... Baffling pulsar leaves astronomers in the dark . Scientists have found that this object, whose radio emission is known to switch on and off periodically, exhibits the same behavior, but in reverse, when observed at X-ray wavelengths. ... Monitoring this pulsar simultaneously in X-rays and radio waves, astronomers have revealed that this source, whose radio emission is known to switch on and off periodically, exhibits the same behavior, but in reverse, when observed at X-ray wavelengths. ...