An example is the so-called “spaghetti” process, which is often illustrated with the fable of an astronaut who ventured too close to the event horizon of a black hole (the point beyond from which no light can escape) and which fell headlong. Although the head and feet were a few feet apart, the difference in the gravitational forces acting on them would be so large that it would stretch like spaghetti.
Interestingly, the effect should be even more dramatic, the smaller the black hole. Sholtz explains that these are relative distances: if you go two meters high and fall through an event horizon that is one meter from the center of a primordial black hole, the discrepancy between the location of the head and the feet is larger compared to the size of the black hole. This means that you will stretch much more than if you fall into a stellar that is a million miles in diameter.
“And it’s just that, oddly enough, they’re more interesting,” Scholtz says. Spaghetti has already been seen through a telescope, when a star got too close to a stellar black hole 215 million light-years from Earth and was ripped off (it didn’t hurt chief astronaut). But if there is a major black hole in our own solar system, it would provide astrophysicists with the opportunity to study this behavior closely – and many others.
So what does Batygin do about the possibility that the coveted ninth planet was a black hole? “It’s a creative idea and we can’t limit what its composition is even,” he says. “I think maybe it’s just my own bias, being a planetary science teacher, but planets are a little more common …”
While Unwin and Scholtz are looking for a primitive black hole to experiment with, Batygin is so interested in a giant planet, citing the fact that the most common type in the entire galaxy are those around the same mass as the New Planet. .
“Meanwhile, most exoplanets orbiting Sun-like stars are in this strange range of being larger than Earth and considerably smaller than Neptune and Uranus,” he says. If scientists find the planet gone, it will be as close as they can get to a window to the other places in the galaxy.
Only time will tell if the last mission will be more successful than Lowell’s. But Batygin is confident that his missions will be totally different. “All the proposals are well differentiated both in the data they seem to be trying to explain, and in the mechanisms they use to explain it,” he says.
Either way, the search for the legendary ninth planet has already helped transform our understanding of the solar system. Who knows what else we will find before the hunt is over.
Zaria Gorvett is a senior journalist for BBC Future and Tweets @ZariaGorvett
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