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Stargazing Lecture

Friday, June 5, 2020
7:00pm to 9:00pm
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Online Event
Measuring the Speed of Stars More Precisely Than Your Car's Speedometer
Ryan Rubenzahl, PhD Candidate, Department of Astronomy, Caltech,
  • Public Event

This event is being moved online in light of the impact of COVID-19. Because this is an online event, the in-person stargazing that normally follows events in this series will not be possible.

Join the YouTube Livestream here:

7:00–7:30 p.m. - Virtual Lecture
7:30–9:00 p.m. - Virtual Panel Q&A and Discussion

The "doppler method" or "wobble method" of detecting planets orbiting other stars, requires precise measurements of the speeds of those distant stars. If we can see a star oscillating towards and away from us, we can infer that an unseen planet is tugging on its parent star as it orbits. This method successfully found the first exoplanet, 51 Peg b, a discovery which earned the Nobel Prize this last year. We now know of over 4000 exoplanets, but we are just on the verge of being able to detect Earth-like planets in the "habitable zones" of Sun-like stars. In this public talk we will learn just how hard it is to precisely measure the speeds of stars to the precision of 9 cm/s (0.2 mph!!!) necessary for finding these Earth-like planets. Next-generation instruments capable of these discoveries may finally be able to answer the question of how common planets like Earth really are in the galaxy.

About the Series

Stargazing Lectures are free lectures at a public level followed by a Q&A panel and guided stargazing with telescopes (weather permitting). All events are held at the Cahill Center for Astronomy and Astrophysics at Caltech. No reservations are needed. Lectures are 30 minutes; stargazing and panel Q&A last 90 minutes. Stay only as long as you want.

Stargazing is only possible with clear skies, but the lecture and panel Q&A takes place regardless of weather.

For directions, weather updates, and more information, please visit:

Download the series flyer (PDF)

For more information, please contact Cameron Hummels by email at