Disappeared Pulsar PSR J1841

Pulsars are fast-spinning stars that emit regular beams of light known for their clocklike regularity.

More than forty years of study, astronomers still can’t nail down what causes these rapidly rotating stars to pulse. But when one, called PSR J1841, turned off for 580 days, it gave astronomers a glimpse of how pulsars behave when they can’t be seen. In December 2008, Fernando Camilo, of Columbia University in New York, was using the Parkes telescope in Australia to search for a known object when he found a steadily flashing star in his field of view. He quickly identified it as a pulsar that was spinning once every 0.9 seconds, a fairly standard rotation. His team continued to study the pulsar over the course of a year to help determine the characteristics of the new discovery, which orbits 22.8 light-years from the sun in the Scutum-Centaurus spiral arm of our Milky Way galaxy. Just as he was about to conclude his follow-up observations, the star disappeared. So Camilo concluded that he and his team had found another strange specimen. Then, in August 2011, the pulsar reappeared. According to Camilo, information gleaned from PSR J1841 could help astronomers understand how pulsars work. Furthermore, the discovery hints at the possibility that other known pulsars could be in the midst of their own long “on” period.