At present, milli-arcsecond imaging is restricted to objects with high brightness, i.e., nonthermal radio emitters. Large improvements in sensitivity coupled with the A+ configuration would allow imaging of thermal radio sources with milli-arcsecond resolution, opening an entirely new area of astrophysical inquiry. Examples of the kinds of objects which could be imaged out to distances ranging from several hundred pc to several kpc include i) interacting binaries containing giant stars (e.g., symbiotic stars and recurrent novae); ii) stellar winds on giant stars-expansion rates could be measured directly; iii) the early stages of nova outbursts; iv) the photospheres of giant stars, and v) circumstellar disks.
We stress that most elements of the expansion project are required simultaneously for these research programs, including: