Space

Planet Nine could be a black hole, and a new telescope will tell us

Planet Nine could be a black h...
One hypothesis suggests a tiny black hole could be orbiting the Sun from out beyond Neptune
One hypothesis suggests a tiny black hole could be orbiting the Sun from out beyond Neptune
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One hypothesis suggests a tiny black hole could be orbiting the Sun from out beyond Neptune
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One hypothesis suggests a tiny black hole could be orbiting the Sun from out beyond Neptune

The closest confirmed black hole to Earth is 1,000 light-years away – but could there be one hiding in our own backyard? It’s been hypothesized that a tiny black hole could be orbiting the Sun beyond Neptune, and now astronomers have proposed how we might find it within the next few years, using an upcoming telescope.

The fringes of the solar system are littered with strange objects, and in recent years we’re getting a clearer picture of what’s out there. There’s the squashed-snowman-shaped Arrokoth, the eccentric dwarf planet known as The Goblin, and the extremely distant world of Farout.

While most of these dwarf planets are tiny, there’s evidence to suggest that something much bigger is lurking in the shadows out there – perhaps a ninth planet, with the mass of five to 10 Earths. The clues are in the stable but eccentric orbits of these smaller fringe objects, and in the tilt of the Sun itself.

But maybe Planet Nine isn’t a planet after all? One seemingly out-there hypothesis suggests that a tiny black hole could have the same effects. It would still have roughy the same mass – several Earths’ worth – but pack it all into a black hole about the size of a grapefruit.

It’s an intriguing idea, but how would you go about actually proving it, one way or the other? After all, searches have turned up empty for a giant planet – finding a grapefruit would be far harder, let alone the fact that black holes are all but invisible.

And that’s where the new study comes in. Astronomers at Harvard have now outlined a method to search for these tiny black holes in the outer solar system. The key would be to watch out for the times they may flare up, as a result of a comet wandering too close and getting torn to shreds by the gravitational pull.

"In the vicinity of a black hole, small bodies that approach it will melt as a result of heating from the background accretion of gas from the interstellar medium onto the black hole," says Amir Siraj, co-author of the study. "Once they melt, the small bodies are subject to tidal disruption by the black hole, followed by accretion from the tidally disrupted body onto the black hole.”

Even this would be difficult to do normally, the team says, because we’d need to know where to look. We wouldn’t know where in its orbit such a black hole might be at any given time.

But an upcoming telescope could be perfectly suited to detecting these flares, wherever they occur. Rather than focus on any particular spot, the Vera C. Rubin Observatory will photograph the entire visible sky every few nights.

This project is known as the Legacy Survey of Space and Time (LSST), and over the course of 10 years it will allow astronomers to track the motion of objects and changes in their brightness, as well as transient events like supernovae.

The telescope should be sensitive enough, and have a wide enough field of view, to really take a clear census of our neighborhood. The LSST is expected to discover almost 40,000 new small objects in the solar system – and hopefully Planet Nine, whatever it is, will be among them.

The team says that if the mysterious object is a black hole, the LSST would be more than capable of detecting flares from it. In fact, the team is confident enough to claim that its existence would be confirmed or ruled out within a year of the observing runs beginning in 2023.

And if “Planet Nine” is indeed a black hole, its discovery would have even stranger implications. All the currently confirmed black holes in the universe are thought to have formed as the dense, collapsed cores of massive stars exploding as supernovae. But a tiny black hole with the mass of just a few planets would have been born in a completely different way.

Scientists like Stephen Hawking have long hypothesized the existence of things called primordial black holes. Calculations suggest that these objects would have been created in the seconds after the Big Bang, as pockets of matter grew incredibly dense and collapsed under their own gravity. Small enough to fit in your hand but packing the mass of a few planets, these primordial black holes could dot the universe, unseen.

If hypothetical, invisible masses throughout the cosmos sounds familiar to you, well, there’s a very good reason for that. These primordial black holes are a potential explanation for the enigmatic dark matter, but have so far evaded detection. So if the LSST can spot a primordial black hole in our own backyard, we may begin to unravel several long-standing mysteries at once.

"This method can detect or rule out trapped planet-mass black holes out to the edge of the Oort cloud, or about a hundred thousand astronomical units," says Siraj. "It could be capable of placing new limits on the fraction of dark matter contained in primordial black holes."

The Vera Rubin Observatory is currently under construction in Chile, with first light expected by the end of the year. After that, the LSST observing run is planned to begin in 2023, so we might not have too much longer to wait for some answers.

The research has been approved for publication in The Astrophysical Journal Letters.

