Kepler Goes Silent

This last week we said goodbye to a truly pioneering space telescope. The Kepler mission was designed to find exoplanets, planets that orbit around other stars. The mission succeeded beyond everyone’s expectations.

Artist’s rendition of the Kepler Spacecraft in orbit around the Sun peering at a distant solar system, press release image from the NASA Kepler website
This little space telescope monitored over 500,000 stars during it’s mission, watching for the minuscule dip in brightness as a panet passed in front of the star. For nine years Kepler stared at those thousands of stars, during that time it discovered over 2,600 exoplanets. Along with the planets came a long list of other discoveries such as binary stars, variable stars, and novae.

After nine productive years this engine of discovery has come to an end. With the spacecraft out of fuel NASA flight engineers sent the last commands, shutting the spacecraft down.

The Keck Observatory and the Kepler Spacecraft had a great partnership. It was not possible to confirm most Kepler’s possible exoplanets using only data from the spacecraft. A large telescope using a high resolution spectrograph, like HIRES on Keck 1, would allow astronomers to not only confirm Kepler’s discovery, but to learn more about each exoplanet.

Using the radial velocity method HIRES data would allow astronomers to pin down the mass of the exoplanet. With the mass of the exoplanet measured it is possible to determine the basic composition, a gas planet like our Jupiter and Saturn, an ice giant like Neptune or Uranus, or a small rocky world more like our Earth. This additional data turned the trove of Kepler discoveries into real information about the universe.

The enormous number of planets discovered by Kepler allows us to start answering some long asked questions… Are planets common around other stars? How many planets are out there? Are there other small rocky worlds, like Earth, where life similar to ours could be found? The key to truly answering these questions is in a large number of samples, provided by Kepler, and statistics and Kepler’s thousands of data points.

Gliese 876b, as seen from a hypothetical moon
Gliese 876b, a gas giant that’s two times more massive than Jupiter, as seen from a hypothetical moon
While before we suspected planets were common, now we know. Using the Kepler data is is possible to create a good estimate on the number of planets in our galaxy. How many are large gas giants? How many are small rocky worlds? How many orbit at the correct distance from the star to have liquid water on the surface?

Almost every star we see in the sky is likely to have at least a few planets. Somewhere between a quarter and half are certain to have small rocky worlds similar to our own Earth. Planets that are in or near the habitable zone where liquid water could harbor life.

Thanks to the Kepler mission we can confidently answer questions that were total mysteries only a couple decades ago. Questions that lead to one of the most perplexing questions in astronomy… Is there anyone else out there?

Image montage showing the Maunakea Observatories, Kepler Space Telescope, and night sky with K2 Fields and discovered planetary systems (dots) overlaid. Credit: Karen Teramura/IFA, Miloslav Druckmüller, NASA

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

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