A group of Chilean astronomers captured two galaxies colliding, with a level of detail never seen before. The image was obtained using the ALMA radio telescope, which has a resolution ten times higher than the Hubble Space Telescope, from where the last record of this region of the Universe was obtained, 360 million light-years from Earth, in the constellation of Ophiuchus.
The finding, which will be announced worldwide tomorrow in Honolulu, Hawaii, during the meeting of the American Astronomical Society, reveals unpublished details about the merger that gives rise to a new galaxy known as NGC 6240.
It is a preview of what will happen in our own Milky Way, when it merges with the neighboring Andromeda in about 5 billion years.
Ezequiel Treister, astronomer at the Astrophysics Institute of the Pontifical Catholic University (IA-PUC) and researcher at the Center for Astrophysics and Related Technologies (CATA) who led the research, explains from Hawaii to Qué Pasa that this is a true feat. "What we observed was the molecular gas or cold gas that is present in the central region of a system composed of two colliding galaxies. What is relevant is that these two galaxies and their black holes are simultaneously growing very rapidly."
The research was able to directly measure the masses of the holes, concluding that they correspond to between 500 and 1 billion times that of the Sun, about 100 times larger than the one found in the center of the Milky Way. "Each galaxy has its supermassive black hole equivalent to hundreds of millions of times the mass of the Sun," the academic points out.
Treister points out that "when we talk about massive, it refers to the amount of matter they contain. When we talk about them being 100 billion times the mass of the Sun, it means that if you measure the gravitational pull that the black hole generates, it's equivalent to what you would have if you put 100 billion suns all together." "These black holes are in the family of the largest black holes that we know of in the universe. What we know now is that in many cases galaxy collisions play a role in this growth. We use ALMA to study the properties of the gas that feeds these holes in a colliding galaxy," adds Treister.
This work has not only made it possible to observe the merging process of these galaxies, but also to distinguish the individual regions where stars are forming. Previously it was impossible to determine which processes could be associated with the influence of the black hole, or what corresponded to star formation, since the images were all mixed up.
"Achieving these images was a years-long process. It could be done now and not before, because of the unique characteristics of ALMA. To achieve an observation and image with such sharpness, what you need is to have as large a telescope as possible. In the case of ALMA, there are 66 antennas, which you move and combine the light. The more you separate the antennas, the bigger the telescope. This time, we achieved a total of 15 kilometers," says Treister, this technique is called interferometry. "This kind of observations are very new, ALMA is the only one that can do it. After that, the data processing is very complex, to achieve this image that took about two years of analysis", adds the professional.
"The black hole is a physical object, like a star or a planet, but it does not emit light. The fundamental difference is that it is such a massive object, so dense, that the escape velocity is greater than the speed of light, so nothing can escape from it. That is why it is called black. Its fundamental property is its amount of matter, its mass, which is what defines a black hole," explains Treister.
These data indicate that most of the gas detected is located between the two black holes and that there is so much of it that it would be equivalent to 10 billion solar masses, or about 15 times more than all the gas found in the Milky Way.
Some of this gas is blown away by intense winds at speeds of around 500 kilometers per second or more. "We think that eventually much of the gas will be expelled from the central region of the galaxy, while a fraction will fall into the black hole, feeding it," says Franz Bauer, an astronomer at the Astrophysics Institute of the Catholic University, who also participated in the research.