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kzb
2006-Oct-13, 11:37 AM
Can anyone point me in the direction of references or websites with data for the latest discussion and data. I'm specifically interested in our LOCAL density of these things, not in the galactic halo, spherical clusters etc.

I'm wondering about the density of ALL massive objects that might be difficult to spot. This would include cooled brown dwarfs and large "planemos".

I reckon to have done some searching, but I can't really find anything definitive and up to date.

GOURDHEAD
2006-Oct-13, 12:32 PM
We are just beginning to find rather large (Pluto-size) objects in the Kuiper belt and have detected none in the postulated Oort cloud. Such detections are at or beyond the limit of our instruments and cleverness. The MW could be populated with comet and asteroid objects at the presumed density of the Oort cloud and we wouldn't know.

kzb
2006-Oct-13, 03:15 PM
Thanks Gourdhead, but just to clarify, I'm after more massive objects than that. Pluto-sized objects are pretty massive, but it's not what I had in mind. I'm after the population density of things large enough to cause major disruption if they closely approached, or passed through, a planetary system such as our own.

I'd guess that would be approximately Jupiter size and above.

Kullat Nunu
2006-Oct-13, 03:35 PM
The number of stars rises sharply as the mass decreases (i.e. red dwarfs are far more common than other types of stars). Surprisingly enough, the curve drops at some point in the red dwarf regime. Based on the number of young brown dwarfs in star forming regions, it seems that there may be less brown dwarfs and planemos than red dwarfs in our stellar neighborhood. Hard to say anything about rogue planets, but it's hard to believe that slingshotted Jupiters are common. Old brown dwarfs and free-floating giant planets are next to impossible to detect with the current technology. Pluto-sized objects may be far more common, but they're even more difficult to detect.

Ronald Brak
2006-Oct-13, 03:35 PM
I wonder how disruptive a Jupiter massed object would be moving through the solar system? It could stir up the oort cloud and increase the chance of comet impact, but chances of comet impact would still be pretty low for earth. It would be unlikely to pass through the solar system on the same plane as the planets, so that would help limit the damage it might cause. If we count Neptune's orbit as the limit of the solar system for the sake of the arguement, then a Jupiter sized object passing at random through that area seems very unlikely to cause harm here on earth. The chance of it coming within one AU of us seems very small and although I have no math to back this up, I don't think that even at one AU distance it would have a great effect on earth's orbit.

astromark
2006-Oct-14, 10:48 AM
I do not have the site to give you the link but, have seen this very idea.
A program that lets you option in an object and its speed, size, angle of approach. My friend loaded a Jupiter to enter this system at the same rate as Jupiter and to come inside the orbit of Earth. Like a comet track. and pressed run.... (at faster speed ) It only took four orbits of the sun to expel all but Mercury. Venus was th rowen out first and very quickly. Mars entered a very ellipse track until the sun got in its way... Earth wandered about slowly moving out until a near miss with Saturn sent us out to the cold.
Try 'orbits' in a google search.

Ronald Brak
2006-Oct-16, 02:50 AM
A Jupiter sized object captured by the sun would certainly make life interesting. But for ones with enough velocity to pass through the solar system, my guess is in most cases we'd be allright. But still that's only a guess.

kzb
2006-Oct-16, 11:55 AM
Let's not run away with the "Jupiter size". When I thought this up, I was thinking more along the lines of brown dwarf, i.e. up to about 80 Jupiter masses.

What I'm trying to get it is, for stellar systems such as ours, what is the average time-lapse between catastrophic interactions with a massive interstellar body?

Kullat Nunu wrote:
<<The number of stars rises sharply as the mass decreases (i.e. red dwarfs are far more common than other types of stars). Surprisingly enough, the curve drops at some point in the red dwarf regime. Based on the number of young brown dwarfs in star forming regions, it seems that there may be less brown dwarfs and planemos than red dwarfs in our stellar neighborhood.>>

This is the kind of thing I'm after. However, how are we SURE the curve dipping at some point in the red dwarf regime is not selection bias? Also, as you state, we can only detect YOUNG brown dwarfs. This again would lead to a selection bias?

As to the seriousness of the interaction, given a close approach, that again would be a statistical thing, based on the angle and relative velocity of approach, mass of object, and just pure luck as to what was in its way at the time.

I mean we can imagine a brown dwarf passing say at Mars orbital distance, and if it just happened all the planets were on the other side of the sun at the time, then I guess not much would happen. But the other side of the coin is, for example, it could put Mars in an Earth-intersecting orbit if it interacted with it at the wrong moment.

antoniseb
2006-Oct-16, 12:15 PM
However, how are we SURE the curve dipping at some point in the red dwarf regime is not selection bias? Also, as you state, we can only detect YOUNG brown dwarfs. This again would lead to a selection bias?

If we can get a look at the population of all objects in nearby star-forming regions then the only bias would be if current star-forming regions (with presumed slightly higher metalicity) produce different ratios of objects than did such regions in earlier epochs. As measures go, this is a good one. The various OGLE-like studies have given numbers which seem to confirm these ratios.

kzb
2006-Oct-16, 05:26 PM
Thanks Antoniseb, are there any good links which give the mass/frequency distribution ?

Another thing we should bear in mind with these interactions is the brown dwarf or large planemo would almost inevitably have its own planetary system. I think a two-Jupiter mass planet has actually been found orbiting a brown dwarf. That would add to the mayhem.

Doodler
2006-Oct-16, 05:36 PM
I wonder how disruptive a Jupiter massed object would be moving through the solar system? It could stir up the oort cloud and increase the chance of comet impact, but chances of comet impact would still be pretty low for earth. It would be unlikely to pass through the solar system on the same plane as the planets, so that would help limit the damage it might cause. If we count Neptune's orbit as the limit of the solar system for the sake of the arguement, then a Jupiter sized object passing at random through that area seems very unlikely to cause harm here on earth. The chance of it coming within one AU of us seems very small and although I have no math to back this up, I don't think that even at one AU distance it would have a great effect on earth's orbit.

Many moons ago, I saw a simulator called "Rogue Star" that would let you throw something around 1% the size of the Sun at the low end through the Solar System at varying speeds. Depending on how close to the Sun it got, and how fast it was going relative to everything else, even somewhat on when the closest approach was on the calendar, the effect of the smallest object it could cover was from not very disruptive (minor to no alterations to orbits in the inner system if it were further than 7AU) to massively disruptive (if it passed within epistellar jovian range to the Sun). In some slow approaches, the Sun and the rogue would end up binary, which would wreak holy havoc on the planets. Some fast flythroughs would result in major disruption to the inner solar system as it approached within a fraction of Mercury's orbital distance to the Sun, but slower approaches were less disruptive typically. At the point of closest approach also tended to be the most disrputive part of the encounter. If the planets were going to shift, it would be at that point, when the Solar System's center of mass was most erratic.

One of the wilder scenarios I had worked up with a Sun sized rogue, actually put the Earth back in something resembling its original orbit, Mercury ended up in a VERY tight cometary orbit around the Sun, and the interloper ran off with Venus in an extremely tight, but circular orbit.