Pulsing Stars May Be Most Accurate Clocks In the Universe
Rapidly spinning stars that pulse over time could be used as the universes’s most accurate clocks. Astronomers have long hoped to use these stars, called pulsars, as time-keepers but slight irregularities in their spinning rates have so far prevented those plans. But a new understanding could enable scientists to compensate for it, thanks to a new discovery that helps explain how they rotate.
Pulsars are created when stars collapse and become so dense that protons and electrons squish together to become neutrons. After the star’s mass is condensed into a small volume, conservation of angular momentum causes the pulsar to rotate extremely rapidly – up to hundreds of revolutions per second, emitting a steady ray of light that sweeps around like a lighthouse beam as they rotate – thus, their light appears to pulse on and off as the beam crosses our line of sight.
Timing the cosmos
A team of astronomers used data from Lovell telescope at the university’s Jodrell Bank Observatory to find that the deviations arise because the pulsars are slowly spinning down, and they are doing so at two different rates, switching between these spin-down rates abruptly and unpredictably. Detailed measurements of a pulsar’s light at any particular time should indicate what its slowdown rate is, and allow astronomers to calculate and apply a correction.
Ripples in space-time
Scientists hope that pulsar clocks can be applied to the question of gravitational waves. Einstein’s theory of general relativity suggests that powerful events such as the merging of two supermassive black holes will create ripples in space-time that spread out through the universe.
These waves have never before been detected, but pulsars may be the key to finding them: if a gravitational wave passed through a pulsar, it would cause the pulsing rate to change. If these changes could be measured very accurately, scientists may be able to prove the existence of gravitational waves.
Many observatories around the world are attempting to use pulsars in order to detect the gravitational waves that are expected to be created by supermassive binary black holes in the universe. This new technique may be able to reveal the gravitational wave signals that are currently hidden because of the irregularities in the pulsar rotation.
Image: Schematic view of a spinning star called a pulsar, which beams out rays of light like a lighthouse. Pulsars provide the most precise natural cosmic clocks known to date.