Modern cosmology is looking for Dark Matter. Some estimates of the composition of the Universe suggest that 90% or more of all the detectable gravitation observed might be coming from “dark matter” (stuff that gravitates but does not emit light.) There’s all sorts of conjectured versions of Dark Matter – hot, cold, large, small – even “wimpy”. And a number of existing models that are pretty broadly accepted by cosmologists simply won’t work with out the existence of Dark Matter and it’s companion entity: Dark Energy.
One of the first places that scientists recently realized that our understanding of Gravitation was lacking something was in the measurement of the differential rotational velocities of spiral galaxies, our own Milky Way included. It was because the Milky Way was rotating in way that suggested there existed a halo of mass far beyond the luminal boundary that people began to talk about this idea of “dark matter”
But now, perhaps, the Milky Way’s funny rotation curve can be explained sans the dark stuff. A new study attempted to follow the same basic ideas as the original research:
“The study concentrated on detecting the dark matter by studying the luminous matter embedded in it in much the same way dark matter was originally discovered. By studying the kinematics of the matter, it would allow astronomers to determine the overall mass present that would dictate the movement. That observed mass could then be compared to the amount of mass predicted of both baryonic matter as well as the dark matter component.
The team, led by C. Moni Bidin used ~300 red giant stars in the Milky Way‘s thick disk to map the mass distribution of the region. To eliminate any contamination from the thin disc component, the team limited their selections to stars over 2 kiloparsecs from the galactic midplane and velocities characteristic of such stars to avoid contamination from halo stars. Once stars were selected, the team analyzed the overall velocity of the stars as a function of distance from the galactic center which would give an understanding of the mass interior to their orbits.
Using estimations on the mass from the visible stars and the interstellar medium, the team compared this visible mass to the solution for mass from the observations of the kinematics to search for a discrepancy indicative of dark matter. When the comparison was made, the team discovered that, ‘[t]he agreement between the visible mass and our dynamical solution is striking, and there is no need to invoke any dark component.’”
Read the full article here.
So, Occam’s Razor now comes into effect. There have been other ways (MOND) that might be used to explain some of the other phenomenon that are presently invoking the chimerical Dark Matter, but apparently the data seen by this particular team kills off MOND even more definitively than it does Dark Matter.
Perhaps there’s something much simpler happening here – and we’re lacking complete data more than we are a complete understanding.