History of Astronomy, From Ancient China to Modern Telescopes, and Astronomical Transients Explained
•March 6, 2026
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Why It Matters
Understanding transients links historic skywatching to cutting‑edge surveys, informing stellar evolution models and guiding investment in rapid‑response observatories that shape astrophysics and STEM outreach.
Key Takeaways
- •ZTF images entire northern sky every two nights for transients.
- •Ancient Chinese records first documented supernova of 1054, Crab Nebula.
- •Supernovae result from iron core collapse halted by neutron pressure.
- •Hubble Ultra Deep Field reveals ~10,000 galaxies in 2.4 arc‑minutes.
- •Modern transient surveys enable rapid multi‑telescope follow‑up of explosions.
Summary
The video features Sam Rose, a Caltech graduate student, explaining astronomical transients—from ancient Chinese supernova sightings to today’s high‑speed sky surveys. She introduces the Zwicky Transient Facility (ZTF), which photographs the entire northern sky every two nights, comparing new images to historical data to flag sudden changes such as exploding stars, comets, or asteroids.
Key scientific points include the mechanics of core‑collapse supernovae: once a star’s core fuses iron, gravity overwhelms fusion, a neutron‑degeneracy pressure shock halts collapse, and the outer layers are expelled in a brilliant explosion. The 1054 supernova recorded by Chinese astronomers created the Crab Nebula, a modern Hubble target. Rose also highlights the Hubble Ultra Deep Field, where a 2.4‑arc‑minute patch contains roughly 10,000 galaxies, underscoring the universe’s vastness.
Memorable moments feature Rose’s pinky‑finger analogy to convey angular size, her pride in humanity’s ability to capture distant galaxies, and personal anecdotes about her path from Bay‑Area libraries to Caltech’s transient team. She demonstrates how modern observatories, coordinated via computers, can operate multiple telescopes simultaneously to chase fleeting events.
The presentation underscores that transient astronomy bridges millennia of observation, fuels our understanding of stellar life cycles, and drives technological advances in rapid data processing and multi‑instrument coordination—critical for future discoveries and for inspiring the next generation of scientists.
Original Description
The universe evolves over the course of billions of years—a timescale almost incomprehensible when compared to human lifespans. But there are some things in the night sky that happen on much shorter timelines. Spectacular explosions of dying massive stars, changing brightness of older stars, and visiting objects from the outer edges of our solar system are all examples of changes in the sky that happen over the course of weeks, months, or years. We call these events, which cause new sources of light to appear and disappear in the sky, "astronomical transients." Astronomers still don't know everything there is to know about the stars and other objects in the sky, so they use giant telescopes and other scientific methods to study the sky nearly every night!
Join Caltech graduate student and astronomer Sam Rose as she explores the history of astronomical transients: from the observations of an exploding star by Chinese astronomers in 1054 CE, to the search for comets in the 17th, 18th, and 19th centuries, to the first large-scale surveys of the sky on photographic plates from Mount Wilson and Palomar observatories starting 80 years ago, to the modern technology used at observatories today.
As a member of the Zwicky Transient Facility (ZTF) collaboration, Sam spends her days and nights searching for and studying these cosmic fireworks. Sam will show how members of the ZTF collaboration use different telescopes to find and classify the thousands of astronomical transients discovered every year.
About the Speaker:
Sam Rose is a graduate student studying astronomy at Caltech advised by Professor Mansi Kasliwal. Sam spends her days (and many nights!) investigating the spectacular explosive deaths of stars and how their remnants go on to form the next generation of stars and planets. Using telescopes on Palomar Mountain, just three hours from Pasadena; on Mauna Kea located on the island of Hawai'i; and on the James Webb Space Telescope way out in space, Sam attempts to understand what happens to different stars at the end their lives, as well as how they spend their afterlives. Sam was raised in the San Francisco Bay area, where she also attended UC Berkeley for her undergraduate degree. Having fallen in love with the night sky after seeing the planet Saturn through a small telescope as a middle school student, Sam majored in physics and astrophysics and came to Caltech to pursue a PhD in 2022. When not doing astronomy, she enjoys reading cheesy science-fiction novels, spending time at the beach ... and reading cheesy science fiction at the beach.
About the program:
In Science Journeys, Caltech graduate students and postdoctoral scholars share their research to inspire scientific curiosity. Programs are designed for middle and high schoolers, but all are welcome. These events are made possible through the generosity of the Friends of Beckman Auditorium. If you have questions, please email Mary Herrera at mhh@caltech.edu.
If you have questions, please email events@caltech.edu
Produced in association with Caltech Academic Media Technologies.
©2026 California Institute of Technology
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