The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun.
A team using the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory, along with other telescopes, has mapped the motions of more than 400 stars up to 13,000 light-years from the Sun.
From this new data they have calculated the mass of material in the vicinity of the Sun, in a volume four times larger than ever considered before.
‘The amount of mass that we derive matches very well with what we see -- stars, dust and gas -- in the region around the Sun,’ says team leader Christian Moni Bidin, of the Universidad de Concepcion, Chile.
‘But this leaves no room for the extra material -- dark matter -- that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!’
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Dark matter is a mysterious substance that cannot be seen, but shows itself by its gravitational attraction for the material around it.
This extra ingredient in the cosmos was originally suggested to explain why the outer parts of galaxies, including our own Milky Way, rotated so quickly, but dark matter now also forms an essential component of theories of how galaxies formed and evolved.
Today it is widely accepted that this dark component constitutes about the 80% of the mass in the universe, despite the fact that it has resisted all attempts to clarify its nature, which remains obscure. All attempts so far to detect dark matter in laboratories on Earth have failed.