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[Silfurdreki]

^that.

A 5 M_solar black hole smashing into the sun at pretty much any speed would destroy the solar system as we know it, though.

Depends on the disc. IIRC, some "interesting" ones have been observed with way more mass in them than they should have.

Remember, before fusion starts inside the protostar and blows the remaining gas away with solar wind and light pressures, there is a considerably greater amount of mass present than after the star ignites.

Two very massive objects will orbit each other around the system's barycenter. With a very small neutron star, and a massive protoplanetary disc, the mass difference between the two may be low enough for a stable barycentric orbit, but the gravitational effect of the neutron star companion would stretch the planetary gas disc, and make any bodies produced inside it have unusally eliptical orbits.

Even still, there might be stable configurations.

Oh, you're thinking of the cloud of gas before the star is actually formed? Sorry, I was always referring to the protoplanetary disk as the debris disk around a newly formed star. Maybe I should have not referred to it as a protostar, my fault on that one.

There are stable gas disks around binary stars, though, and they come in two types, p- and s-type. P-type disks are around both stars and s-type are around one of them with the companion star being off in the distance. Coincidentally, I just today was at my department's journal club where a guy talked about this in the form of this paper. The paper is about a planet around a binary (p-type orbit) with an extremely circular orbit, and to answer the question of why it's so circular (it's strange since the binary stars would affect the orbit and make it eccentric by exerting a torque on the planet) they model a gas disk around the stars. The gas disk supposedly damps the effects of the binary on the planet.

Now, having two stars or one star and a neutron star would not make much of a difference if they had the same mass. So in theory you could just switch one of the stars for a NS and have the same orbital dynamics.

[SealyStar]

Nice thread. OP knows me as the "battery gun guy" now

So... fluid dynamics. About how much pressure needs to be exerted on water before it starts getting compressed "appreciably"? I know that deep in the ocean (e.g. Marianas Trench), there's enough pressure for it.

[da_nang]

Nice thread. OP knows me as the "battery gun guy" now

So... fluid dynamics. About how much pressure needs to be exerted on water before it starts getting compressed "appreciably"? I know that deep in the ocean (e.g. Marianas Trench), there's enough pressure for it.

Define "appreciably" .

[MonkeyHead]

AFAIK, water is nigh on incompressible. Enough pressure to cause a measurable compression would probably lead to the formation of hot ice, which in itself is a cool concept.

[da_nang]

Well, assuming it's an isothermal compression, you'd need roughly 14900 atm of pressure to reduce the volume by 50% from 1 atm.

So, a lot. Like 15 times deeper than the Mariana Trench.

[SealyStar]

At the bottom of the trench the water column above exerts a pressure of 1,086 bars (15,750 psi), over 1000 times the standard atmospheric pressure at sea level. At this pressure the density of water is increased by 4.96%, making 95 litres of water under the pressure of the Challenger Deep contain the same mass as 100 litres at the surface.

Ah, this is what I was thinking of.

Like, how much pressure/depth do you need to compress it by 1%?

[da_nang]

Isothermally, roughly 217 atm from 1 atm at 20ºC. Or 220 bars.

[10ebbor10]

On that note, at what pressure does it turn solid at room temperature. Or does that not happen because water is some exception.

[MonkeyHead]

If the spoilered chart below is accurate (and I suspect it is), then around 1 GPa.

Spoiler:  State diagram for water (click to show/hide)

[Helgoland]

There's a metallic state of water?

[SealyStar]

There's a metallic state of water?

Well, now we know the top-tier crafting material for The Elder Scrolls VI: Skyrobliviwindaggerfallrena

[Silfurdreki]

There's a metallic state of water?

Not that I know a lot about material science, but I would guess it's similar to metallic hydrogen. It's basically liquid hydrogen that conducts electricity.

[Cryxis, Prince of Doom]

Ptw

[MonkeyHead]

My fault. I should have locked it when the fad passed. I may indeed lock it in a day or two if it sinks back to the depths.

[Cryxis, Prince of Doom]

Ptw

You just year-necro'd a thread to ptw.

.-. Some one just sent me a link to it
I didn't know it was dead
I didn't get a warning for it



Can I still ask random science questions?