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What if Planet 9 is a Primordial Black Hole?

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Re: What if Planet 9 is a Primordial Black Hole?

#81

Post by geoffmunn »

Sharlin wrote: post #78
geoffmunn wrote: post #73

I've been wondering - if the black hole was very small (I've read elsewhere that it would be grapefruit sized), would it be possible to build some kind of box around it so you couldn't accidentally go into the event horizon?

There's no material that you could make the box or shell out of that could withstand the gravitational forces near the black hole. Even the gravity differential (tidal forces) is strong enough to rip anything apart (the so-called spaghettification). And if you made the shell large enough (planet-diameter), it would collapse into a spherical body just from its self-gravity, never mind the additional gravity of the PBH…

But given that it's so small, what would the gravitational forces be if you made a shell with a 100km radius? Or pick a number - surely at some point it might be practical to build something.

Re: What if Planet 9 is a Primordial Black Hole?

#82

Post by markonen »

jl6 wrote: post #67
ISL wrote: post #14

One should not miss Figure 1 of the arXiv preprint, which is, alas, absent from the final PRL. https://arxiv.org/pdf/1909.11090.pdf It is among the rarest journal-article figures in physics. If I'd been asked to referee the paper, I'd have campaigned hard to keep it in.

Was it removed because “exact scale” only makes sense if the article is printed on a specific paper size, which isn’t specified?

Objects in a PDF are specified in points, which is a physical measure (1/72 of an inch, or 0.3528 mm).

Re: What if Planet 9 is a Primordial Black Hole?

#83

Post by echelon »

dyslexit wrote: post #65
deepspace wrote: post #8

Earlier quoted context omitted.

Agree with cool, but not with terrifying. According to the paper, the mass would be ~5-15 M⊕ at a distance of 300-1000AU, so not a threatening object in any way.

And at 5M⊕ would have a diameter of about 9cm (or at 10M⊕ about the size of a bowling ball).

How would we ever find that? Gravitational lensing of the background stars?

Do we stand a chance of uncovering it at all?

Edit: from the abstract,

> The observational constraints on a PBH in the outer Solar System significantly differ from the case of a new ninth planet. This scenario could be confirmed through annihilation signals from the dark matter microhalo around the PBH

Wild.

Re: What if Planet 9 is a Primordial Black Hole?

#84

Post by m_mueller »

slaymaker1907 wrote: post #59
ISL wrote: post #14

One should not miss Figure 1 of the arXiv preprint, which is, alas, absent from the final PRL. https://arxiv.org/pdf/1909.11090.pdf It is among the rarest journal-article figures in physics. If I'd been asked to referee the paper, I'd have campaigned hard to keep it in.

My guess is that they wanted it removed since it is more useful communicating outside the field and that printing out that figure would take a lot of ink. Even if the journal doesn’t do much actual printing, I know many researchers that prefer to print out articles before reading them.

could have replaced it with a white filled circle though, or a grayscale version that uses much less ink.

Re: What if Planet 9 is a Primordial Black Hole?

#85

Post by ziotom78 »

ISL wrote: post #14

One should not miss Figure 1 of the arXiv preprint, which is, alas, absent from the final PRL. https://arxiv.org/pdf/1909.11090.pdf It is among the rarest journal-article figures in physics. If I'd been asked to referee the paper, I'd have campaigned hard to keep it in.

I too rushed to check if the figure survived to the referees' comments. Alas, what a pity!

Re: What if Planet 9 is a Primordial Black Hole?

#86

Post by mseepgood »

127 wrote: post #4
wrnr wrote: post #3

A person should be allowed to dream sometimes, how freaking cool would this be. A block hole right in our neighbourhood, even closer than Alpha Centauri. Just imagine what kind of things can be learned from studying it.

Cool, and absolutely terrifying.

I don't see how this is more terrifying than, say, have a sun in the neighbourhood.

Re: What if Planet 9 is a Primordial Black Hole?

#87

Post by m_mueller »

p1mrx wrote: post #52
behnamoh wrote: post #36

Earlier quoted context omitted.

Falling into Jupiter is an eye-opening experience tho, esp. if you fall into the "big eye" (pun intended). Just the sheer massive size of a turbulent, harsh planet that covers all the horizon... The world becomes flat much faster near such a planet.

We're already on a planet that covers the horizon; some say there's more beyond the horizon. Would Jupiter look subjectively bigger, if you couldn't also see the Earth for comparison?

I guess it wouldn't, but it probably would be a much longer fall until either pressure is crushing you or your heatshield fails.

Re: What if Planet 9 is a Primordial Black Hole?

#88

Post by m_mueller »

Sharlin wrote: post #75
xingyzt wrote: post #38

If true, would this be the smoothest planet in the solar system?

I guess that technically the IAU definition of planethood would not exclude a primordial black hole, but I doubt that's the intended interpretation.

someone, somewhere who sat in the planet definition committee: "seriously? again? what else didn't we think about...."

Re: What if Planet 9 is a Primordial Black Hole?

#89

Post by p1mrx »

sidcool wrote: post #74
p1mrx wrote: post #54

Earlier quoted context omitted.

This paper postulates a black hole with 5-15 times Earth's mass, which is considerably less than the sun.

I see. That's lighter that Jupiter. Do PBHs have singularity like regular black holes?

If PBHs are real, then they should be identical to "regular" black holes, just smaller.

Wikipedia says "Physicists are undecided whether the prediction of singularities means that they actually exist, or that current knowledge is insufficient to describe what happens at such extreme densities."

Re: What if Planet 9 is a Primordial Black Hole?

#90

Post by ncmncm »

scarmig wrote: post #43
hadlock wrote: post #32

Earlier quoted context omitted.

Ted Kazinski was concerned that high energy particle physics would create a blackhole large enough to become self sustaining. If I remember correctly, high energy physics creates tiny black holes during particle collisions, but they "evaporate" faster than they can absorb mass. So to answer your question with my limited understanding, yes, there's a lower limit to stable black holes. Beyond the critical mass, they si…

> Beyond the critical mass, they simply evaporate in a matter of seconds. For a sense of scale, a black hole with a mass of 2.2 * 10^5 kg will evaporate in roughly 1 second. A 1 kg black hole would evaporate in roughly 100 attoseconds.

"Evaporate", meaning "vaporize everything for miles around", right?

And for the 10^5 kg one, "vaporize the entire planet" if one is nearby?

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