Unlike the now iconic giant black hole the size of our solar system at the center of a nearby elliptical galaxy, M87, with its massive jet erupting at close speed of light, the central black hole of the Milky Way, SgrA *, which by May 201
UC Berkeley’s Reinhard Genzel and UCLA’s Andrea Gez were awarded the Nobel Prize in Physics in 2020 based on groundbreaking research – “Theoretical basis for black holes and the supermassive object at the Galactic Center” – which demonstrates that this supermassive compact object in the center of our galaxy, SgrA *, is a black hole. “Each of them leads a group of astronomers who, since the early 1990s, have focused on a region called Sagittarius A * in the center of the Milky Way galaxy. The orbits of the brightest stars, which are closest to the middle of the Milky Way, have been mapped with increasing accuracy. The measurements of these two groups agree, and both find an extremely heavy, invisible object that pulls the mess of stars, causing them to rush around at dizzying speeds. About four million solar masses are gathered together in a region no larger than our solar system. “
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Near a high-speed light jet
This speed of light of the M87s is called Superluminal motion, which was captured from images of the Chandra X-Ray Observatory between 2012 and 2017 of material ejected into the jet, fired from a black hole hundreds and thousands of years earlier. when objects move close to the speed of light in a direction that is close to our line of sight. The jet moves almost as fast towards us as the light it generates, creating the illusion that the jet is moving much faster than the speed of light. In the case of the M87 *, the jet points close to our direction, leading to these exotic visible speeds.
Two critical numbers – Mass and Spin
Supermassive black holes such as SgrA * are characterized by only two numbers: mass and spin, which have a critical impact on galaxy formation and evolution, according to a new study by the Harvard Center for Astrophysics (CfA) and the Center for Interdisciplinary Astrophysics Research and Research (CIERA). ) at Northwestern University. According to Avi Loeb, Frank B. Baird Jr. professor of science at Harvard and CfA astronomer and co-author of the study. “Black holes release a huge amount of energy, which removes gases from galaxies and therefore shapes their history of star formation.”
While scientists know that the mass of central black holes has a critical effect on their host galaxy, measuring the impact of their rotation is not easy. As Loeb says, “the effect of the rotation of a black hole on the orbits of nearby stars is subtle and difficult to measure directly.”
Genzel and Gez observe the movement of stars around SgrA *, said Loeb. “They measured its mass, but not its rotation. We received the first strict SgrA * rotation limit, ”adding that the find would not have been possible without the original work won by Genzel and Ghez.
To gain a better understanding of how SgrA * influenced the formation and evolution of the Milky Way, Loeb and Dr. Giacomo Fragione of CIERA have instead studied the stellar orbits and spatial distribution of S-stars, the nearest stars, which orbit SgrA * and travel at speeds of up to a few percent of the speed of light – to limit or restrict the rotation of the black hole.
“We’ve concluded that the supermassive black hole at the center of our galaxy is spinning slowly,” Fragione said. “This could have major implications for the detection of activity at the center of our galaxy and future observations of the Horizon of Events telescope.
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The unveiling of S-Stars
S-stars appear to be organized in two preferred planes. Loeb and Fragione have shown that if SgrA * has a significant rotation, the star’s preferred orbital planes at birth will become incompatible from the present time. “For our study, we used the recently discovered S-stars to show that the rotation of a black hole SgrA * should be less than 10 percent of its maximum value, corresponding to a black hole rotating at the speed of light,” he said. Loeb. “Otherwise, the common orbital planes of these stars will not remain flat during their lifetime, as seen today.”
Jets like giant flywheels
The results of the study indicate another important detail about SgrA *: it is unlikely to have a jet. “The jets are thought to be powered by rotating black holes that act like giant flywheels,” Loeb said, adding that Fragione added that “there is actually no evidence of reactive activity in SgrA *. The upcoming analysis of data from the Event Horizon telescope will shed more light on this issue. “
Source: “Upper spin limit of SgrA based on stellar orbits in its vicinity”, G. Fragione and A. Loeb, The Astrophysical Journal Letters.
The Daily Galaxy, Max Goldberg, through the Harvard CfA and the 2020 Nobel Prize in Physics
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