Transcripts of 11609_Transformer_Pulsar_H264_Good_1920x1080_29

[Music] [Music] Narrator: About 4,400 light-years away, in the constellation Sextans, there is an extraordinary binary system that pairs a rapidly spinning neutron star, or pulsar, with a star about one-fifth the mass of the sun. Thanks to its rapid rotation and intense magnetic field, the pulsar produces a strong radio signal, which is how astronomers first discovered it. Many similar binaries are known, what's strange about this one is that sometimes the radio beacon just disappears. Then the system lights up in X-rays and gamma rays. Here's what researchers think may be happening. The two stars orbit so closely that gas from the sun-like star overflows and a stream falls toward the pulsar. But the pulsar produces an outflow of its own, Its spin and magnetic field accelerate charged particles to near the speed of light, creating a high-energy wind. During the radio phase, this pulsar wind easily holds back the gas stream. Now and then, and for reasons as yet unknown, the companion's stream surges, pushing close enough to the pulsar that it collects into a disk. Once in the disk, the gas gradually spirals toward the neutron star. At an altitude of about 50 miles, the gas chokes off the pulsar wind, unleashing the full torrent of the companion's gas stream. Gas reaching closest to the neutron star becomes transformed into dual particle jets, which fire out of the disk in opposite directions at nearly light-speed. Gamma rays observed by NASA's Fermi satellite may arise along the edge of the jet, while enhanced X-ray emission observed by other spacecraft may come from shock waves rocking the inner accretion disk. Eventually, and for reasons not understood, the companion's flow ebbs. The pulsar wind again becomes dominant, choking off the flow and blowing away the accretion disk. The pulsar flips back to its radio-emitting mode. Astronomers think this system represents a rare glimpse of a relatively brief phase. Mass transfer from a companion can rejuvenate an old, slow pulsar, spinning it up to tens of thousands of rpm. We may be seeing a system where this phase is on the verge of ending. When it does, the pulsar's wind will erode what's left of its companion until only the pulsar remains. Although astronomers have studied the system in both low- and high-energy states, they haven't yet observed this transformation in progress. Now, they are watching closely, waiting to document the next dramatic change of this exceptional binary. [Beeping] [Beeping] [Beeping]