Astronomy IS physics!
You might want to make that APPLIED physics rather than just plain physics.
You could always get a degree in Interdisciplinary Studies, but the recruiters who come on campus looking to place graduates usually favor specific majors and leave Interdisciplinary degree students by the wayside.
Eventually you are going to have to CHOSE ONE!
(Even if it is after graduation when you choose a career.)
When it comes to that, people either follow their passion or go for the most marketable degree.