Do all stars have "Oort Clouds" ??

[Widdekind]

Our Sun's Oort Cloud seems to extend at least a light-year away from the Sun.

 

 

QUESTION:

 

Arguing from the Cosmological Principal ("what's here is there"), could other stars have colossal cometary "Oort Clouds" too ? If so, comets could, conceivably, populate an appreciable fraction of the inter-stellar space between stars -- the disk of the Milky Way Galaxy might be a "blizzard" of such icy bodies*.

*

The

Outer Oort Cloud

was once believed to boast about a Jupiter's mass worth of comets (~

0.001 M

_sol

). The

Inner Oort Cloud

is believed to boast "tens or hundreds of times as many cometary nuclei as the outer halo" (~

0.1 M

_sol

). Thus, there is an outside chance, that (inter)stellar "

Cometary Clouds

" could be a galaxy-wide "blizzard" of icy bodies of not-inconsequential total mass.

Edited June 2, 2010 by Widdekind

[ajb]

It is a very interesting question.

 

As there is no reason to think that the formation of the Solar System is particularly privileged or special in any way, then one would expect some other stars to have structures like our Oort cloud.

 

Though I do not know exactly what the observational status of the Oort cloud is nor how much we really know about it.

[sagan1976]

Hi all. "This be my first reply, maties. Arghhh!"

I have the idea that the Oort Cloud is still hypothetical, or at least unsupported by observation. Am i wrong?

[louis wu]

Hi all. "This be my first reply, maties. Arghhh!"

I have the idea that the Oort Cloud is still hypothetical, or at least unsupported by observation. Am i wrong?

You are right that there is a lack of direct observation for the Oort cloud, unless you consider objects such as Sedna are part of it.

 

There are arguments from the statistics of observed orbits of long term comets that indicate an Oort band out somewhere at 45000+ AU. How much 'stuff' is there is unknown until we can go there and see.

[Widdekind]

It is a very interesting question.

 

As there is no reason to think that the formation of the Solar System is particularly privileged or special in any way, then one would expect some other stars to have structures like our Oort cloud.

 

Though I do not know exactly what the observational status of the Oort cloud is nor how much we really know about it.

 

The vast majority of the ISM is "warm" (T > 6000 K) to "hot" (T > 10,000 K). How would this affect comets, ~1 lt.yr. out from the nearest star ?

 

The Sun is currently traversing the Local Interstellar Cloud (T ~ 6000 K), through which it has been passing for perhaps 100,000 years. The LIC is embedded at the boundary of the Local Bubble, which is some sort of Supernova Remnant, hot enough to emit X-Rays, through which the Sun has been traveling for 5-10 million years. Why wouldn't these temperatures, equaling or exceeding the surface of our Sun, "boil away" Oort Cloud comets ?

 

The Oort Cloud & Kuiper Belt both lie beyond the Sun's magnetosphere:

 

[Spyman]

Why wouldn't these temperatures, equaling or exceeding the surface of our Sun, "boil away" Oort Cloud comets ?

"The Local Interstellar Cloud ... is very tenuous, with 0.1 atoms per cubic centimeter"

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

[Widdekind]

What about the Temperature being hotter than the surface of the Sun; or, that our Sun has (supposedly) dragged the Oort Cloud through the Local Bubble & Local Interstellar Cloud for millions of years ?

[louis wu]

What about the Temperature being hotter than the surface of the Sun; or, that our Sun has (supposedly) dragged the Oort Cloud through the Local Bubble & Local Interstellar Cloud for millions of years ?

You have to consider the heat capacity of the medium. In so hard a vacuum there is very little energy per m³, despite the fact that individual molecules have a high velocity (temperature equivalent). There just is not enough energy to do much melting of comets.

[Spyman]

What about the Temperature being hotter than the surface of the Sun; or, that our Sun has (supposedly) dragged the Oort Cloud through the Local Bubble & Local Interstellar Cloud for millions of years ?

Lets assume a frozen comet of water ice with a temperature of -330ºC, a radius of 10km and a mass of 2×10¹⁴kg.

