can 'planet' become blackhole?


by Chitose
Tags: blackhole, planet
gabriel.dac
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#19
Nov21-13, 11:05 AM
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Quote Quote by PAllen View Post
Well, there is a difference between no process of known physics (which does not mean impossible in an absolute sense for the obvious reason of unknown physics), versus an in-feasible process. Adding matter to a planet violates no known laws of physics - it is just insurmountable engineering challenge. The key is that per known physics, the only thing that can break the Fermi-exclusion principle to crush quarks together (which would have to happen to get earth into cm radius) is mass well beyond the Chandrasekhar limit.
Look.

Where do black holes come from? From dying stars. Very big stars. The star gains no extra mass but it can still become a black hole. How? The density increases. or do you think the star is just "swallowing" more mass until it becomes a black hole? No, that's not how stuff works
PAllen
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Nov21-13, 11:24 AM
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Quote Quote by gabriel.dac View Post
Look.

Where do black holes come from? From dying stars. Very big stars. The star gains no extra mass but it can still become a black hole. How? The density increases. or do you think the star is just "swallowing" more mass until it becomes a black hole? No, that's not how stuff works
It is how it works. Stars that produce BH's already have all the mass they need. The don't need to add mass because they already have enough - over 10 solar masses. There is a fixed minimum mass for BH's to form by any current process. If you already have enough mass, you just need to find a way to drain it of energy without blowing it apart. If you have too little mass, you have to add mass. There is no process consistent with known physics to compress a planet to its SC radius.

Recall the figures I gave you earlier about required density of black holes for different amounts of matter. The more mass, the less density you need. Since the densest possible state that isn't a BH is a quark star, you need enough mass for quark star density to be at its SC radius. This is several solar masses (I don't have the exact figure).
PAllen
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#21
Nov21-13, 11:43 AM
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Maybe a clearer way to put this is that per quantum chromodynamics (including the fermi-exclusion principle) there is no way to get beyond the quark star density. Thus, to get a BH, you need enough mass for gravity to become stronger than the strong force. This is what happens if you accumulate enough quark star matter (several solar masses) to exceed its SC radius at that density. Then gravity dominates, and classically the mass collapses further, producing a singularity and other exotic phenomena. What really happens inside the SC radius when the quark star matter is inside it is more realistically described as unknown, because that is the realm of quantum gravity unification - gravity is as strong as the strong force. A consistent, usable, theory for this state is unknown - but we do think we know that around this unknown would be an event horizon.
Chronos
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#22
Nov21-13, 04:57 PM
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Quote Quote by gabriel.dac View Post
That is a possibility too, but I'm not wrong. It is also impossible to bring more mass to Earth :p
Actually, the earth has continually gained mass since it began to form. In the early days of the solar system, the mass gain was pretty dramatic. The heavy bombardment period [which possibly occurred due to the migration of one of more gas giants to their present orbits] bulked the old girl up too. Nowadays, the mass gain is a pedestrian ~300 metric tons per day due to accumulation of space dust and meterorites [ http://www.universetoday.com/94392/g...t-hits-earth/].
gabriel.dac
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#23
Nov21-13, 05:43 PM
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Quote Quote by Chronos View Post
Actually, the earth has continually gained mass since it began to form. In the early days of the solar system, the mass gain was pretty dramatic. The heavy bombardment period [which possibly occurred due to the migration of one of more gas giants to their present orbits] bulked the old girl up too. Nowadays, the mass gain is a pedestrian ~300 metric tons per day due to accumulation of space dust and meterorites [ http://www.universetoday.com/94392/g...t-hits-earth/].
I know. I'm still right, it is impossible to bring more mass to Earth.
PAllen
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Nov21-13, 06:04 PM
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Wasting more time on this than I should, I have computed a formula for the minimum mass needed for matter of a given average density to form a horizon and catastrophically collapse (inside the horizon). This formula is a lower bound (assuming no rotation for example - which would raise the required minimum; most real BH and neutron stars are believed to have high spin).

M = 4.28 * 10^9 / √ρ solar masses, with ρ given in kg/m^3

Note, using ρ = 10^18 (a smidgen higher than the value given neutron star cores) gives 4.28 solar masses. This has a ring of truth to it, since the lowest mass reliably observed for BH candidates are close to 10 solar masses. Given rotation, that average density is lower than core density, and unknown limitations on formation process, this is consistent.

