Niven's Smoke Ring

How plausible is Larry Niven's "smoke ring," from the novels "The
Integral Trees" and "Smoke Ring"?

Can the gas torus be sustained in that density, or would the gas giant
supplying the gas sweep it back up in a relatively short period?

Mike Miller, Materials Engineer

Mike Miller wrote:
How plausible is Larry Niven's "smoke ring," from the novels "The
Integral Trees" and "Smoke Ring"?

Can the gas torus be sustained in that density, or would the gas giant
supplying the gas sweep it back up in a relatively short period?

Well, gas giants don't have free oxygen in this universe as far as we know.
So, you've first got to handwave a largely oxygen gas giant.
(Based on my exhaustive survey of 4)

I'm not completely happy that you can have an accretion disk that small
and relatively benign, but I haven't done the numbers.
I suspect that if you do them, there will be a couple of reasons why
it won't work.
Volume of gas from even an oxygen nitrogen gas giant is not high enough.
The shear would be much more violent.
I'm unhappy about where all the phosphorus, potassium, and all the other
elements needed for life come from, and how their cycles work.

Ian Stirling wrote in message ...

Well, gas giants don't have free oxygen in this universe as far as we know.
So, you've first got to handwave a largely oxygen gas giant.
(Based on my exhaustive survey of 4)

Well, yes, you do need a mostly oxygen gas giant, but that would
describe Uranus (so many puns, so little time) or Neptune. The bulk of
their mass is in the form of a water "ice" mantle amounting to several
times Earth's mass. With oxygen being the predominant component of
water by mass, you could say Uranus and Neptune fit the bill as
"largely oxygen gas giants". IIRC, the gas giant supplying the gas
torus in the Integral Trees was similar to Neptune in size.

However, you don't need that oxygen to be free on the gas giant, not
initially. Earth didn't start with an oxygen atmosphere; it was made
by life that survived in the original reducing atmosphere. Cracked
from water, IIRC.

Volume of gas from even an oxygen nitrogen gas giant is not high enough.
The shear would be much more violent.

The shear would be more violent? Between different 'altitudes' in the
gas torus, you mean?

I'm unhappy about where all the phosphorus, potassium, and all the other
elements needed for life come from, and how their cycles work.

Asteroids and other system debris?

One thing I don't follow though: why doesn't the gas giant sweep up
such a massive gas torus again? How do you strip that much gas in the
first place?

Mike Miller, Materials Engineer

"Mike Miller" wrote in message
om...
Ian Stirling wrote in message
...


One thing I don't follow though: why doesn't the gas giant sweep
up
such a massive gas torus again? How do you strip that much gas
in the
first place?

Wasn't there a dwarf star somewhere in the system?

"do$feratu" wrote in message ...

Wasn't there a dwarf star somewhere in the system?

There was a neutron star in the center and a yellow star slightly
larger than Sol outside the smoke ring.

http://members.optushome.com.au/guests/NSFPhys05.gif

It looks like the gas giant was actually DEEP inside the neutron
star's Roche limit (which would've been around 1 million kilometers);
Niven's math needed some work on several points about the Smoke Ring
setting. (For example, the neutron star would've needed to be about
1/10000th of a solar mass to generate the observed orbital period of
the smoke ring.)

Mike Miller, Materials Engineer

Mike Miller wrote:

"do$feratu" wrote in message ...

Wasn't there a dwarf star somewhere in the system?

There was a neutron star in the center and a yellow star slightly
larger than Sol outside the smoke ring.

http://members.optushome.com.au/guests/NSFPhys05.gif

It looks like the gas giant was actually DEEP inside the neutron
star's Roche limit (which would've been around 1 million kilometers);
Niven's math needed some work on several points about the Smoke Ring
setting. (For example, the neutron star would've needed to be about
1/10000th of a solar mass to generate the observed orbital period of
the smoke ring.)

Mike Miller, Materials Engineer

I'm no expert, but it seems like you are assuming the SR system is
still as it was born. Some of this discrepancy might be plausibly
attributed to later capture of and/or collisions between celestial objects..?

Just thinking out loud.