Source: Center for Astrophysics/Harvard & Smithsonian

9 comments
Nilanjan Dasgupta
Don't waste time, money and efforts behind new telescope for finding out that ninth planet could be one black hole. because black whole is not any planet, black whole is everywhere in Universe. It can be spotted anywhere in any universe. It can be seen in any shape and size. Black Whole and its dark matter cannot be pin pointed to one static location, they can be spotted anywhere, sometime multiple black holes can also be spotted.
Kpar
Didn't Hawking suggest that black holes can "evaporate" over time? If created in the Big Bang, it seems unlikely that we would have have the remains of a "primordial" black hole as part of our solar system.
Nobody
I seriously doubt that a black hole created by gravity could be that small. If it was formed by the big bang by some other means, it should have grown tremendously in size by now and be at the center of our solar system and not on the fringe of it.
Expanded Viewpoint
Gupta, your comment makes absolutely no sense whatsoever. Evidently, you do not know of or understand molecular forces and how/why liquids always form a sphere in free fall. Stars are spheres for the exact same reason; an equilibrium of attracting forces pulls them into that shape.
Kpar, black holes are a "one way trip" device. Stuff goes in, but doesn't come back out again. Not even light can escape one, that is why they are black, no light reflects off of their surface. But, their effects upon other physical objects and light can be observed. So it would be a contradiction in logic, for a black hole to evaporate. What could possibly cause any "vapors" to come off of it, other than a bigger black hole??
Black holes are at absolute zero, because there could not possibly be any atomic motion (heat) left with all of that gravitational force pulling down on every atom in there. In fact, there would not even be any elements at all in there, just a mass of fairly homogenized matter with all of the space squeezed out of it.
At zero atomic movement, no electrons would be whirling around the nucleus of any atoms, even if they were able to survive crossing over the event horizon. It's all just a mass of matter, harder than a diamond, enormously heavy, and a magnet for anything that comes within the effect of its gravitational field. So if Hawking ever did suggest that a black hole can evaporate over time, he should have given some kind of an explanation for the postulated phenomena.
There was no "Big Bang", except for the TV show. That theory was disproved back in the early 1970s, when after about 20 years of near daily examinations of the spectral lines of hundreds of thousands of stars, an astronomer found that no two of them were even close, let alone a match! They are as different as snowflakes. If all matter came from some fictitious singularity, then all of the stars would be the same exact age and all spectral lines would match up pretty closely, but they do not. And then we have the question of where did that singularity come from? Who made it and how and from what? And WHY?? Where does space begin and end? What is on the other side of the boundary?
neutrino23
Black holes do evaporate, according to Hawking. At the even horizon virtual pairs of particles and antiparticles are changed to real particles by the gravitational pull of the black hole. One particle escapes and the other falls into the black hole. To conserve energy this particle has negative energy which reduces the mass of the black hole.

https://en.wikipedia.org/wiki/Hawking_radiation

This happens very slowly. The "temperature" of the black hole is inversely proportional to its mass. Something that was several times as massive as the earth would absorb more material and radiation than it emitted.

Very small black holes can evaporate quickly. There was a lively debate about whether microscopic black holes created by the LHC at Cern would absorb the earth before they evaporated.
Expanded Viewpoint
Oh, silly ol' me!! I had forgot that Hawking was God!! Please forgive my little faux pas there! If he said it, it must be true, therefore, no proof of black holes "evaporating" needs to be presented, right? No mechanism or source of energy for that mechanism to operate needs to be proved out either! That's just sooo over the top awesome!
Virtual pairs of particles and anti-particles are somehow magically changed over into real particles?? What the heck was he smoking when he came up with that garbage?? Has anyone ever seen that process happen, or is it just a theory that is sold to us as a fact? What propels the other particle away from the black hole? If it never made it into the mass we call a black hole, then it's really NOT evaporating away from it, is it? At best, you could only say that by some unproven theory, that half of what was attracted to a black hole actually got captured by it. But there's no evidence nor proof of that happening, is there?
How can you have negative energy?? Darkness is the absence of light, Coldness is the absence of heat. There is nothing colder than zero degrees Kelvin, because that is the point where ALL atomic motion ceases. It is unobtainable, because there is always some amount of energy present. The more energy there is in a system, the hotter it is, because there are more atomic and molecular collisions occurring per second, which is what we measure as heat. It is a higher and higher amount of vibration going on, as temperatures increase.

Randy
tkj
Expanded Viewpoint

Did not Dr. Hawking postulate a 'half-life' for black holes ?? ... and something there is about 'Hawking Radiation' , too, no?
Worzel
I find the whole idea of any ''unseen'' black hole within the solar system, utterly preposterous. The effects of such a black hole would have to be entirely visible, with matter pouring into it, due to its intense gravity.
I think this lot are really stretching credibility to the ridiculous, to maintain their funding.
Les LaZar
Wouldn't a black hole generating enough heat (friction in the accretion disk?) to "melt small objects" be very bright in the infrared and be easily detectable?