Planetary cones of focused interstellar gases.
Abstract
It is noted that neutral interstellar hydrogen and helium within the solar system are focused into cones by the sun and planets. Conditions are investigated under which the problem of determining the orbit of an interstellar atom in the gravitational fields of both the sun and a planet can be reduced to a two-body problem involving just the planet and the atom. The maximum extent of planetary cones that may be determined with this two-body approximation is estimated, and a scaling procedure is outlined for the neutral density distribution around planetary bodies. Specific planetary-cone densities as well as hydrogen and helium column densities along the axis of the cones are calculated for earth, Jupiter, Saturn, and Uranus. The results show that the extent of the Jovian cone may exceed 1 AU, the column densities in the terrestrial cone would hardly be detectable against the interplanetary background, and the largest hydrogen column densities would be expected to be upwind of the planets. Ways to observe the planetary focusing effect are considered, and it is concluded that the Jovian cone should be clearly observable in Lyman-alpha.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1976
- Bibcode:
- 1976A&A....52..363F
- Keywords:
-
- Gas Density;
- Gravitational Effects;
- Helium;
- Hydrogen Clouds;
- Interplanetary Gas;
- Interstellar Gas;
- Planetary Gravitation;
- Density Distribution;
- Earth (Planet);
- Focusing;
- Jupiter (Planet);
- Saturn (Planet);
- Solar Gravitation;
- Spatial Distribution;
- Uranus (Planet);
- Astrophysics