This paper defines the essential quantitative and qualitative characteristics of a U.S. force structure required to meet the two-MRC standard for the near term and midterm.

CENTERFORSECURITYPOLICY: Center for Security Policy | The Measure of a Superpower: A Two Major Regional Contingency Military for the 21st Century

Although the authors note that the findings in the paper still require further study, they noted some interesting characteristics of each planet, labeled b, c, d and e in the image to the right.

FORBES: Astronomers Conduct 'Reconnaissance' Of Another Solar System