When "*" is used for the list of selected columns, the result set is expected to minimally include, for each selector, a column for each single-valued non-residual property of the selector's node type, including those explicitly declared on the node type and those inherited from the node's supertypes.
For example, the result set for the following query would contain at least the '[jcr:primaryType]' column, since it is the only single-valued, non-residual property defined on the '[nt:base]' node type. The '[jcr:mixinTypes]' property is also non-residual, but the results need not include it since it's multi-valued.