Uploaded February 2023 | Updated September 2026, 3 weeks ago

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Guest Speaker: Sahil Hegde, Ph.D. candidate, UCLA
Summary: In this video, you will learn about population 3 stars. Sahil begins by describing the life cycle of a star. By observing the spectra of a star, astronomers can determine the star's composition and its temperature. The absorption lines in the spectra show the chemical composition of the star. First stars differ from later stars since they mostly comprise neutral hydrogen (75%) and a little helium (25%). Sahil explains why these first stars are huge compared to later stars and live for only a few million years. Scientists have been unable to observe the first stars directly for several reasons. So, astronomers are searching for them indirectly by searching them at different wavelengths.
If you are interested in what are Population 3 stars and what happened to them, this video will help you answer some of these questions. We hope you enjoy this video!

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Chapters
0:00 Introduction
1:37 Stellar Overview
5:53 Phase I of stellar evolution
13:57 Phase II of stellar evolution
14:49 Phase II of stellar evolution
15:40 Phase IV of stellar evolution
19:05 Observing stars
22:04 Stellar evolution and HR diagram
26:31 How first-generation are different from the stars we see now
32:39 Phase I stellar evolution for first-generation stars
37:11 Timeline of first-generation stars
40:38 First-generation stars and black holes
41:12 How do we observe the first stars?

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#deepsky
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#cosmology