hole, anything that gets too close is doomed to go out of the event horizon. The closest point to a black hole that the material can orbit without being irresistibly attracted to the interior by the immense mass is called the most stable internal orbit, and this is the most important. hence the eruptions observed.
The relativistic speeds are those that are so great that the effects of Einstein's theory of relativity become significant. In the case of accretion disk around Sagittarius A *, the gas travels at about 30% of the speed of light.
These measures were only possible thanks to international collaboration and state-of-the-art instrumentation. The GRAVITY instrument that made this work possible combines the light of four ESO VLT telescopes to create a virtual telescope 130 meters in diameter, already used to probe the nature of Sagittarius A *.
Earlier this year, GRAVITY and SINFONI, another VLT instrument, allowed the same team to accurately measure the close flight of the S2 star as it passed through the extreme gravitational field near Sagittarius A * and revealed effects predicted by Einstein's general relativity in such an extreme environment. During the close flyover of S2, a strong infrared emission was also observed.
"We were watching S2 closely and, of course, we are still watching Sagittarius A *," said Pfuhl. "In our observations, we were lucky enough to notice three bright bursts around the black hole – it was a lucky coincidence!"
This emission, emitted by very energetic electrons very close to the black hole, was visible in the form of three prominent flashes of light and corresponded exactly to the theoretical predictions of hot spots in orbit around the black hole of four million solar masses. Eruptions are thought to arise from magnetic interactions in the very hot gas in orbit very close to Sagittarius A *.
The solar mass is a unit used in astronomy. It is equal to the mass of our nearest star, the Sun, and has a value of 1,989 × 1030 kg. This means that Sgr A * has a mass of 1,300 billion times that of the Earth.
Reinhard Genzel, of the Max Planck Institute for Extraterrestrial Physics (MPE), who led the study, explained: "It was always one of our dream projects, but we did not dare hope that it would become possible as soon as possible The long-standing hypothesis that Sagittarius A * is a supermassive black hole, Genzel concluded that "the result is a striking confirmation of the paradigm of the massive black hole".
This research was undertaken by scientists from the Max Planck Institute for Extraterrestrial Physics (MPE), the Paris Observatory, Grenoble Alpes University, CNRS, the Institute Max Planck for Astronomy, the University of Cologne and the Centro Centro Português Centro e Gravitação and ESO.
The Daily Galaxy via ESO and Quanta
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