Oort cloud

With regard to the Oort cloud, I understanf that it is believed to extend
somewhere in the region of 3 light years from the Sun. Given that this is
true and presumably other stars would have similar "clouds" left over from
their creation. Now Alpha Centauri is in the region of 5 years away,
Supposedly it may have an Oort equivalent, ergo there must be some
intermingling of materials between both systems. I have yet to read
speculation on this, I would guess therefore that this is possibly one of
the reasons comets are born. Your thoughts please.

Yep, you're correct in thinking solar systems exchange orbital material -
IIRC, this is one hypothesis for Sedna, the newly found planetesimal,
because it's too far out to be explaned by our current understanding of how
the solar system formed.

"Canuck" wrote in message ...
With regard to the Oort cloud, I understanf that it is believed to extend
somewhere in the region of 3 light years from the Sun. Given that this is
true and presumably other stars would have similar "clouds" left over from
their creation. Now Alpha Centauri is in the region of 5 years away,
Supposedly it may have an Oort equivalent, ergo there must be some
intermingling of materials between both systems. I have yet to read
speculation on this, I would guess therefore that this is possibly one of
the reasons comets are born. Your thoughts please.

"Canuck" wrote
With regard to the Oort cloud, I understanf that it is believed to extend somewhere in the region of 3 light years from the Sun.

Yeah. I always had a problem with this, because the nearest star is
only about 4.3 LY away. As F=G*m1*m2/r^2, the furthest reaches of
this cloud in the direction of that star would experience FAR more
gravitational attraction from the other star than from our sun.

This would presumably perturb the cloud violently, and I suppose mass would
be "stolen" from our sun. (And vice versa if the other star had a similar-
sized "Oort" cloud of its own.)

Maybe the cloud is kinda "covalently shared" between our sun, the nearest
star, and any other close-by ones, so that in theory rocks at the edge of
the cloud could spend some time "orbiting" one star, and some time orbiting
one or more others. You heard it here first. This be the "Poyser Covalency
Conjecture", with a nod to Ahad, bwaa-haa-haa!



Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

In message , Fleetie
writes
"Canuck" wrote
With regard to the Oort cloud, I understanf that it is believed to
extend somewhere in the region of 3 light years from the Sun.

Yeah. I always had a problem with this, because the nearest star is
only about 4.3 LY away. As F=G*m1*m2/r^2, the furthest reaches of
this cloud in the direction of that star would experience FAR more
gravitational attraction from the other star than from our sun.

This would presumably perturb the cloud violently, and I suppose mass would
be "stolen" from our sun. (And vice versa if the other star had a similar-
sized "Oort" cloud of its own.)

Maybe the cloud is kinda "covalently shared" between our sun, the nearest
star, and any other close-by ones, so that in theory rocks at the edge of
the cloud could spend some time "orbiting" one star, and some time orbiting
one or more others. You heard it here first. This be the "Poyser Covalency
Conjecture", with a nod to Ahad, bwaa-haa-haa!

There's also the possibility that the cloud does not exist, and that the
theory behind it is erroneous :-)

Do a search for R A Lyttleton, for instance. Here's a paper to start
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974Ap%26SS..31..385L.

And there was a recent paper by Napier et al. saying that there should
be 1000x more Halley-class comets than are actually seen
http://star.arm.ac.uk/preprints/425.pdf.
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Support the DEC Tsunami Appeal http://www.dec.org.uk/.
Remove spam and invalid from address to reply.

Wasn't it Canuck who wrote:
With regard to the Oort cloud, I understanf that it is believed to extend
somewhere in the region of 3 light years from the Sun. Given that this is
true and presumably other stars would have similar "clouds" left over from
their creation. Now Alpha Centauri is in the region of 5 years away,
Supposedly it may have an Oort equivalent, ergo there must be some
intermingling of materials between both systems. I have yet to read
speculation on this, I would guess therefore that this is possibly one of
the reasons comets are born. Your thoughts please.

I've never believed in the Oort cloud.

I reckon that the experimental errors in the observations that the
theory is based on are just enough permit a scenario where comets
ejected from the Kuiper belts of other stars drift independently around
the galaxy for billions of years and occasionally whizz through the
solar system, entering it with an initially hyperbolic orbit.

Interactions between Kuiper belt objects cause some to get flung inwards
and become low inclination comets, and others to get flung outwards and
drift independently through the galaxy.

My guess is that when we land a probe on a high inclination comet, we'll
find that its material doesn't match that of our early solar system,
because the comet started its life around a star with a different
composition.

--
Mike Williams
Gentleman of Leisure

Mike Williams wrote on my wonderfully colourful screen:

I've never believed in the Oort cloud.

I reckon that the experimental errors in the observations that the
theory is based on are just enough permit a scenario where comets
ejected from the Kuiper belts of other stars drift independently
around
the galaxy for billions of years and occasionally whizz through the
solar system, entering it with an initially hyperbolic orbit.

So how do you explain some three to five comets arriving in our skies
from interstellar space - every single year? Alright, not all of them
make it to Macholz or Linear/NEAT brightness, but the frequency is
certainly high enough.

Besides how would comets simply be _ejected_ from the Kuiper belts
around stars? In our solar system taken as an average, the Kuiper belt
is still tightly gravity bound to the Sun, at only ~ 50 or so ast units
out, compared to the 300,000 ast units (circa 5 light years) typically
separating any two given stars in the Sun's neighbourhood.

There just _has_ to be some kind of a wider circulating shell of left
over material from the formation of the solar system, imho.

R

Wasn't it Rob who wrote:
Mike Williams wrote on my wonderfully colourful screen:

I've never believed in the Oort cloud.

I reckon that the experimental errors in the observations that the
theory is based on are just enough permit a scenario where comets
ejected from the Kuiper belts of other stars drift independently
around
the galaxy for billions of years and occasionally whizz through the
solar system, entering it with an initially hyperbolic orbit.

So how do you explain some three to five comets arriving in our skies
from interstellar space - every single year? Alright, not all of them
make it to Macholz or Linear/NEAT brightness, but the frequency is
certainly high enough.

Just that there are an awful lot of loose comets drifting about.

Besides how would comets simply be _ejected_ from the Kuiper belts
around stars? In our solar system taken as an average, the Kuiper belt
is still tightly gravity bound to the Sun, at only ~ 50 or so ast units
out, compared to the 300,000 ast units (circa 5 light years) typically
separating any two given stars in the Sun's neighbourhood.

We know that a fair number of comets got flung inwards from the Kuiper
belt in the early life of the solar system, and it still occasionally
happens today. The gravitational interactions that do this have an equal
chance of accelerating or decelerating them.

To fall from a circular orbit into an elliptical orbit that takes it
into the inner solar system, the object needs to lose almost all its
orbital velocity. Escape velocity from any position is just double the
circular orbit velocity at that altitude, so fairly similar amounts of
deceleration and acceleration cause a fall or an ejection. For every
object that decelerates from V to nearly zero there's another one that
accelerates to 2V and escapes.

--
Mike Williams
Gentleman of Leisure

JRS: In article , dated Wed, 19
Jan 2005 14:17:20, seen in news:uk.sci.astronomy, Mike Williams
posted :

To fall from a circular orbit into an elliptical orbit that takes it
into the inner solar system, the object needs to lose almost all its
orbital velocity. Escape velocity from any position is just double the
circular orbit velocity at that altitude, so fairly similar amounts of
deceleration and acceleration cause a fall or an ejection. For every
object that decelerates from V to nearly zero there's another one that
accelerates to 2V and escapes.

Escape kinetic energy from any position is just double the
circular kinetic energy at that altitude, so fairly similar amounts of
positive and negative energy transfer cause a fall or an ejection.
Escape speed is Root2 * orbital speed.

For every object that decelerates to nearly zero there's another several
that escape, because to fall inwards the momentum change must be correct
but to escape it need only be sufficient or more.

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Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
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Fleetie wrote:
"Canuck" wrote
With regard to the Oort cloud, I understanf that it is believed to
extend somewhere in the region of 3 light years from the Sun.

Yeah. I always had a problem with this, because the nearest star is
only about 4.3 LY away. As F=G*m1*m2/r^2, the furthest reaches of
this cloud in the direction of that star would experience FAR more
gravitational attraction from the other star than from our sun.

This would presumably perturb the cloud violently, and I suppose mass
would
be "stolen" from our sun. (And vice versa if the other star had a
similar-
sized "Oort" cloud of its own.)

Maybe the cloud is kinda "covalently shared" between our sun, the
nearest
star, and any other close-by ones, so that in theory rocks at the
edge of
the cloud could spend some time "orbiting" one star, and some time
orbiting
one or more others.

Ahad's virtual bridge theory not keep objects in the middle--

"At the *precise* point of equilibrium between the individual
gravitational forces emanating from each system there will exist a
"knife edge" scenario, where bodies would be perturbed into a rapid
motion towards either star system (whichever star system 'wins' the
object so to speak with its greater gravitational might). This
precisely pivotal point would likely be devoid of any objects for
mining, and the starship "command" must plan the journey accordingly."

Rob wrote:
There just _has_ to be some kind of a wider circulating shell of left
over material from the formation of the solar system, imho.


Most of the goons here rubbishing Oort cloud. Abdul Ahad first to
hypotheises "Ahad's virtual bridge theory" to reach nearest star---

http://www.geocities.com/javid_hssn/...ad-bridge.html