Is the solar system entering a nearby interstellar cloud

Journal Article · Sat Jul 15 04:00:00 EDT 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156294· OSTI ID:6695841

Vidal-Madjar, A; Laurent, C; Bruston, P; Audouze, J

A model, based on different observations of the local interstellar medium, indicates the presence of a very close interstellar cloud in front of the Scorpius-Ophiuchus association (almost in the direction of the galactic center) approaching the solar system from a distance of about 0.03 pc at a velocity of about 15--20 km s/sup -1/. These observations are as follows:1. The strong gradient of the hydrogen density in the interstellar medium deduced from current observations of this gas inside the solar system (n/sub H/approx.0.1 cm/sup -3/) and in front of many nearby stars in the anticenter direction (n/sub H/approx.0.01 cm/sup -3/).2. The anisotropy of the UV flux (around 950 A) from the brightest and closest O and B stars.3. The important variation of the deuterium to hydrogen ratio, which ranges from 2 x 10/sup -6/ in the ..cap alpha.. Cen A direction to 4 x 10/sup -5/ in the Aga Aur direction.A mechanism based on a selective radiation pressure effect that acts on deuterium atoms and not on hydrogen atoms explains satisfactorily the large spread in the deuterium abundance in the local interstellar medium. The operation of this mechanism requires that the geometrical configuration remain stable for approximately 10/sup 7/ years. This requirement implies the existence of a nearby interstellar cloud.Possible candidates do exist in the proper sky direction. One candidate, extensively discussed, presents a persistent interstellar absorption pattern over an angle of 40/sup 0/ related to a high column density, although covering only a few degrees in the sky, would lead to the same consequence. The presence of such condidates is not all contradicted by the interstellar reddening and absorption line observations.Other implications of the presence of such a close cloud are presented.

• Research Organization: Laboratoire de Physique Stellaire et Planetaire, Verrieres-le-Buisson
• OSTI ID: 6695841
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 223:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
COSMIC DUST
COSMIC GASES
CRYOGENIC FLUIDS
DEUTERIUM
DUSTS
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
GASES
HYDROGEN
HYDROGEN ISOTOPES
INTERSTELLAR SPACE
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
NONMETALS
NUCLEI
ODD-ODD NUCLEI
RADIATION PRESSURE
RADIATIONS
SOLAR SYSTEM
SPACE
STABLE ISOTOPES
STELLAR RADIATION
ULTRAVIOLET RADIATION
VARIATIONS