The dynamical density of matter in the solar vicinity can be estimated
using vertical oscillations of stars around the galactic plane.
Öpik (1915)
found that the summed contribution of all known
stellar populations and interstellar gas is sufficient to explain the
vertical oscillations of stars - in other words, there is no need to
assume the existence of a dark population. Similar analyses were made by
Kapteyn (1922)
and
Jeans (1922),
who used the term
"Dark Matter" to denote the invisible matter. Kapteyn found for the
dynamical density of matter near the Sun 0.099
M
/
pc3, Jeans got 0.143 in the same units.
Oort (1932)
analysis suggested that the total density is about 0.092
M /
pc3, and the density of stars, including expected
number of white dwarfs, is approximately equal to the dynamical
density. He concluded that the total mass of nebulous or meteoric dark
matter near the Sun is very small.
Kuzmin (1952, 1955) and his students Eelsalu (1959) and Jõeveer (1972, 1974) confirmed the earlier results by Öpik, Kapteyn and Oort. A number of other astronomers, including more recently Oort (1960) and Bahcall (1984, 1987), found results in agreement with the Jeans result. Their results mean that the amount of invisible matter in the solar vicinity should be approximately equal to a half of the amount of visible matter.
Modern data by Kuijken & Gilmore (1989), Gilmore et al. (1989) have confirmed the results by Kapteyn (1922), Oort (1932), Kuzmin (1952, 1955) and his collaborators. Thus we come to the conclusion that there is no evidence for the presence of large amounts of dark matter in the disk of the Galaxy. If there is some invisible matter near the galactic plane, then its amount is small, of the order of 15 percent of the total mass density.