The stars orbiting the black hole once again confirm the predictions of general relativity
The article describes the fact that after tracking a star named S2, it was proved that S2's orbit is not a fixed positional ellipse, but a phenomenon known as the Schwarzschild precession, that is, the orbit rotates like a spiral chart, which follows general relativity well.
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S2 is a star that orbits the supermassive black hole at the center of the Milky Way. Recently, researchers have verified the predictions of general relativity in the most extreme environments that people can monitor by observing S2, adding empirical evidence to its establishment.
Combining decades of observations, astronomers have found that S2's orbit is not a fixed, unchanging ellipse, but a rose-like shape — a phenomenon known as the Schwarzschild precession.
Schwarzschild advances hypothetical diagrams. Image source: ESO
This is the first time that a Schwarzschild precession has been observed around a supermassive black hole, suggesting that general relativity also applies to the orbits of stars in the most extreme gravitational environments. In addition, general relativity equations can also be used to accurately predict orbital changes – the calculation results of S2's orbits are precisely matched to observations.
ReinhardGenzel, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics (MPE) in Germany and a member of the GRAVITY team, said: "Einstein predicted in general relativity that the orbit of an object around another object is not a closed curve like Newton's theory of gravitation, but advances forward within the plane of motion."
Illustration: Gravity gravity is a new type of instrument that can continuously combine the light of the European Southern Observatory's (ESO) Very Large Telescope Interferometer (VLTI) to form a telescope equivalent to 130 meters of aperture angular resolution and 200 square meters of collection area. Image source: ESO
"This famous phenomenon has been observed for the first time by monitoring Mercury's orbit around the Sun, the first evidence to support the theory of general relativity. A hundred years later, we found the same phenomenon by observing the orbits of stars orbiting the dense jet power supply Sagittarius A* at the center of the Milky Way. ”
Mercury color enhancement. Image source: Wallup
The orbit of S2 around Sagittarius A* is oblong-elliptical and runs for 16 years. When it travels to a perigee point, it is less than 17 light hours away from the black hole, which is equivalent to more than four times the distance from the sun to Neptune.
Such a distance sounds far away, but when you're confronted with a giant celestial body like Sagittarius A*, it's ridiculously close. And the gravitational pull of a black hole can accelerate the stars that pass around it to nearly 3 percent of the speed of light. S2 is one of the closest stars in orbit at the center of the Milky Way.
Sagittarius A* (abbreviated as Sgr A*, asterisk * pronounced "star" or "star") is a very bright and dense radio wave source located in the galactic center of the Milky Way, which rotates approximately every 11 minutes and is part of Sagittarius A. Sagittarius A* is likely to be the closest supermassive black hole to Earth, so it is also considered the best target for studying black hole physics. Image source: Wikipedia
This is not the first time that people have tested the theory of relativity by looking at S2. Astronomers have been keeping a close eye on the star since the 1990s. In 2018, the GRAVITY team announced that the way S2's light was curved as it approached Sagittarius A* confirmed a prediction of general relativity, the most extreme test environment to date. The following year, another team validated the results with their own paper, which used a set of independent observational data.
The more than 330 measurements currently used by the GRAVITY team cover observations from 1992 to the end of 2019 to verify that the observed precessions match general relativity predictions. As a result, they bet on the right chips.
Stefan Gillessen, an astrophysicist at mpE, said: "After tracking the orbit of star S2 for more than twenty-five years, the evidence we have found through precision measurements strongly confirms the existence of Schwarzschild precession around sagittarius A* orbit of S2. ”
In addition, to calculate the precession of S2, the exact mass of Sagittarius A* needs to be obtained. Available evidence suggests that it has a mass of about 4 million times that of the Sun. To fit the observed orbit, the relativistic equation requires a mass parameter of exactly 4 million times the mass of the Sun.
Illustration: The supermassive black hole in the core of the supergiant elliptical galaxy in the constellation Virgo, the Virgo A galaxy (M87), is estimated to have a mass of about 6.5 billion times that of the Sun. This image was taken by the Event Horizon Telescope and is the first actual image of a black hole in history. A supermassive black hole is a type of black hole with a mass of 105 to 109 times the mass of the Sun (1035 to 1039 kg). It is now generally believed that there are supermassive black holes at the centers of all galaxies, including those of the Milky Way. Source: Wikipedia
This discovery reaffirms the quality of Sagittarius A*. Astronomers can also use this to study the space around the orbit. If there is another massive object nearby, such as an intermediate-mass black hole, it affects the orbit. If the orbit is not affected, there are no nearby objects capable of affecting it.
Astrophysicists Guy Perrin and Karine Perraut, from the Murphysiote and Grenoble Observatory in Paris, France, respectively, point out: "The S2 measurements follow general relativity well, allowing us to strictly limit the range of invisible matter that exists around Sagittarius A*, such as dark matter or smaller black holes. This has important implications for understanding the formation and evolution of supermassive black holes. ”
From the effects of gravitational lensing, a dark material circle was found inside galaxy cluster CL0024+17, shown in blue in this Hubble Space Telescope image. (In cosmology, dark matter Dark Matter refers to matter that does not interact with electromagnetic forces, that is, does not absorb, reflect, or emit light.) People can only know through the effects of gravity, and a large amount of dark matter has been found in the universe. Source: Wikipedia
Just one star can send us so much information. Astronomy is so wonderful.
The study has been published in Astronomy and Astrophysics.
BY: MICHELLE STARR
MY: I
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