You may have heard of Planet Nine – a hypothetical planet believed to exist in the outer reaches of the solar system. One possibility is that it is not a planet at all but a tiny black hole. New research outlines a potential strategy for detecting this alleged black hole, in research that could begin as early as next year.
Harvard astronomers Avi Loeb and Amir Siraj proposed a new strategy for detecting a grapefruit-sized black hole in the outer solar system, in a document that was accepted for publication in The Astrophysical Journal Letters. By using the Vera C. Rubin observatory, still under construction in Chile, astronomers could indirectly detect this object by observing it doing what the black holes do best: swallowing stuff.
The reason for thinking that a black hole could be hiding is linked to an unexplained set of astronomical observations. Something – we don’t know what – seems to affect a group of objects beyond the orbit of Neptune. One possible explanation is an undetected planet, nicknamed Planet Nine, with a mass between 5 and 10 land masses and in elongated orbit between 400 and 800 AU from the Sun, in which 1 AU is the average distance from Earth to the Sun. Recently, scientists proposed another explanation: a primordial black hole of similar mass.
That we can have an old black hole inside our solar system is not as strange as it may seem. As Loeb explained to Gizmodo, it is possible that the primordial black holes are responsible for what scientists think is dark matter in the universe. If that is the case, there should be a huge number of black holes out there, so it is not insane to think that one of them has been trapped in our solar system.
“It will obviously be extremely exciting, because we have been researching the nature of dark matter for almost half a century,” Loeb wrote in an email to Gizmodo. “If the black hole is dark matter, there should be 50 quadrillion like this in the Milky Way alone to form the entire mass of the Milky Way galaxy, which weighs a trillion solar masses.”
A quadrillion, by the way, is a 1 followed by 15 zeros.
Finding an object with a grapefruit-sized event horizon sounds daunting, but these massively heavy objects can wreak havoc in their local environment. This is exactly what Loeb and Siraj are counting on, because the supposed black hole should suck up the occasional Oort cloud object, namely the comets.
Caught in the claws of the black hole and gradually approaching its fate, a comet should start to melt when it interacts with the hot gases that accumulate in the region. This process is expected to produce a signature of radiation detectable from Earth, which scientists call an accretion eruption.
“Our article shows that if planet 9 is a black hole, the comets residing on the periphery of the solar system – the so-called Oort cloud – would have an impact on it, would be destroyed by its strong gravitational tide and would produce a rocket illuminating as they accumulate. on it quickly, in less than a second, “Loeb told Gizmodo.
If the comet is large enough, it should be detectable thanks to the Legacy Survey of Space and Time (LSST), which should start next year at the Rubin Observatory. This telescope is ideal for the task due to its exceptionally large field of vision. Astronomers have only a rough idea of where to look for Planet New or the black hole, but the LSST will cover half the sky and make 824 repeat visits to each location over a 10-year period.
“If planet 9 is a black hole, we expected to see at least a few flares about a year after the LSST began monitoring the sky,” said Loeb.
It is not the first proposition to detect a potential black hole. Earlier this year, Edward Witten, a physicist at the Institute for Advanced study, devised a proposal in which hundreds of spacecraft would be sent to the outer solar system. Modifications to their sensitive clocks would signal the presence of a strong gravitational field produced by a tiny black hole. It sounds cool, but the new proposal from Loeb and Siraj is more practical.
“If indeed it turns out to be a plausible strategy, the idea that Loeb and Siraj present is really nice,” Jakub Scholtz, post-doctoral fellow at the Institute of Phenomenology of Particle Physics, told Gizmodo. University of Durham in the United Kingdom. “It would be a game change for Planet Nine as a primary black hole scenario.”
Scholtz, along with his colleague James Unwin of the University of Illinois at Chicago, published a paper last year arguing that Planet Nine could actually be a black hole. He said the chances of our solar system catching a black hole are around 50 to 50, so if the authors can test this, “we should go ahead and do it.”
Either way, the LSST project will produce significant results, as the lack of black hole evidence could indicate other possibilities, like Planet Nine being in fact a planet. The mind wonders how much we still don’t know about our own solar system.