Post by Andrei Tchentchik on Jun 26, 2019 18:41:42 GMT 2
(.#229).- The gargantuan black hole central of the Galaxy is revealed little by little.
The gargantuan black hole central of the Galaxy is revealed little by little.
By Tristan Vey - Updated on 24/01/2019 at 11:11
Simulation of radio emissions around the central black hole of the galaxy. European Southern Observatory / Bronzwaer / Davelaar / Moscibrodzka / Falcke / Radboud University.
A first image of the immediate environment of the supermassive black hole that is nestled in the heart of the Milky Way has just been published. It could precede a first "portrait" of black hole, expected in the months to come.
Astronomers have never been so close to "seeing" the supermassive central black hole that lies at the heart of our galaxy. This strange object results from an extreme concentration of matter, at least four million times the mass of our Sun, in a tiny volume. Such a density causes a gravitational well that no object can escape when it comes too close, not even light. This boundary thus delimits a sphere of absolute black within which we do not know exactly what is happening. To be more exact, classical physical theories are ineffective to describe clearly what could happen there. For example, the theory of general relativity predicts that matter continues to collapse until it is concentrated in a geometric point of infinite density, which does not really make sense.
In the case of the central black hole of our galaxy, called SgrA *, the radius of this perfectly opaque sphere of influence should be about 20 times that of our Sun. But no telescope has yet managed to observe it. It must be said that observing such a small black ball located in a dark region 25,000 light-years away from us is not obvious ... This is not exactly what astronomers seek to flush out. Rather, they try to detect the radio waves emitted by the plasma that is spinning at astronomical speeds by wrapping around the black hole and hope to see there outline the outline of the dark ball of which we spoke above.
The different radio telescopes mobilized to realize this first image of the immediate environment of the supermassive central black hole of our galaxy. S. Issaoun, Radboud University / D. Pesce, CfA.
To achieve this, astronomers need to network antennas around the world to "simulate" a gigantic radio telescope the size of the Earth. This requires that the signals received by each of the antennas are synchronized extremely finely, using atomic clocks, but also that we know the position of each to a fraction of a millimeter ... To take the measure of the technical prowess, it requires to take into account parameters as fine as the deformation of the ground related to the position of the Moon, or the drift of the continents.
The task is complex, but not impossible. The first results of the international collaboration The Global Millimeter VLBI Array have just been published in the journal The Astrophysical Journal. Sara Issaoun, from Radbourne University in Nijmegen, The Netherlands, is the first author of this article to unveil the first image of the radio environment of the central black hole in our galaxy. This is based on observations made in 2017, which gives an idea of the complexity of the treatment that was necessary to achieve this cliche.
In the top left, a simulation of radio emissions around the black hole. At the top right, the image that one would have after dispersion of the light by the interstellar medium with a telescope "perfect". Bottom right, raw observation, then bottom left, corrected for dispersion :
Bronzwaer / Davelaar / Moscibrodzka / Falcke / Radboud University.
The resulting image looks like a simple spot of diffuse light, but it is not free of information. For starters, it does not present any material roll. "This is a big surprise," said Frédéric Gueth, deputy director of the Institute of millimeter radio astronomy (IRAM), two branches in France and Spain, participated in the observations. The black holes emit in principle two large jets, perpendicular to the plane in which they turn on themselves. "It can mean two things: either the black hole is inclined toward us in such a way that we are in the direction of its axis of rotation, or the jets are very weak, see nonexistent," says Frédéric Gueth.
"This confirms the recent observations we made with the Gravity instrument installed on the Very Large Telescope in Chile," said Guy Perrin, astronomer at the Paris Observatory, leans for the first option. "We do not see the central black hole in front, but by the pole, with an inclination of 20 to 30) only."
For now, no trace of the central black hole itself, but this does not surprise the researchers. "We observe at a certain wavelength (3 mm in this case, equivalent to a frequency of 86 GHz, Ed) that is diffused by the interstellar medium," says Frédéric Gueth. Further observations were made at a wavelength three times shorter (ie a higher frequency three) in a similar project, the Horizon Telescope Event, but they do not have not yet been published. As the resolution depends on the wavelength, these images will be a priori three times better defined. And these radio waves also have the advantage of being less dispersed by the interstellar medium. The first portrait of the long-awaited central black hole in the galaxy may be near.
