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New type of black holes – Non interacting low-mass black hole
- QueensGambit 7y agoThe low-mass black hole is thought to be 3.3 times the mass of our sun. Previously, the smallest black hole discovered was 3.8 times the mass of our sun. I guess this opens up a new breed of stars that are somewhere between massive neutron star and low-mass black hole.
- deleted 7y ago[deleted]
- keithwhor 7y agoA completely non-radiating mass — that’s smaller than any black hole we’ve seen — in a binary orbit with a radiating star. Doesn’t this fit the general criteria of a Dyson Sphere or Swarm? Not to be all tin foil hat, just neat to think about.
- pas 7y agoDyson spheres/swarms do radiate heat (infrared).
- haolez 7y agoWhy? Couldn’t it absorb almost all energy that “touches” it? Making it impossible for us to detect the tiny amount of heat generated? Genuine question.
- tempguy9999 7y ago> Why? Physics. Entropy. If it absorbed energy that touched it, it would heat up. You could then use the difference between it and its cooler surroundings to run an engine. Waste heat from the engine could then be absorbed to keep the engine running. You'd have created a perpetual motion machine, which is considered impossible.
- Enginerrrd 7y agoBut how hot does it really need to get? A solar panel doesn't heat up to sun temperatures, and a heat pump operating between the sun and the vacuum of space could be really efficient. The heat could be rejected elsewhere, no?
- pas 7y agoThe important thing about space is that's there's no elsewhere. In a closed system of a star, the sphere, and the outer space eventually energy will flow from the star to the outer space region. There's no perfect insulation. (See also Maxwell's demon.) Of course detection is a different matter altogether. Hiding better and better is possible. But if you really want to hide a Dyson swarm is not the best way :)
- bsmith89 7y agoNo; not without heating up (since the inside of the sphere can't radiate it back to the star at the center). As the sphere heats up it radiates outwards in increasingly energetic spectra. Since entropy (in this case in the form of unusable heat) always goes up, the sphere couldn't stay dark forever.
- yellowapple 7y agoWhat about radiating it in a specific direction (one that just happens to be away from us)?
- contravariant 7y agoHeat radiates in all directions by definition. It is theoretically possible to direct it to some extent (at the cost of raising entropy elsewhere) but it would require massive effort for no good reason.
- haolez 7y agoThat was one of the alternatives that I was thinking as well :)
- ClumsyPilot 7y agoYou could never direct 100% of it, since any matter not at absolute zero has to radiate longer wavelengths. Once you do direct it, someone will still see you if they are in the path of the beam. It appears to be an exercise in futility.
- PeterisP 7y agoEnergy can't disappear or be consumed - if energy doesn't get released out then it gets absorbed i.e. accumulates; if it accumulates then the Dyson sphere heats up a lot, if it heats up then it glows with blackbody radiation.
- haolez 7y agoCan we detect tiny amounts of blackbody radiation? Not that such a sphere would release tiny amounts, but I'm curious about this as well.
- deleted 7y ago[deleted]
- evanb 7y agoWe can detect the CMB which, using the Stefan-Boltzmann law [s-b] and a CMB temperature of 2.725 K, is about 3.12e-6 Watts/square meter. But, the CMB is pervasive. The blackbody sphere you're asking about is very far away, and the amount of power you'd receive scales like the inverse square of the distance from the sphere to us here. So forget it, the CMB's blackbody energy flux on/near Earth is ENORMOUS compared to the star's. [s-b] https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law
- hinkley 7y agoAnyone who figures out how to cheat the 2nd Law of Thermodynamics probably has no interest talking to riffraff like us. Just be glad they haven't harvested us for something and move on with your life and civilization. And whatever you do, don't make [eye] contact.
- NikolaeVarius 7y agoReading the article, it seems that non-interacting is referring to the fact that the black hole is hard to detect as there is no other star or gas source to cause it to generate X-Rays as matter falls into it. I find the name interesting since, mini black holes are one hypothesis concerning Dark Matter, and also Weakly Interacting Massive Particles. Google also doesn't seem like Non-interacting black holes are common nomenclature. How do these names get created?
- pas 7y agoSomeone writes a paper using the terminology, others refer to it, and it sticks.
- willis936 7y agoConsidering "weakly interacting" is already a very stuck name. By most accounts these are typical black holes, which do not interact weakly, let alone not at all. I don't think this name will stick.
- greglindahl 7y ago"quiescent" is already in wide use referring to black holes, and "quiescent" appears in the 2nd paragraph of this paper. Some stellar binary systems are called "interacting".
- fhars 7y agoAnd according to the full title of the paper, it is not the black hole that is noninteracting, it is the binary system.
- greglindahl 7y agoIn the case of WIMPs, the authors thought the name was funny, and published several conference posters before trying to publish in ApJ. The editor of ApJ normally rejects cute names, but let this one through because it was already in the literature. He regretted that decision when the MACHO paper arrived...
- hinkley 7y agoI still think one of the most terrifying tropes in sci fi is not alien invasion but destruction by black hole. It's impersonal, and once it starts it's inevitable, because of physics. I really hope we never learn of the existence of black holes in the kiloton range. If you think intelligences can annihilate themselves with nukes... how about sucking your planet away from the inside out?
- Roboprog 7y agoAt what mass is Hawking Radiation a significant factor? Toss something over that either hoovers up your planet, or bakes it if a near miss. Tricky to store, though.
- DuskStar 7y agoHawking Radiation is only a significant factor at far lower masses than the Earth. There's a nice calculator here [0], with an example 10^12 kg black hole producing ~350 megawatts. Working backwards, 1 megaton per second (4x10^9 megawatts) gives us a black hole of 3x10^8 kg. 0: http://xaonon.dyndns.org/hawking/ http://xaonon.dyndns.org/hawking/
- contravariant 7y agoAlthough that pretty much means that Hawking radiation very much is a significant factor on any humanly achievable mass.
- DuskStar 7y agoAnd puts some hard, theoretical limits on using black holes as total conversion reactors. Reducing the power output to a terawatt requires 2x10^10kg... Probably not practical. (It would also have a radius of 0.03 femtometers. A proton? ~0.84)
- Roboprog 7y agoIs there a Planck constant type value for minimal singularities?
- sohkamyung 7y agoWhile the title of the paper says a low-mass black hole, the abstract does say it could also be a high mass neutron star: > Constraints on the giant’s mass and radius imply that the unseen companion is 3.3+2.8−0.7 solar masses, indicating that it is a noninteracting low-mass black hole or an unexpectedly massive neutron star. Presumably, further observations will help determine what it is.
- noname6 7y agoThis is happening in binary systems. The black hole is not emitting any detectable X-rays from objects falling into it. There are none falling into it then. It is non interacting. But we know it is non interacting because it Doppler shifts a nearby object in the binary systems these scientists are observing. Being a binary system, unless the objects are at beyond perfect equilibrium with respect to their accelerations, the objects will eventually collide (in a true binary system). In other words, the Doppler shifting object must be actually falling, however slowly, into the black hole. My question is this: Can we assume that the object is heating up and emiting additional x rays