The discovery will be presented this week by John Lucico of the University of Notre Dame (USA) at a national meeting of British astronomers in Hull (UK).
Pulsars emit electromagnetic radiation at very regular intervals—ranging from milliseconds to seconds—which makes them very suitable as natural clocks. Using various radio telescopes, including the one in Westerbork, LoSecco observed variations and delays in the arrival times of these pulses. The data suggest that there are sometimes invisible mass concentrations between the pulsar and the radio telescope that deflect the radio radiation. According to LoSecco, these invisible masses could be made of dark matter.
The irregularities in arrival times due to dark matter have a specific path and a size proportional to the mass. Light passing near a region of dark matter will be deflected by its presence and will be delayed.
Careful analysis of 65 so-called millisecond pulsars has shown that dozens of these events were caused by dark matter interference.
“We take advantage of the fact that the Earth is moving, the Sun is moving, the pulsar is moving, and even dark matter is moving,” says Lucico. “We see the deviations in arrival time because they are caused by the change in the distance between the mass we observe and the line of sight of the pulsar, which acts as a clock.”
A mass the size of the Sun could cause a delay of about ten microseconds. LoSecco’s observations of Earth have a resolution of nanoseconds, 10,000 times smaller. One event involved a disturbance caused by an object about one-fifth the mass of the Sun, an object that LoSecco believes is a good candidate for dark matter.