F I N .
The gargantuan black hole central of the Galaxy is revealed little by little.
By Tristan Vey - Updated on 24/01/2019 at 11:11
Simulation of radio emissions around the central black hole of the galaxy. European Southern Observatory / Bronzwaer / Davelaar / Moscibrodzka / Falcke / Radboud University.
A first image of the immediate environment of the supermassive black hole that is nestled in the heart of the Milky Way has just been published. It could precede a first "portrait" of black hole, expected in the months to come.
Astronomers have never been so close to "seeing" the supermassive central black hole that lies at the heart of our galaxy. This strange object results from an extreme concentration of matter, at least four million times the mass of our Sun, in a tiny volume. Such a density causes a gravitational well that no object can escape when it comes too close, not even light. This boundary thus delimits a sphere of absolute black within which we do not know exactly what is happening. To be more exact, classical physical theories are ineffective to describe clearly what could happen there. For example, the theory of general relativity predicts that matter continues to collapse until it is concentrated in a geometric point of infinite density, which does not really make sense.
In the case of the central black hole of our galaxy, called SgrA *, the radius of this perfectly opaque sphere of influence should be about 20 times that of our Sun. But no telescope has yet managed to observe it. It must be said that observing such a small black ball located in a dark region 25,000 light-years away from us is not obvious ... This is not exactly what astronomers seek to flush out. Rather, they try to detect the radio waves emitted by the plasma that is spinning at astronomical speeds by wrapping around the black hole and hope to see there outline the outline of the dark ball of which we spoke above.
The different radio telescopes mobilized to realize this first image of the immediate environment of the supermassive central black hole of our galaxy. S. Issaoun, Radboud University / D. Pesce, CfA.
To achieve this, astronomers need to network antennas around the world to "simulate" a gigantic radio telescope the size of the Earth. This requires that the signals received by each of the antennas are synchronized extremely finely, using atomic clocks, but also that we know the position of each to a fraction of a millimeter ... To take the measure of the technical prowess, it requires to take into account parameters as fine as the deformation of the ground related to the position of the Moon, or the drift of the continents.
The task is complex, but not impossible. The first results of the international collaboration The Global Millimeter VLBI Array have just been published in the journal The Astrophysical Journal. Sara Issaoun, from Radbourne University in Nijmegen, The Netherlands, is the first author of this article to unveil the first image of the radio environment of the central black hole in our galaxy. This is based on observations made in 2017, which gives an idea of the complexity of the treatment that was necessary to achieve this cliche.
In the top left, a simulation of radio emissions around the black hole. At the top right, the image that one would have after dispersion of the light by the interstellar medium with a telescope "perfect". Bottom right, raw observation, then bottom left, corrected for dispersion :
Bronzwaer / Davelaar / Moscibrodzka / Falcke / Radboud University.
The resulting image looks like a simple spot of diffuse light, but it is not free of information. For starters, it does not present any material roll. "This is a big surprise," said Frédéric Gueth, deputy director of the Institute of millimeter radio astronomy (IRAM), two branches in France and Spain, participated in the observations. The black holes emit in principle two large jets, perpendicular to the plane in which they turn on themselves. "It can mean two things: either the black hole is inclined toward us in such a way that we are in the direction of its axis of rotation, or the jets are very weak, see nonexistent," says Frédéric Gueth.
"This confirms the recent observations we made with the Gravity instrument installed on the Very Large Telescope in Chile," said Guy Perrin, astronomer at the Paris Observatory, leans for the first option. "We do not see the central black hole in front, but by the pole, with an inclination of 20 to 30) only."
For now, no trace of the central black hole itself, but this does not surprise the researchers. "We observe at a certain wavelength (3 mm in this case, equivalent to a frequency of 86 GHz, Ed) that is diffused by the interstellar medium," says Frédéric Gueth. Further observations were made at a wavelength three times shorter (ie a higher frequency three) in a similar project, the Horizon Telescope Event, but they do not have not yet been published. As the resolution depends on the wavelength, these images will be a priori three times better defined. And these radio waves also have the advantage of being less dispersed by the interstellar medium. The first portrait of the long-awaited central black hole in the galaxy may be near.
F I N .
