Speaking of brown dwarfs… The boundaries of planethood can sometimes be blurry. For example, a free-floating object several times the mass of Jupiter might be considered a rogue planet (a planet that isn’t gravitationally bound to a star) or a brown dwarf (a “failed star” that isn’t massive enough to fuse helium). Learn more in our guide to rogue planets — what they are, how they form, and how they challenge categorization. Pictured: An artist’s impression of a rogue planet. Image credit: NASA/JPL-Caltech.
A world’s a world, no matter how small. That’s Kate Howells’ view when it comes to moons. Even tiny planetary satellites are fascinating worlds unto themselves, as she explores in her book “Moons: The Mysteries and Marvels of our Solar System.” The author (who also serves as The Planetary Society’s public education specialist) discusses moons big and small in her interview in The Planetary Society’s book club, featured in this month’s Planetary Radio: Book Club Edition.
It’s been a huge year for space policy and advocacy. In this week’s Planetary Radio, The Planetary Society’s space policy team unpacks what happened, why funding uncertainty matters, and what comes next for space science. You can also watch last week’s virtual Q&A with the team about what’s happened since our October Day of Action and what to expect in the coming months.
Our team is taking some time off for the holidays. That’s why there are no Mission Briefings in this week’s Downlink. We’ll skip those next week, too, but will still bring you other great space content to kick off 2026. Happy Holidays!