Caltech Astronomy Public Lecture Series - Cosmic Fireworks: How Astronomers Explore the Changing Sky - Sam Rose - 08/22/2025

What causes the cosmic flashes that we see in the sky? What will the Rubin Observatory observe when it begins operation in a few months? Join us for a 30-minute lecture about cosmic fireworks, 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 Announcements 8:22 Introduction to Presenter 9:21 Cosmic Fireworks Presentation 48:09 Spectroscopy Demonstration 52:14 Cosmic Fireworks Presentation Finale 57:53 Cosmic Fireworks Q&A 58:06 "What causes the different colors of asteroids?" 58:40 "What was the astronomical event that you were up all night observing?" 1:01:05 "What are astronomical timescales that are very long versus very short?" 1:03:13 Intermission 1:08:56 Q&A Panel Introductions 1:11:30 "Can you give us some more information about the Sequoia Dark Sky Festival?" 1:13:14 "How does a diffraction grating work to split up the light to colors?" 1:19:41 "If you see hydrogen and sodium lines in a spectrum, how do you know their abundances?" 1:24:41 "What is special about the news of two black holes merging recently?" 1:30:20 "Are there any updates on the status of T Corona Borealis (Blaze Star)?" 1:35:54 "Is the universe's timeline cyclical?" 1:45:31 "What will the universe look like in the very distant future?" 1:47:10 "Do Starlink satellites negatively affect your research?" 1:50:58 "Why can't astronomers just put all of their telescopes in space?" 1:53:52 "Are there any updates with 3I/Atlas, the interstellar comet?" 1:55:35 "What is your favorite part of your research?" 2:01:03 Concluding Remarks Title: Cosmic Fireworks: How Astronomers Explore the Changing Sky Lecturer: Sam Rose Abstract: The Universe evolves over the course of billions of years—a timescale almost incomprehensible to humans. But there are some things in the night sky that change much faster. Spectacular explosions of massive stars dying, pulsing stars, and comets and asteroids drifting through our Solar System are all examples of changes in the sky that happen over the course of weeks, months, or years. These events which cause new sources of light to appear and disappear in the sky are called “astronomical transients.” In this talk, we will explore the history of astronomical transients: including observations of an exploding star by Chinese astronomers in 1054 CE, the search for comets over the centuries, and the first large-scale surveys of the sky using the Mt. Wilson and Palomar observatories. We will also cover the next-generation efforts to detect these events using Caltech's very own Zwicky Transient Facility (ZTF) and the brand new Vera Rubin Observatory, which will reveal millions of new asteroids and supernovae across the sky in the coming years.