What does it mean?
Period – Periods apply to things that repeat, and measure how long it takes them to repeat. For instance, the period of the Earth to turn around its axis is 24 hours, while the period for the Earth to travel around the sun is 365 days.
In human speak please!
Many astronomical phenomena have noticeable periodicities in the light emitted or in other properties. Planets like the Earth have spin periods around their own centers, as well as orbital periods around the stars which they are orbiting. Other objects, like comets, also have periods around the stars which they orbit. Even stars can have periods orbiting around objects like other stars, black holes, or even the centers of their galaxies. However, all of these periods are likely to be much longer than 5.6 seconds. For instance, it takes over 230 million years for the sun to revolve around the center of the Milky Way. Can you find an astronomical object that has a period as short as a few seconds or less?