No livable planets without life

Life is caught in a chicken-and-egg situation. For life to exist on a planet, the planet must of course have the right conditions for life. The planet must be habitable. But a planet’s habitability depends in large part on whether it already has life. It’s a lot easier for a planet with life to be habitable. So a planet needs life to be able to host life….


Planet Nine from Outer Space!

This post could also be titled: How blogging and social media help make science happen. Here is the story.  Planet Nine was conjectured in late January 2016. In February 2016 I started to think about where Planet Nine may have come from. This led to 3 blog posts, each exploring a different origins story for…


Planet Nine: Solar System renegade?

We are discussing the origins of Planet Nine.  In part 1 we explored whether it could have been produced during an orbital instability in the early Solar System.  In part 2 we showed that Planet Nine could have been captured from another star.  Here we will explore another plausible idea that is a little less…