A pulsar is generally believed to be a rapidly rotating neutron star that emits pulses of radiation (such as x-rays and radio waves) at known regular intervals. A millisecond pulsar is one with a rotational period in the range of 1-10 milliseconds. When a pulsar is created in a supernova, is is born spinning, but slows down over millions of years. However, if the pulsar is in a binary system, the influx of material into its accretion disk may help the pulsar spin up to the millisecond range. Note: This animation zooms into a black hole and its accretion disk to show a millisecond pulsar in close-up. Animator: Dana Berry (Skyworks Digital). Writer: Michael D. McClare (HTSI).