Orion OB1 Association

The Orion OB1 stellar association is the group of hot giant stars in a large cluster. They are spectral types O and B. There are are thousands of lower-mass stars also in this group, and some protostars. 
The association is part of the larger Orion Molecular Cloud Complex. It is the most closely studied OB association.
The Orion OB1 association has these subgroups:
Signs of stellar debris disk have been found in the 1a and 1b subgroups. That is a circumstellar disk of dust and debris in orbit around a star.