 

The Local Fluff is ~30 lightyears across and if the orbital speed and circumference of the comet around the Sun is very low compared to the Solar Systems speed and path, then the extra trajectory of the comets orbit can be neglected. Then the comet "punches" a hole with a Volume of 30×299792458×60×60×24×365.25×π×10000²= ~89×10²⁴m³.

 

While creating this hole in the Local Fluff the comet will collide with 0.1×100×100×100 Hydrogen Atoms per cubic meter, which have a mass of 1.00794×1.660538782×10^-27kg each. The accumulated mass on the comet during the travel will thus be 100000×1.67×10^-27×89×10²⁴= ~15000kg.

 

Adding 15000kg with a temperature of 6000ºC to a massive body of 2×10¹⁴kg with a temperature of -330ºC will increase the average temperature to (6000×15000-330×2×10¹⁴)/(2×10¹⁴+15000)= -329.99999953ºC.

 

The comet would, after ~100000 years of travel through the Local Fluff, exit at the other end with a temperature of roughly 0.0000005ºC higher than what it entered with.

 

Even if we disregard the possibility of the comet cooling itself by emitting thermal radiation it would still survive much much longer than the duration the Milky Way is thought to have been around.

[Widdekind]

Thanks for the numbers. What about the photon field, wouldn't it, too, be at 6000 K ?

[Spyman]

What about the photon field, wouldn't it, too, be at 6000 K ?

Yes, the Hydrogen Atoms in the Local Interstellar Cloud are emitting thermal radiation, but the amount of heat energy are dependent of the density of the cloud. Less atoms available for emitting heat means that less photons will be radiated and less photons radiated gives a weaker photon field. Since the cloud is so insubstantial thin the photon field is going to be irrelevant faint too.

 

I don't have the knowledge how to calculate the amount of radiation expelled from the cloud and then recieved on a moving object through it. But by intuition my impression is that the rise of temperature from thermal radiation will be inferior compared to heat transfer when the reciever is in direct contact with the emitter. I think the comets will get a much higher temperature increase from the material they are able to scoope up while going through than from the thermal radiation off the surronding cloud.

 

Granted any comets from the Oort Cloud will get heat from both collisions with matter in the Local Fluff and from heat radiation emitted off it, but the comets are also able to release heat by emitting thermal radiation.

 

By observation we do know that there are comets with vast orbits extending far out from the Sun, in which they spend or have spent a significant duration beyond the Sun's magnetosphere. Evidence tells us that comets are able to survive out there, they don't get "vaporised" by the hot dust outside.

[Widdekind]

I found this:

 

Long Period Comets (LPCs) older than Solar System ??

 

From Kenneth R. Lang. The Cambridge Guide to the Solar System, pg. 365-66:

 

LPCs enter the planetary realm at all possible angles, and with every inclination to the Earth's orbital plane... LPCs move in all directions. Roughly half of them move along their trajectories in the retrograde direction, opposite to the orbital motion of the planets...

 

Where did the Oort Cloud comets originally come from ? They could not have formed in their current position, b/c the material at such large distances from the young Sun would have been too sparse to coalesce...

 

It [Oort Cloud] is located... up to 100,000 AU from the Sun. By comparison, the distance from the Sun to the nearest star, Proxima Centauri, is 271,000 AU... At greater distances, the stars in the neighborhood of our Solar System compete for gravitational control, and each is imagined to have its own retinue of comets.

 

 

 

CONCLUSION:

 

• LPCs show no "gravitational correlation" to typical, Solar System-like, motions.
  
• They could not have formed as from our Sun's collapsing cloud core
  
• 3/4 of the distance between Sol & Proxima Centauri (200,000 out of 271,000 AU) is occupied by LPCs
  

 

This is completely consistent, w/ LPCs be extra-Solar objects, whose ices & rocks might predate our particular planet.

