Rubin Planetarium Video - Exoplanet Transits

Extrasolar planets, or exoplanets, are planets that orbit around stars other than the Sun. Exoplanets are hard to see because of the glare from their bright stars. This video illustrates how we can detect and characterize an exoplanet by measuring the dip in light it causes every time it passes in front of its star. It compares light curves for the same planet transiting two different stars of different sizes.

Because LSST will regularly measure the brightness of billions of stars, it will also be capable of detecting exoplanets with the transit method. It is expected that LSST will discover “hot Jupiters” and “hot Neptunes,” gas-giant planets that orbit close to their stars. Most remarkably, LSST will have the sensitivity to detect exoplanets around stars in the Large Magellanic Cloud, which may mark the first time an exoplanet is discovered around a star in another galaxy.



In front of you, you see a big star with a planet orbiting around it. This is an imagined view of what it might look like if we watched an exoplanetary system through an impossibly powerful telescope.


With existing telescopes we can make very precise measurements of the brightness of stars. Starting at this time a light curve of the brightness of this star is shown along the bottom of the dome. The small fluctuations in the light curve are due to intrinsic variations in the brightness of the star as well as errors in measurement.

If the planet happens to be orbiting its star so that it passes in front of the star (as seen from Earth), well see a little dip in the brightness of the star. We can determine the size of the star by how much of the starʼs light it blocks. A bigger planet will block more of its starʼs light.


At this time we see another dip in brightness as the planet transits again. The dip in brightness will repeat every time the planet orbits around the star. We can use the time difference between dips to figure out how long it takes for the planet to complete one orbit.


Now we transition to a red dwarf star, which is smaller and cooler than the sun. Most stars in the universe are of this type. If a planet of the same size orbits this smaller star, it will block a larger fraction of the starʼs light, causing a bigger dip. When weʼre looking for relatively small planets like Earth, it might be easier to find them if we look for them orbiting in front of smaller stars!

Contact and Usage Survey

If you use this video for any purpose, please fill out this survey so the LSST team can understand usage and make any improvements necessary:

Contact: Amanda Bauer, Head of LSST Education and Public Outreach

Additional References


Fiske Planetarium, University of Colorado Boulder

Zach Berta-Thompson (

Special Recognition

Data to Dome initiative

Taylor Washington (CU Boulder) helped create the code for transit light curve visualization in the dome.

About the Video

Release date:April 12, 2023, 2:23 p.m.
Duration:03 m 17 s
Frame rate:30 fps

About the Object


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