Is Life Possible Around Black Holes?
Updated: Jun 14, 2024
Black holes are gravitational fields so massive that no matter or radiation traveling through space can escape. The mass of a black hole is so great that they swallow even light that gets close enough to them. Black holes are the result of supernovae, one of the most energetic events in the Universe. Although they seem to be the last place in the Universe where life can exist, there have been interesting studies on this subject.
Could There Be Life Around Black Holes?
The Habitability of a Planet
All possible places and conditions in the Universe where life could arise are completely unknown. There could be forms based on very different foundations than life on Earth, there could be creatures that evolved very differently. But the only known life is on Earth, and this leads us to create a general template that includes Earth conditions rather than considering all other possibilities. Measurements such as the "Earth Similarity Index" determine the probability of a planet harboring life by comparing it with Earth.
According to NASA, life requires the following criteria: liquid water, conditions for the formation of complex organic molecules and an energy source to keep metabolism alive. But can a black hole fulfill these conditions?
The Habitable Zone of Black Holes
Every star has a "Habitable Zone" or "Goldilocks Zone". Planets in this zone may have liquid water on their surface. Liquid water is one of the most important criteria for life.
Black holes do not emit light like stars; they are, as their name suggests, dark. But according to Dr. Pavel Bakala of Silesian University in the Czech Republic, a black hole's enormous gravity can compress and energize the Cosmic Microwave Background Radiation (CMB), which is very close to absolute temperature (-273.15 °C), and transform it into the infrared, visible and even ultraviolet side of the spectrum.
Cosmic Microwave Background Radiation
What's more, a black hole can focus light to a single point, making the KMAI shine like the Sun in the sky. Thus, a black hole could be a source of heat and light for planets, just like a star.
In order for the planet to receive enough KMAI radiation, the black hole must rotate very close to the event horizon. But in order to have a stable orbit very close to the event horizon, the surface of the black hole must be spinning at speeds close to the speed of light. The slower the black hole is spinning, the farther away you have to move to get a stable orbit, which means the planet can't get enough KMAI light.
A habitable planet must also have day and night alternation. According to Bakala, the shadow of a black hole can create night on the planet. The shadow of a black hole is created when a black hole bends most of the light around it, preventing it from reaching us. Photons enter a temporary orbit around the black hole and are blown out into space after a few orbits. This creates a gravitational shadow larger than the event horizon. The planet passing through this shadow will be immersed in the nighttime.
In the photo of the M87 black hole, the dark area is actually the shadow of the black hole. The event horizon is much smaller.
In addition, for life to exist around it, a black hole must have a mass of at least 163 million suns. Smaller black holes, such as the 4 million solar mass Sagittarus A* at the center of the Milky Way Galaxy, tend to tear apart stars and planets approaching them with tidal forces. More massive black holes do not experience such tidal disruption until the event horizon.
Some Problems for Life Around Black Holes
The Earth's axis tilt is currently just over 23 degrees. But over periods of 41,000 years, the tilt varies between 22.1 and 24.5 degrees. These are small changes over fairly long periods of time, so the seasons on Earth are balanced. But for a planet orbiting a black hole, the axis tilt is likely to be very unstable. According to Dr. Lorenzo Iorio of the Italian Ministry of Education, Universities and Research, the axis tilt of such a planet could change by tens of degrees in just 400 years!
Another problem is that the extremely powerful bursts of ultraviolet light that a black hole could produce would destroy the planet's atmosphere. According to calculations by Harvard University theorist Avi Loeb, a planet so close to the surface of a black hole would not stand a chance.
Even if such a planet exists, it will be very difficult to detect it. But some future missions are promising: In 2034, ESA plans to launch the Laser Interferometer Space Antenna (LISA) mission, which is highly sensitive to detect gravitational waves. NASA's Dr. Jeremy Schnittman has this to say about this:
''LISA will be sensitive enough to see a possible Earth-sized black hole planet in the Milky Way Galaxy. For a Jupiter-sized planet, it will be able to look a thousand times farther away.''
Sources:
P. Sutter. Is Life Possible Around Black Holes? ( https://www.space.com/is-life-possible-around-black-holes.html )
C. Stuart. Can Life Exist Around A Black Hole? ( https://www.sciencefocus.com/space/can-life-exist-around-a-black-hole )
D. Clery. Could A Habitable Planet Orbit A Black Hole? ( https://www.science.org/content/article/could-habitable-planet-orbit-black-hole )
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