The movie “Interstellar“, released in 2014, shows how astronauts travel to the surroundings of Gargantua, a supermassive black hole.
They go there in search of planets in which humanity, which is in mortal danger on Earth, can survive.
The film, which had the advice of Nobel and black hole expert Kip Thorne, recounts how travelers perch on the planet of Miller, a promising ocean world.
There they experience a curious phenomenon: the intense gravity of the neighboring black hole distorts spacetime so that time slows down for people who approach the huge object, compared to an observer located further away.
In this way, if the crew member of a ship located beyond sends a message in Morse code, sending a beep every second, On the surface of Miller’s planet, 60,000 beeps would be received in just one second.
That is why when travelers return to the ship, after having spent only a few hours there, several years have passed in the device.
This fun theoretical scenario of imagining what a planet would be like in the orbit of a black hole is very interesting because it allows us to test what is known and prepare the way for future discoveries, even if it is not known if possible.
With this idea in mind, astrophysicist Jeremy Schnittman, from NASA’s Goddard Space Flight Center, has published an article on the arXiv prepublication server in which he speculates about this and other effects on the environment of supermassive black holes.
Inspired by the film, the scientist reviews under what conditions a world located in the orbit of a supermassive black hole could be habitable.
Although a planet has never been sighted in the orbit of one of these objects (technology does not allow it to do so) Schnittman relates how the wild environment of these monsters may become appropriate. At least in theory.
“Almost all of my research, over the past 20 years, has focused on some aspect of black holes,” Schnittman told ABC. “And, when I saw the movie” Interstellar”, I started working on a NASA initiative to model the structure of exoplanet atmospheres, so I thought a lot in terms of habitability.
Therefore, I think this article is a logical combination between both issues.
That has led him to elucidate whether it would be possible for supermassive black holes to have a habitability zone around him, just like the stars.
The question is whether in that region, not very close to the star but not too far away, it would be possible that there were planets whose temperature range in equilibrium allowed them to have liquid water on the surface.
This temperature range is, as the author of this study has written, approximately 0 to 100 ° C.
The first thing to keep in mind is that if the Sun were replaced by a black hole of the same mass, the orbit of our planet would not undergo any change, as the author of the work recalled, who intends to publish in the magazine “American Journal of Physics”.
The gravitational pull would be exactly the same.
No change would be noticed unless the Earth was placed very close to the surface (the so-called event horizon) of a small black hole, in which case it would end up shattered like a cookie by the relentless tidal forces.
But there is an important problem. The black hole would literally leave us in the dark.
After all, these objects are star bodies so dense that nothing, not even photons, can escape the “embrace” of their gravity.
Therefore, not a single photon would reach Earth and heat its atmosphere to allow the existence of liquid water.
In fact, it is estimated that on our planet the total solar incident flow is 1250 W / m ^ 2.
However, perhaps the picture is not so black, never better.
As Schnittman has proposed, the accretion discs that usually surround these objects could provide the necessary energy for planets whose temperature range was adequate to house liquid water on the surface.
Accretion discs are flattened rings in which huge amounts of gas and dust, coming from interstellar space and the death of stars, turn and are routed to their “death,” in the gravitational pit that is the black hole. In fact, the closer the matter gets to the surface of the hole, the faster it spins.
This matter is hot and emits high amounts of energy and light.
In addition, it can be said that the environment of the black hole itself is an accelerator of particles, which bombard the surroundings, and that it generates a magnetic field capable of generating powerful jets of matter and energy, the jets, which reach astronomical lengths.
All this, however, does not make it impossible for habitable planets around a black hole. In theory, it would be enough if your accretion disk was not too “aggressive”:
“If we could reduce the accretion rate enough, the temperature would be simply adequate,” said Jeremy Schnittman.
In fact, as you have detailed, if the mass of the black hole were of the order of one billion suns (10^9 solar masses), and its accretion rate was typical (similar to that of a quasar), a planet could be habitable if it were at a distance of 500 radii from the black hole.
“That would lead to the accretion disk looking very similar to the Sun in the sky,” explained the researcher. “In addition, the disk would clean the space of remains”.
However, today we know that “most of the supermassive black holes we know in the Universe are too bright and too hot to house life as we know it,” the researcher acknowledged.
In the environment of black holes there is another peculiarity: the distortion of spacetime.
The same effect that time does not advance at the same time near and far from the black hole, is responsible for the frequency of the photons (the number of times they oscillate per second), is not equal.
Therefore, a planet located very close to a black hole would see how the light that comes from the accretion disk moves towards the blue, and increases the dose of UV radiation.
As Schnittman emphasizes, it could become so energetic that it would end up being harmful to the supposed living beings that lived in the “shadow” of the black hole, if these were similar to the terrestrial ones, of course.
“Of course, other life forms could love ultraviolet light!” Commented the researcher.
Curiously, and as seen in the first image of a black hole in history, from the surface of the planet you could see how one part of the ring would be brighter than another, because of the red and blue shifting of the light, caused by its high speed.
Gravity is the least strong of the fundamental interactions, but its effect is considerable: for example, it is able to remove the bowels of the moons around Jupiter and Saturn.
In the case of a planet that fell very close to a black hole, it would be able to “anchor” one of the faces of these worlds (as it happens to the Moon, which always gives the same face to the Earth), deform them or even destroy them (what is known as tidal disruption).
Logically, the destroyed worlds are not habitable; Probably, the mareally anchored worlds (like the Moon) are not either, because it is more difficult (though not impossible) for the heat to be distributed: normally one face is scorched and the other frozen.
In the case of Gargantua, the supermassive black hole of the movie “Interstellar”, the safety distance is just above the event horizon.
Therefore, Miller’s planet is not only not destroyed but experiences extraordinary tides because of the gravitational pull of its hole.
In addition to that, the researcher has elucidated around other potential sources of energy that could heat a world around a black hole and make it habitable. Jeremy Schnittman has considered how background radiation, whose energy increases in the black hole environment, neutrinos, dark matter or gravitational waves, could also provide energy to a planet, at least in theory.
Source: Radiosantiago