There are a couple of black holes that might come close to this lower limit:

GRO J0422+32 : http://arxiv.org/abs/astro-ph/0308490

However, there is history of upward revisions of BH masses:

XTE J1650-500 was reported as having a BH mass of 3.8 solar masses, but was retracted by the same authors and revised up close to 10 solar masses: http://arxiv.org/abs/0902.2852

IGR J17091–3624 was reported at < 3 solar masses, but the same author (with another) later measured 15 solar masses. See discussion in: http://arxiv.org/abs/1209.2506v1
PAllen
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Nov21-13, 06:07 PM
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Quote Quote by gabriel.dac View Post
I know. I'm still right, it is impossible to bring more mass to Earth.
In practice, yes. However it violates no laws of physics. The difference with compressing the earth to 2 cm, is that there is no process consistent with the standard model of physics which can achieve this.
Chitose
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#26
Nov23-13, 12:33 AM
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sorry if like i'm not respond, I just try to understand what you guys are talking.

so... in theory, not just star but anything can become blackhole as long as it's escape velocity greater than light. right?

I also post same question in my country as well,
some says, if planet mass keep increase, it's core will hot melt ignite the gas and become star themselves... really?
and also, it will become like pulsar before become blackhole.
Drakkith
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Nov23-13, 01:19 AM
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Quote Quote by Chitose View Post
sorry if like i'm not respond, I just try to understand what you guys are talking.

so... in theory, not just star but anything can become blackhole as long as it's escape velocity greater than light. right?

I also post same question in my country as well,
some says, if planet mass keep increase, it's core will hot melt ignite the gas and become star themselves... really?
and also, it will become like pulsar before become blackhole.
1. If you keep adding mass, will the core eventually ignite and the "planet" turn into a star?

That depends on what you add. If we added elements lighter than iron, and we added that mass quick enough so that the core was unable to give off heat fast enough to cool, then yes, eventually the core will be so hot that fusion will occur. Note that the amount of mass you need to add depends on what material forms the new core. Adding about 0.075 solar masses of hydrogen would be enough to ignite fusion, whereas helium would require at least 0.5 solar masses. Heavier elements require even more mass to reach the ignition temperature.

If we add iron or anything heavier, we do not see fusion, as the cores collapses before it ever heat up high enough to fuse them. (And they are endothermic reactions anyways)

2. Will it become a pulsar before a black hole?

That depends. If we add a LOT of mass (about 15-20 solar masses) we'd create a huge star that would eventually collapse directly into a black hole instead of a neutron star.
Chronos
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Nov23-13, 01:43 AM
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Quote Quote by gabriel.dac View Post
I know. I'm still right, it is impossible to bring more mass to Earth.
The earth has gained mass over its entire history - its fact, not opinion, with an entirely reasonable physical explanation. Facts trump any theory.
Fermifaq
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#29
Nov25-13, 01:54 AM
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ref can 'planet' become blackhole?

yes...but its not easy ( or perhaps even possible ) if you are in a big hurry timewise

I am quite sure there are 1000's of blackholes in the universe right now that where once planets BUT you can be almost 100% certain that they became black holes after becoming a star (the planet acting as a stellar seed)

Could a planet naturally become a black hole without going through the star phase ? probably not in a universe that's only 14 billion years old. But it might just be possible to figure out a fantastical flukey 'natural schema' that could pave the way. That would be a lot of work and quite probably require far too much artistic license to be worth while investigating.

Ultra-Cold Brown Dwarf Discovered?
http://news.discovery.com/space/astr...ker-110312.htm

Somewhat related to the OP (and time) Black Dwarf
http://en.wikipedia.org/wiki/Black_dwarf

Stages en route to black hole-dom
http://en.wikipedia.org/wiki/Electro...generate_gases





DIY Cold Black hole using a planet as a seed


There might well be an exotic mix of matter that you can drop onto the planet which effectively turns it into an anti fusion reactor. Some weird energy harmonics that means fusion is A) less likely and B) more endothermic.

Sort of the opposite of the carbon harmonic ( some weirdness which means more carbon is created than one would initially envisage) In this case we are after less heat.

Off the cuff i would go with a lead core and sprinkle on nickel/iron at absolute zero & perhaps some lighter atomic spice that likes emitting e-rays or spewing magnetic flux ( shedding energy and aiding cooling )


Issues or solutions to fast track black hole creation ?
http://en.wikipedia.org/wiki/Helium_flash

http://en.wikipedia.org/wiki/Carbon_detonation





Chitose, be rest assured the question in your OP will eventually be inverted and make its way into the physics exam hall. I pity the poor student faced with the question " what is the minimum time frame in which one could construct a dark black hole "


...i just figured out a way but im not telling anyone


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