From Nature:
In the largest survey of its kind to date, astronomers scouring the space around the Solar System for signs of dark matter — the hypothetical material believed to account for more than 80% of the mass in the Universe — have come up empty-handed. If confirmed, the surprising result would upend a long-established consensus, researchers not involved in the study say. For decades, cosmic theories have relied on dark matter — which exerts gravitational pull but emits no light — to be the hidden scaffolding that explains how structure arose in the Universe, how galaxies formed and how the rapidly spinning Milky Way manages to keep from flying apart. Without dark matter, theorists say, the visible material in the Universe, such as stars and gas, would not have the heft to do the job alone. “If the results stand up, it’s going to be very difficult to make them compatible with the conventional view of dark matter,” says Scott Tremaine, an astrophysicist at the Institute for Advanced Study in Princeton, New Jersey, who was not involved in the study.
The researchers measured the velocity of more than 400 stars within 4,000 parsecs (13,000 light years) of the Sun in a limited volume — a 15-degree cone — below the flattened disk of the Milky Way Galaxy, and then used those observations to extrapolate the velocities of stars on the other side of the disk, above the plane. This volume is approximately four times greater than that surveyed by other teams in previous studies. The researchers found that at most, only about one-tenth the amount of dark matter predicted by models could exist in the volume of space they examined, Moni Bidin says.
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