What to Do With a Nearby Black Hole

For the discussion of the sciences. Physics problems, chemistry equations, biology weirdness, it all goes here.

Moderators: gmalivuk, Moderators General, Prelates

User avatar
cyanyoshi
Posts: 388
Joined: Thu Sep 23, 2010 3:30 am UTC

What to Do With a Nearby Black Hole

Postby cyanyoshi » Wed Dec 14, 2016 9:27 am UTC

Let's assume that we found a planet-sized black hole orbiting the Solar System that wasn't too far away, like maybe the hypothetical Planet Nine (yeah, that's a real stretch, I know). What kind of missions would you design to get the most scientific knowledge out of this awesome discovery? Quantum gravity is a big mystery, so I'd assume there could be a huge leap forward in this area with the right experiments. Could there be any other practical use for a black hole (energy extraction, time travel)?

Tub
Posts: 395
Joined: Wed Jul 27, 2011 3:13 pm UTC

Re: What to Do With a Nearby Black Hole

Postby Tub » Wed Dec 14, 2016 11:36 am UTC

Pretty much any free telescope would be pointed at it immediately. Mapping out its orbit (and making sure it won't collide with anything important), getting dark pictures, maybe being lucky enough to observe some infalling object.

The most precise telescopes might be able to confirm or refute the existence of Hawking radiation.
If it is planet-sized, its apparent temperature will be lower than the CMBR, but maybe high enough to measure. Maybe the instruments we used to map the CMBR will be useful here.

We'll also try to point every other detector in the right direction. Does it radiate neutrinos? Electrons? Protons? Antimatter? We'll have to elevate a few of these detectors into space for precise results.

The theory says that the BH's radiation has a black body spectrum with an apparent temperature inversely related to the BHs mass. If the radiation exists, we will want to confirm the mass of the black hole experimentally. With a bit of luck, the BHs orbit is close enough to the other planets to measure its influence on their orbits. If that's not precise enough, we'll have to send drones into it or around it and measure their trajectories.

We'll also want to measure its charge. Sending electrically charged drones should work, but with electromagnetism being a long-range force, maybe there's an easier way.

We will want to dump stuff into it anyway, to measure time dilation near the event horizon. Small drones that emit a precise and measurable clock signal. I'm not sure if we have experimentally verified relativity effects at those curvature levels yet. If we haven't, then this is a great opportunity to do so. If we have, then it's still a great opportunity to add more evidence onto the pile.

User avatar
sevenperforce
Posts: 658
Joined: Wed Feb 04, 2015 8:01 am UTC

Re: What to Do With a Nearby Black Hole

Postby sevenperforce » Wed Dec 14, 2016 2:31 pm UTC

I don't recall whether the focal-line terminus of a massive object depends only on mass or on mass and radius combined. If the latter, a nearby planet-sized black hole would basically give us a ready-made lensing telescope more powerful than anything we could build for the next thousand years.

User avatar
Eebster the Great
Posts: 3085
Joined: Mon Nov 10, 2008 12:58 am UTC
Location: Cleveland, Ohio

Re: What to Do With a Nearby Black Hole

Postby Eebster the Great » Wed Dec 14, 2016 6:52 pm UTC

Tub wrote:If it is planet-sized, its apparent temperature will be lower than the CMBR, but maybe high enough to measure.

The temperature of a Schwarzschild black hole of mass m at infinity is (in Planck units) 1/(8πm). Planet Nine has a predicted mass of around 3 × 1033, yielding a temperature of 1 × 10-35 = 2 mK. Surprisingly, modern instruments have a sensitivity for monopoles better than 1 mK, so this is actually measurable. That doesn't really matter though, because the black hole is blocking far more radiation than it is emitting anyway. What we would actually observe would be a cold spot in the CMBR much closer to absolute zero than its surroundings.

Unfortunately, the Schwarzschild radius is just 2M, so for a black hole with the predicted mass of Planet Nine, that would be a mere 9 cm. Needless to say, this is not measurable.

A smaller black hole would be hotter but proportionally smaller, so there isn't really any resolution to this.

Tub
Posts: 395
Joined: Wed Jul 27, 2011 3:13 pm UTC

Re: What to Do With a Nearby Black Hole

Postby Tub » Wed Dec 14, 2016 11:23 pm UTC

Eebster the Great wrote:Unfortunately, the Schwarzschild radius is just 2M, so for a black hole with the predicted mass of Planet Nine, that would be a mere 9 cm. Needless to say, this is not measurable.