[Spyman]

The Oort cloud is thought to be a remnant of the original protoplanetary disc that formed around the Sun approximately 4.6 billion years ago. The most widely accepted hypothesis is that the Oort cloud's objects initially coalesced much closer to the Sun as part of the same process that formed the planets and asteroids, but that gravitational interaction with young gas giant planets such as Jupiter ejected the objects into extremely long elliptic or parabolic orbits. Simulations of the evolution of the Oort cloud from the beginnings of the Solar System to the present suggest that the cloud's mass peaked around 800 million years after formation, as the pace of accretion and collision slowed and depletion began to overtake supply.

 

Analysis of the carbon and nitrogen isotope ratios in both the Oort cloud and Jupiter-family comets shows little difference between the two, despite their vastly separate regions of origin. This suggests that both originated from the original protosolar cloud, a conclusion also supported by studies of granular size in Oort cloud comets and by the recent impact study of Jupiter-family comet Tempel 1.

 

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

[Widdekind]

...Simulations of the evolution of the Oort cloud from the beginnings of the Solar System to the present suggest that the cloud's mass peaked around 800 million years [~3.8 Gya] after formation, as the pace of accretion and collision slowed and depletion began to overtake supply.

 

That sounds suspiciously like a claim, that the population of the Oort Cloud, coincides closely with the Late Heavy Bombardment (LHB). If so, that may have been when water was deposited upon the planets of the Inner Solar System.

 

Perhaps, then, Venus never had oceans, as it was already a runaway Greenhouse, before water was deposited; and/or Venus, farther from Jupiter, received less water than the Earth. Were that the case, one would expect the most water to have been dumped on Mars, the least on Mercury, with Earth & Venus in between.

 

This is also completely consistent, with the proposal of Panspermia, given that the LHB (~3.9 Gya) coincides closely with the first fossils of Life upon this particular planet (~3.8 Gya).

 

"...ages between

2.76 and 3.92 billion years ago (Ga)

. The lack of impact melt older than

3.92 Ga

supports the concept of a short, intense period of bombardment in the Earth-moon system at

~3.9 Ga

. This was an anomalous spike of impact activity on the otherwise declining impact- frequency curve"

(

Science

)

.

 

 

 

 

---

Merged post follows:

Consecutive posts merged

 

 

 

This site says that Epsilon Eridani, an 0.85 M_sol K2-class Orange Dwarf about 11 light-years away, & 1 billion years old, has a "Comet Belt" corresponding to our own Kuiper Belt:

 

 

Since that star system is so similar to our own, perhaps that points to the presence of an Oort-like Cloud as well ? Note, in the previous picture, the radically reduced size of the older Sun's Kuiper Belt, compared to the younger Epsilon Eridani's comet belt. That might mean, that a significant fraction of the Sun's Kuiper Belt has been gravitationally "shorn away", over the past 4 billion years, through interactions with passing stars.

Edited June 10, 2010 by Widdekind
Consecutive posts merged.

[Widdekind]

Most comets may be from other solar systems | COSMOS magazine

 

Most comets may be from other solar systems

 

Computer simulations have revealed that famous long-period comets such as Halle-bop (pictured) are likely to have originated in another solar system...

 

more than 90% of comets in the Oort Cloud were captured from other stars when the Sun spread apart from its ‘birth cluster’. Levinson said it is common for stars to be born in ‘clusters’, fed by a large cloud of gas held together by its own gravity. Around each of these stars will form comets, many of which will be stripped from the star by the gravity of the cluster.

 

When some of the stars grow old enough, they emit strong stellar winds that literally blow the gas from the cluster, destroying its gravitational hold on the stars. Once this occurs the cluster starts to disperse, and if a star leaves the cluster at the same velocity as a comet from another star, the comet can be captured.

 

Trillions of comets on average originally form around each star, and the study’s computer simulations show up to a quarter of this average can end up in an Oort Cloud.

 

The fact the Sun stole so many comets doesn’t mean other stars missed out on the chance to have an Oort Cloud of their own. “It’s not a zero sum game,” said Levison, and noted for all of the comets captured by stars when the cluster dispersed, there are many times more floating around in inter-stellar space.

[KennyC]

Thanks for the great info and links Widdekind!

 

Most comets may be from other solar systems | COSMOS magazine

[JohnStu]

these oort clouds came from the supernova explosion long ago

Edited January 6, 2013 by JohnStu