"the new planet ... tak[es] 647 days to complete an orbit around its star, 40 days less than Mars. This orbit places it within the habitable zone of the system,

"the new planet ... tak[es] 647 days to complete an orbit around its star, 40 days less than Mars. This orbit places it within the habitable zone of the system, meaning it is at the right distance from its star to sustain liquid water on its surface" 1. That orbit make it really cold relative to Earth - like Mars is. 2. It doesn't say that the planet has a human-breathable atmosphere; it might, but it might not - like Mars. Also, 3. Gravity force is gMm/R^2 right? Let's say same density as earth, and that density is uniform. Now, the mass relates to the radius by R^3, so the gravity force will be higher by 6^{1/3}, or about 1.817x higher than Earth. So, would you say this is a habitable planet? It's kind of a stretch.