There is no recognized astronomical unit called "astrominal unit." It's possible there's a typo or misunderstanding.

Here are some possibilities you might be thinking of:

* Astronomical Unit (AU): This is a standard unit of measurement in astronomy, equal to the average distance between the Earth and the Sun. It's approximately 93 million miles (150 million kilometers).

* Lunar Distance (LD): This is the average distance between the Earth and the Moon, about 384,400 kilometers (238,855 miles).

* Parsec: This is a unit used to measure very large distances in space. One parsec is about 3.26 light-years, or 206,265 astronomical units.

If you could provide more context or details about where you encountered the term "astrominal unit," I might be able to provide a more specific answer.