Thu. Oct 6th, 2022

The first image of the surroundings of a supermassive black hole in the heart of the Milky Way

Thanks to a network of 13 radio telescopes, astronomers have made unprecedented observations of a supermassive black hole located in the heart of the Milky Way. Scientists have managed to unlock the secret and take the best-ever image of Sagittarius A*.

After integrating the powerful ALMA observatory into the global radio telescope networków astronomers have discovered that emissions from a supermassive black hole located at the center of our galaxy are coming from a much smaller region than previously thought. This may indicate that the radio jet from supermassive black hole Sagittarius A* (Sgr A*) is directed almost exactly toward Earth.

So far, the hazy cloud of hot gas has prevented astronomers from taking sharp images of Sgr A* and has raised doubts about its true nature. Matter thatóra falls into the black hole heats up and emits light, but the hot gas and dust surrounding Sgr A* reflects this light, making accurate observations difficult.

The work of the international team of scientistsów was published in the journal „Astrophysical Journal”.

– Galactic center is full of wok matterół black hole, whichóra acts like frosted glass, through which theóre difficult to see anything,” said Eduardo Ros of the Max Planck Institute for Radio Astronomy in Germany, wspópublication router.

The situation changed after joining the global radio telescope networkóat the ALMA observatory located in Chile. This has greatly improved observational capabilities. Using a technique called Very Long Baseline Interferometry (VLBI) for observations, która connects many telescopesów, by creating an Earth-sized virtual telescope, we were able to map the exact scattering properties of the light blocking our view of Sgr A*. Removing most of the effectóin scattering gave the first image of the black hole’s surroundings.

Using the acquired data, the scientists created several computer models to simulate what is inside the dense cloud of plasma, dust and gas surrounding the black hole. The high image quality allowed the team to constrain theoretical models. Analysis has shown that most of the radio emission comes from just three hundred millionths of a degree, and the source of theóthe background has a symmetrical morphology.

– This may indicate that the radio emission comes from a disk of falling gas rather than a radio jet – explained study leader Sara Issaoun of Radboud University Nijmegen in the Netherlands. – However, if this were the case, Sgr A* would be an exception in cfóIn comparison with other radio-emitting black holes. Alternatively, it could be that the radio jet is directed exactly at us – added.

– It may actually be the case that we are looking at this beast from a very detailedóln the viewpoint – admitted Heino Falcke, Issaoun’s recent supervisor at the same university. He added that this is very unusual, but nothing can be ruled out.

VLBI interferometer and ALMA. Photo. S. Issaoun, Radboud University / D. Pesce, CfA

Supermassive black holes are common in the centers of galaxies and can generate the most energetic phenomena in the known Universe. It is believed that the matter circulating around theół of these black holes falls on them, and part of it is ejected in opposite directions along the dwóch narrow streams, called jets, at speeds close to the speed of light, which usually produces a lot of radio radiation.

Sgr A* is the closest supermassive black hole to us and has a mass of about 4 millionóin the masses of the Sun. Its apparent size in the sky is less than 100 millionths of a degree, equivalent to the size of a tennis ball on the Moon as seen from Earth. To measure this, the VLBI technique is required. The resolution achieved with VLBI is further enhanced by the frequency of observation. The highest frequency to date for VLBI is 230 GHz. The current observations were conducted at 86 GHz.

– The first observations of Sgr A* at 86 GHz date back 26 years and were made with only a few telescopesów. Over the years, data quality and image processing capabilities have steadily improved as the number of telescopes has increasedów – admitted J. Anton Zensus, director of the Max Planck Institute for Radio Astronomy.

Participation in ALMA radio telescope observations is important because of its sensitivity and location on the pósouthern hemisphere. OpróALMA’s observations involved the róalso twelve radio telescopesóin located in America Pónortheast and Europe. The resolution achieved was twice that of previous observations at this frequency and produced the first image of Sgr A*, który is devoid of interstellar scattering (an effect caused by density irregularities in the ionized material along the line of sight between Sgr A* and Earth).

– Although scattering causes blurring and distorts the image of Sgr A*, the incredible resolution of these observations has allowed us to determine the exact properties of the scattering – pointed out Michael Johnson of the Harvard-Smithsonian Center for Astrophysics, author of the technique, which makes theórej it was possible to remove the scattering and obtain an image. – We can remove most of the effectóin scattering and to see what the black hole’s environment looks like – added by.

Future research on róThe different wavelengths will provide complementary information, which is the key to a better understanding of black holes, the most exotic objectsóin the known Universe.

Sourceóbackground: Max Planck Institute for Radio Astronomy, photo. S. Issaoun, M. Mościbrodzka, Radboud University/ M. D. Johnson, CfA. Pictured: U góry on the left – simulation of Sgr A* at 86 GHz. U góry on the right – simulation with added scattering effects. Bottom right – scattered observation image, this is how we see Sgr A* in the sky. Bottom left – uncompressed image, after removing effectóin scattering along our line of sight. This is what Sgr A* really looks like.