Is There a Secret 9th (or 10th?) Planet Full of Aliens?

<p>Tristan meets up with brilliant physics youtuber Angela Collier to talk about the search for hidden planets, and what might be living on it.</p><p><a href="https://www.youtube.com/@acollierastro" rel="noopener noreferrer" target="_blank">Go watch Angela's videos on YouTube.</a></p><p>Get new episodes early&nbsp;<a href="https://nebula.tv/probablynotaliens" rel="noopener noreferrer" target="_blank">on Nebula!</a></p><p><br></p><p><strong>Subscribe</strong>&nbsp;to&nbsp;<em>It's Probably (not) Aliens</em>&nbsp;for weekly episodes about cool ancient history! And give us a&nbsp;<strong>5-star review</strong>&nbsp;if you have the time. It would really help us out!</p><p><br></p><p><strong>Tristan Johnson</strong>&nbsp;<a href="https://twitter.com/TristanPEJ" rel="noopener noreferrer" target="_blank">Twitter</a>&nbsp;|&nbsp;<a href="http://www.stepbackhistory.com/" rel="noopener noreferrer" target="_blank">YouTube</a></p><p><strong>Scott Niswander</strong>&nbsp;<a href="https://twitter.com/scottniswander" rel="noopener noreferrer" target="_blank">Twitter</a>&nbsp;|&nbsp;<a href="https://www.youtube.com/user/NerdSyncProductions" rel="noopener noreferrer" target="_blank">YouTube</a></p><p><a href="https://twitter.com/ProbsNotAliens" rel="noopener noreferrer" target="_blank">Follow the show on Twitter</a>&nbsp;for more updates!</p><p><br></p><p>Ask us questions and send us topics to talk about at&nbsp;<a href="http://probsnotaliens.com/" rel="noopener noreferrer" target="_blank">ProbsNotAliens.com</a></p><p><a href="https://rodkim.com/" rel="noopener noreferrer" target="_blank"><em>Music by Rod Kim</em></a>&nbsp;|&nbsp;<a href="https://twitter.com/Skutchdraws" rel="noopener noreferrer" target="_blank"><em>Cover art by Skutch</em></a></p><p>See Privacy Policy at <a href="https://art19.com/privacy" rel="noopener noreferrer" target="_blank">https://art19.com/privacy</a> and California Privacy Notice at <a href="https://art19.com/privacy#do-not-sell-my-info" rel="noopener noreferrer" target="_blank">https://art19.