siriometer

plural siriometers

1. A unit of distance equal to one million astronomical units or 15.813 light-years.

   The siriometer dates its pedigree from the founder of stellar astronomy, William Herschel. As is well known, the distance unit used by Herschel is the mean distance of the first magnitude stars, which distance was called by him the distance of Sirius.

   1925, The Observatory, volume 48, page 143

   1 more example

   He had used the star Sirius as his standard, so he decided to call the distance to Sirius, whatever it might turn out to be in miles or kilmetres, one 'siriometer'. Herschel calculated that the grindstone measured 1,000 siriometers across and was 100 siriometers thick.

   2013, Kitty Ferguson, Measuring the Universe: The Historical Quest to Quantify Space, Random House, →OCLC