Hm, I thought that'd just be an issue of bigger lenses and didn't do the math. Sure, it's small, but it's also very close. But you're right, current telescopes don't have the required resolution to isolate a 9 cm object several light minutes away.

So it seems like we should get started on that probe.

Frenetic Pony
Posts: 177
Joined: Fri Jan 27, 2012 6:31 am UTC

Re: What to Do With a Nearby Black Hole

Postby Frenetic Pony » Thu Dec 15, 2016 2:26 am UTC

Shoot Mathew McConaughey into it :mrgreen:

User avatar
Eebster the Great
Posts: 3085
Joined: Mon Nov 10, 2008 12:58 am UTC
Location: Cleveland, Ohio

Re: What to Do With a Nearby Black Hole

Postby Eebster the Great » Thu Dec 15, 2016 5:28 am UTC

9 cm is pretty small. If modern space telescopes have an angular resolution of 100 mas = 0.5 μrad, then using the approximation tan x = x, the black hole wouldn't be observable until it was a mere 200 km away. Of course, that ignores the problem of contrast; the black hole provides almost no contrast against the nearly black background. You could only see it if it blocked out a star, and that is an extremely low probability.

User avatar
plytho
¡This cheese is burning me!
Posts: 156
Joined: Sun Mar 02, 2008 6:23 pm UTC

Re: What to Do With a Nearby Black Hole

Postby plytho » Mon Dec 19, 2016 10:27 am UTC

The thread title sounds like a helpdesk question from an awesome future.

"We just moved in to this starsystem but there's a black hole in the neighborhood. What can we do about it? Has anyone else dealt with one of these?"
Pronouns: he him his
Avatar: The High Frontier by Angus McKie

cphite
Posts: 1277
Joined: Wed Mar 30, 2011 5:27 pm UTC

Re: What to Do With a Nearby Black Hole

Postby cphite » Mon Dec 19, 2016 10:23 pm UTC

plytho wrote:The thread title sounds like a helpdesk question from an awesome future.

"We just moved in to this starsystem but there's a black hole in the neighborhood. What can we do about it? Has anyone else dealt with one of these?"


"One of these"? Tsk.

User avatar
gmalivuk
GNU Terry Pratchett
Posts: 26453
Joined: Wed Feb 28, 2007 6:02 pm UTC
Location: Here and There
Contact:

Re: What to Do With a Nearby Black Hole

Postby gmalivuk » Mon Dec 19, 2016 11:04 pm UTC

cphite wrote:
plytho wrote:The thread title sounds like a helpdesk question from an awesome future.

"We just moved in to this starsystem but there's a black hole in the neighborhood. What can we do about it? Has anyone else dealt with one of these?"


"One of these"? Tsk.

What's the problem you think "one of these" has?
Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.
---
If this post has math that doesn't work for you, use TeX the World for Firefox or Chrome

(he/him/his)

User avatar
Sizik
Posts: 1215
Joined: Wed Aug 27, 2008 3:48 am UTC

Re: What to Do With a Nearby Black Hole

Postby Sizik » Tue Dec 20, 2016 1:36 am UTC

gmalivuk wrote:What's the problem you think "one of these" has?


I think it's the massist language they're objecting to.

Or should it be "radiist"?
gmalivuk wrote:
King Author wrote:If space (rather, distance) is an illusion, it'd be possible for one meta-me to experience both body's sensory inputs.
Yes. And if wishes were horses, wishing wells would fill up very quickly with drowned horses.

User avatar
thoughtfully
Posts: 2253
Joined: Thu Nov 01, 2007 12:25 am UTC
Location: Minneapolis, MN
Contact:

Re: What to Do With a Nearby Black Hole

Postby thoughtfully » Tue Jan 03, 2017 1:51 am UTC

Sorry about being late to the thread.

You magically solve the instability problem, park it at a safe distance, and turn matter into energy at a rather nice efficiency. I seem to recall that Lunar-massed is a convenient size.

plytho wrote:Has anyone else dealt with one of these?"

Very old thread

Yeah, it's also a great quantum gravity probe :wink:
Image
Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.
-- Antoine de Saint-Exupery


Return to “Science”

Who is online

Users browsing this forum: No registered users and 8 guests