One petametre equals 10 to the 15th power metres, or one trillion kilometres. Astronomers use this scale to measure distances between nearby stars or the spans of nebulae. For scale, one light-year is roughly nine and a half petametres.
Heard on the job
The outer edge of the Oort cloud extends to about one petametre from the sun.
Insider tip
While the petametre is perfectly valid in the SI system, most astronomers still prefer to use light-years or parsecs for interstellar distances.