Illuminating the “Emptiness” of Space with Radio Beacons - Stella Ocker - 06/26/2026

What fills the seemingly empty void between the stars? And how can mysterious cosmic beacons help us uncover the structure of the invisible universe? Join us for a lecture by postdoctoral fellow Stella Ocker as she discusses these topics and more. Her presentation will be followed by a panel Q&A consisting of several astrophysicists to answer your questions about astronomy and space science. Timestamps and description below: 00:00 Start of Stream 00:07 Announcements 06:59 Introduction of Presenter 08:09 Emptiness of Space Presentation 39:42 End of Presentation 39:53 Emptiness of Space Q&A 40:11 "Where does the gas in the voids originate?" 41:22 "How do you identify the unique distribution of matter along each line of sight?" 43:22 "Can you determine the composition of the gas or just its density?" 44:54 "Do we know how far away the galaxies hosting FRBs are?" 46:40 Intermission 50:31 Q&A Panel Introductions 53:09 "Do you make use of the 21-cm line of neutral hydrogen in your research?" 55:18 "Do we use FRBs to discover galaxies?" 56:26 "Does gravitational lensing affect your plasma dispersion measurement?" 59:09 "How big are our radio telescopes? How can we map our galaxy while inside of it?" 1:02:44 "How is the new DSA radio telescope different from the previous version DSA-110?" 1:06:27 "Are there radio telescopes in the southern hemisphere?" 1:07:27 "Is the intergalactic plasma homogeneous and isotropic on cosmological scales?" 1:10:19 "Does dark matter distort radio waves?" 1:12:38 "How well can we approximate the location and timing of FRBs? 1:15:41 "What are the opportunities for humanity's advancements from astronomical discoveries?" 1:20:21 "Is the plot of Interstellar real?" 1:22:25 "Why causes the change of speed of light through the gas plasma?" 1:24:35 "What are your favorite science fiction films?" 1:27:17 "How do we model these systems accounting for the finite speed of light?" 1:30:27 "Does the gas move on short timescales? seconds? years? megayears? 1:33:40 "Could you explain your research to a middle school class in one minute?" 1:35:33 "How do you choose which telescopes on which to request time?" 1:39:29 "Does dark matter obey the same laws of physics that normal matter does?" 1:41:43 "Why do certain atmospheric flows change their direction during interactions?" 1:46:08 "How do the pulsar emission processes affect how we detect them?" 1:49:30 "What is the relationship between redshift and the radio signals creating them?" 1:52:07 "Do we use AI in our work or are there other applications for AI in astrophysics?" 1:56:00 "Could we detect an FRB in our own galaxy?" 1:58:17 "What is the average lifetime of a star and how long does the explosion last?" 2:02:42 Concluding Remarks Title: Illuminating the “Emptiness” of Space with Radio Beacons Lecturer: Stella Ocker Abstract: While stars are the most obvious naked-eye feature in the night sky, they actually constitute a tiny fraction of all the ordinary matter in the universe. Most of the visible matter in the cosmos takes the form of diffuse ionized gas, or “plasma,” distributed between stars and galaxies. In this talk I will discuss how pulsars and fast radio bursts are used as cosmic flashlights to illuminate the distribution of this plasma within our Milky Way and across cosmic time. I will share the exciting prospects for studying these cosmic radio sources with upcoming surveys led by Caltech, which will ultimately lead us to a deeper understanding of galaxy evolution and the universe itself. Stella Ocker: https://stella-ocker.github.io/ Stargazing Lecture on the DSA Radio Telescope: https://www.youtube.com/live/7cnN62osaUA Stargazing Lecture on Fast Radio Bursts:    • Fast Radio Bursts - Liam Connor - 12/10/2021   Many thanks to our new cameramanJordan Colley:   / jordancolley