Astronomers have known since the 1990s that planets exist around pulsars. It’s a reasonable hypothesis that planets might also exist around black holes, which have a weaker impact on their local environment than rotating neutron stars. In 2019, Harvard astrophysicist Avi Loeb and NASA’s Jeremy Schnittman proposed that inhabited planets might exist around the black holes harbored at the center of most galaxies. Such planets are similar to the fictional water-world planet Miller, the closest planet in the star system orbiting the supermassive black hole, Gargantua, in the movie Interstellar.
High-Energy Particles and Winds at 10% Speed of Light
A new paper by astrobiologist Manasvi Lingam and astrophysicist Eric Perlman from Florida Institute of Technology, along with researchers from the University of Rome, University of Maryland and Goddard Space Flight Center, examines the radiation and winds emanating from black hole activity and how they may exert effects on nearby planets. The study focuses on two key mechanisms: how black hole winds can heat atmospheres and drive atmospheric escape, as well as how they can stimulate the formation of nitrogen oxides and thus lead to ozone depletion.
“Most galaxies have black holes in their nuclei,” wrote Perlman in an email to The Daily Galaxy. “Our galaxy has Sagittarius A*, which is 4.2 million times the mass of our Sun. Fortunately, it takes in very little matter, and is not a source of high-energy radiation and particles,” he explained. “But most galaxies go through active stages. What we wanted to know was, what happened to the life-hosting planets in a galaxy when that happens?”
To study how black holes can affect a planet’s atmosphere, the team developed mathematical models to estimate the maximal distance up to which these effects are rendered significant for Earth-like planets in the Milky Way. This demonstrated that this impact may extend approximately over 3,000 lightyears. In the case of quasars hosting larger supermassive black holes, the research found such effects could actually influence the black hole’s host galaxy as a whole.
“It turns out that when you have a supermassive black hole that is active, it not only produces radiation, but it also produces a lot of high energy particles that are powered by the black hole,” Florida Institute of Technology astrobiologist, Mansavi Lingam said. “It is easy to visualize it as a fast-moving wind, like an extremely amplified hurricane. You have this wind of high energy particles that is emanating from the black hole’s vicinity at 10% the speed of light, more than thousand times faster than our current spacecraft.”
Not Bio Friendly –Black Hole “Indigestion”
The radiation emitting from the black holes is essentially the particles of light known as photons. But if black holes are mainly known for nothing escaping out of them, why is this light being emitted as well as the high-energy particles in the wind? What happens is there is a lot of gas that surrounds the black hole during its active phase. The black hole starts eating up some of that gas. But it doesn’t eat it up in a totally efficient way: as the black hole is consuming more and more gas, the gas is falling in towards the black hole.
While it is falling inward towards the black hole, it’s getting heated. Much like when you rub your hands together and the friction generates heat, the friction experienced by the gas spiraling inwards towards the black hole leads to it getting heated and eventually releasing energy in the form of photons.
Think of it as a form of interstellar indigestion, Lingam said.
Impact Zone: 3,000 maybe 5,000 Light Years
“This radiation can bombard the atmospheres,” he said. “It can lead to those atmospheres getting eroded away. It can supply lots of UV radiation, it can be harmful to biology and so on. Some of the same ramifications apply to the high-speed winds from the black hole as well. These were some of the many effects that we looked at.”
There’s still a lot of black hole wind research that remains to be done. Lingam noted that the model considers the uniform expansion of wind throughout space, whereas future work would need to examine the emission of radiation and winds in the form of jets, which he hopes to investigate with Perlman and his Italian colleagues.
Earth is 26,000 Light Years from the Milky Way Center
For those who are worried about radiation and winds from the Milky Way’s supermassive black hole affecting Earth, there is no reason to be concerned.
“The good thing which we learned during the course of this work is that a lot of these effects extend up to 3,000 light-years, maybe 5,000 light years, in some extreme cases,” Lingam said. “But the earth fortunately is located 26,000 light years from the center of the Milky Way, so it’s comfortably outside that zone of influence, if we can call it that, of the black hole activity. Therefore, we might consider ourselves fortunate to inhabit this relatively peaceful region of our galaxy.”
The Last Word
“Our research indicates that planets in close proximity to active supermassive black holes would receive exceptionally high doses of ultraviolet radiation and high-energy particles,” Manasvi Lingam told The Daily Galaxy, “both of which would pose many obstacles to habitability such as atmospheric erosion, ozone depletion, biological damage, and much more.”
“Perhaps the most likely scenario for ‘life’ near a neutron star or black hole involves colonization … by robotic missions from a civilization around another nearby star,” astronomer James Cordes at Cornell University, told The Daily Galaxy in 2021. Cordes’ research focus includes neutron stars, pulsars, and the search for extraterrestrial intelligence. “Such a mission,” he notes, “would be very costly and might not be warranted given the power of remote sensing. However, an ancient but advanced civilization might afford such a luxury.”