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365 Days of Astronomy - Weekly Edition Podcast
Ep. 775: The Hydrogen 21-cm Line

Ep. 775: The Hydrogen 21-cm Line

365 Days of Astronomy - Weekly Edition vor 8 Monaten

Full Raw Episode with Q&A

0:00

57:00

Streamed live on Dec 15, 2025.

Atomic hydrogen is the raw material for stars, but there’s a
problem. It’s cold & dark, but it can do a very rare trick,
releasing a photon in a very specific wavelength, known as the 21
centimeter line. And thanks to this wavelength astronomers have
mapped out star forming regions across the Milky Way, the
Universe and into the Dark Ages! This forbidden transition of
Hydrogen has led to the mapping of galaxy rotation, a cool
classroom application of quantum mechanics, and weirdly no Nobel
prize. In this episode, Fraser and Pamela take a look at this
line's out-of-proportion awesomeness!

This show is supported through people like you on
Patreon.com/AstronomyCast

In this episode, we'd like to thank: Andrew Poelstra, BogieNet,
Brian Cagle, Burry Gowen, David, David Rossetter, Ed, Gerhard
Schwarzer, Jason Kwong, Jeanette Wink, Michael Purcell, Sergey
Manouilov, Siggi Kemmler, Sérgio Sancevero