I have been unable to find any research on particle density over 1 cSecond above or below the ecliptic in regions with a gravitational field with an acceleration less than 1/1000 of meter per second squared. Any help would be appreciated.

Is there any research to determine the distribution of this material related to the the Massive objects in the the system ?

It would seem logical that there is some amount of material falling from the Oort cloud toward the Sun and other mass concentrations in the Ecliptic disc defined by Jupiter's rather than Earth's Orbit.

Typical regions of interest would be the volume not dominated by the Sun's, Jupiter's or any other planet's gravitational field.

This question came from an analysis of material which enter into orbits far from the center of mass.

The most likely, common, particles are those emitted by the Sun which are between escape velocity and its (1/(root2 = 1.414) = 0.707) related orbital velocity. If the direction of the resulting orbit is random (or even partially random), particles going in opposing directions will collide and some will drop out of orbit.

The question came up in relation to a ion drive based space craft powered by mirror concentrated light beams, received by a large collector.

The cross-section of the collector is large enough that even at the low velocity of 1 c Seconds per hour it would encounter drag from the interplanetary medium.

The solar wind would assist acceleration, so that is not an issue,

Mapping the density outside significant mass concentrations and Ecliptic defined by Jupiter's orbit might find lower density volumes.

Thanks for the help.

  • 1
    $\begingroup$ This question isn't very clear and doesn't show much evidence of prior research. "Matter falling from the Oort cloud" means long-period comets, which sometimes interact with Jupiter (or other planets), becoming short-period comets or perhaps being expelled from the solar system. I hope this gives you a start towards clarifying the question. $\endgroup$
    – antlersoft
    Mar 22, 2021 at 14:07

1 Answer 1


I assume you want density expressed in units of average mass in kg per cubic light second.

An ecliptic plane is infinitely thin, so we might assume this is irrelevant to the question. Perhaps you meant "not including matter within a Jupiter radii of the Jupiter ecliptic," but this isn't very clear from the question.

The Solar System is defined as all objects gravitationally bound to the Sun, so it doesn't have a volume per se. For example, when Oumuamua cruised by the Sun, it was never part of the Solar System because it always had greater than escape velocity. But the interplanetary medium is not a perfect vacuum, but is rather about 5 particles per cubic centimeter. Even the interstellar medium isn't quite a vacuum.

If we assume the edge of the Solar System is at the edge of the Oort cloud at 50,000 AU, which is given as an answer to Where does the Solar System end? Then the volume of the Solar System is $4/3\pi r^3$ or $5.24\times 10^{14}$ cubic AU, or $6.5\times 10^{22}$ cubic light seconds. The mass of the Solar System is well approximated by the mass of the Sun, or about $2\times 10^{30}$ kg. So the Solar System average density is about $3.07\times 10^{7}$ kg per cubic light second.

  • $\begingroup$ Very useful answer, hope my corrections answered some of the issues, Your volume calculation is a good intro into system dimensions, The typical Interplanetary medium density estimation is 1 atom to 1 cm cubed = 1 cc. There are 1,000,000 = 1e6 cc in a meter and 27e24 meters in a cubic light second. thus 27 e30 Atoms per cubic cSec. A Hydrogen Atom is 1.67 e-27 Kg resulting in 3.6e4 Kg per cubic cSec within an order of magnitude of the ratio of air to water. At 1 light second per hour (83 Kps) space is not empty. Space $\endgroup$
    – LOIS 16192
    Jun 17, 2021 at 15:32

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