REACHing Out are bi-weekly mini-episodes where we answer YOUR Questions. This week we're actually digging into a question both Brian and Meredith had on a past episode: "What is Planet 9?"  Joining us with the answer is Dr. Mike Brown, Richard and Barbara Rosenberg Professor of Planetary Astronomy at the California Institute of Technology.   Hosts: Brian Holden and Meredith Stepien Written by: Nate DuFort with Sandy Marshall, Meredith Stepien and Brian Holden. Co-Created, Produced by: Nate DuFort and Sandy Marshall Edited by: Nate DuFort Music composed by: Jesse Case Logo by: Steven Lyons   Special thanks to Dr. Mike Brown, Richard and Barbara Rosenberg Professor of Planetary Astronomy at the California Institute of Technology.   We’d also like to thank Kay Ferrari at NASA’s Jet Propulsion Laboratory, and everyone at NASA Space Place. Dr. Mike Brown, Richard and Barbara Rosenberg Professor of Planetary Astronomy at the California Institute of Technology https://mikebrown.caltech.edu/   The Search for Planet Nine Konstantin Batygin and Mike Brown https://findplanetnine.blogspot.com/   “How I Killed Pluto, and Why It Had It Coming” by Mike Brown https://www.amazon.com/How-Killed-Pluto-Why-Coming-ebook/dp/B003F3FJTG/ref=sr_1_1?crid=BDGZGZ51KG8&keywords=why+i+killed+pluto+mike+brown&qid=1645974183&s=digital-text&sprefix=why+i+killed+pluto+mike+brown%2Cdigital-text%2C66&sr=1-1   Want to support our friend Mick and The Past and the Curious podcast while pre-ordering  his latest book I See Lincoln's Underpants? Head on over to the Kickstarter to find out how: https://www.kickstarter.com/projects/heartallybooks/i-see-lincolns-underpants-from-the-past-and-the-curious And then go listen to The Past and the Curious available wherever you get podcasts!