Fact constellation is a measure of online analytical processing, which is a collection of multiple fact tables sharing dimension tables, viewed as a collection of stars. It can be seen as an extension of the star schema.
A fact constellation schema has multiple fact tables. It is also known as galaxy schema. It is a widely used schema and more complex than star schemas and snowflake schemas. It is possible to create a fact constellation schema by splitting the original star schema into more star schemas. It has many fact tables and some common dimension tables.