Black holes are one of the most terrifying and destructive forces in the universe, but some scientists suggest that the radiation of these objects, which they create during the absorption of surrounding matter, can contribute to the emergence of biomolecular building blocks of life and even stimulate photosynthesis. On a general scale, this could mean that there may be many more worlds in our galaxy capable of supporting life than our current hypotheses suggest.
For their new study, the results of which were recently published in the Astrophysical Journal, astrophysicists created computer models to study in more detail the specifics of radiation disks of gas and dust, called active galactic nuclei (AGNs), which orbit supermassive black holes. Some of the brightest objects in the Universe, they are formed as a result of the curvature of matter by the gravity of a black hole. This process is accompanied by the release of a large amount of energy.
Since the early 1980s, it has been believed among scientists that the radiation from these objects creates a dead zone around active galactic nuclei. Some researchers have even suggested that AGNs are the reason why we have not yet discovered complex forms of extraterrestrial life, in particular, towards the center of our galaxy. In the center of the Milky Way lies the huge black gifts Sagittarius A *. According to the conclusions of previous studies, any Earth-like planet, which will be located within a radius of 3200 light years from the center of the active nucleus of the galaxy, under the influence of powerful X-ray and ultraviolet radiation of the AGN will not be able to maintain its atmosphere.
Is life possible near black holes?
The computer models created by the researchers showed that planets with an atmosphere comparable in density to Earth's and higher, and located far enough from the AGN, will be able to preserve their atmospheres and, moreover, will be able to support life on their surface. Scientists explain that at a certain distance from the center of AGNs, the latter, like stars, have so-called "habitable zones" where the amount of ultraviolet radiation is not so high as to destroy all life that may be there.
At such levels of radiation, scientists say, planetary atmospheres will not collapse. At the same time, this radiation will be able to break down molecules, creating the compounds necessary to obtain the structural elements - proteins, lipids and DNA - necessary at least for the life that we know. For black holes the size of the same Sagittarius A * located in the center of our galaxy, the "habitable zone" will begin about 140 light years from the center of the black hole (1 light year = 10 trillion kilometers), the researchers say. In this case, the negative effects of its radiation will be significantly reduced already within a radius of 100 light years from the center of the AGN.
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Black holes and photosynthesis. What do they have in common?
Scientists also examined the effects of this radiation on photosynthesis - the process of synthesizing organic substances from inorganic ones due to the energy of light, through which plants produce oxygen, and some types of bacteria and algae also produce glucose. As noted above, AGNs are capable of emitting huge volumes of the key element required for photosynthesis - light. According to Manasvi, this aspect would be especially important for the so-called orphan planets, objects with a mass comparable to the planetary and spherical in shape and which are essentially planets, but not gravitationally tied to any star. According to scientists, in the "habitable zone" of galaxies the size of our Milky Way, there may be about 1 billion of these wandering planets.
By calculating the area over which AGNs will be able to support photosynthesis, scientists have found that a huge number of galaxies, in particular those with supermassive black holes at their centers, can support this kind of photosynthesis. For example, for a galaxy the size of ours, this region would span about 1100 light years around its center. As for the small and denser, so-called ultracompact dwarf galaxies, more than half of their area will be suitable for photosynthesis, scientists say.
With a fresh look at X-rays and ultraviolet radiation, the researchers say, it's clear that the negative effects of AGNs have been greatly exaggerated in the past. Scientists explain that many species of the same terrestrial bacteria are able to create a special biofilm around themselves that protects them from ultraviolet radiation, so it should not be ruled out that life in areas of space with an increased radiation background could also adapt to such survival methods.
The new study also argues that X-rays and gamma rays, which are also actively emitted by AGN in huge quantities, will be easily absorbed by the Earth-like atmosphere of exoplanets and, apparently, will not significantly affect the life forms that may inhabit them.
As for the AGN of our galaxy, according to the researchers, the negative effects of its radiation will be significantly reduced already within a radius of 100 light years from the AGN center.
Nikolay Khizhnyak