How to Discover 2,332+ Planets

The Kepler spacecraft launched into heliocentric orbit in March 2009, atop a Delta II rocket. It carried just a single scientific instrument, designed for a sole purpose. Kepler’s photometer continuously measured the brightness of over 145,000 stars in its field of view, searching for dips in brightness that might indicate the presence of a planet or other object blocking some of the stars’ light from reaching Earth. To date, NASA has used data collected by the Kepler photometer to confirm the existence of 2,337 planets (and counting) orbiting distant stars.

So what does it take to discover such a massive number of planets? On June 22, the Lawrence Hall of Science hosted three key Kepler mission scientists who discussed the search for habitable Earth-like planets in the Milky Way galaxy. We were proud to provide our Hall members and community with this special opportunity to interact with knowledgeable scientists from NASA and UC Berkeley.

Dr. Gibor Basri (Co-Investigator on Kepler and Professor Emeritus of Astronomy at UC Berkeley) provided a general background on the Kepler mission, the spacecraft, and the technique it uses to detect planets. It’s not enough for Kepler’s photometer to simply catch a single drop in the brightness of a star. Rather, by observing multiple transits of potential planets in front of their stars, scientists can determine the size of the planets, the distances from their star, and how long it takes them to complete one orbit.

Dr. Courtney Dressing (Kepler scientist and Assistant Professor of Astronomy at UC Berkeley) talked about what happened when, in 2013, Kepler malfunctioned and could no longer accurately aim at the stars it was meant to observe. Instead of scrapping the mission altogether, NASA scientists and engineers proposed the K2 mission, a new way of using the spacecraft to continue the search for exoplanets. They worked out that they would use the pressure exerted by photons emitted from the Sun on Kepler to balance the spacecraft and to aim at new regions of space. K2 continues Kepler’s search for other worlds, and has provided new opportunities to observe star clusters, young and old stars, active galaxies, and even supernovae.

Finally, Dr. Martin Still (Deputy Program Scientist for the Exoplanet Exploration Program at NASA) stepped to the podium to discuss Kepler’s legacy and to look ahead at future NASA exoplanet exploration missions. The data collected by Kepler essentially created a new category of astronomy: the study of exoplanets. Upcoming missions like the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope will build on Kepler’s legacy, providing yet more data on the exoplanets we have already discovered, while searching for new ones.

“This all started with Kepler,” Dr. Still said. “There is a whole array, a fleet of future spacecraft carrying telescopes into orbit to detect and characterize exoplanets. Eventually, the hope is to identify environments where life can exist.”

Drs. Basri, Dressing, and Still were joined at the event by the Hall’s own Alan Gould, the co-investigator for the education and public outreach (EPO) component of the Kepler mission. As an EPO partner for Kepler, the Hall developed several activities, exhibits, and curricular materials to inform the general public about the exciting discoveries being made. The Hall developed a series of interactive Planetarium shows, created a DIY star map showing the region being observed by Kepler, and incorporated the exploration of Kepler’s planetary detection methods into our GEMS, FOSS, and Hands-On Universe curricula.

The Hall also helped to develop a traveling science exhibition, called “Alien Earths.” The exhibit explored fundamental questions about the search for exoplanets and extraterrestrial life through multimedia and hands-on interactive activities. Specifically, the Hall created an activity that showed the photometer method that Kepler uses to detect planets. Created in conjunction with the Space Sciences Institute in Boulder, Colorado, the “Alien Earths” exhibit travelled across the country educating people about the formation of stars and planets, as well as the search for life.

“I’m delighted that places like the Lawrence Hall of Science are involved in the mission,” Dr. Dressing told us before the event. “At the end of the day, we’re doing scientific exploration not just for us, but for all of humanity. It’s important that students and family members of all ages get a chance to see and to share in the joy of the Kepler mission.”