Dark matter theories take a blow

Posted by Emma Woollacott

If dark matter exists, it's not hiding out in our neighbourhood, baffled scientists have revealed.

According to widely accepted theories, as much as 80 percent of the universe's mass is believed to consist of dark matter, which can only be detected indirectly by the gravitational force it exerts.

However, a new study by a team of astronomers in Chile has found that these theories just don't fit the facts.

A team using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory, along with other telescopes, has calculated the mass of material in the vicinity of the sun - and there doesn't seem to be any dark matter at all.

"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 Christian Moni Bidin of the Universidad de Concepción in 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!"

Existing models of how galaxies form and rotate suggest that the Milky Way is surrounded by a halo of dark matter, with plenty to be found in the region around the sun. But the lack of success in finding any implies that, if this halo does exist, it would have to be a very odd shape to miss us out.

"Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for. So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found," says Moni Bidin.

"Our results contradict the currently accepted models. The mystery of dark matter has just become even more mysterious. Future surveys, such as the ESA Gaia mission, will be crucial to move beyond this point."